Long-Term Debt - Convertible Senior Notes Dues 2032 (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended		9 Months Ended
	Jul. 31, 2016	Mar. 31, 2012	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Jun. 30, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Carrying amount			$ 698,195		$ 698,195
Unamortized debt discount			9,448		9,448
Gain on repurchase of long-term debt			244	$ 0	546	$ 0
Convertible Senior Notes Maturing March 2032 [Member]
Debt Instrument [Line Items]
Carrying amount		$ 200,000	185,116		185,116			$ 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		$ 35,400	9,448		9,448			$ 15,000
Repurchased principal amount	$ 7,600						$ 7,300
Repurchase amount	7,000						$ 6,500
Accrued Interest included in repurchase amount	$ 100
Gain on repurchase of long-term debt			200		500
Amortization of debt issuance costs and discounts			$ 500		$ 1,000