Long-Term Debt - Convertible Senior Notes Dues 2032 (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2016	Mar. 31, 2012	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Debt Instrument [Line Items]
Carrying amount	$ 733,256		$ 733,256		$ 733,256
Unamortized debt discount	11,400		11,400		11,400
Gain on repurchase of long-term debt			302	$ 0	302	$ 0
Convertible Senior Notes Maturing March 2032 [Member]
Debt Instrument [Line Items]
Carrying amount	192,750	$ 200,000	192,750		192,750		$ 200,000
Interest rate (as a percent)		3.25%
Frequency of periodic payment		semi-annually
Maturity date		Mar. 15, 2032
Initial conversion ratio		0.0399752
Initial conversion price per share		$ 25.02
Redemption price as a percentage of principal amount		100.00%
Repurchase price as a percentage of principal amount		100.00%
Expected life used to estimate fair value		6 years
Effective interest rate (as a percent)		6.90%
Carrying amount of equity component		$ 22,500
Unamortized debt discount	11,400	$ 35,400	11,400		11,400		$ 15,000
Repurchased principal amount	7,300		7,300		7,300
Repurchase amount	6,500		6,500		6,500
Gain on repurchase of long-term debt	300
Repurchase discount	800		$ 800		$ 800
Amortization of debt issuance costs and discounts	$ 500