Segment, Geographic and Other Revenue Information - Narrative (Detail) $ in Millions		6 Months Ended	12 Months Ended
		Jun. 30, 2019 USD ($) Operating_Segment	Dec. 31, 2018 USD ($) Operating_Segment
Segment Reporting [Abstract]
Number of business segments | Operating_Segment		3	2
Assets | $	[1]	$ 156,199	$ 159,422

[1] Amounts may not add due to rounding.