Employee Benefit Benefits and Stock-Based Compensation - Non-cash compensation expensed and capitalized (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock-based compensation expense
Stock- based compensation expense	$ 152	$ 136	$ 102
Capitalized Noncash Compensation	(1)	(1)	(1)
Non-cash compensation expense	151	135	101
Share-based Compensation Arrangement by Share-based Payment Award Accelerated Compensation Cost	5	9	12
Outperform Stock Options
Stock-based compensation expense
Stock- based compensation expense	21	14	10
Restricted Stock Units and Shares
Stock-based compensation expense
Stock- based compensation expense	38	40	22
401(k) Match Expense
Stock-based compensation expense
Stock- based compensation expense	24	23	13
Restricted Stock Unit Bonus Grant
Stock-based compensation expense
Stock- based compensation expense	59	46	57
Management Incentive and Retention Plan
Stock-based compensation expense
Stock- based compensation expense	$ 10	$ 13	$ 0