Schedule I - Condensed Financial Information of Parent (Statement of Cash Flows) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended			54 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	$ 1,791	$ 2,715	$ 2,901
Investing Activities:
Proceeds from asset sales, net of expenses	38	62	46
Decrease in restricted cash	419	44	(15)
(Purchase) sale of short term investments, net	(728)	(7)	(20)
Net cash used in investing activities	(656)	(1,774)	(895)
Financing Activities:
Borrowings (payments) under the revolver, net	836	1,139	2,788
Purchase of treasury stock	(308)	(322)	(301)	(1,300)
Common stock dividends paid	(144)	(119)	(30)
Payments for deferred financing costs	(158)	(176)	(40)
Net cash used in financing activities	(1,262)	(1,136)	(1,867)
Effect of exchange rate changes on cash	(51)	(59)	5
Total (decrease) increase in cash and cash equivalents	(103)	(258)	276
Cash and cash equivalents, beginning	1,642	1,900	1,624
Cash and cash equivalents, ending	1,539	1,642	1,900	1,539
SUPPLEMENTAL DISCLOSURES:
Cash payments for interest, net of amounts capitalized	1,351	1,398	1,509
Cash payments for income taxes, net of refunds	480	570	647
Parent Company
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	449	418	694
Investing Activities:
Proceeds from asset sales, net of expenses	(4)	(5)	0
Investment in and net advances to subsidiaries	(69)	201	(168)
Return of capital	740	230	660
Decrease in restricted cash	96	50	44
Additions to property, plant and equipment	(31)	(11)	(24)
(Purchase) sale of short term investments, net	(1)	1	1
Net cash used in investing activities	731	466	513
Financing Activities:
Borrowings (payments) under the revolver, net	0	0	(295)
Borrowings of notes payable and other coupon bearing securities	1,525	750	0
Repayments of notes payable and other coupon bearing securities	(2,117)	(1,210)	(236)
Loans (to) from subsidiaries	263	(152)	(236)
Purchase of treasury stock	(308)	(322)	(301)
Proceeds from issuance of common stock	1	13	8
Common stock dividends paid	(144)	(119)	(30)
Payments for deferred financing costs	(20)	(17)	(1)
Net cash used in financing activities	(800)	(1,057)	(1,091)
Effect of exchange rate changes on cash	0	(1)	0
Total (decrease) increase in cash and cash equivalents	380	(174)	116
Cash and cash equivalents, beginning	131	305	189
Cash and cash equivalents, ending	511	131	305	511
SUPPLEMENTAL DISCLOSURES:
Cash payments for interest, net of amounts capitalized	373	442	479
Cash payments for income taxes, net of refunds	$ (2)	$ 11	$ 0