Long-Term Debt - By Issue (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Mar. 31, 2013
Long Term Debt
Total debt	$ 2,628,134		$ 3,024,166
Less debt issuance costs	33,478		42,317
Total amounts outstanding	2,594,656		2,981,849
Less current maturities	16,680		46,460
Long-term debt	2,577,976		2,935,389
Accounting pronouncements reclassifications
Other assets	16,936		35,852
Long-term debt	2,577,976		2,935,389
Accounting Standards Update ("ASU") 2015-03 - Simplifying the Presentation of Debt Issuance Costs | Early adoption reclassification amounts
Long Term Debt
Long-term debt			(42,300)
Accounting pronouncements reclassifications
Other assets			(42,300)
Long-term debt			(42,300)
Senior term loan
Long Term Debt
Total debt	237,500		250,000
6 1/8% senior notes, due 2019
Long Term Debt
Total debt	400,000		$ 400,000
Total amounts outstanding	$ 400,000
Stated interest rate (as a percent)	6.125%		6.125%
7 5/8% senior notes, due 2020
Long Term Debt
Total debt			$ 350,000
Stated interest rate (as a percent)	7.625%	7.625%	7.625%
5.125% senior notes due 2021
Long Term Debt
Total debt	$ 700,000		$ 700,000
Total amounts outstanding	$ 700,000
Stated interest rate (as a percent)	5.125%		5.125%	5.125%
6 3/8% Senior Notes, due 2022
Long Term Debt
Total debt	$ 350,000		$ 350,000
Total amounts outstanding	$ 350,000
Stated interest rate (as a percent)	6.375%		6.375%
5 1/4% Senior Notes due 2023
Long Term Debt
Total debt	$ 400,000		$ 400,000
Total amounts outstanding	$ 400,000
Stated interest rate (as a percent)	5.25%		5.25%		5.25%
5.500% senior notes due 2024
Long Term Debt
Total debt	$ 500,000		$ 500,000
Total amounts outstanding	$ 500,000
Stated interest rate (as a percent)	5.50%		5.50%	5.50%
Other obligations
Long Term Debt
Total debt	$ 40,634		$ 74,166