Income Taxes - Tax Provision and Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income before income tax expense
Domestic	$ (29,538)	$ 116,693	$ 54,443
Foreign	4,494	3,924	2,167
(Loss) income from operations before income taxes	(25,044)	120,617	56,610
Current tax expense (benefit)
Federal	16,318	8,721	(5,158)
State	6,062	3,489	133
Foreign	(2,981)	(9,639)	3,713
Total current	19,399	2,571	(1,312)
Deferred tax (benefit) expense
Federal	(480,712)	4,701	51,817
State	(39,255)	3,279	5,419
Foreign	2,061	756
Total deferred	(517,906)	8,736	57,236
Total income tax (benefit) provision	$ (498,507)	$ 11,307	$ 55,924
Reconciliation of the statutory federal income tax rate to the actual effective income tax rate
Federal taxes (as a percent)	35.00%	35.00%	35.00%
State and local income taxes (as a percent)	6.30%	1.20%	6.10%
Nondeductible expenses (as a percent)	(16.00%)	0.30%	3.00%
Goodwill impairment (as a percent)	(20.50%)
Compensation (as a percent)	29.50%	(1.50%)	2.80%
Contingent liability settlement (as a percent)	22.90%	0.60%
Foreign (as a percent)	11.30%	(8.50%)	5.20%
Valuation allowance (as a percent)	2962.30%	(17.10%)	55.30%
Federal tax reform enactment - deferred rate change (as a percent)	(1043.50%)
Other miscellaneous items (as a percent)	3.30%	(0.60%)	(8.60%)
Actual effective income tax rate (as a percent)	1990.60%	9.40%	98.80%
Amount of pretax income
Federal taxes	$ (8,765)	$ 42,216	$ 19,814
State and local income taxes	(1,567)	1,498	3,435
Nondeductible expenses	4,018	371	1,717
Goodwill impairment	5,131
Compensation	(7,376)	(1,817)	1,559
Contingent liability settlement	(5,740)	756
Foreign	(2,840)	(10,268)	2,955
Valuation allowance	(741,872)	(20,675)	31,288
Federal tax reform enactment-deferred rate change	261,329
Other miscellaneous items	(825)	(774)	(4,844)
Total income tax (benefit) provision	(498,507)	11,307	55,924
Reconciliation of liability for unrecognized tax benefits
Balance at the beginning of the period	26,792	2,198
Additions based on current year positions	2,979
Additions based on prior year positions	2,836	3,749
Settlement payments	(216)	(4,000)
Unrecognized tax benefits			33,569
Cumulative advance deposits on account			(31,371)
Decreases due to settlements and/or reduction in reserve	(1,322)	(9,091)
Currency translation adjustments		2,565
Currency translation adjustments	(119)
Balance at the end of the period	$ 30,950	$ 26,792	$ 2,198