Derivative Instruments - Impact of Netting Agreements and Margin Deposits (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Asset derivatives:
Derivative instruments, recorded in the Condensed Consolidated Balance Sheet, gross	$ 67,555	$ 33,053
Liability derivatives:
Derivative instruments, recorded in the Condensed Consolidated Balance Sheet, gross	71,374	257,943
Commodity derivatives
Asset derivatives:
Derivative instruments, recorded in the Condensed Consolidated Balance Sheet, gross	67,555	33,053
Derivative instruments subject to master netting agreements	(42,886)	(23,373)
Margin deposits remitted to counterparties	0	0
Derivative instruments, net	24,669	9,680
Liability derivatives:
Derivative instruments, recorded in the Condensed Consolidated Balance Sheet, gross	71,374	257,943
Derivative instruments subject to master netting agreements	(42,886)	(23,373)
Margin deposits remitted to counterparties	0	0
Derivative instruments, net	$ 28,488	$ 234,570

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

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