Segment Information (Schedule Of Revenue And Long-Lived Assets, By Geographical Areas) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 620,302	$ 590,214	$ 568,959	$ 592,703	$ 621,787	$ 618,264	$ 627,533	$ 596,117	$ 2,372,178	$ 2,463,701	$ 2,457,914
Long-lived assets	1,543,258				1,526,276				1,543,258	1,526,276	1,487,562
United States
Segment Reporting Information [Line Items]
Revenues									2,144,105	2,191,560	2,145,098
Long-lived assets	1,506,862				1,487,591				1,506,862	1,487,591	1,452,532
Mexico
Segment Reporting Information [Line Items]
Revenues									149,438	197,470	233,116
Long-lived assets	36,222				38,428				36,222	38,428	34,741
Other
Segment Reporting Information [Line Items]
Revenues									78,635	74,671	79,700
Long-lived assets	174				257				174	257	289
Total Foreign Countries [Member]
Segment Reporting Information [Line Items]
Revenues									228,073	272,141	312,816
Long-lived assets	$ 36,396				$ 38,685				$ 36,396	$ 38,685	$ 35,030