Income Taxes (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components of income (loss) from continuing operations before income taxes
Domestic		$ 146,383,000	$ 236,200,000	$ 140,738,000
Foreign		(45,689,000)	(19,574,000)	(1,411,000)
Income from continuing operations before income taxes		100,694,000	216,626,000	139,327,000
Current benefit (provision):
Federal		(8,652,000)	(19,385,000)	0
State		(1,237,000)	267,000	(8,926,000)
Foreign		(2,335,000)	(2,481,000)	(4,470,000)
Total current benefit (provision)		(12,224,000)	(21,599,000)	(13,396,000)
Deferred benefit (provision):
Federal		299,693,000	(58,250,000)	(42,659,000)
State		2,356,000	(6,232,000)	3,285,000
Foreign		(5,539,000)	5,827,000	1,535,000
Total deferred benefit (provision)		296,510,000	(58,655,000)	(37,839,000)
Total income tax benefit (provision), net		$ 284,286,000	$ (80,254,000)	$ (51,235,000)
Actual tax provision reconciliation to the amounts computed by applying statutory federal tax rate to income (loss) from continuing operations before taxes
Statutory rate		35.00%	35.00%	35.00%
State income taxes, net of Federal benefit		(12.20%)	5.00%	3.80%
Permanent differences		(0.30%)	1.40%	1.70%
Tax credits		(8.10%)	(4.20%)	(8.40%)
Valuation allowance		4.60%	(0.30%)	1.40%
Enactment of Tax Cuts and Job Act of 2017		(301.40%)	0.00%	0.00%
Other		0.10%	0.10%	3.30%
Total effective tax rate		(282.30%)	37.00%	36.80%
Deferred tax assets:
Net operating losses, credit and other carryforwards	$ 278,540,000	$ 278,540,000	$ 178,925,000
Unrealized losses on investments, net	22,260,000	22,260,000	47,737,000
Accrued expenses	23,583,000	23,583,000	39,596,000
Stock-based compensation	9,148,000	9,148,000	14,389,000
Other assets	11,890,000	11,890,000	15,008,000
Total deferred tax assets	345,421,000	345,421,000	295,655,000
Valuation allowance	(66,886,000)	(66,886,000)	(75,372,000)
Deferred tax assets after valuation allowance	278,535,000	278,535,000	220,283,000
Deferred tax liabilities:
Depreciation and amortization	(708,599,000)	(708,599,000)	(962,838,000)
Other liabilities	(1,509,000)	(1,509,000)	(1,319,000)
Total deferred tax liabilities	(710,108,000)	(710,108,000)	(964,157,000)
Total net deferred tax liabilities	(431,573,000)	(431,573,000)	(743,874,000)
Net operating loss carryforwards	798,500,000	798,500,000
Amount of Unrecognized Deferred Tax Liability, Undistributed Earnings of Foreign Subsidiaries	0	0
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	303,500,000	303,500,000
Change in allowance for foreign tax credit carryover as result of the Tax Cuts and Jobs Act		0
Tax on deemed mandatory repatriation of unrepatriated foreign earnings as result of Tax Cuts and Jobs Act		0
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance as of beginning of period		63,502,000	62,366,000	$ 44,839,000
Additions based on tax positions related to the current year		1,116,000	2,132,000	11,748,000
Additions based on tax positions related to prior years		258,000	3,000	5,779,000
Reductions based on tax positions related to prior years		(852,000)	(734,000)	0
Reductions based on tax settlements		0	(265,000)	0
Reductions based on expirations of statute of limitations		(728,000)	0	0
Balance as of end of period	63,296,000	63,296,000	63,502,000	$ 62,366,000
Unrecognized tax benefits if recognized, could affect our effective tax rate	63,300,000	63,300,000	$ 63,500,000
Foreign
Deferred tax liabilities:
Net operating loss carryforwards	168,400,000	168,400,000
Federal
Deferred tax liabilities:
Tax credit available to offset future tax liabilities	126,200,000	126,200,000
State
Deferred tax liabilities:
Tax credit available to offset future tax liabilities	$ 84,000,000.0	$ 84,000,000.0