Derivatives and Hedging - Free Standing Derivative Instruments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Futures contracts | Mortgage banking income and corporate and correspondent investment sales
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	$ (3)	$ (240)
Option contracts related to mortgage servicing rights | Mortgage banking income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	0	(105)
Forward contracts related to residential mortgage loans held for sale | Mortgage banking income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	(2,665)	(1,455)
Interest rate lock commitments | Mortgage banking income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	785	822
Interest rate contracts for customers | Corporate and correspondent investment sales
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	6,796	3,540
Commodity contracts for customers | Corporate and correspondent investment sales
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	0	(2)
Purchased equity option related to equity-linked CDs | Other expense
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	3,630	5,291
Written equity option related to equity-linked CDs | Other expense
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	(3,134)	(4,556)
Forward and swap contracts related to commercial loans | Other income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	(6,958)	(13,947)
Spot contracts related to commercial loans | Other income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	996	(1,108)
Foreign currency exchange contracts for customers | Corporate and correspondent investment sales
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	$ 2,350	$ 431