Long-Term Debt (Details) $ in Thousands		1 Months Ended	3 Months Ended				12 Months Ended
	Jun. 19, 2012 USD ($)	Dec. 31, 2015 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jul. 09, 2014 USD ($)	Jun. 30, 2014 USD ($)	Oct. 16, 2013 USD ($)
Long-Term Debt
Face amount			$ 2,936,244				$ 2,936,244	$ 2,749,771
Face amount, current portion			7,907				7,907	4,472
Face amount, long-term			2,928,337				2,928,337	2,745,299
Unamortized debt issuance costs			(15,500)				(15,500)	(17,835)
Total debt			2,920,744				2,920,744	2,731,936
Book value, current		$ 7,600	7,907	$ 7,600	$ 4,040	$ 3,933	7,907	4,472		$ 4,455	$ 5,062		$ 6,168
LONG-TERM DEBT, net of debt issuance costs and current maturities		$ 3,306,064	2,912,837	3,306,064	3,077,604	2,951,133	2,912,837	2,727,464		$ 2,753,322	$ 2,437,351		$ 1,441,875
Amortization of debt issuance costs							4,645	3,037	$ 927
Expected Future Amortization of Debt Issuance Costs [Abstract]
2017							3,410
2018							3,300
2019							3,296
2020							2,283
2021							1,865
Thereafter							1,346
Total							15,500
Repurchases of senior notes							43,421	0	0
Gain on early extinguishment of debt			28,532	$ 0	$ 0	$ 0	28,532	0	$ 0
Percentage of aggregate principal amount held by trustee or holders to declare notes due and payable (at least)	51.00%
Credit Facility | TLP
Long-Term Debt
Face amount			0				0	250,000
Unamortized debt issuance costs			0				0	0
Total debt			0				0	250,000
Revolving Credit Facility
Expected Future Amortization of Debt Issuance Costs [Abstract]
Maximum borrowing capacity			2,484,000				2,484,000
Additional borrowing capacity			150,000				$ 150,000
Leverage ratio							3.9
Interest coverage ratio							5.3
Revolving Credit Facility | Minimum
Expected Future Amortization of Debt Issuance Costs [Abstract]
Commitment fees charged on unused credit							0.38%
Covenant interest coverage ratio							2.75
Revolving Credit Facility | Maximum
Expected Future Amortization of Debt Issuance Costs [Abstract]
Commitment fees charged on unused credit							0.50%
Covenant leverage ratio		4.75
Revolving Credit Facility | Alternate base rate
Expected Future Amortization of Debt Issuance Costs [Abstract]
Variable interest rate base							base rate
Revolving Credit Facility | Alternate base rate | Minimum
Expected Future Amortization of Debt Issuance Costs [Abstract]
Interest rate margin added to variable rate base							0.50%
Revolving Credit Facility | Alternate base rate | Maximum
Expected Future Amortization of Debt Issuance Costs [Abstract]
Interest rate margin added to variable rate base							1.50%
Revolving Credit Facility | LIBOR option
Expected Future Amortization of Debt Issuance Costs [Abstract]
Variable interest rate base							LIBOR
Interest rate margin added to variable rate base							0.94%
Reference rate							2.00%
Revolving Credit Facility | LIBOR option | Minimum
Expected Future Amortization of Debt Issuance Costs [Abstract]
Interest rate margin added to variable rate base							1.50%
Revolving Credit Facility | LIBOR option | Maximum
Expected Future Amortization of Debt Issuance Costs [Abstract]
Interest rate margin added to variable rate base							2.50%
Revolving Credit Facility | Expansion Capital Facility
Long-Term Debt
Face amount			1,229,500				$ 1,229,500	702,500
Unamortized debt issuance costs			0				0	0
Total debt			1,229,500				1,229,500	702,500
Expected Future Amortization of Debt Issuance Costs [Abstract]
Maximum borrowing capacity			1,446,000				1,446,000
Revolving Credit Facility | Working Capital Facility
Long-Term Debt
Face amount			618,500				618,500	688,000
Unamortized debt issuance costs			0				0	0
Total debt			618,500				618,500	688,000
Expected Future Amortization of Debt Issuance Costs [Abstract]
Maximum borrowing capacity			1,038,000				$ 1,038,000
Revolving Credit Facility | Letters of credit
Expected Future Amortization of Debt Issuance Costs [Abstract]
Reference rate							2.25%
5.125% Senior Notes due 2019
Long-Term Debt
Face amount			388,467				$ 388,467	400,000
Unamortized debt issuance costs			(4,681)				(4,681)	(6,242)
Total debt			$ 383,786				$ 383,786	393,758
Expected Future Amortization of Debt Issuance Costs [Abstract]
Debt issued												$ 400,000
Fixed interest rate			5.125%				5.125%
Repurchase amount			$ 11,500				$ 11,500
Repurchases of senior notes			7,000
Gain on early extinguishment of debt			4,500
Write off of debt issuance cost			100
6.875% Notes due 2021
Long-Term Debt
Face amount			388,289				388,289	450,000
Unamortized debt issuance costs			(7,545)				(7,545)	(10,280)
Total debt			$ 380,744				$ 380,744	439,720						$ 450,000
Expected Future Amortization of Debt Issuance Costs [Abstract]
Fixed interest rate			6.875%				6.875%
Repurchase amount			$ 61,700				$ 61,700
Repurchases of senior notes			36,400
Gain on early extinguishment of debt			24,000
Write off of debt issuance cost			1,200
6.650% Notes due 2022
Long-Term Debt
Face amount			250,000				250,000	250,000
Unamortized debt issuance costs			(3,166)				(3,166)	(1,313)
Total debt			$ 246,834				$ 246,834	248,687
Expected Future Amortization of Debt Issuance Costs [Abstract]
Fixed interest rate	6.65%		6.65%				6.65%
Repayments of debt	$ 25,000
Other long-term debt
Long-Term Debt
Face amount			$ 61,488				$ 61,488	9,271
Unamortized debt issuance costs			(108)				(108)	0
Total debt			$ 61,380				$ 61,380	$ 9,271
Other long-term debt | Minimum
Expected Future Amortization of Debt Issuance Costs [Abstract]
Fixed interest rate			1.17%				1.17%
Other long-term debt | Maximum
Expected Future Amortization of Debt Issuance Costs [Abstract]
Fixed interest rate			7.08%				7.08%
Letters of credit | Working Capital Facility
Expected Future Amortization of Debt Issuance Costs [Abstract]
Outstanding cash borrowings			$ 45,400				$ 45,400
Senior Notes
Expected Future Amortization of Debt Issuance Costs [Abstract]
Leverage ratio		4.25
Debt issued	250,000
Covenant penalty rate		0.50%		0.50%
Debt covenant terms, default trigger amount	$ 10,000