Fair Value Measurements - Liability Measured on Recurring Basis, Unobservable Input Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Recurring Basis, Unobservable Input Reconciliation, Liability, Gain (Loss), Statement of Income [Extensible List]	us-gaap:BusinessCombinationContingentConsiderationArrangementsContingentConsiderationBenefit	us-gaap:BusinessCombinationContingentConsiderationArrangementsContingentConsiderationBenefit
Contingent Consideration
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 82,236	$ 10,956
Contingent consideration liability recorded as the result of acquisitions (see Note 3)	10,517	72,209
Fair value adjustments recorded to income	(304)	(698)
Contingent payments made	(15,740)	(231)
Ending balance	$ 76,709	$ 82,236