Business Combination - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Jan. 04, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Business Acquisition [Line Items]
Intangible assets		$ 60,900		$ 60,900
Goodwill		137,823		137,823		$ 0
Net income available to common stockholders		267,281	$ 274,817	874,000	$ 707,576
SVB Leerink
Business Acquisition [Line Items]
Total purchase price	$ 273,230
Retention pool for acquiree employees	$ 60,000
Vesting period of retention pool for acquiree employees	5 years
Post-combination expenses	$ 9,100
Intangible assets	60,900
Goodwill	$ 137,823
Net income available to common stockholders		$ (1,418)		$ 8,229