Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net operating loss carryforwards
Effective income tax rate (as a percent)	33.30%	32.10%	35.50%	32.50%
Uncertain tax positions
Liabilities for uncertain tax positions	$ 0	$ 0	$ 0	$ 0