Derivatives and Hedging - Free Standing Derivative Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
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	$ 41	$ (800)	$ (752)	$ (1,379)
Interest rate lock commitments | Mortgage banking income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	8,333	689	17,655	1,835
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	734	1,528	1,028
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	2,803	40	(3,104)	(49)
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	14,687	2,664	18,824	6,092
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	(704)	(3,992)	(2,592)	(5,009)
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	586	3,531	2,210	4,527
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	(14,790)	(999)	11,191	1,697
Spot contracts related to commercial loans | Other income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	2,053	700	2,824	198
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	$ 3,923	$ 3,611	$ 8,624	$ 7,462