Goodwill and Acquired Intangibles - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Amortization expense for acquired finite lived intangible assets	$ 312	$ 284	$ 68
Amortization of finite lived intangible assets in 2018	296
Amortization of finite lived intangible assets in 2019	285
Amortization of finite lived intangible assets in 2020	263
Amortization of finite lived intangible assets in 2021	256
Amortization of finite lived intangible assets in 2022	253
Amortization of finite lived intangible assets after 2022	$ 1,600
Minimum
Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible assets are amortized	3 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible assets are amortized	20 years
Customer programs | Minimum
Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible assets are amortized	9 years
Customer programs | Maximum
Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible assets are amortized	20 years
Customer relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible assets are amortized	4 years
Customer relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible assets are amortized	10 years
Other | Minimum
Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible assets are amortized	3 years
Other | Maximum
Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible assets are amortized	10 years