Derivative Instruments and Hedging Activities Short U.S. Treasury Securities (Details) - USD ($) |
Sep. 30, 2018 |
Jun. 30, 2018 |
Dec. 31, 2017 |
Sep. 30, 2017 |
Jun. 30, 2017 |
Dec. 31, 2016 |
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| Derivative [Line Items] | ||||||
| Notional | $ 41,330,283,000 | $ 28,618,861,000 | $ 31,226,878,000 | $ 24,113,321,000 | $ 16,988,116,000 | $ 18,802,500,000 |
| Derivative Financial Instruments, Liabilities [Member] | ||||||
| Derivative [Line Items] | ||||||
| Notional | 11,521,000,000 | 8,335,507,000 | ||||
| Fair Value | (797,504,000) | (31,903,000) | ||||
| Short US Treasury Securities [Member] | Derivative Financial Instruments, Liabilities [Member] | ||||||
| Derivative [Line Items] | ||||||
| Fair Value | (752,861,000) | 0 | ||||
| Short US Treasury Securities [Member] | Short [Member] | ||||||
| Derivative [Line Items] | ||||||
| Notional | $ 800,000,000.0 | $ 0 |
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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Fair value of the assets less the liabilities of a derivative or group of derivatives. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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