Income Taxes (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Income tax provision	$ 23,112,000	$ 26,890,000	$ 55,285,000	$ 64,711,000
Effective income tax rates	40.80%	37.60%	39.90%	38.00%
Actual income tax rates	46.40%	40.50%	41.50%	39.20%
Unrecognized income tax benefits	11,300,000		11,300,000		11,300,000
Unrecognized income tax benefits, if recognized, that would favorably affect the effective income tax rate	6,600,000		6,600,000		6,600,000
Accrued interest expense related to unrecognized income tax benefits	3,200,000		3,200,000		2,600,000
Interest expense related to unrecognized income tax benefits recognized	200,000	100,000	600,000	200,000
Unrecognized income tax benefits to be recognized in the next twelve months	$ 5,000,000		$ 5,000,000