Income Taxes (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Components of income (loss) from continuing operations before income taxes
Domestic		$ 151,002,000	$ 146,383,000	$ 236,200,000
Foreign		(158,962,000)	(45,689,000)	(19,574,000)
Income (loss) from continuing operations before income taxes		(7,960,000)	100,694,000	216,626,000
Current benefit (provision):
Federal		(1,472,000)	(8,652,000)	(19,385,000)
State		(184,000)	(1,237,000)	267,000
Foreign		(2,690,000)	(2,335,000)	(2,481,000)
Total current benefit (provision)		(4,346,000)	(12,224,000)	(21,599,000)
Deferred benefit (provision):
Federal		(19,189,000)	299,693,000	(58,250,000)
State		(7,365,000)	2,356,000	(6,232,000)
Foreign		227,000	(5,539,000)	5,827,000
Total deferred benefit (provision)		(26,327,000)	296,510,000	(58,655,000)
Total income tax benefit (provision), net		$ (30,673,000)	$ 284,286,000	$ (80,254,000)
Actual tax provision reconciliation to the amounts computed by applying statutory federal tax rate to income (loss) from continuing operations before taxes
Statutory rate		21.00%	35.00%	35.00%
State income taxes, net of Federal benefit		(94.40%)	(12.20%)	5.00%
Permanent differences		(16.90%)	(0.30%)	1.40%
Tax credits		68.60%	(8.10%)	(4.20%)
Valuation allowance		(491.90%)	4.60%	(0.30%)
Enactment of Tax Cuts and Job Act of 2017		0.00%	(301.40%)	0.00%
Rates different than statutory		116.60%	0.00%	0.00%
Other		11.60%	0.10%	0.10%
Total effective tax rate		(385.40%)	(282.30%)	37.00%
Deferred tax assets:
Net operating losses, credit and other carryforwards	$ 278,540,000	$ 284,300,000	$ 278,540,000
Unrealized losses on investments, net	22,260,000	41,852,000	22,260,000
Accrued expenses	23,583,000	22,148,000	23,583,000
Stock-based compensation	9,148,000	10,210,000	9,148,000
Other assets	11,890,000	22,366,000	11,890,000
Total deferred tax assets	345,421,000	380,876,000	345,421,000
Valuation allowance	(66,886,000)	(109,762,000)	(66,886,000)
Deferred tax assets after valuation allowance	278,535,000	271,114,000	278,535,000
Deferred tax liabilities:
Depreciation and amortization	(708,599,000)	(731,447,000)	(708,599,000)
Other liabilities	(1,509,000)	(1,290,000)	(1,509,000)
Total deferred tax liabilities	(710,108,000)	(732,737,000)	(710,108,000)
Total net deferred tax liabilities	(431,573,000)	(461,623,000)	(431,573,000)
Net operating loss carryforwards		797,000,000
Amount of unrecognized deferred tax liability, undistributed earnings of foreign subsidiaries		0
Benefit as result of change in enacted tax rate	(304,000,000)	1,000,000	304,000,000
Change in allowance for foreign tax credit carryover as result of the Tax Cuts and Jobs Act		0
Income tax provision on deemed mandatory repatriation of foreign earnings		0
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance as of beginning of period		63,296,000	63,502,000	$ 62,366,000
Additions based on tax positions related to the current year		4,361,000	1,116,000	2,132,000
Additions based on tax positions related to prior years		2,539,000	258,000	3,000
Reductions based on tax positions related to prior years		(656,000)	(852,000)	(734,000)
Reductions based on tax settlements		0	0	(265,000)
Reductions based on expirations of statute of limitations		0	(728,000)	0
Balance as of end of period	63,296,000	69,540,000	63,296,000	$ 63,502,000
Unrecognized tax benefits if recognized, could affect our effective tax rate	$ 63,000,000	70,000,000	$ 63,000,000
Foreign
Deferred tax liabilities:
Net operating loss carryforwards		237,000,000
Federal
Deferred tax liabilities:
Tax credit available to offset future tax liabilities		133,000,000
State
Deferred tax liabilities:
Tax credit available to offset future tax liabilities		$ 98,000,000