Business Combination - Revenue and Expenses from SVB Leerink (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Business Acquisition [Line Items]
Net interest income	$ 520,644	$ 493,222	$ 1,562,933	$ 1,379,528
Noninterest income	294,009	210,070	908,135	558,277
Noninterest expense	391,324	309,445	1,140,510	880,601
Income before income tax expense	386,793	376,673	1,241,525	982,978
Income tax expense	105,075	95,308	331,624	246,561
Net income attributable to noncontrolling interests	(14,437)	(6,548)	(35,901)	(28,841)
Net income available to common stockholders	267,281	$ 274,817	874,000	$ 707,576
SVB Leerink
Business Acquisition [Line Items]
Net interest income	277		961
Noninterest income	53,773		188,925
Noninterest expense	55,200		177,675
Income before income tax expense	(1,150)		12,211
Income tax expense	(558)		3,121
Net income attributable to noncontrolling interests	826		861
Net income available to common stockholders	$ (1,418)		$ 8,229