Reportable Segments - Summary of Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment Reporting Information
Net interest income (expense)	$ 401,481	$ 254,429
Provision for credit losses	96,943	10,122
Net interest income after provision for credit losses	304,538	244,307
Noninterest income	136,963	103,504
Noninterest expense	374,599	253,075
Income tax expense	13,086	21,287
Income after income tax expense	53,816	73,449
Income attributable to non-controlling interest	1,917	2,955
Preferred stock dividends	2,493	2,493
Net income available to common shareholders	49,406	68,001
Total assets	48,594,383	24,418,715	$ 46,651,553
Consumer Banking
Segment Reporting Information
Net interest income (expense)	193,832	140,702
Provision for credit losses	44,369	7,226
Net interest income after provision for credit losses	149,463	133,476
Noninterest income	81,414	60,503
Noninterest expense	228,859	156,521
Income tax expense	1,982	8,741
Income after income tax expense	36	28,717
Income attributable to non-controlling interest	0	0
Preferred stock dividends	0	0
Net income available to common shareholders	36	28,717
Total assets	14,463,055	8,036,742
Commercial Banking
Segment Reporting Information
Net interest income (expense)	185,986	96,685
Provision for credit losses	52,574	2,896
Net interest income after provision for credit losses	133,412	93,789
Noninterest income	55,773	42,499
Noninterest expense	114,455	83,413
Income tax expense	16,306	11,759
Income after income tax expense	58,424	41,116
Income attributable to non-controlling interest	1,917	2,955
Preferred stock dividends	0	0
Net income available to common shareholders	56,507	38,161
Total assets	24,859,839	12,735,702
Enterprise Services
Segment Reporting Information
Net interest income (expense)	21,663	17,042
Provision for credit losses	0	0
Net interest income after provision for credit losses	21,663	17,042
Noninterest income	(224)	502
Noninterest expense	31,285	13,141
Income tax expense	(5,202)	787
Income after income tax expense	(4,644)	3,616
Income attributable to non-controlling interest	0	0
Preferred stock dividends	2,493	2,493
Net income available to common shareholders	(7,137)	1,123
Total assets	$ 9,271,489	$ 3,646,271