Unaudited Quarterly Financial Data - Supplemental Consolidated Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 607,558	$ 543,127	$ 523,523	$ 567,402	$ 588,735	$ 583,892	$ 585,767	$ 551,014	$ 2,241,610	$ 2,309,408	$ 1,969,909
Interest expense	16,078	15,387	10,596	43,265	55,067	63,248	56,364	38,128	85,326	212,807	75,921
Net interest income	591,480	527,740	512,927	524,137	533,668	520,644	529,403	512,886	2,156,284	2,096,601	1,893,988
Provision for (reduction) credit losses	(38,433)	(52,018)	66,481	243,480	17,383	36,536	23,946	28,551	219,510	106,416	87,870
Noninterest income	621,783	547,583	368,848	301,934	313,344	294,009	333,750	280,376	1,840,148	1,221,479	744,984
Noninterest expense	664,799	491,021	479,636	399,585	460,752	391,324	383,522	365,664	2,035,041	1,601,262	1,188,193
Income before income tax expense	586,897	636,320	335,658	183,006	368,877	386,793	455,685	399,047
Income tax expense	148,096	162,265	87,869	49,357	94,061	105,075	119,114	107,435	447,587	425,685	351,561
Net income before noncontrolling interests	438,801	474,055	247,789	133,649	274,816	281,718	336,571	291,612	1,294,294	1,184,717	1,011,348
Net income attributable to noncontrolling interests	(45,891)	(27,748)	(14,260)	1,973	(11,960)	(14,437)	(18,584)	(2,880)	(85,926)	(47,861)	(37,508)
Preferred stock dividends	(4,594)	(4,594)	(4,594)	(3,369)					(17,151)	0	0
Net income available to common stockholders	$ 388,316	$ 441,713	$ 228,935	$ 132,253	$ 262,856	$ 267,281	$ 317,987	$ 288,732	$ 1,191,217	$ 1,136,856	$ 973,840
Earnings per common share—basic (usd per share)	$ 7.49	$ 8.53	$ 4.44	$ 2.56	$ 5.10	$ 5.19	$ 6.12	$ 5.49	$ 23.05	$ 21.90	$ 18.35
Earnings per common share—diluted (usd per share)	$ 7.40	$ 8.47	$ 4.42	$ 2.55	$ 5.06	$ 5.15	$ 6.08	$ 5.44	$ 22.87	$ 21.73	$ 18.11