Segment Information - Schedule of Segment Information for Entity's Continuing Operations (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Net sales		$ 584,937	$ 404,933	$ 1,663,960	$ 1,179,763
Gross profit		82,655	60,143	235,961	161,214
Depreciation and amortization expense	[1]	3,875	3,170	11,922	9,085
Operating profit (loss)		10,700	956	25,584	(3,401)
Commercial [Member]
Segment Reporting Information [Line Items]
Net sales		459,558	336,372	1,288,985	968,942
Gross profit		66,362	51,464	192,209	139,886
Depreciation and amortization expense	[1]	1,630	942	4,873	2,527
Operating profit (loss)		20,779	16,301	59,494	41,880
Public Sector [Member]
Segment Reporting Information [Line Items]
Net sales		89,688	68,572	261,131	210,843
Gross profit		10,271	8,664	25,947	21,317
Depreciation and amortization expense	[1]	287	111	863	219
Operating profit (loss)		4,779	3,772	10,501	9,152
Canada [Member]
Segment Reporting Information [Line Items]
Net sales		35,724		113,890
Gross profit		6,055		17,852
Depreciation and amortization expense	[1]	326		994
Operating profit (loss)		780		3,283
Corporate And Other [Member]
Segment Reporting Information [Line Items]
Net sales		(33)	(11)	(46)	(22)
Gross profit		(33)	15	(47)	11
Depreciation and amortization expense	[1]	1,632	2,117	5,192	6,339
Operating profit (loss)		$ (15,638)	$ (19,117)	$ (47,694)	$ (54,433)

[1] Primary fixed assets relating to network and servers are managed by the Corporate headquarters. As such, depreciation expense relating to such assets is included as part of Corporate & Other.