Segment Information (Schedule Of Revenue And Long-Lived Assets, By Geographical Areas) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Revenues	$ 509,694	$ 506,504	$ 521,812	$ 498,376	$ 507,937	$ 509,587	$ 515,897	$ 469,429	$ 2,036,386	$ 2,002,850	$ 1,815,020
Long-lived Assets	993,843				942,136				993,843	942,136	841,055
United States [Member]
Segment Reporting Information [Line Items]
Revenues									1,772,179	1,772,628	1,614,183
Long-lived Assets	979,798				931,658				979,798	931,658	824,649
Mexico [Member]
Segment Reporting Information [Line Items]
Revenues									172,016	147,938	121,821
Long-lived Assets	13,659				9,993				13,659	9,993	16,119
Other [Member]
Segment Reporting Information [Line Items]
Revenues									92,191	82,284	79,016
Long-lived Assets	386				485				386	485	287
Total Foreign Countries [Member]
Segment Reporting Information [Line Items]
Revenues									264,207	230,222	200,837
Long-lived Assets	$ 14,045				$ 10,478				$ 14,045	$ 10,478	$ 16,406