Derivatives Fair Value of Convertible Debt Hedges (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Convertible 2022 note hedge asset	$ 41,619,000		$ 41,619,000		$ 25,471,000
Convertible 2021 note hedge asset	41,660,000		41,660,000		0
Fair Values Convertible Debt Hedges, Net	(12,016,000)		(12,016,000)
Fair Values Convertible Debt Hedges, Gain (Loss)	(2,550,000)	$ 1,192,000	(2,700,000)	$ 2,282,000
Fair Value, Inputs, Level 2 | Convertible Debt Conversion Feature [Member] | Fair Value, Measurements, Recurring
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Convertible Debt 2021 Conversion Feature, Fair Value	47,557,000		47,557,000		30,708,000
Fair Value, Inputs, Level 2 | Convertible Debt 2022 Conversion Feature [Domain] | Fair Value, Measurements, Recurring
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Convertible Debt Conversion Feature	(47,738,000)		(47,738,000)
Fair Value, Inputs, Level 2 | Convertible Debt Bond Hedge [Member] | Fair Value, Measurements, Recurring
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Convertible 2022 note hedge asset	41,619,000		41,619,000		25,471,000
Convertible 2021 note hedge asset	41,660,000		41,660,000
Convertible Subordinated Debt | Convertible Senior Notes at 4.50% February 2022 [Domain]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Convertible Debt Conversion Feature	(47,738,000)		(47,738,000)		0
Convertible Debt Conversion Feature Gain (Loss)	(14,487,000)	0	(18,879,000)	0
Convertible Debt Note Hedge Gain (Loss)	13,078,000	0	16,880,000	0
Convertible Subordinated Debt | Convertible Senior Notes at 5.00% February 2021 [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Convertible Debt 2021 Conversion Feature, Fair Value	47,557,000		47,557,000		$ 30,708,000
Convertible Debt Conversion Feature Gain (Loss)	(15,330,000)	7,732,000	(16,849,000)	13,579,000
Convertible Debt Note Hedge Gain (Loss)	$ 14,189,000	$ (6,540,000)	$ 16,148,000	$ (11,297,000)