Convertible Senior Notes (Liability Component) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Debt Disclosure [Abstract]
Principal	$ 275,000,000		$ 275,000,000
Less: Debt discount, net	(28,324,000)	[1]	(38,912,000)	[1]
Net carrying amount	246,676,000		236,088,000
Fair value of Notes	$ 262,000,000
Remaining contractual life	2 years 4 months 24 days

[1] Included in the consolidated balance sheets within convertible senior notes (due 2017) and amortized to interest expense over the remaining life of the Notes using the effective interest rate method