Quarterly Information (Unaudited) (Details) (USD $)	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
QUARTERLY INFORMATION
Revenue	$ 1,583,536,000	$ 1,573,295,000	$ 1,563,860,000	$ 1,536,276,000	$ 1,541,094,000	$ 1,570,720,000	$ 1,513,344,000	$ 1,425,376,000	$ 6,256,967,000	$ 6,050,534,000	$ 5,136,435,000
Earnings from Continuing operations	54,945,000	64,311,000	46,767,000	34,876,000	47,664,000	56,933,000	40,914,000	25,857,000	200,899,000	171,368,000	124,608,000
Net earnings	53,844,000	75,091,000	46,723,000	34,321,000	48,095,000	56,524,000	40,033,000	25,125,000	209,979,000	169,777,000	118,170,000
Earnings from Continuing operations per Common Share
Continuing operations (USD per share)	$ 1.07	$ 1.26	$ 0.92	$ 0.68	$ 0.93	$ 1.11	$ 0.80	$ 0.50	$ 3.93	$ 3.34	$ 2.38
Continuing operations (USD per share)	$ 1.07	$ 1.26	$ 0.91	$ 0.68	$ 0.92	$ 1.10	$ 0.79	$ 0.50	$ 3.91	$ 3.31	$ 2.37
Net earnings per common share:
Basic (USD per share)	$ 1.05	$ 1.47	$ 0.92	$ 0.67	$ 0.94	$ 1.10	$ 0.78	$ 0.49	$ 4.11	$ 3.31	$ 2.25
Diluted (USD per share)	$ 1.05	$ 1.47	$ 0.91	$ 0.67	$ 0.93	$ 1.10	$ 0.77	$ 0.48	$ 4.09	$ 3.28	$ 2.25
Quarterly Information (Unaudited) (Textual) [Abstract]
Income tax benefit per diluted common share									$ 0.10	$ 0.01
Income tax benefit										1,000,000
Tax benefit from favorable resolution of a tax item									5,000,000
State Of Michigan [Member]
Quarterly Information (Unaudited) (Textual) [Abstract]
Income tax benefit per diluted common share										$ 0.10
Changes In Tax Law Impact On Net Earnings										(5,350,000)
United Kingdom [Member]
Quarterly Information (Unaudited) (Textual) [Abstract]
Income tax benefit per diluted common share									$ 0.02
Changes In Tax Law Impact On Net Earnings									$ (856,000)		$ 400,000