Long-Term Debt (Details)		3 Months Ended
	Jul. 16, 2013 USD ($) $ / shares	Mar. 31, 2017 USD ($) TradingDay	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Jul. 31, 2013 $ / shares
Debt Instrument [Line Items]
Interest expense related to amortization of debt discount		$ 1,931,000	$ 1,826,000
1.50% Cash Convertible Senior Notes Due 2018 [Member]
Debt Instrument [Line Items]
Aggregate principal of convertible notes	$ 150,000,000
Interest rate for notes	1.50%
Consecutive trading days		30 days
Trading price condition (in dollars per share) | $ / shares	$ 25.30
Initial cash conversion rate	51.3769
Initial conversion price (in dollars per share) | $ / shares	$ 19.4640
Deferred loan costs	$ 3,900,000
Par amount of convertible note	1,000
Fair value of cash conversion derivative	$ 36,800,000
Interest expense related to amortization of debt discount		$ 1,900,000
Effective interest rate		5.70%
Debt instrument, unamortized discount		$ 10,200,000		$ 12,100,000
Warrants strike price (in dollars per share) | $ / shares					$ 25.95
Conversion price premium percentage					60.00%
1.50% Cash Convertible Senior Notes Due 2018 [Member] | Minimum [Member]
Debt Instrument [Line Items]
Number of trading days | TradingDay		20