Income Taxes (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Tax Disclosure [Abstract]
Income before income tax	$ 182,400,000	$ 144,603,000	$ 501,325,000	$ 421,725,000
Provision for income taxes	55,870,000	37,769,000	154,998,000	112,864,000
Effective tax rate	30.60%	26.10%	30.90%	26.80%
Decrease in unrecognized tax benefits for the period			500,000
Unrecognized tax benefits approximate amount of estimated reduction within the next twelve months	$ 14,000,000		$ 14,000,000