New Accounting Standard - Sales Recognition - Summary of Impact of Adoption of Topic 606 On Balance Sheet (Detail) - USD ($)	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cash and cash equivalents	$ 142,655,000		$ 105,831,000	$ 202,882,000
Accounts receivable, net	1,931,736,000		1,814,560,000
Inventories	148,503,000		194,529,000
Inventories not available for sale			36,956,000
Other current assets	115,683,000		152,467,000
Total current assets	2,338,577,000		2,304,343,000
Property and equipment, net	72,954,000		75,252,000
Goodwill	166,841,000		131,431,000
Intangible assets, net	112,179,000		100,778,000
Deferred income taxes	7,967,000		17,064,000
Other assets	77,429,000		56,783,000
Total assets	2,775,947,000		2,685,651,000
Accounts payable—trade	978,104,000		899,075,000
Accounts payable—inventory financing facility	304,130,000		319,468,000
Accrued expenses and other current liabilities	190,733,000		175,860,000
Current portion of long-term debt	1,395,000		16,592,000
Deferred revenue	62,300,000		88,979,000
Total current liabilities	1,536,662,000		1,499,974,000
Long-term debt	195,525,000		296,576,000
Deferred income taxes	683,000		717,000
Other liabilities	56,088,000		44,915,000
Total liabilities	1,788,958,000		1,842,182,000
Stockholders’ equity:
Preferred stock
Common stock	355,000		358,000
Additional paid-in capital	323,622,000		317,155,000
Retained earnings	704,665,000		550,220,000
Accumulated other comprehensive loss – foreign currency translation adjustments	(41,653,000)		(24,264,000)
Total stockholders’ equity	986,989,000		843,469,000	$ 713,443,000	$ 685,742,000
Total liabilities and stockholders' equity	2,775,947,000		$ 2,685,651,000
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	145,184,000
Inventories not available for sale	(118,936,000)
Other current assets	(39,684,000)
Total current assets	(13,436,000)
Other assets	13,762,000
Total assets	326,000
Accounts payable—trade	84,504,000
Accrued expenses and other current liabilities	16,557,000
Deferred revenue	(121,526,000)
Total current liabilities	(20,465,000)
Other liabilities	11,443,000
Total liabilities	(9,022,000)
Stockholders’ equity:
Preferred stock
Retained earnings	9,311,000	$ 7,176,000
Accumulated other comprehensive loss – foreign currency translation adjustments	37,000
Total stockholders’ equity	9,348,000
Total liabilities and stockholders' equity	326,000
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cash and cash equivalents	142,655,000
Accounts receivable, net	1,786,552,000
Inventories	148,503,000
Inventories not available for sale	118,936,000
Other current assets	155,367,000
Total current assets	2,352,013,000
Property and equipment, net	72,954,000
Goodwill	166,841,000
Intangible assets, net	112,179,000
Deferred income taxes	7,967,000
Other assets	63,667,000
Total assets	2,775,621,000
Accounts payable—trade	893,600,000
Accounts payable—inventory financing facility	304,130,000
Accrued expenses and other current liabilities	174,176,000
Current portion of long-term debt	1,395,000
Deferred revenue	183,826,000
Total current liabilities	1,557,127,000
Long-term debt	195,525,000
Deferred income taxes	683,000
Other liabilities	44,645,000
Total liabilities	1,797,980,000
Stockholders’ equity:
Preferred stock
Common stock	355,000
Additional paid-in capital	323,622,000
Retained earnings	695,354,000
Accumulated other comprehensive loss – foreign currency translation adjustments	(41,690,000)
Total stockholders’ equity	977,641,000
Total liabilities and stockholders' equity	$ 2,775,621,000