Quarterly Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 2,017,438	$ 2,006,275	$ 1,993,351	$ 1,813,372	$ 1,777,961	$ 1,707,763	$ 1,686,345	$ 1,622,273	$ 7,830,436	$ 6,794,342	$ 6,956,311
Gross profit	735,423	744,333	749,446	661,175	619,704	631,788	631,213	589,264	2,890,377	2,471,969	2,568,144
Earnings from continuing operations	$ 296,448	$ 178,912	$ 164,058	$ 172,247	$ 161,162	$ 130,084	$ 118,290	$ 99,356	$ 811,665	$ 508,892	$ 595,881
Earnings from continuing operations (in dollars per basic share)	$ 1.90	$ 1.15	$ 1.05	$ 1.11	$ 1.04	$ 0.84	$ 0.76	$ 0.64	$ 5.21	$ 3.28	$ 3.78
Earnings from continuing operations (in dollars per diluted share)	$ 1.88	$ 1.14	$ 1.04	$ 1.09	$ 1.03	$ 0.83	$ 0.76	$ 0.64	$ 5.15	$ 3.25	$ 3.74
Net earnings									$ 811,665	$ 508,892	$ 869,829
Net earnings (in dollars per basic share)									$ 5.21	$ 3.28	$ 5.52
Net earnings (in dollars per diluted share)									$ 5.15	$ 3.25	$ 5.46