Noninterest Income - Foreign Exchange Fees (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 285,382	$ 221,371	$ 507,822	$ 438,628
Revenue not from contract with customer	83,466	112,379	162,960	175,498
Foreign exchange fees	36,256	38,506	83,761	76,554
Spot contract commissions
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	33,093	34,696	74,027	69,725
Forward contract commissions
Disaggregation of Revenue [Line Items]
Revenue not from contract with customer	3,052	3,778	9,391	6,773
Option premium fees
Disaggregation of Revenue [Line Items]
Revenue not from contract with customer	$ 111	$ 32	$ 343	$ 56