Business Acquisition Business Acquisitions (Supplementary Information On Unaudited Pro Forma Financial Results Of Acquisition) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2014
2012 Business Acquisitions [Member]
Business Acquisition, Pro Forma Revenue	$ 417,250	$ 385,974
Business Acquisition, Pro Forma Net Income (Loss)	120,210	114,889
Business Acquisition, Pro Forma Earnings Per Share, Basic	$ 2.60	$ 2.47
Business Acquisition, Pro Forma Earnings Per Share, Diluted	$ 2.58	$ 2.44
2013 Business Acquisitions [Member]
Business Acquisition, Pro Forma Revenue	470,190		545,952
Business Acquisition, Pro Forma Net Income (Loss)	122,187		108,600
Business Acquisition, Pro Forma Earnings Per Share, Basic	$ 2.64		$ 2.34
Business Acquisition, Pro Forma Earnings Per Share, Diluted	$ 2.62		$ 2.31
2014 Business Acquisitions [Member]
Business Acquisition, Pro Forma Revenue			626,906	672,701
Business Acquisition, Pro Forma Net Income (Loss)			$ 132,480	$ 119,773
Business Acquisition, Pro Forma Earnings Per Share, Basic			$ 2.85	$ 2.51
Business Acquisition, Pro Forma Earnings Per Share, Diluted			$ 2.81	$ 2.49