Debt - Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Debt
Total long-term debt	$ 1,003,140	$ 495,346
Less: current maturities	17,500	34,000
Long-term debt, net of current maturities	985,640	461,346
2023 Senior Notes
Debt
Total long-term debt	490,335
2015 Term Loan Facility
Debt
Total long-term debt	338,415
2.5 Percent Convertible Notes
Debt
Total long-term debt	$ 174,390	167,441
2014 Term Loan Facility
Debt
Total long-term debt		$ 327,905