Derivative Instruments - Derivatives Not Designated as Hedging Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Derivative instruments, gain (loss)
Notional Amount	$ 5,837,562		$ 5,837,562
Derivatives not designated as hedges
Derivative instruments, gain (loss)
Net gain (loss) of derivatives included in the Consolidated Statements of Income	(16,127)	$ (4,191)	(25,499)	$ 8,731
Notional Amount	5,516,487		5,516,487		$ 1,390,750
Derivatives not designated as hedges | Interest rate contracts
Derivative instruments, gain (loss)
Net gain (loss) of derivatives included in the Consolidated Statements of Income	(17,300)		(17,300)
Notional Amount	4,694,964		4,694,964		1,095,449
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	(19,764)	51	(21,307)	157
Derivatives not designated as hedges | Forward foreign exchange contracts
Derivative instruments, gain (loss)
Notional Amount	291,999		291,999		254,274
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	3,307	(3,706)	(5,302)	8,050
Derivatives not designated as hedges | Interest rate lock commitments
Derivative instruments, gain (loss)
Notional Amount	266,949		266,949		28,007
Derivatives not designated as hedges | Interest rate lock commitments | Net (losses) gains on sales of loans and leases
Derivative instruments, gain (loss)
Net gain (loss) of derivatives included in the Consolidated Statements of Income	337	(244)	1,117	798
Derivatives not designated as hedges | Forward loan sales commitments
Derivative instruments, gain (loss)
Notional Amount	218,061		218,061
Derivatives not designated as hedges | Forward loan sales commitments | Net (losses) gains on sales of loans and leases
Derivative instruments, gain (loss)
Net gain (loss) of derivatives included in the Consolidated Statements of Income	(11)	0	(11)	0
Derivatives not designated as hedges | Swap agreement
Derivative instruments, gain (loss)
Notional Amount	12,644		12,644		$ 13,020
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	$ 4	$ (292)	$ 4	$ (274)