Business Combination - Revenue and Expenses from SVB Leerink (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Business Acquisition [Line Items]
Net interest income	$ 529,403	$ 466,443	$ 1,042,289	$ 886,306
Noninterest income	333,750	192,689	614,126	348,207
Noninterest expense	383,522	305,739	749,186	571,156
Income before income tax expense	455,685	324,313	854,732	606,305
Income tax expense	119,114	77,287	226,549	151,253
Net income attributable to noncontrolling interests	(18,584)	(9,228)	(21,464)	(22,293)
Net income available to common stockholders	317,987	$ 237,798	606,719	$ 432,759
SVB Leerink
Business Acquisition [Line Items]
Net interest income	242		684
Noninterest income	67,035		135,152
Noninterest expense	61,935		122,475
Income before income tax expense	5,342		13,361
Income tax expense	1,449		3,623
Net income attributable to noncontrolling interests	35		35
Net income available to common stockholders	$ 3,858		$ 9,703