Parent Company Only Condensed Financial Information - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Adjustments to reconcile net income to net cash used for operating activities:
Gains on equity warrant assets, net	$ (138,078)	$ (89,142)	$ (54,555)
Gains on investment securities, net	(134,670)	(88,094)	(45,547)
Amortization of share-based compensation	66,815	45,675	36,900
Other, net	(74,240)	(54,039)	15,909
Net cash provided by operating activities	1,164,129	933,562	646,865
Cash flows from investing activities:
Net (increase) decrease in loans	(4,773,775)	(5,175,409)	(3,170,099)
Acquisition of SVB Leerink	102,328	0	0
Net cash used for investing activities	(9,371,882)	(4,800,375)	(5,970,496)
Cash flows from financing activities:
Principal payments of long-term debt	(358,395)	0	(97,781)
Proceeds from issuance of common stock, ESPP and ESOP	24,818	18,387	27,003
Net proceeds from the issuance of preferred stock	340,138	0	0
Common stock repurchase	(352,511)	(147,123)	0
Net cash provided by financing activities	11,417,997	4,515,277	5,700,956
Net increase in cash and cash equivalents	3,210,244	648,464	377,325
Cash and cash equivalents at beginning of period	3,571,539	2,923,075	2,545,750
Cash and cash equivalents at end of period	6,781,783	3,571,539	2,923,075
Parent Company
Condensed Cash Flow Statements, Captions [Line Items]
Net income available to common stockholders	1,136,856	973,840	490,506
Adjustments to reconcile net income to net cash used for operating activities:
Gains on equity warrant assets, net	(138,078)	(89,142)	(54,555)
Gains on investment securities, net	(45,345)	(13,546)	(17,060)
Distributions of earnings from investment securities	49,776	47,596	14,015
Net income of subsidiaries	(775,867)	(154,987)	(120,735)
Cash dividends from bank subsidiary	733,000	140,000	90,000
Amortization of share-based compensation	66,815	45,675	36,900
Decrease in other assets	27,205	51,169	12,959
Increase in other liabilities	21,391	21,619	11,774
Other, net	8,084	(31,024)	316
Net cash provided by operating activities	765,715	187,334	125,084
Cash flows from investing activities:
Net decrease (increase) in investment securities from purchases, sales and maturities	128,635	73,742	(152,015)
Net (increase) decrease in loans	(15,245)	0	13,337
Net cash used for investing activities	(171,888)	37,127	(143,231)
Cash flows from financing activities:
Principal payments of long-term debt	(358,395)	0	(51,546)
Proceeds from issuance of common stock, ESPP and ESOP	24,818	18,387	27,003
Net proceeds from the issuance of preferred stock	340,138	0	0
Common stock repurchase	352,511	147,123	0
Net cash provided by financing activities	(345,950)	(128,736)	(24,543)
Net increase in cash and cash equivalents	247,877	95,725	(42,690)
Cash and cash equivalents at beginning of period	553,049	457,324	500,014
Cash and cash equivalents at end of period	800,926	553,049	457,324
Bank Subsidiary | Parent Company
Adjustments to reconcile net income to net cash used for operating activities:
Net income of subsidiaries	(1,036,618)	(933,641)	(446,769)
Cash flows from investing activities:
Increase (decrease) in investment in subsidiaries	(42,952)	(31,292)	(38,927)
Nonbank Subsidiaries | Parent Company
Adjustments to reconcile net income to net cash used for operating activities:
Net income of subsidiaries	(57,371)	(25,212)	(13,002)
Cash flows from investing activities:
Increase (decrease) in investment in subsidiaries	23,275	(5,323)	34,374
Acquisition of SVB Leerink	$ 265,601	$ 0	$ 0