Acquisitions (Details) (U.S. and Canadian Business of Comex [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
U.S. and Canadian Business of Comex [Member]
Summary of pro-forma consolidated financial information
Net sales	$ 3,042,995	$ 2,849,091	$ 5,409,551	$ 5,123,962
Net income	$ 291,447	$ 249,693	$ 406,904	$ 352,502
Net income per common share:
Basic (in dollars per share)	$ 3.00	$ 2.44	$ 4.14	$ 3.44
Diluted (in dollars per share)	$ 2.94	$ 2.39	$ 4.06	$ 3.37