Debt Including Capital Lease Obligations - 4.25% Convertible Senior Notes (Details)		2 Months Ended	3 Months Ended			9 Months Ended
	Jan. 31, 2014 USD ($)	Feb. 27, 2015 USD ($)	Sep. 30, 2015 USD ($) $ / shares	Sep. 30, 2014 USD ($)		Sep. 30, 2015 USD ($) $ / shares	Sep. 30, 2014 USD ($)		Feb. 15, 2015 USD ($)	Feb. 05, 2015 USD ($)	Jan. 07, 2015 USD ($)	Dec. 31, 2014 USD ($)		Feb. 28, 2013 USD ($)	Feb. 05, 2013
Interest Expense, Debt [Abstract]
Amortization of discount on the debt component						$ 3,805,000	$ 9,144,000
Loss on debt extinguishment, unamortized discount writeoff			$ 0	$ 0		$ (36,212,000)	$ (521,000)
4.25% Convertible Senior Notes
Debt Instrument [Line Items]
Stated interest rate on debt instrument			4.25%	4.25%		4.25%	4.25%					4.25%
Conversion rate of debt into equity						0.0445524000
Conversion price (in dollars per share) | $ / shares			$ 22.45			$ 22.45
Principal amount of debt component			$ 49,000,000	$ 200,000,000	[1]	$ 49,000,000	$ 200,000,000	[1]	$ 200,000,000			$ 200,000,000	[1]
Unamortized discount			(3,199,000)	(26,806,000)		(3,199,000)	(26,806,000)					(23,569,000)
Net carrying amount of debt component			45,872,000	173,194,000		45,872,000	173,194,000					$ 176,431,000
Interest Expense, Debt [Abstract]
4.25% coupon interest			521,000	2,125,000		2,366,000	6,375,000
Amortization of deferred financing fees			28,000	117,000		114,000	352,000
Amortization of discount on the debt component			870,000	3,141,000		3,805,000	9,144,000
Total interest expense related to the Convertible Notes			$ 1,419,000	$ 5,383,000		$ 6,285,000	$ 15,871,000
Redemption price percentage		0.00%
Repurchased convertible notes, principal											$ 151,000,000
Repurchased convertible notes, carrying value										$ 138,000,000
Loss on debt extinguishment, unamortized discount writeoff		$ 17,000,000
Senior Secured Notes, 7 Point 875 Percent, Due 2021 [Member] | Senior notes
Debt Instrument [Line Items]
Stated interest rate on debt instrument			7.875%	7.875%		7.875%	7.875%					7.875%		7.875%	7.875%
Principal amount of debt component														$ 425,000,000
Interest Expense, Debt [Abstract]
Redemption price percentage						103.00%
Debt Instrument, Redemption, Cash Proceeds from Equity Offerings [Member] | Senior Secured Notes, 7 Point 875 Percent, Due 2021 [Member] | Senior notes
Interest Expense, Debt [Abstract]
Redemption price percentage	0.00%					107.90%
Loss on debt extinguishment, unamortized discount writeoff	$ 1,000,000

[1] As of December 31, 2014 and September 30, 2014, the Convertible Notes' "if-converted" value did not exceed their principal amount because our common stock price was below the conversion price of the Convertible Notes.