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
	Mar. 31, 2014	Mar. 31, 2013
Non-cash compensation expense and capitalized non-cash compensation
Nonvested restricted stock and restricted stock units (RSUs)	3,000,000
OSOs outstanding	2,000,000
Stock-based compensation expense	$ 10	$ 37
Capitalized Non-cash Compensation	0	0
Non-cash compensation expense and capitalized non-cash compensation	10	37
Outperform Stock Options
Non-cash compensation expense and capitalized non-cash compensation
Stock-based compensation expense	2	5
Restricted Stock Units and Shares
Non-cash compensation expense and capitalized non-cash compensation
Stock-based compensation expense	6	7
401(k) Match Expense
Non-cash compensation expense and capitalized non-cash compensation
Stock-based compensation expense	7	8
Restricted Stock Unit Bonus Grant
Non-cash compensation expense and capitalized non-cash compensation
Stock-based compensation expense	(5)	15
Management Incentive and Retention Plan
Non-cash compensation expense and capitalized non-cash compensation
Stock-based compensation expense	$ 0	$ 2
Non-qualified stock options
Non-cash compensation expense and capitalized non-cash compensation
OSOs outstanding	11,000