Description of Business and Summary of Significant Accounting Policies - Fair Value Reporting (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]
Total assets measured at fair value	[1]	$ 5,551	$ 31,873
Total liabilities measured at fair value	[1]	10,095	24,976
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation:
Beginning balance		24,976	37,096
(Gains) or losses included in earnings	[2]	(16,543)	(1,391)
Reductions recorded against goodwill		0	(13,718)
Foreign currency translation adjustments	[3]	(260)	(1,620)
Business acquisitions		1,922	8,440
Settlements		0	(3,831)
Ending balance		10,095	24,976
Fair value, measurement with unobservable inputs reconciliation, recurring basis, liability, gain (loss) included in earnings, unrealized still held at year end		$ (16,543)	(1,391)
Derivative
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation:
Fair value Input, discount rate		12.60%
Contingent Accrued Earn-out Acquisition Consideration
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]
Derivative liabilities	[1],[4]	$ 10,095	24,976
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation:
Beginning balance		25,000
Ending balance		10,100	25,000
Certificates of Deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	[1]	4,493	26,714
Mutual Funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	[1]	1,058	5,159
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]
Total assets measured at fair value	[1]	5,551	31,873
Total liabilities measured at fair value	[1]	0	0
Fair Value, Inputs, Level 1 | Certificates of Deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	[1]	4,493	26,714
Fair Value, Inputs, Level 1 | Mutual Funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	[1]	1,058	5,159
Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]
Total liabilities measured at fair value	[1]	0	0
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]
Total liabilities measured at fair value	[1]	10,095	24,976
Fair Value, Inputs, Level 3 | Contingent Accrued Earn-out Acquisition Consideration
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]
Derivative liabilities	[1],[4]	10,095	24,976
Mutual Funds | Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities		$ 0	$ 0

[1] During the year ended December 31, 2019 and 2018, respectively, there were no transfers between fair value levels 1, 2, or 3.

[2] Recorded as an adjustment to reported general and administrative expenses

[3] Recorded as a component of other comprehensive income within stockholders' equity

[4] The income valuation approach is applied and the valuation inputs include the contingent payment arrangement terms, projected cash flows, rate of return, and probability assessments.