Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2013

Fair Value Disclosures [Abstract]

Fair Value Assets and Liabilities Measured On Recurring Basis [Text Block]

							Fair Value Measurements Using
	Carrying Amount			Fair Value			Quoted Prices In Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (Level 3)
	(Millions)
Assets (liabilities) at September 30, 2013:
Measured on a recurring basis:
ARO Trust investments	$	31		$	31		$	31	$	—		$	—
Energy derivatives assets not designated as hedging instruments	6			6			—		1			5
Energy derivatives liabilities not designated as hedging instruments	(3		)	(3		)	—		(1		)	(2		)
Additional disclosures:
Notes receivable and other	82			148			1		7			140
Long-term debt, including current portion (a)	(10,358		)	(11,026		)	—		(11,026		)	—
Guarantee	(32		)	(29		)	—		(29		)	—
Assets (liabilities) at December 31, 2012:
Measured on a recurring basis:
ARO Trust investments	$	18		$	18		$	18	$	—		$	—
Energy derivatives assets not designated as hedging instruments	5			5			—		—			5
Energy derivatives liabilities not designated as hedging instruments	(1		)	(1		)	—		—			(1		)
Additional disclosures:
Notes receivable and other	95			138			2		8			128
Long-term debt, including current portion (a)	(10,734		)	(12,388		)	—		(12,388		)	—
Guarantee	(33		)	(31		)	—		(31		)	—

(a) Excludes capital leases