Quarterly Financial Data (Components Of Quarterly Financial Data) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Data [Line Items]
Revenues	$ 1,357,801	$ 1,398,021	$ 1,381,370	$ 1,336,164	$ 1,363,877	$ 1,404,113	$ 1,446,096	$ 1,366,161	$ 5,473,356	$ 5,580,247	$ 5,289,953
Operating Income	33,380	67,675	76,299	31,599	37,795	55,213	80,143	55,690	208,953	228,841	207,928
Income before income tax provision	21,363	53,378	62,849	16,775	23,677	41,158	64,697	41,422	154,365	170,954	148,072
Income Tax Provision	9,669	22,821	19,952	2,770	11,881	15,854	22,897	15,776	55,212	66,408	59,629
Net Income	$ (11,694)	$ (30,557)	$ (42,897)	$ (14,005)	$ (11,796)	$ (25,304)	$ (41,800)	$ (25,646)
Basic Earnings per Share	$ 0.21	$ 0.54	$ 0.76	$ 0.25	$ 0.21	$ 0.45	$ 0.75	$ 0.46	$ 1.75	$ 1.87	$ 1.60
Diluted Earnings per Share	$ 0.20	$ 0.53	$ 0.75	$ 0.25	$ 0.21	$ 0.45	$ 0.74	$ 0.46	$ 1.73	$ 1.85	$ 1.58
Cash Dividends	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10
Minimum [Member]
Quarterly Financial Data [Line Items]
Market price	38.79	39.21	32.25	29.12	25.97	26.51	30.89	28.26
Maximum [Member]
Quarterly Financial Data [Line Items]
Market price	45.98	46.04	39.81	38.12	29.91	37.30	38.78	34.69