Schedule I - Condensed Statements of Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Income Statements, Captions [Line Items]
Net income	$ 1,084	$ 89	$ 79	$ 76	$ (175)	$ 104	$ 92	$ 109	$ 1,328	$ 130	$ 388
Comprehensive income (loss) adjustments:
Unrealized gains (losses) on derivative instruments, net of income tax expense (benefit) of $1, $3 and ($4)									4	(7)	(9)
Defined benefit plan adjustments, net of income tax expense of $3, $11 and $—									5	23
Foreign currency translation, net of income tax benefit of ($201), ($9) and ($5)									614	(513)	(60)
Reclassification adjustments:
Losses on derivative instruments included in net income, net of income tax expense of $—, $7 and $6									(1)	21	12
Amortization of actuarial losses and prior service costs included in net income									1	1	1
Comprehensive income (loss) attributable to IQVIA Holdings Inc.									1,925	(344)	335
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Net income									1,309	115	387
Comprehensive income (loss) adjustments:
Unrealized gains (losses) on derivative instruments, net of income tax expense (benefit) of $1, $3 and ($4)									4	(7)	(9)
Defined benefit plan adjustments, net of income tax expense of $3, $11 and $—									5	23
Foreign currency translation, net of income tax benefit of ($201), ($9) and ($5)									607	(497)	(56)
Reclassification adjustments:
Losses on derivative instruments included in net income, net of income tax expense of $—, $7 and $6									(1)	21	12
Amortization of actuarial losses and prior service costs included in net income									1	1	1
Comprehensive income (loss) attributable to IQVIA Holdings Inc.									$ 1,925	$ (344)	$ 335