Long-Term Debt (Details) - Class of Stock [Domain] $ / shares in Units, shares in Millions	3 Months Ended				6 Months Ended			12 Months Ended
	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2011 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2012 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Mar. 11, 2015 USD ($) $ / shares	Mar. 09, 2015 shares	Mar. 05, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($)	Apr. 04, 2011 USD ($) $ / shares	Mar. 30, 2011 shares	Mar. 29, 2011 USD ($) $ / shares shares
Debt Instrument [Line Items]
Interest Expense, Debt, Excluding Amortization	$ 2,491,000		$ 1,438,000		$ 4,323,000	$ 2,876,000
Accretion of Discount	4,985,000		2,255,000		8,184,000	4,434,000
Amortization of Financing Costs	675,000		326,000		1,117,000	652,000
Proceeds from Issuance of Warrants					42,881,000	0
Senior Notes	475,200,000				475,200,000								$ 216,206,000
Payments for (Proceeds from) Hedge, Financing Activities					(38,594,000)	0
Debt Instrument, Unamortized Discount	(63,314,000)				(63,314,000)								(12,165,000)
Deferred financing costs	(7,486,000)				(7,486,000)								(1,629,000)
Proceeds from (Payments for) Other Financing Activities					4,500,000	0
Debt Instrument, Interest Rate, Effective Percentage														7.00%
Payments of Debt Issuance Costs					(9,403,000)	0
Interest Expense	8,151,000		4,019,000		13,624,000	7,962,000
Long-term Debt, Fair Value	576,736,000				576,736,000								255,300,000
Note Warrant2 [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Warrants		$ 37,300,000		$ 27,600,000
Class of Warrant or Right [Domain]
Debt Instrument [Line Items]
Proceeds from Issuance of Warrants		5,600,000		$ 4,100,000
Convertible Note Hedge 2 [Member]
Debt Instrument [Line Items]
Proceeds from (Payments for) Other Financing Activities		7,700,000							$ 5,600,000
Convertible Note Hedge [Member]
Debt Instrument [Line Items]
Proceeds from (Payments for) Other Financing Activities		59,400,000							42,700,000
Convertible Note Hedge 1 [Member]
Debt Instrument [Line Items]
Proceeds from (Payments for) Other Financing Activities		51,700,000							37,100,000
Convertible Note/ Hedge Warrant, net [Member]
Debt Instrument [Line Items]
Proceeds from (Payments for) Other Financing Activities		16,500,000							$ 10,900,000
Convertible Notes 2016 [Member] | Convertible Notes 2016 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount													230,000,000
Convertible Note Overallotment [Member]
Debt Instrument [Line Items]
Senior Notes												$ 41,000,000				$ 30,000,000
Convertible Debt [Member]
Debt Instrument [Line Items]
Senior Notes	546,000,000				546,000,000								230,000,000
Payments of Debt Issuance Costs		(9,300,000)					$ (8,000,000)
Convertible Debt [Member] | Convertible Notes 2016 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	230,000,000				230,000,000								230,000,000
Interest Expense, Debt, Excluding Amortization	1,438,000		1,438,000		2,875,000	2,876,000
Accretion of Discount	2,416,000		2,255,000		4,750,000	4,434,000
Amortization of Financing Costs	326,000		326,000		652,000	652,000
Senior Notes	221,607,000				221,607,000								216,206,000
Debt Instrument, Unamortized Discount	(7,415,000)				(7,415,000)								(12,165,000)
Deferred financing costs	(978,000)				(978,000)								(1,629,000)
Debt Conversion, Converted Instrument, Amount								$ 1,000
Debt Instrument, Convertible, Conversion Price | $ / shares														$ 55.12
Debt Instrument, Interest Rate, Stated Percentage														2.50%
Debt Instrument, Convertible, Conversion Ratio								18.1426
Interest Expense	4,180,000		4,019,000		8,277,000	7,962,000
Convertible Debt [Member] | Convertible Notes 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	316,000,000				316,000,000								0
Interest Expense, Debt, Excluding Amortization	1,053,000		0		1,448,000	0
Accretion of Discount	2,569,000		0		3,434,000	0
Amortization of Financing Costs	349,000		0		465,000	0
Senior Notes	253,593,000				253,593,000								0
Debt Instrument, Unamortized Discount	(55,899,000)				(55,899,000)								0
Deferred financing costs	(6,508,000)				(6,508,000)								$ 0
Debt Conversion, Converted Instrument, Amount		$ 1,000
Debt Instrument, Convertible, Conversion Price | $ / shares										$ 72.37
Debt Instrument, Interest Rate, Stated Percentage										1.50%
Debt Instrument, Convertible, Conversion Ratio		13.8172
Interest Expense	$ 3,971,000		$ 0		5,347,000	$ 0
Convertible Notes 2020 [Member] | Convertible Notes 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 316,000,000
Convertible Debt 1 [Member]
Debt Instrument [Line Items]
Senior Notes												$ 275,000,000				$ 200,000,000
Balance Sheet by Location [Domain] | Convertible Debt [Member]
Debt Instrument [Line Items]
Senior Notes										$ 256,700,000				$ 187,000,000
Other Long-term Liabilities [Member] | Convertible Debt [Member]
Debt Instrument [Line Items]
Payments of Debt Issuance Costs		$ (7,000,000)					(6,500,000)
Equity [Member] | Convertible Debt [Member]
Debt Instrument [Line Items]
Senior Notes										$ 59,300,000				43,000,000
Senior Convertible Notes [Equity net of tax]														$ 28,000,000
Class of Warrant or Right, Outstanding | shares											0.6	3.8			0.5	3.5
Warrant Option Strike Price | $ / shares												$ 88.46				$ 63.44
Payments of Debt Issuance Costs					$ 2,430,000		$ (1,500,000)