Noninterest Income - Foreign Exchange Fees (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 247,037	$ 205,905	$ 756,847	$ 644,533
Revenue not from contract with customer	300,546	88,104	461,518	263,602
Foreign exchange fees	43,881	40,309	127,642	116,863
Spot contract commissions
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	38,794	36,836	112,821	106,561
Forward contract commissions
Disaggregation of Revenue [Line Items]
Revenue not from contract with customer	4,613	3,371	14,004	10,144
Option premium fees
Disaggregation of Revenue [Line Items]
Revenue not from contract with customer	$ 474	$ 102	$ 817	$ 158