Income Taxes (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Income Tax Disclosure [Abstract]
Effective tax rate (in hundredths)	26.10%	28.40%
Net discrete items	$ 4,525,000	$ (1,610,000)
Pre-discrete tax rate	27.80%	27.80%
Significant change in unrecognized tax benefits is reasonably possible, estimated range of change, lower bound	90,000,000
Significant change in unrecognized tax benefits is reasonably possible, estimated range of change, upper bound	$ 140,000,000