Commitments and Contingencies (Narrative) (Details) $ in Thousands		12 Months Ended
	Feb. 25, 2019 USD ($)	Dec. 31, 2019 USD ($) $ / Person	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Commitments and Contingencies [Line Items]
Rent expense, operating leases		$ 37,800	$ 22,300
Self-insured health insurance, liability		362	232
Derivative liability		10,095	24,976	$ 37,096
Contingent liability for accrued earn-out acquisition consideration		1,474	11,209
Contingent liability for accrued earn-out acquisition consideration		8,621	13,767
Health insurance expenses, claims of self Insured plan		$ 2,600	2,100
Maximum
Commitments and Contingencies [Line Items]
Self-insured health insurance limit, per person | $ / Person		120,000
Self-insured health Insurance, aggregate liability based on participants and claims (percentage)		125.00%
Self-insured health insurance, estimated cumulative liability for annual contract		$ 2,900
Computer equipment | Minimum
Commitments and Contingencies [Line Items]
Term of lease		3 years
Computer equipment | Maximum
Commitments and Contingencies [Line Items]
Term of lease		5 years
Contingent Accrued Earn-out Acquisition Consideration
Commitments and Contingencies [Line Items]
Derivative liability		$ 10,100	25,000
Settled Litigation
Commitments and Contingencies [Line Items]
Loss contingency, legal expenses sought to be paid	$ 19,650
Pending Litigation
Commitments and Contingencies [Line Items]
Loss contingency, legal expenses sought to be paid		500
INDIA
Commitments and Contingencies [Line Items]
Self-insured health insurance, liability		$ 3,200	$ 1,600
INDIA | Maximum
Commitments and Contingencies [Line Items]
Self-insured health insurance limit, per person | $ / Person		28,000