Business Acquisition Business Acquisitions (Supplementary Information On Unaudited Pro Forma Financial Results Of Acquisition) (Details) - 2015 Business Acquisition [Member] - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Business Acquisition, Pro Forma Revenue	$ 581,869	$ 515,936
Business Acquisition, Pro Forma Net Income (Loss)	$ 115,527	$ 86,487
Business Acquisition, Pro Forma Earnings Per Share, Basic	$ 2.39	$ 1.81
Business Acquisition, Pro Forma Earnings Per Share, Diluted	$ 2.38	$ 1.80