Geographic Information (Revenues By Geographic Areas) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 922,793	$ 995,250	$ 997,827	$ 953,317	$ 926,254	$ 980,814	$ 949,938	$ 876,501	$ 3,869,187	$ 3,733,507	$ 3,326,106
United States [Member]
Segment Reporting Information [Line Items]
Revenues									3,441,141	3,308,226	2,951,673
Canada [Member]
Segment Reporting Information [Line Items]
Revenues									223,270	238,590	227,756
Other foreign countries [Member]
Segment Reporting Information [Line Items]
Revenues									$ 204,776	$ 186,691	$ 146,677