Segment Reporting - Summary of Operating Results of Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 153,468	$ 169,289
Provision for credit losses	83,429	11,210
Noninterest income	35,069	30,664
Noninterest expense	537,653	113,440
Income tax (benefit) expense	(33,234)	17,102
Net (loss) income	(399,311)	58,201
Total assets	17,237,918	17,452,911	$ 17,800,229
Banking
Segment Reporting Information [Line Items]
Net interest income (expense)	157,557	174,396
Provision for credit losses	83,429	11,210
Noninterest income	25,343	20,087
Noninterest expense	528,066	97,324
Income tax (benefit) expense	(30,922)	19,862
Net (loss) income	(397,673)	66,087
Total assets	17,142,981	17,347,134
Financial Services
Segment Reporting Information [Line Items]
Net interest income (expense)	(352)	(630)
Noninterest income	10,208	10,285
Noninterest expense	8,710	7,652
Income tax (benefit) expense	95	373
Net (loss) income	1,051	1,630
Total assets	90,600	100,175
Corporate
Segment Reporting Information [Line Items]
Net interest income (expense)	(3,737)	(4,477)
Noninterest income	(482)	292
Noninterest expense	877	8,464
Income tax (benefit) expense	(2,407)	(3,133)
Net (loss) income	(2,689)	(9,516)
Total assets	$ 4,337	$ 5,602