Segment Information (Schedule Of Revenue And Long-Lived Assets, By Geographical Areas) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenues	$ 646,365	$ 629,735	$ 619,130	$ 562,684	$ 567,365	$ 528,643	$ 519,508	$ 501,221	$ 2,457,914	$ 2,116,737	$ 2,008,991
Long-lived assets	1,487,562				1,346,863				1,487,562	1,346,863	1,362,638
United States
Segment Reporting Information [Line Items]
Revenues									2,145,098	1,837,525	1,760,214
Long-lived assets	1,452,532				1,321,206				1,452,532	1,321,206	1,341,703
Mexico
Segment Reporting Information [Line Items]
Revenues									233,116	210,228	183,058
Long-lived assets	34,741				25,309				34,741	25,309	20,614
Other
Segment Reporting Information [Line Items]
Revenues									79,700	68,984	65,719
Long-lived assets	289				348				289	348	321
Total Foreign Countries [Member]
Segment Reporting Information [Line Items]
Revenues									312,816	279,212	248,777
Long-lived assets	$ 35,030				$ 25,657				$ 35,030	$ 25,657	$ 20,935