Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 423,223	$ 381,519	$ 311,623
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	128,192	125,437	86,463
Stock-based compensation expense	21,336	22,021	22,036
Deferred income taxes	22,388	6,242	4,279
Excess tax benefit from stock-based payments	(14,445)	(17,814)	(18,348)
Other	7,348	6,593	9,630
Changes in operating assets and liabilities, net of effects from acquisitions:
Receivables	14,704	(61,739)	(44,670)
Inventory	(83,188)	(122,590)	(69,222)
Prepaid income taxes/income taxes payable	17,474	18,428	49,993
Accounts payable	(4,222)	(5,474)	49,641
Other operating assets and liabilities	(2,973)	18,274	26,631
Net cash provided by operating activities	529,837	370,897	428,056
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(170,490)	(140,950)	(90,186)
Acquisitions, net of cash acquired	(160,517)	(775,921)	(408,384)
Payments for (Proceeds from) Other Investing Activities	(1,014)	4,123	7,036
Net cash used in investing activities	(329,993)	(920,994)	(505,606)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	8,168	9,324	15,392
Excess tax benefit from stock-based payments	14,445	17,814	18,348
Taxes paid related to net share settlements of stock-based compensation awards	(7,581)	(443)	0
Debt issuance costs	(97)	(3,750)	(16,940)
Proceeds from issuance of senior notes	0	0	600,000
Borrowings under revolving credit facilities	313,142	1,587,644	437,023
Repayments under revolving credit facilities	(445,282)	(1,098,518)	(748,086)
Borrowings under term loans	0	11,250	35,000
Repayments under term loans	(22,500)	(16,875)	(16,875)
Borrowings under receivables securitization facility	3,858	95,050	41,500
Repayments under receivables securitization facility	(35,758)	(150)	(121,500)
Repayments of other debt, net	(29,696)	(40,051)	(45,062)
Payments of other obligations	(22,791)	(41,992)	(32,859)
Proceeds from (Payments for) Other Financing Activities	0	(300)	0
Net cash (used in) provided by financing activities	(224,092)	519,003	165,941
Effect of exchange rate changes on cash and equivalents	(2,960)	(4,789)	2,327
Net (decrease) increase in cash and equivalents	(27,208)	(35,883)	90,718
Cash and equivalents, beginning of period	114,605	150,488	59,770
Cash and equivalents, end of period	87,397	114,605	150,488
Supplemental disclosure of cash paid for:
Income taxes, net of refunds	180,126	176,955	110,862
Interest	54,917	59,678	45,253
Supplemental disclosure of noncash investing and financing activities:
Notes payable and other obligations, including notes issued and debt assumed in connection with business acquisitions	28,348	96,258	8,360
Contingent consideration liabilities	0	5,854	3,854
Non-cash property and equipment additions	$ 8,846	$ 2,293	$ 6,615