Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net earnings	$ 163,677,000	$ 90,683,000	$ 84,690,000
Adjustments to reconcile net earnings to net cash provided by (used in) operating activities:
Depreciation and amortization of property and equipment	21,721,000	25,787,000	27,493,000
Amortization of intangible assets	15,737,000	16,812,000	10,637,000
Provision for losses on accounts receivable	4,776,000	5,245,000	2,452,000
Write-downs of inventories	2,912,000	2,776,000	2,934,000
Write-off of property and equipment	393,000	418,000	0
Non-cash stock-based compensation	15,355,000	12,826,000	11,058,000
Deferred income taxes	9,126,000	19,139,000	10,517,000
Loss on sale of foreign entity		3,646,000
Loss on extinguishment of debt	624,000
Gain on sale of real estate			(338,000)
Changes in assets and liabilities:
Increase in accounts receivable	(46,883,000)	(208,065,000)	(168,966,000)
Decrease (increase) in inventories	46,534,000	(14,046,000)	(50,712,000)
Decrease (increase) in other assets	12,424,000	3,342,000	(50,181,000)
Increase (decrease) in accounts payable	29,844,000	(237,457,000)	193,582,000
Increase (decrease) in deferred revenue	9,178,000	(27,184,000)	10,633,000
Increase (decrease) in accrued expenses and other liabilities	7,229,000	(988,000)	12,278,000
Net cash provided by (used in) operating activities	292,647,000	(307,066,000)	96,077,000
Cash flows from investing activities:
Acquisitions, net of cash and cash equivalents acquired	(74,938,000)	(186,932,000)	(10,297,000)
Purchases of property and equipment	(17,251,000)	(19,230,000)	(12,266,000)
Proceeds from sale of foreign entity	479,000	1,517,000
Proceeds from sale of real estate			1,378,000
Net cash used in investing activities	(91,710,000)	(204,645,000)	(21,185,000)
Cash flows from financing activities:
Borrowings on senior revolving credit facility	569,232,000	1,151,216,000	772,218,000
Repayments on senior revolving credit facility	(686,732,000)	(1,033,716,000)	(772,218,000)
Borrowings on accounts receivable securitization financing facility	3,357,000,000	3,961,389,000	2,802,000,000
Repayments on accounts receivable securitization financing facility	(3,188,000,000)	(3,975,889,000)	(2,851,500,000)
Borrowings under Term Loan A		175,000,000
Repayments under Term Loan A	(166,250,000)	(8,750,000)
Repayments under other financing agreements	(2,372,000)	(5,636,000)	(1,309,000)
Payments on capital lease obligations	(999,000)	(1,089,000)	(445,000)
Net (repayments) borrowings under inventory financing facility	(15,338,000)	141,037,000	48,603,000
Payment of debt issuance costs	(270,000)	(1,123,000)	(3,360,000)
Payment of payroll taxes on stock-based compensation through shares withheld	(3,230,000)	(5,318,000)	(2,219,000)
Repurchases of common stock	(22,069,000)		(50,000,000)
Net cash (used in) provided by financing activities	(159,028,000)	397,121,000	(58,230,000)
Foreign currency exchange effect on cash, cash equivalents and restricted cash balances	(5,061,000)	16,089,000	(1,937,000)
Increase (decrease) in cash, cash equivalents and restricted cash	36,848,000	(98,501,000)	14,725,000
Cash, cash equivalents and restricted cash at beginning of year	107,445,000	205,946,000	191,221,000
Cash, cash equivalents and restricted cash at end of year	$ 144,293,000	$ 107,445,000	$ 205,946,000