Segment Information - Summary of Revenue Disaggregated by Reportable Operating Segments (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Disaggregation of Revenue	$ 2,193,068	$ 2,144,051
Hardware Net Sales [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	1,315,025	1,311,201
Software Net Sales [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	577,995	537,115
Services Net Sales [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	300,048	295,735
Gross Revenue Recognition (Principal) [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	2,073,481	2,038,527
Net Revenue Recognition (Agent) [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	119,587	105,524
North America Segment [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	1,654,781	1,674,381
North America Segment [Member] | Hardware Net Sales [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	1,109,489	1,128,486
North America Segment [Member] | Software Net Sales [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	308,738	305,163
North America Segment [Member] | Services Net Sales [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	236,554	240,732
North America Segment [Member] | Gross Revenue Recognition (Principal) [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	1,569,641	1,600,514
North America Segment [Member] | Net Revenue Recognition (Agent) [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	85,140	73,867
EMEA Segment [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	478,836	418,886
EMEA Segment [Member] | Hardware Net Sales [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	195,971	174,969
EMEA Segment [Member] | Software Net Sales [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	234,423	201,082
EMEA Segment [Member] | Services Net Sales [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	48,442	42,835
EMEA Segment [Member] | Gross Revenue Recognition (Principal) [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	450,977	392,259
EMEA Segment [Member] | Net Revenue Recognition (Agent) [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	27,859	26,627
APAC Segment [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	59,451	50,784
APAC Segment [Member] | Hardware Net Sales [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	9,565	7,746
APAC Segment [Member] | Software Net Sales [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	34,834	30,870
APAC Segment [Member] | Services Net Sales [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	15,052	12,168
APAC Segment [Member] | Gross Revenue Recognition (Principal) [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	52,863	45,754
APAC Segment [Member] | Net Revenue Recognition (Agent) [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	6,588	5,030
Large Enterprise / Corporate [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	1,499,579	1,466,061
Large Enterprise / Corporate [Member] | North America Segment [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	1,171,428	1,160,748
Large Enterprise / Corporate [Member] | EMEA Segment [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	309,075	292,288
Large Enterprise / Corporate [Member] | APAC Segment [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	19,076	13,025
Commercial [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	377,245	417,472
Commercial [Member] | North America Segment [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	344,045	386,076
Commercial [Member] | EMEA Segment [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	20,533	17,742
Commercial [Member] | APAC Segment [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	12,667	13,654
Public Sector [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	316,244	260,518
Public Sector [Member] | North America Segment [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	139,308	127,557
Public Sector [Member] | EMEA Segment [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	149,228	108,856
Public Sector [Member] | APAC Segment [Member]
Segment Reporting Information [Line Items]
Disaggregation of Revenue	$ 27,708	$ 24,105