Stock-Based Compensation - Non-cash compensation expense and capitalized non-cash compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Non-cash compensation expense and capitalized non-cash compensation
Nonvested restricted stock and restricted stock units (RSUs)	4,000,000		4,000,000
OSOs outstanding	2,000,000		2,000,000
Stock-based compensation expense	$ 31	$ 50	$ 116	$ 103
Capitalized Non-cash Compensation	(1)	(1)	(1)	(1)
Non-cash compensation expense and capitalized non-cash compensation	30	49	115	102
Outperform Stock Options
Non-cash compensation expense and capitalized non-cash compensation
Stock-based compensation expense	2	4	18	10
Restricted Stock Units and Shares
Non-cash compensation expense and capitalized non-cash compensation
Stock-based compensation expense	10	16	31	29
401(k) Match Expense
Non-cash compensation expense and capitalized non-cash compensation
Stock-based compensation expense	6	5	19	18
Restricted Stock Unit Bonus Grant
Non-cash compensation expense and capitalized non-cash compensation
Stock-based compensation expense	12	20	41	36
Management Incentive and Retention Plan
Non-cash compensation expense and capitalized non-cash compensation
Stock-based compensation expense	$ 1	$ 5	$ 7	$ 10
Non-qualified stock options
Non-cash compensation expense and capitalized non-cash compensation
OSOs outstanding	43,000		43,000