Segment Information - Net Sales by Offering for North America, EMEA and APAC (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue from External Customer [Line Items]
Revenues from external customers	$ 1,912,547	$ 1,747,726	$ 5,434,034	$ 5,331,090
North America Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	1,515,162	1,371,459	4,163,110	4,018,605
EMEA Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	355,708	345,180	1,125,057	1,161,850
APAC Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	41,677	31,087	145,867	150,635
Hardware Net Sales [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	1,166,742	1,106,969	3,181,844	3,253,278
Hardware Net Sales [Member] | North America Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	1,020,083	953,431	2,704,212	2,724,916
Hardware Net Sales [Member] | EMEA Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	137,416	147,497	451,892	505,844
Hardware Net Sales [Member] | APAC Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	9,243	6,041	25,740	22,518
Software Net Sales [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	502,138	441,304	1,548,043	1,471,610
Software Net Sales [Member] | North America Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	295,730	259,602	907,683	828,231
Software Net Sales [Member] | EMEA Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	186,839	168,603	560,073	551,920
Software Net Sales [Member] | APAC Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	19,569	13,099	80,287	91,459
Services Net Sales [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	243,667	199,453	704,147	606,202
Services Net Sales [Member] | North America Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	199,349	158,426	551,215	465,458
Services Net Sales [Member] | EMEA Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	31,453	29,080	113,092	104,086
Services Net Sales [Member] | APAC Segment [Member]
Revenue from External Customer [Line Items]
Revenues from external customers	$ 12,865	$ 11,947	$ 39,840	$ 36,658