Stockholders' Equity (Details) - $ / shares	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Equity [Abstract]
Shares paid for tax withholding for share based compensation	321,008	389,969
Shares paid for tax withholding for share based compensation, average price	$ 50.32	$ 46.41
Forfeited restricted stock awards transferred to treasury stock	73,455	40,392
Par value of treasury stock	$ 0.01		$ 0.01