Income Taxes (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Effective income tax
Effective tax rate (as a percent)	34.60%	36.80%	37.10%	40.20%
Annual estimate
Effective income tax
Effective tax rate (as a percent)			37.00%