Quarterly report pursuant to Section 13 or 15(d)

Derivative Instruments and Hedging Activities Interest Rate Sensitive Assets/Liabilities (Details)

v3.8.0.1
Derivative Instruments and Hedging Activities Interest Rate Sensitive Assets/Liabilities (Details) - USD ($)
$ in Thousands
Sep. 30, 2017
Jun. 30, 2017
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Dec. 31, 2015
Derivatives, Fair Value [Line Items]            
Available-for-sale securities, at fair value $ 20,199,094   $ 13,128,857      
Mortgage servicing rights, at fair value 930,613 $ 898,025 693,815 $ 455,629 $ 427,813 $ 493,688
Interest-Only-Strip [Member]            
Derivatives, Fair Value [Line Items]            
Available-for-sale securities, at fair value $ 60,354   $ 71,084