Segment Information - Net Sales by Offering for North America, EMEA and APAC (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue from External Customer [Line Items]
Revenues from external customers	$ 1,936,478	$ 1,912,547	$ 6,049,264	$ 5,434,034
North America Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	1,558,168	1,515,162	4,771,696	4,163,110
EMEA Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	341,280	355,708	1,152,183	1,125,057
APAC Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	37,030	41,677	125,385	145,867
Hardware Net Sales [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	1,173,151	1,166,742	3,668,411	3,181,844
Hardware Net Sales [Member] | North America Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	1,028,045	1,020,083	3,180,501	2,704,212
Hardware Net Sales [Member] | EMEA Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	138,685	137,416	466,909	451,892
Hardware Net Sales [Member] | APAC Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	6,421	9,243	21,001	25,740
Software Net Sales [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	488,417	502,138	1,514,406	1,548,043
Software Net Sales [Member] | North America Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	306,925	295,730	898,290	907,683
Software Net Sales [Member] | EMEA Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	165,301	186,839	553,164	560,073
Software Net Sales [Member] | APAC Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	16,191	19,569	62,952	80,287
Services Net Sales [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	274,910	243,667	866,447	704,147
Services Net Sales [Member] | North America Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	223,198	199,349	692,905	551,215
Services Net Sales [Member] | EMEA Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	37,294	31,453	132,110	113,092
Services Net Sales [Member] | APAC Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	$ 14,418	$ 12,865	$ 41,432	$ 39,840