Long-Term Debt (Convertible Senior Notes Dues 2032) (Details)	1 Months Ended
	Mar. 31, 2012 USD ($) $ / shares	Sep. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)
Debt Instrument [Line Items]
Long-term debt, carrying value		$ 792,719,000
Unamortized debt discount		16,511,000	$ 20,900,000
Convertible Senior Notes 2032 [Member]
Debt Instrument [Line Items]
Long-term debt, carrying value	$ 200,000,000	200,000,000
Debt instrument interest rate	3.25%
Debt instrument, frequency of periodic payment	semi-annually
Debt instrument, maturity date	Mar. 15, 2032
Initial conversion ratio	0.0399752
Per share conversion price | $ / shares	$ 25.02
Debt instrument, redemption price, percentage of principal amount redeemed	100.00%
Unamortized debt discount	$ 35,400,000	$ 16,511,000
Expected life used to estimate fair value	6 years
Effective interest rate	6.90%
Carrying amount of equity component	$ 22,500,000