|
Derivative Instruments and Hedging Activities Interest Rate Sensitive Assets/Liabilities (Details) (USD $)
In Thousands, unless otherwise specified |
Jun. 30, 2014
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Mar. 31, 2014
|
Dec. 31, 2013
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Jun. 30, 2013
|
Mar. 31, 2013
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Dec. 31, 2012
|
|---|---|---|---|---|---|---|
| Derivatives, Fair Value [Line Items] | ||||||
| Available-for-sale Securities | $ 13,108,251 | $ 12,256,727 | ||||
| Notional Disclosures [Abstract] | ||||||
| Derivative, Notional Amount | 43,379,217 | 43,576,146 | 37,366,610 | 44,262,605 | 27,041,328 | 22,377,656 |
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Derivative Financial Instruments, Assets [Member]
|
||||||
| Derivative, Fair Value, Net [Abstract] | ||||||
| Derivative, Fair Value, Net | 331,601 | 549,859 | ||||
| Notional Disclosures [Abstract] | ||||||
| Derivative, Notional Amount | 38,499,739 | 30,383,908 | ||||
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Derivative Financial Instruments, Liabilities [Member]
|
||||||
| Derivative, Fair Value, Net [Abstract] | ||||||
| Derivative, Fair Value, Net | (17,097) | (22,081) | ||||
| Notional Disclosures [Abstract] | ||||||
| Derivative, Notional Amount | 8,523,478 | 10,876,702 | ||||
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Forward Contracts [Member]
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||||||
| Derivative, Fair Value, Net [Abstract] | ||||||
| Derivative, Cost | (439,317) | 790,392 | ||||
| Notional Disclosures [Abstract] | ||||||
| Derivative, Notional Amount | (372,000) | (1,022,000) | 603,000 | (2,721,000) | 2,150,000 | 953,000 |
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Forward Contracts [Member] | Derivative Financial Instruments, Assets [Member]
|
||||||
| Derivative, Fair Value, Net [Abstract] | ||||||
| Derivative, Fair Value, Net | 9,063 | 33,425 | ||||
| Notional Disclosures [Abstract] | ||||||
| Derivative, Notional Amount | 1,450,000 | 4,097,000 | ||||
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Forward Contracts [Member] | Derivative Financial Instruments, Liabilities [Member]
|
||||||
| Derivative, Fair Value, Net [Abstract] | ||||||
| Derivative, Fair Value, Net | (13,566) | (125) | ||||
| Notional Disclosures [Abstract] | ||||||
| Derivative, Notional Amount | 1,822,000 | 400,000 | ||||
|
Options Held [Member]
|
||||||
| Notional Disclosures [Abstract] | ||||||
| Derivative, Notional Amount | 0 | 1,500,000 | 0 | (210,000) | 0 | 0 |
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Options Held [Member] | Derivative Financial Instruments, Assets [Member]
|
||||||
| Derivative, Fair Value, Net [Abstract] | ||||||
| Derivative, Fair Value, Net | 28 | |||||
| Notional Disclosures [Abstract] | ||||||
| Derivative, Notional Amount | 0 | |||||
|
Options Held [Member] | Derivative Financial Instruments, Liabilities [Member]
|
||||||
| Derivative, Fair Value, Net [Abstract] | ||||||
| Derivative, Fair Value, Net | 0 | |||||
| Notional Disclosures [Abstract] | ||||||
| Derivative, Notional Amount | 0 | |||||
|
Long [Member] | Forward Contracts [Member]
|
||||||
| Derivative, Fair Value, Net [Abstract] | ||||||
| Derivative, Cost | 1,423,492 | 2,749,648 | ||||
| Notional Disclosures [Abstract] | ||||||
| Derivative, Notional Amount | 1,450,000 | 2,550,000 | ||||
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Long [Member] | Forward Contracts [Member] | Derivative Financial Instruments, Assets [Member]
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||||||
| Derivative, Fair Value, Net [Abstract] | ||||||
| Derivative, Fair Value, Net | 9,063 | 17,771 | ||||
|
Long [Member] | Forward Contracts [Member] | Derivative Financial Instruments, Liabilities [Member]
|
||||||
| Derivative, Fair Value, Net [Abstract] | ||||||
| Derivative, Fair Value, Net | 0 | (125) | ||||
|
Long [Member] | Options Held [Member]
|
||||||
| Derivative, Fair Value, Net [Abstract] | ||||||
| Derivative, Cost | (5,469) | |||||
| Notional Disclosures [Abstract] | ||||||
| Derivative, Notional Amount | 1,000,000 | |||||
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Short [Member] | Forward Contracts [Member]
|
||||||
| Derivative, Fair Value, Net [Abstract] | ||||||
| Derivative, Cost | (1,862,809) | (1,959,256) | ||||
| Notional Disclosures [Abstract] | ||||||
| Derivative, Notional Amount | (1,822,000) | (1,947,000) | ||||
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Short [Member] | Forward Contracts [Member] | Derivative Financial Instruments, Assets [Member]
|
||||||
| Derivative, Fair Value, Net [Abstract] | ||||||
| Derivative, Fair Value, Net | 0 | 15,654 | ||||
|
Short [Member] | Forward Contracts [Member] | Derivative Financial Instruments, Liabilities [Member]
|
||||||
| Derivative, Fair Value, Net [Abstract] | ||||||
| Derivative, Fair Value, Net | (13,566) | 0 | ||||
|
Short [Member] | Options Held [Member]
|
||||||
| Derivative, Fair Value, Net [Abstract] | ||||||
| Derivative, Cost | 4,453 | |||||
| Notional Disclosures [Abstract] | ||||||
| Derivative, Notional Amount | (1,000,000) | |||||
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Interest Rate Risk Associated with the Investment Portfolio [Member] | Long [Member] | Forward Contracts [Member]
|
||||||
| Notional Disclosures [Abstract] | ||||||
| Derivative, Notional Amount | 1,450,000 | 400,000 | ||||
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Interest Rate Risk Associated with the Investment Portfolio [Member] | Short [Member] | Forward Contracts [Member]
|
||||||
| Notional Disclosures [Abstract] | ||||||
| Derivative, Notional Amount | 1,822,000 | 1,947,000 | ||||
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Interest-Only-Strip [Member]
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| Derivatives, Fair Value [Line Items] | ||||||
| Available-for-sale Securities | $ 66,764 | $ 75,575 |