Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (7,900,000)	$ (60,300,000)	$ (24,000,000.0)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	64,400,000	73,800,000	76,300,000
Signing bonus amortization	54,500,000	46,400,000	53,900,000
Deferred income tax expense (benefit)	9,100,000	(13,500,000)	9,500,000
Amortization of debt discount and debt issuance costs	11,700,000	7,300,000	3,100,000
Debt extinguishment costs	0	2,400,000	0
Non-cash compensation and pension expense	11,100,000	44,700,000	18,200,000
Signing bonus payments	(58,700,000)	(29,100,000)	(31,600,000)
Change in other assets	(10,900,000)	(20,600,000)	(3,900,000)
Change in lease liabilities	(15,300,000)	(15,800,000)	0
Change in accounts payable and other liabilities	29,300,000	8,300,000	(73,700,000)
Other non-cash items, net	100,000	3,900,000	1,500,000
Net cash provided by operating activities	97,300,000	63,000,000.0	29,300,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for capital expenditures	(40,800,000)	(54,500,000)	(57,800,000)
Net cash used in investing activities	(40,800,000)	(54,500,000)	(57,800,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Transaction costs for issuance and amendment of debt	0	(24,300,000)	0
Principal payments on debt	(6,500,000)	(31,600,000)	(9,800,000)
Proceeds from revolving credit facility	23,000,000.0	0	0
Payments on revolving credit facility	(23,000,000.0)	0	0
Net proceeds from issuing equity instruments	0	49,500,000	0
Payments to tax authorities for stock-based compensation	(700,000)	(800,000)	(6,200,000)
Net cash used in financing activities	(7,200,000)	(7,200,000)	(16,000,000.0)
NET CHANGE IN CASH AND CASH EQUIVALENTS	49,300,000	1,300,000	(44,500,000)
CASH AND CASH EQUIVALENTS—Beginning of year	146,800,000	145,500,000	190,000,000.0
CASH AND CASH EQUIVALENTS—End of year	196,100,000	146,800,000	145,500,000
Supplemental Cash Flow Information [Abstract]
Cash payments for interest	77,500,000	63,300,000	50,700,000
Cash payments for taxes, net of refunds	(1,800,000)	4,400,000	4,800,000
Proceeds from Lease Payment, Operating Activity	9,900,000	15,500,000	0
Depreciation and amortization	64,400,000	73,800,000	76,300,000
Net Cash Provided by (Used in) Operating Activities	$ 97,300,000	$ 63,000,000.0	$ 29,300,000