Commitments and Contingencies (Narrative) (Details) $ / shares in Units, $ in Thousands			4 Months Ended	12 Months Ended
	Feb. 25, 2019 USD ($)	Apr. 10, 2018 $ / shares shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2018 USD ($) $ / Person	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Commitments and Contingencies [Line Items]
Rent expense, operating leases				$ 22,300	$ 6,600	$ 6,400
Operating Leases, Rent Expense, Sublease Rentals				1,100	1,100	1,000
Self-insured health insurance, liability			$ 232	232	332
Derivative Liability			24,976	24,976	37,096	$ 8,510
Contingent liability for accrued earn-out acquisition consideration			11,209	11,209	33,096
Contingent liability for accrued earn-out acquisition consideration			13,767	$ 13,767	4,000
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			3,300	$ 3,300
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			$ 24,980	$ 24,980	$ 37,100
SARs | Chief Executive Officer
Commitments and Contingencies [Line Items]
Shares received | shares		5,953,975
Base price per share (in dollars per share) | $ / shares		$ 7.95
Settled Litigation | SARs | Chief Executive Officer
Commitments and Contingencies [Line Items]
Shares deemed accrued and eligible to vest on closing date of Acquisition Event (in shares) | shares			1,000,000
Increase in SARs accrued and eligible to vest each anniversary | shares			750,000
Subsequent Event | Settled Litigation
Commitments and Contingencies [Line Items]
Loss contingency, legal expenses sought to be paid	$ 25,000
Loss contingency, damages sought	$ 952