Income Taxes (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Income tax provision	$ 25,518,000	$ 19,042,000
Effective income tax rates	38.10%	38.50%
Actual income tax rates	38.20%	38.70%
Unrecognized income tax benefits	2,400,000		3,100,000
Unrecognized income tax benefits, if recognized, that would favorably affect the effective income tax rate	900,000		1,700,000
Accrued interest expense related to unrecognized income tax benefits	200,000		200,000
Interest expense related to unrecognized income tax benefits recognized	100,000	200,000
Unrecognized income tax benefits to be recognized in the next twelve months	$ 100,000