Segment Information (Schedule Of Revenue And Long-Lived Assets, By Geographical Areas) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues	$ 518,832	$ 508,676	$ 498,681	$ 482,802	$ 528,783	$ 534,448	$ 534,644	$ 495,654	$ 2,008,991	$ 2,093,529	$ 2,139,289
Long-lived assets	1,362,638				1,154,470				1,362,638	1,154,470	1,013,782
United States [Member]
Segment Reporting Information [Line Items]
Revenues									1,760,214	1,821,026	1,857,624
Long-lived assets	1,341,703				1,134,433				1,341,703	1,134,433	989,815
Mexico [Member]
Segment Reporting Information [Line Items]
Revenues									183,058	191,453	187,124
Long-lived assets	20,614				19,879				20,614	19,879	23,734
Other [Member]
Segment Reporting Information [Line Items]
Revenues									65,719	81,050	94,541
Long-lived assets	321				158				321	158	233
Total Foreign Countries [Member]
Segment Reporting Information [Line Items]
Revenues									248,777	272,503	281,665
Long-lived assets	$ 20,935				$ 20,037				$ 20,935	$ 20,037	$ 23,967