SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
VALUATION AND QUALIFYING ACCOUNTS
Federal benefit for the state-related portion of the deferred tax valuation allowance		$ 88
Deferred tax valuation allowance
VALUATION AND QUALIFYING ACCOUNTS
Balance at Beginning of Period	$ 382
Charged (Credited) to Costs and Expenses	398	294
Charged to Other Accounts		88
Balance at End of Period	780	382
Other asset valuation allowance
VALUATION AND QUALIFYING ACCOUNTS
Balance at Beginning of Period	68	10
Charged (Credited) to Costs and Expenses	(12)	58	$ 10
Balance at End of Period	56	68	10
Environmental reserves
VALUATION AND QUALIFYING ACCOUNTS
Balance at Beginning of Period	7	8	8
Charged (Credited) to Costs and Expenses			1
Deductions	(1)	(1)	(1)
Balance at End of Period	$ 6	$ 7	$ 8