Quarterly report pursuant to Section 13 or 15(d)

Fair Value by Balance Sheet Grouping (Details)

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Fair Value by Balance Sheet Grouping (Details) - USD ($)
$ in Thousands
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]            
Available-for-sale securities, at fair value $ 19,293,354   $ 21,220,819      
Mortgage servicing rights, at fair value 1,450,261 $ 1,301,023 1,086,717 $ 898,025 $ 747,580 $ 693,815
Residential mortgage loans held-for-sale, at fair value 28,813   30,414 $ 31,946   $ 40,146
Cash and cash equivalents 417,515   419,159      
Restricted cash 564,705   635,836      
Derivative assets, at fair value 257,917   309,918      
Equity securities, at fair value 30,425   29,413      
Federal Home Loan Bank stock 40,845   53,826      
Equity investments 3,000   3,000      
Repurchase agreements 17,205,823   19,451,207      
Federal Home Loan Bank advances 865,024   1,215,024      
Revolving credit facilities 170,000   20,000      
Convertible senior notes 283,268   282,827      
Convertible senior notes, at fair value 304,451   306,351      
Derivative liabilities, at fair value 39,429   31,903      
Federal Home Loan Bank of Des Moines [Member]            
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]            
Federal Home Loan Bank stock 40,845   53,826      
Federal Home Loan Bank advances $ 865,024   $ 1,215,024