Schedule I - Condensed Financial Information of Parent (Statement of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	$ 2,884	$ 2,134	$ 1,791
Investing Activities:
Decrease in restricted cash	(61)	(159)	419
Purchase of short term investments, net	(55)	(17)	(728)
Net cash used in investing activities	(2,108)	(2,366)	(656)
Financing Activities:
Borrowings (payments) under the revolver, net	1,465	959	836
Purchase of treasury stock	(79)	(482)	(308)
Common stock dividends paid	(290)	(276)	(144)
Payments for deferred financing costs	(105)	(90)	(158)
Payments to Noncontrolling Interests	(476)	(326)	(485)
Proceeds from (Payments for) Other Financing Activities	(44)	(7)	27
Net cash (used in) provided by financing activities	(747)	28	(1,262)
Effect of exchange rate changes on cash	9	(52)	(51)
Total Increase (decrease) in cash and cash equivalents	48	(260)	(119)
Cash and cash equivalents, beginning	1,257	1,517
Cash and cash equivalents, ending	1,305	1,257	1,517
SUPPLEMENTAL DISCLOSURES:
Cash payments for interest, net of amounts capitalized	(1,273)	(1,265)	(1,351)
Cash payments for income taxes, net of refunds	(487)	(388)	(480)
Parent Company
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	818	475	449
Investing Activities:
Expenses related to asset sales	0	0	(4)
Investment in and net advances to subsidiaries	(650)	(221)	(69)
Return of capital	247	501	740
Decrease in restricted cash	29	49	96
Additions to property, plant and equipment	(12)	(11)	(31)
Purchase of short term investments, net	0	0	(1)
Net cash used in investing activities	(386)	318	731
Financing Activities:
Borrowings of notes payable and other coupon bearing securities	500	575	1,525
Repayments of notes payable and other coupon bearing securities	(808)	(915)	(2,117)
Loans from subsidiaries	183	0	263
Purchase of treasury stock	(79)	(482)	(308)
Proceeds from issuance of common stock	1	4	1
Common stock dividends paid	(290)	(276)	(144)
Payments for deferred financing costs	(12)	(6)	(20)
Payments to Noncontrolling Interests	(2)	0	0
Proceeds from (Payments for) Other Financing Activities	(3)	(18)	0
Net cash (used in) provided by financing activities	(510)	(1,118)	(800)
Effect of exchange rate changes on cash	1	0	0
Total Increase (decrease) in cash and cash equivalents	(77)	(325)	380
Cash and cash equivalents, beginning	186	511	131
Cash and cash equivalents, ending	109	186	511
SUPPLEMENTAL DISCLOSURES:
Cash payments for interest, net of amounts capitalized	296	314	373
Cash payments for income taxes, net of refunds	$ 6	$ 0	$ (2)