Convertible Notes Convertible Notes (Interest Expense for the February 2018 Notes) (Details) $ in Thousands, shares in Millions		12 Months Ended
	Feb. 11, 2014 USD ($)	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Nov. 23, 2016 USD ($)	Nov. 22, 2016 USD ($)	Nov. 21, 2015 USD ($)	Nov. 20, 2015 USD ($)	Sep. 30, 2014	Feb. 12, 2014 USD ($)
Debt Instrument [Line Items]
Purchased call options cost		$ (14,400)	$ 0	$ (30,951)
February 2018 Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount		4,852	17,585		$ 4,600	$ 4,300	$ 14,100	$ 3,100		$ 29,700
Deferred issuance costs					$ 1,400	$ 1,300	$ 4,100	$ 900
Interest Expense, Debt, Excluding Amortization		9,338	11,786
Amortization of debt issuance costs		2,863	2,980
Amortization of Debt Discount (Premium)		9,870	10,160
Total		$ (22,071)	$ (24,926)
February 2018 Note Purchase Call Option [Member]
Debt Instrument [Line Items]
Number of hedge counterparties (in Counterparties)									2
Purchased call options cost	$ 31,000
Number of shares of common stock covered by the purchased call options purchased (in Shares) | shares		13.8