Derivatives and Hedging - Free Standing Derivative Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 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	$ (12)	$ 14	$ (764)	$ (1,365)
Interest rate lock commitments | Mortgage banking income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	(4,438)	191	13,217	2,026
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	285	1,528	1,313
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	2,115	530	(989)	481
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	(62)	7,398	18,762	13,490
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	(1,094)	(2,187)	(3,686)	(7,196)
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	930	1,942	3,140	6,469
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	(15,885)	13,787	(4,694)	15,484
Spot contracts related to commercial loans | Other income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	2,076	(1,263)	4,900	(1,065)
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	$ 3,400	$ 4,085	$ 12,024	$ 11,547