Debt - Summary (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Debt
Total long-term debt	$ 1,005,161	$ 495,346
Less: current maturities	17,500	34,000
Long-term debt, net of current maturities	987,661	461,346
2023 Senior Notes
Debt
Total long-term debt	490,108
2015 Term Loan Facility
Debt
Total long-term debt	342,459
Convertible Notes 2.5 Percent
Debt
Total long-term debt	$ 172,594	167,441
2014 Term Loan Facility
Debt
Total long-term debt		$ 327,905