Fair Value of Financial Instruments - Fair Value of Commodity Derivative Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Mar. 31, 2016
Prepaid expenses and other current assets
Derivative assets (liabilities)
Net (liability) asset	$ 38,500
Accrued expenses and other payables
Derivative assets (liabilities)
Net (liability) asset	44,000
Commodity contracts
Assets:
Derivative Assets	47,786	$ 80,061
Netting of counterparty contracts, assets	(8,431)	(3,384)
Net cash collateral provided (held)	326	(18,176)
Commodity derivatives in condensed consolidated balance sheet, assets	39,681	58,501
Liabilities:
Derivative Liabilities	(72,891)	(32,595)
Netting of counterparty contracts, liabilities	8,431	3,384
Cash collateral provided (held)	16,503	599
Commodity derivatives in condensed consolidated balance sheet, liabilities	(47,957)	(28,612)
Derivative assets (liabilities)
Net (liability) asset	(8,276)	29,889
Commodity contracts | Prepaid expenses and other current assets
Derivative assets (liabilities)
Net (liability) asset	39,681	58,501
Commodity contracts | Accrued expenses and other payables
Derivative assets (liabilities)
Net (liability) asset	(47,957)	(28,612)
Level 1 | Commodity contracts
Assets:
Derivative Assets	8,018	47,361
Liabilities:
Derivative Liabilities	(24,674)	(3,983)
Level 2 | Commodity contracts
Assets:
Derivative Assets	39,768	32,700
Liabilities:
Derivative Liabilities	$ (48,217)	$ (28,612)