Gains and Losses Included in Net (Income) from Liabilities Measured at Fair Value (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total realized and unrealized (gains) losses included in net (income) loss, liabilities	$ 62	$ (15)	$ 96	$ (45)
Total (gains) losses included in net (income) loss attributable to liabilities still held, liabilities	63	(16)	100	(42)
Net Investment Income
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total realized and unrealized (gains) losses included in net (income) loss, liabilities	0	0	0	0
Total (gains) losses included in net (income) loss attributable to liabilities still held, liabilities	0	0	0	0
Net Investment (Gains) Losses
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total realized and unrealized (gains) losses included in net (income) loss, liabilities	62	(15)	96	(45)
Total (gains) losses included in net (income) loss attributable to liabilities still held, liabilities	$ 63	$ (16)	$ 100	$ (42)