Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2015

Fair Value Disclosures [Abstract]

Derivative instrument assets and liabilities measured at fair value on a recurring basis

The following assets and liabilities were measured at fair value on a recurring basis during the applicable period:

			Fair value measurements at reporting date using
Description	As of June 30, 2015		Quoted prices in active markets for identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
	(Thousands)
Assets
Derivative instruments, at fair value	$	349,152	$	—	$	349,152	$	—
Liabilities
Derivative instruments, at fair value	$	43,696	$	—	$	43,696	$	—

			Fair value measurements at reporting date using
Description	As of December 31, 2014		Quoted prices in active markets for identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
	(Thousands)
Assets
Derivative instruments, at fair value	$	458,460	$	—	$	458,460	$	—
Liabilities
Derivative instruments, at fair value	$	22,942	$	132	$	22,810	$	—