Derivative Instruments - Derivatives Not Designated as Hedging Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Derivative instruments, gain (loss)
Terminated interest rate swaps	$ 298,941		$ 298,941		$ 106,102
Interest rate contracts
Derivative instruments, gain (loss)
Terminated interest rate swaps	279,710		279,710		102,401
Risk participation agreements
Derivative instruments, gain (loss)
Terminated interest rate swaps	163		163		202
Forward foreign exchange contracts
Derivative instruments, gain (loss)
Terminated interest rate swaps	34		34		0
Interest rate lock commitments
Derivative instruments, gain (loss)
Terminated interest rate swaps	18,592		18,592		2,765
Forward loan sales commitments
Derivative instruments, gain (loss)
Terminated interest rate swaps	0		0		$ 0
Derivatives not designated as hedges
Derivative instruments, gain (loss)
Net gain (loss) of derivatives included in the Consolidated Statements of Income	(281)	$ (16,127)	27,969	$ (25,499)
Derivatives not designated as hedges | Interest Rate Swap [Member]
Derivative instruments, gain (loss)
Loss on termination of interest rate swaps		17,300		17,300
Terminated interest rate swaps		1,100,000		1,100,000
Derivatives not designated as hedges | Interest rate contracts | Other noninterest income
Derivative instruments, gain (loss)
Net gain (loss) of derivatives included in the Consolidated Statements of Income	(2,314)	(20,085)	3,459	(21,345)
Derivatives not designated as hedges | Risk participation agreements | Other noninterest expense
Derivative instruments, gain (loss)
Net gain (loss) of derivatives included in the Consolidated Statements of Income	(310)	321	(523)	38
Derivatives not designated as hedges | Forward foreign exchange contracts | Other noninterest expense
Derivative instruments, gain (loss)
Net gain (loss) of derivatives included in the Consolidated Statements of Income	(1,606)	3,307	9,615	(5,302)
Derivatives not designated as hedges | Interest rate lock commitments | Net gains on sales of loans and leases
Derivative instruments, gain (loss)
Net gain (loss) of derivatives included in the Consolidated Statements of Income	68	337	15,840	1,117
Derivatives not designated as hedges | Forward loan sales commitments | Net gains on sales of loans and leases
Derivative instruments, gain (loss)
Net gain (loss) of derivatives included in the Consolidated Statements of Income	3,881	(11)	(421)	(11)
Derivatives not designated as hedges | Swap agreement | Other noninterest income
Derivative instruments, gain (loss)
Net gain (loss) of derivatives included in the Consolidated Statements of Income	$ 0	$ 4	$ (1)	$ 4