Parent Company Only Condensed Financial Information - Condensed Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Income Statements, Captions [Line Items]
Interest income	$ 588,735	$ 583,892	$ 585,767	$ 551,014	$ 542,897	$ 513,313	$ 481,301	$ 432,398	$ 2,309,408	$ 1,969,909	$ 1,465,140
Interest expense	(55,067)	(63,248)	(56,364)	(38,128)	(28,437)	(20,091)	(14,858)	(12,535)	(212,807)	(75,921)	(44,771)
Gains on equity warrant assets, net									138,078	89,142	54,555
Gains on investment securities, net									134,670	88,094	64,603
Income tax (expense) benefit	(94,061)	(105,075)	(119,114)	(107,435)	(105,000)	(95,308)	(77,287)	(73,966)	(425,685)	(351,561)	(355,463)
Net income available to common stockholders	$ 262,856	$ 267,281	$ 317,987	$ 288,732	$ 266,264	$ 274,817	$ 237,798	$ 194,961	1,136,856	973,840	490,506
Parent Company
Condensed Income Statements, Captions [Line Items]
Interest income									4,473	3,307	2,077
Interest expense									(31,666)	(32,037)	(34,932)
Dividend income from bank subsidiary									733,000	140,000	90,000
Gains on equity warrant assets, net									138,078	89,142	54,555
Gains on investment securities, net									45,345	13,546	37,132
Fund management fees and other noninterest income									21,567	26,388	24,613
General and administrative expenses									(94,712)	(70,976)	(63,077)
Income tax (expense) benefit									(40,218)	(14,383)	10,367
Loss before net income of subsidiaries									775,867	154,987	120,735
Net income available to common stockholders									1,136,856	973,840	490,506
Parent Company | Bank Subsidiary
Condensed Income Statements, Captions [Line Items]
Loss before net income of subsidiaries									1,036,618	933,641	446,769
Equity in undistributed net income of subsidiaries									303,618	793,641	356,769
Parent Company | Nonbank Subsidiaries
Condensed Income Statements, Captions [Line Items]
Loss before net income of subsidiaries									57,371	25,212	13,002
Equity in undistributed net income of subsidiaries									$ 57,371	$ 25,212	$ 13,002