Quarterly Financial and Market Information (Unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Financial and Market Information
Net revenues	$ 1,768	$ 841	$ 1,075	$ 1,172	$ 1,407	$ 754	$ 1,146	$ 1,449	$ 4,856	$ 4,755	$ 4,447
Cost of sales	682	237	377	364	729	241	346	455
Operating (loss) income	484	227	227	513	25	162	467	674	1,451	1,328	469
Net income	$ 354	$ 226	$ 185	$ 384	$ 99	$ 148	$ 335	$ 503	$ 1,149	$ 1,085	$ 418
Basic earnings per common share (in dollars per share)	$ 0.31	$ 0.20	$ 0.16	$ 0.34	$ 0.09	$ 0.13	$ 0.29	$ 0.42	$ 1.01	$ 0.93	$ 0.34
Diluted earnings per common share (in dollars per share)	$ 0.31	$ 0.20	$ 0.16	$ 0.33	$ 0.08	$ 0.13	$ 0.29	$ 0.42	$ 1.01	$ 0.92	$ 0.33