Fair Value (Tables)

6 Months Ended

Jun. 30, 2016

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis

The following two tables summarize the fair value measurements of our (i) energy commodity derivative contracts; (ii) interest rate swap agreements; and (iii) cross-currency swap agreements, based on the three levels established by the Codification (in millions). The tables also identify the impact of derivative contracts which we have elected to present on our accompanying consolidated balance sheets on a gross basis that are eligible for netting under master netting agreements.



	Balance sheet asset fair value measurements by level														Net amount
	Level 1		Level 2		Level 3		Gross amount		Contracts available for netting			Cash collateral held(b)			Net amount
As of June 30, 2016
Energy commodity derivative contracts(a)	$	6	$	317	$	—	$	323	$	(32	)	$	—		$	291
Interest rate swap agreements	$	—	$	836	$	—	$	836	$	—		$	—		$	836
Cross-currency swap agreements	$	—	$	13	$	—	$	13	$	(13	)	$	—		$	—
As of December 31, 2015
Energy commodity derivative contracts(a)	$	48	$	589	$	2	$	639	$	(12	)	$	(37	)	$	590
Interest rate swap agreements	$	—	$	385	$	—	$	385	$	(8	)	$	—		$	377
Cross-currency swap agreements	$	—	$	—	$	—	$	—	$	—		$	—		$	—



	Balance sheet liability fair value measurements by level																Net amount
	Level 1			Level 2			Level 3			Gross amount			Contracts available for netting		Collateral posted(c)		Net amount
As of June 30, 2016
Energy commodity derivative contracts(a)	$	(19	)	$	(47	)	$	—		$	(66	)	$	32	$	18	$	(16	)
Interest rate swap agreements	$	—		$	—		$	—		$	—		$	—	$	—	$	—
Cross-currency swap agreements	$	—		$	(34	)	$	—		$	(34	)	$	13	$	—	$	(21	)
As of December 31, 2015
Energy commodity derivative contracts(a)	$	(4	)	$	(10	)	$	(17	)	$	(31	)	$	12	$	—	$	(19	)
Interest rate swap agreements	$	—		$	(25	)	$	—		$	(25	)	$	8	$	—	$	(17	)
Cross-currency swap agreements	$	—		$	(52	)	$	—		$	(52	)	$	—	$	—	$	(52	)

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(a)	Level 1 consists primarily of New York Mercantile Exchange natural gas futures. Level 2 consists primarily of OTC West Texas Intermediate swaps and options. Level 3 consists primarily of power derivative contracts.


(b)	Cash margin deposits held by us associated with our energy commodity contract positions and OTC swap agreements and reported within “Other current liabilities” on our accompanying consolidated balance sheets.


(c)	Cash margin deposits posted by us associated with our energy commodity contract positions and OTC swap agreements and reported within “Other current assets” on our accompanying consolidated balance sheets.

Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation

The table below provides a summary of changes in the fair value of our Level 3 energy commodity derivative contracts (in millions):

Significant unobservable inputs (Level 3)

	Three Months Ended June 30,						Six Months Ended June 30,
	2016			2015			2016			2015
Derivatives-net asset (liability)
Beginning of Period	$	(2	)	$	(49	)	$	(15	)	$	(61	)
Total gains or (losses) included in earnings	(3		)	—			(9		)	—
Settlements	5			12			24			24
End of Period	$	—		$	(37	)	$	—		$	(37	)
The amount of total gains or (losses) for the period included in earnings attributable to the change in unrealized gains or (losses) relating to assets held at the reporting date	$	—		$	1		$	—		$	3

Schedule of Debt [Table Text Block]

The estimated fair value of our outstanding debt balances is disclosed below (in millions):



	June 30, 2016				December 31, 2015
	Carrying value		Estimated fair value		Carrying value		Estimated fair value
Total debt	$	43,620	$	43,061	$	43,227	$	37,481

We used Level 2 input values to measure the estimated fair value of our outstanding debt balances as of both June 30, 2016 and December 31, 2015.