Fair Value Measurements - Fair Value of Contingent Consideration Liabilities (Details) - USD ($)	3 Months Ended				12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at December 31, 2018				$ 0	$ 0
Contingent consideration related to acquisition of Exonics					172,041,000
Increase in fair value of contingent consideration	$ 1,500,000	$ 2,959,000	$ 0	$ 0	4,459,000	$ 0	$ 0
Balance at December 31, 2019	176,500,000				176,500,000	0
Intangible asset	$ 400,000,000.0				$ 400,000,000.0	$ 0