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, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
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	$ 22	$ 31	$ 48	$ 116
Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount	0	(1)	0	1
Non-cash compensation expense and capitalized non-cash compensation	22	30	48	115
Outperform Stock Options
Non-cash compensation expense and capitalized non-cash compensation
Stock-based compensation expense	2	2	6	18
Restricted Stock Units and Shares
Non-cash compensation expense and capitalized non-cash compensation
Stock-based compensation expense	10	10	22	31
Performance Restricted Stock Units [Member]
Non-cash compensation expense and capitalized non-cash compensation
Stock-based compensation expense	4	0	7	0
401(k) Match Expense
Non-cash compensation expense and capitalized non-cash compensation
Stock-based compensation expense	6	6	18	19
Restricted Stock Unit Bonus Grant
Non-cash compensation expense and capitalized non-cash compensation
Stock-based compensation expense	0	12	(5)	41
Management Incentive and Retention Plan
Non-cash compensation expense and capitalized non-cash compensation
Stock-based compensation expense	$ 0	$ 1	$ 0	$ 7
Non-qualified stock options
Non-cash compensation expense and capitalized non-cash compensation
OSOs outstanding	9,000		9,000