Commitments and Contingencies (Narrative) (Details) $ / shares in Units, $ / Person in Thousands, $ in Thousands			3 Months Ended	4 Months Ended
	Apr. 05, 2019 USD ($)	Apr. 10, 2018 $ / shares shares	Mar. 31, 2019 USD ($) $ / Person	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($)
Commitments and Contingencies [Line Items]
Self-insured health insurance, liability			$ 232
Derivative Liability			12,466	$ 24,976	$ 37,096
Derivative Financial Instrument, Liabilities, Fair Value Disclosure, Noncurrent			10,175	11,209
Derivative Financial Instrument, Liabilities, Fair Value Disclosure, Current			$ 2,291	13,767
Maximum [Member]
Commitments and Contingencies [Line Items]
Self-insured health insurance limit, per person | $ / Person			120
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
Contingent Accrued Earn-out Acquisition Consideration [Member]
Commitments and Contingencies [Line Items]
Derivative Liability			12,466	24,976
Contingent liability for accrued earn-out acquisition consideration			10,200	11,200
Business Combination, Contingent Consideration, Liability, Current			$ 2,300	$ 13,800
Stock Appreciation Rights (SARs) [Member] | Chief Executive Officer [Member]
Commitments and Contingencies [Line Items]
Deferred Compensation Arrangement with Individual, Shares Issued | shares		5,953,975
Deferred Compensation Arrangement With Individual, Acquisition Event, Base Price Per Share | $ / shares		$ 7.95
Settled Litigation [Member] | Stock Appreciation Rights (SARs) [Member] | Chief Executive Officer [Member]
Commitments and Contingencies [Line Items]
Deferred Compensation Arrangement with Individual, Acquisition Event, Involuntary Termination, Shares Deemed Accrued And Eligible To Vest | shares				1,000,000
Deferred Compensation Arrangement with Individual, Acquisition Event, Involuntary Termination, Increase On Each Anniversary, Shares Deemed Accrued And Eligible To Vest | shares				750,000
Subsequent Event [Member] | Settled Litigation [Member]
Commitments and Contingencies [Line Items]
Loss Contingency, Damages Sought, Legal Expenses, Value	$ 20,000