Reportable Segments - Summary of Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Segment Reporting Information
Net interest income	$ 378,359	$ 254,057	$ 779,840	$ 508,486
Provision for credit losses	78,726	13,569	175,669	23,691
Net interest income after provision for credit losses	299,633	240,488	604,171	484,795
Noninterest income	133,054	109,718	270,017	213,222
Noninterest expense	400,241	236,849	774,840	489,924
Income tax expense (benefit)	6,213	19,314	19,299	40,601
Income after income tax expense	26,233	94,043	80,049	167,492
Income attributable to non-controlling interest	2,469	3,616	4,386	6,571
Preferred stock dividends	2,494	2,494	4,987	4,987
Net income available to common shareholders	21,270	87,933	70,676	155,934
Total assets	50,062,460	24,626,830	50,062,460	24,626,830	$ 46,651,553
Interest income	438,370	310,781	933,762	617,675
Noninterest income	133,054	109,718	270,017	213,222
Total	571,424	420,499	1,203,779	830,897
Consumer Banking
Segment Reporting Information
Net interest income	206,285	138,094	400,117	278,796
Provision for credit losses	(10,924)	4,691	33,445	11,917
Net interest income after provision for credit losses	217,209	133,403	366,672	266,879
Noninterest income	85,276	66,163	166,690	126,666
Noninterest expense	207,319	152,757	436,178	309,278
Income tax expense (benefit)	15,752	10,971	17,734	19,712
Income after income tax expense	79,414	35,838	79,450	64,555
Income attributable to non-controlling interest	0	0	0	0
Preferred stock dividends	0	0	0	0
Net income available to common shareholders	79,414	35,838	79,450	64,555
Total assets	14,694,025	7,713,169	14,694,025	7,713,169
Interest income	143,666	105,487	290,335	216,172
Noninterest income	85,276	66,163	166,690	126,666
Total	228,942	171,650	457,025	342,838
Commercial Banking
Segment Reporting Information
Net interest income	169,473	96,726	355,459	193,411
Provision for credit losses	89,650	8,878	142,224	11,774
Net interest income after provision for credit losses	79,823	87,848	213,235	181,637
Noninterest income	43,831	42,455	99,604	84,954
Noninterest expense	105,324	80,892	219,779	164,305
Income tax expense (benefit)	3,440	10,340	19,746	22,099
Income after income tax expense	14,890	39,071	73,314	80,187
Income attributable to non-controlling interest	2,469	3,616	4,386	6,571
Preferred stock dividends	0	0	0	0
Net income available to common shareholders	12,421	35,455	68,928	73,616
Total assets	24,318,452	12,865,821	24,318,452	12,865,821
Interest income	252,825	179,350	551,685	353,741
Noninterest income	43,831	42,455	99,604	84,954
Total	296,656	221,805	651,289	438,695
Enterprise Services
Segment Reporting Information
Net interest income	2,601	19,237	24,264	36,279
Provision for credit losses	0	0	0	0
Net interest income after provision for credit losses	2,601	19,237	24,264	36,279
Noninterest income	3,947	1,100	3,723	1,602
Noninterest expense	87,598	3,200	118,883	16,341
Income tax expense (benefit)	(12,979)	(1,997)	(18,181)	(1,210)
Income after income tax expense	(68,071)	19,134	(72,715)	22,750
Income attributable to non-controlling interest	0	0	0	0
Preferred stock dividends	2,494	2,494	4,987	4,987
Net income available to common shareholders	(70,565)	16,640	(77,702)	17,763
Total assets	11,049,983	4,047,840	11,049,983	4,047,840
Interest income	41,879	25,944	91,742	47,762
Noninterest income	3,947	1,100	3,723	1,602
Total	$ 45,826	$ 27,044	$ 95,465	$ 49,364