Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2017

Fair Value Disclosures [Abstract]

Schedule of assets and liabilities measured at fair value on a recurring basis during the applicable period

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 March 31, 2017		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	$	59,391	$	—	$	59,391	$	—
Liabilities
Derivative instruments, at fair value	$	136,462	$	—	$	136,462	$	—

			Fair value measurements at reporting date using
Description	As of December 31, 2016		Quoted prices in active markets for identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
	(Thousands)
Assets
Trading securities	$	286,396	$	—	$	286,396	$	—
Derivative instruments, at fair value	$	33,053	$	—	$	33,053	$	—
Liabilities
Derivative instruments, at fair value	$	257,943	$	—	$	257,943	$	—