Segment Reporting - Core Earnings Adjustments to GAAP (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Adjustments Required To Reconcile Core Earnings [Line Items]
Net income (loss)	$ 153	$ 83	$ 281	$ 210
Net tax effect	(41)	(30)	(78)	(64)
Operating Segments [Member]
Adjustments Required To Reconcile Core Earnings [Line Items]
Net income (loss)	175	131	312	238
Net tax effect	(53)	(39)	(93)	(72)
Total Adjustments [Member] | Adjustments [Member]
Adjustments Required To Reconcile Core Earnings [Line Items]
Net income (loss)	(22)	(48)	(31)	(28)
Core Earnings adjustments to GAAP	(34)	(57)	(46)	(36)
Net tax effect	12	9	15	8
Net Impact of Derivative Accounting [Member] | Total Adjustments [Member] | Adjustments [Member]
Adjustments Required To Reconcile Core Earnings [Line Items]
Core Earnings adjustments to GAAP	(23)	(51)	(28)	(20)
Net Impact of Goodwill and Acquired Intangible Assets [Member] | Total Adjustments [Member] | Adjustments [Member]
Adjustments Required To Reconcile Core Earnings [Line Items]
Core Earnings adjustments to GAAP	$ (11)	$ (6)	$ (18)	$ (16)