Business Combination - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended
	Jan. 04, 2019	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Business Acquisition [Line Items]
Intangible assets		$ 60,900
Goodwill		135,190		$ 0
Net income available to common stockholders		288,732	$ 194,961
SVB Leerink
Business Acquisition [Line Items]
Total purchase price	$ 270,939
Previously agreed upon purchase price	280,000
Post-combination expenses	9,100
Retention pool for acquiree employees	$ 60,000
Vesting period of retention pool for acquiree employees	5 years
Intangible assets	$ 60,900
Goodwill	$ 135,190
Net income available to common stockholders		$ 5,845