Business Combination - Revenue and Expenses from SVB Leerink (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Business Acquisition [Line Items]
Net interest income	$ 512,886	$ 419,863
Noninterest income	280,376	155,518
Noninterest expense	365,664	265,417
Income before income tax expense	399,047	281,992
Income tax expense	107,435	73,966
Net income attributable to noncontrolling interests	(2,880)	(13,065)
Net income available to common stockholders	288,732	$ 194,961
SVB Leerink
Business Acquisition [Line Items]
Net interest income	442
Noninterest income	68,117
Noninterest expense	60,540
Income before income tax expense	8,019
Income tax expense	2,174
Net income attributable to noncontrolling interests	0
Net income available to common stockholders	$ 5,845