Equity-Based Compensation Information Related to Stock Options (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Equity-based compensation
Pretax expense for stock options	$ 11	$ 7	$ 5
After-tax expense for stock options	7	5	4
Proceeds from stock options exercised	121	95	71
Income tax benefit related to stock options exercised
Tax benefit classified in operating activities in the Consolidated Statements of Cash Flows	3	5	13
Excess tax benefit classified in financing activities in the Consolidated Statements of Cash Flows	22	13	33
Intrinsic value of stock options exercised	102	60	62
Total fair value of stock options vesting	11	7	5
Stock options exercised, shares	3,565	3,099	2,541
Non-vested stock option compensation expense not yet recognized	$ 14
Non-vested stock options weighted average period for total compensation expense to be recognized	2 years