Derivative Instruments (Tables)

12 Months Ended

Dec. 31, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Offsetting Assets

The table below reflects the impact of netting agreements and margin deposits on gross derivative assets and liabilities as of December 31, 2018 and 2017.

As of December 31, 2018	Derivative instruments, recorded in the Consolidated Balance Sheet, gross		Derivative instruments subject to master netting agreements			Margin deposits remitted to counterparties			Derivative instruments, net
	(Thousands)
Asset derivatives:
Derivative instruments, at fair value	$	481,654	$	(256,087	)	$	—		$	225,567
Liability derivatives:
Derivative instruments, at fair value	$	336,051	$	(256,087	)	$	(40,283	)	$	39,681

As of December 31, 2017	Derivative instruments, recorded in the Consolidated Balance Sheet, gross		Derivative instruments subject to master netting agreements			Margin deposits remitted to counterparties		Derivative instruments, net
	(Thousands)
Asset derivatives:
Derivative instruments, at fair value	$	241,952	$	(86,856	)	$	—	$	155,096
Liability derivatives:
Derivative instruments, at fair value	$	139,089	$	(86,856	)	$	—	$	52,233

Offsetting Liabilities

The table below reflects the impact of netting agreements and margin deposits on gross derivative assets and liabilities as of December 31, 2018 and 2017.

As of December 31, 2018	Derivative instruments, recorded in the Consolidated Balance Sheet, gross		Derivative instruments subject to master netting agreements			Margin deposits remitted to counterparties			Derivative instruments, net
	(Thousands)
Asset derivatives:
Derivative instruments, at fair value	$	481,654	$	(256,087	)	$	—		$	225,567
Liability derivatives:
Derivative instruments, at fair value	$	336,051	$	(256,087	)	$	(40,283	)	$	39,681

As of December 31, 2017	Derivative instruments, recorded in the Consolidated Balance Sheet, gross		Derivative instruments subject to master netting agreements			Margin deposits remitted to counterparties		Derivative instruments, net
	(Thousands)
Asset derivatives:
Derivative instruments, at fair value	$	241,952	$	(86,856	)	$	—	$	155,096
Liability derivatives:
Derivative instruments, at fair value	$	139,089	$	(86,856	)	$	—	$	52,233