Derivative Instruments - Impact of Netting Agreements and Margin Deposits (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Asset derivatives:
Derivative instruments, recorded in the Condensed Consolidated Balance Sheet, gross	$ 134,698	$ 417,397
Liability derivatives:
Derivative instruments, recorded in the Condensed Consolidated Balance Sheet, gross	67,871	23,434
Commodity derivatives
Asset derivatives:
Derivative instruments, recorded in the Condensed Consolidated Balance Sheet, gross	134,698	417,397
Derivative instruments subject to master netting agreements	(63,823)	(19,909)
Margin deposits remitted to counterparties	0	0
Derivative instruments, net	70,875	397,488
Liability derivatives:
Derivative instruments, recorded in the Condensed Consolidated Balance Sheet, gross	67,871	23,434
Derivative instruments subject to master netting agreements	(63,823)	(19,909)
Margin deposits remitted to counterparties	0	0
Derivative instruments, net	$ 4,048	$ 3,525

Amount of obligation to return cash collateral under master netting arrangements offset against derivative assets.

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