Derivative Instruments - Impact of Netting Agreements and Margin Deposits (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Asset derivative instruments, at fair value
Gross derivative instruments, recorded in the Condensed Consolidated Balance Sheets	$ 771,634	$ 481,654
Liability derivative instruments, at fair value
Gross derivative instruments, recorded in the Condensed Consolidated Balance Sheets	339,995	336,051
Commodity derivatives
Asset derivative instruments, at fair value
Gross derivative instruments, recorded in the Condensed Consolidated Balance Sheets	771,634	481,654
Derivative instruments subject to master netting agreements	(288,898)	(256,087)
Margin deposits remitted to counterparties	0	0
Derivative instruments, net	482,736	225,567
Liability derivative instruments, at fair value
Gross derivative instruments, recorded in the Condensed Consolidated Balance Sheets	339,995	336,051
Derivative instruments subject to master netting agreements	(288,898)	(256,087)
Margin deposits remitted to counterparties	(23,372)	(40,283)
Derivative instruments, net	$ 27,725	$ 39,681

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

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