Revenue from Contracts with Customers - Summary of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Noninterest income	$ 32,047	$ 37,917	$ 38,018	$ 40,554	$ 32,319	$ 32,122	$ 41,568	$ 38,010	$ 54,264	$ 27,770	$ 20,897	$ 19,419	$ 148,536	$ 144,019	$ 122,350
Noninterest expense	$ (108,366)	$ (109,661)	$ (104,561)	$ (101,610)	$ (100,022)	$ (119,539)	$ (98,237)	$ (104,196)	$ (114,302)	$ (106,144)	$ (59,085)	$ (58,887)	(424,198)	$ (421,994)	$ (338,418)
Noninterest income from contracts with customers within the scope of ASC 606
Disaggregation of Revenue [Line Items]
Noninterest income													33,513
Service charges and fees on deposit accounts
Disaggregation of Revenue [Line Items]
Noninterest income													22,858
Wealth management revenue
Disaggregation of Revenue [Line Items]
Noninterest income													5,099
Other charges and fees for customer services
Disaggregation of Revenue [Line Items]
Noninterest income													5,556
Noninterest income within the scope of other GAAP topics
Disaggregation of Revenue [Line Items]
Noninterest income													115,023
Other
Disaggregation of Revenue [Line Items]
Noninterest expense													$ (1,063)