Condensed Consolidated Statements of Income and Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Net sales	$ 4,586,294	$ 3,905,641
Cost of goods sold	3,150,487	2,749,920
Gross profit	1,435,807	1,155,721
Operating expenses:
Selling, administrative and other expenses	1,133,771	877,356
Depreciation and amortization	58,363	38,132
Provision for doubtful accounts	2,701	3,128
Total operating expenses	1,194,835	918,616
Non-operating expenses (income):
Interest expense	24,109	6,779
Other	(12,456)	(13,449)
Total non-operating expenses (income)	11,653	(6,670)
Income before income taxes	229,319	243,775
Income taxes	52,743	83,615
Net income	$ 176,576	$ 160,160
Basic net income per common share (usd per share)	$ 1.20	$ 1.08
Diluted net income per common share (usd per share)	1.20	1.08
Dividends declared per common share (usd per share)	$ 0.72	$ 0.675
Weighted average common shares outstanding (in shares)	146,727	148,154
Dilutive effect of stock options and non-vested restricted stock awards (in shares)	595	634
Weighted average common shares outstanding - assuming dilution (in shares)	147,322	148,788
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustment	$ 42,880	$ 57,020
Net investment hedge, net of income taxes of 2018 — $6,180	(16,710)	0
Pension and postretirement benefit adjustments, net of income taxes of 2018 — $2,648; 2017 — $3,571	7,164	5,732
Other comprehensive income, net of tax	33,334	62,752
Comprehensive income	$ 209,910	$ 222,912