Schedule I - CONDENSED STATEMENT OF CASH FLOWS (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Cash flows provided by/(used in) operating activities	$ 786	$ (2,323)	$ 42
Cash flows from investing activities
Payments to acquire investments	(22)	(12)	(23)
Cash flows used in investing activities	(2,135)	(55)	(121)
Cash flows from financing activities
Repayments of long-term debt	(1,130)	(7,846)	(268)
Payments Related to Tax Withholding for Share-based Compensation	(22)	(11)	(7)
Proceeds from the issuance of common stock	6	11	6
Repurchase of common stock	(311)	0	0
Cash flows used in financing activities	297	429	(1,260)
Net increase/(decrease) in cash, cash equivalents, and restricted cash	(1,052)	(1,949)	3,244
Total cash, cash equivalents, and restricted cash	1,657	2,709	4,658	$ 1,414
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Cash flows provided by/(used in) operating activities	(138)	1,504	(37)
Cash flows from investing activities
Payments to acquire investments	0	(700)	0
Cash flows used in investing activities	0	(700)	0
Cash flows from financing activities
Repayments of long-term debt	(2)	0	0
Payments Related to Tax Withholding for Share-based Compensation	(22)	0	0
Proceeds from the issuance of common stock	6	0	0
Repurchase of common stock	(311)	0	0
Other financing	(2)	0	(8)
Cash flows used in financing activities	(331)	0	(8)
Net increase/(decrease) in cash, cash equivalents, and restricted cash	(469)	804	(45)
Total cash, cash equivalents, and restricted cash	$ 457	$ 926	$ 122	$ 167

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Amount of cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage. Excludes amount for disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.

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Amount of cash inflow (outflow) from investing activities, including discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.

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Amount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.

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