Fair Value of Financial Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis - Footnotes (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2019	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payment of contingent consideration for acquisitions		$ 250	$ 0
Monte Carlo Simulation Valuation Model
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Undiscounted maximum payment under the contingent consideration arrangements	$ 5,200
Accrued Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration		2,800		$ 3,400
Other Noncurrent Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration		$ 2,100		$ 2,100