Quarterly Financial Data (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Data [Abstract]
Revenues	$ 1,101	$ 867	$ 836	$ 540	$ 528	$ 515	$ 487	$ 431	$ 3,344	$ 1,960	$ 1,410
Income before income taxes	210	239	264	170	146	201	217	181	883	744	622
Net income	$ 121	$ 161	$ 178	$ 106	$ 91	$ 124	$ 136	$ 112	$ 566	$ 463	$ 386