Segment Information - Schedule of Segment Information for Entity's Continuing Operations (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net sales		$ 564,118	$ 510,580	$ 546,430	$ 542,832	$ 544,770	$ 543,275	$ 556,082	$ 522,760	$ 2,163,960	$ 2,166,887	$ 2,239,557
Gross profit		$ 84,795	$ 85,134	$ 90,417	$ 83,596	$ 79,628	$ 81,457	$ 85,145	$ 78,498	343,942	324,728	318,927
Operating profit (loss)										40,746	10,628	34,901
Commercial [Member]
Segment Reporting Information [Line Items]
Net sales										1,647,431	1,709,249	1,737,830
Gross profit										268,554	261,376	259,228
Depreciation and amortization expense	[1]									5,133	5,683	6,491
Operating profit (loss)										94,516	75,284	81,429
Public Sector [Member]
Segment Reporting Information [Line Items]
Net sales										258,945	274,650	351,617
Gross profit										32,749	33,676	35,946
Depreciation and amortization expense	[1]									527	829	1,162
Operating profit (loss)										9,770	8,885	14,064
Canada [Member]
Segment Reporting Information [Line Items]
Net sales										195,846	171,208	150,193
Gross profit										30,835	28,060	23,838
Depreciation and amortization expense	[1]									1,013	1,090	1,320
Operating profit (loss)										4,580	423	3,994
United Kingdom [Member]
Segment Reporting Information [Line Items]
Net sales										62,359	12,235
Gross profit										12,419	2,064
Depreciation and amortization expense	[1]									297	48
Operating profit (loss)										(1,963)	(5,205)
Corporate & Other [Member]
Segment Reporting Information [Line Items]
Net sales										(621)	(455)	(83)
Gross profit										(615)	(448)	(85)
Depreciation and amortization expense	[1]									6,470	6,531	6,811
Operating profit (loss)										(66,157)	(68,759)	(64,586)
Consolidated [Member]
Segment Reporting Information [Line Items]
Net sales										2,163,960	2,166,887	2,239,557
Gross profit										343,942	324,728	318,927
Depreciation and amortization expense	[1]									13,440	14,181	15,784
Operating profit (loss)										$ 40,746	$ 10,628	$ 34,901

[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.