Comprehensive Income - Schedule of Changes in Balances of Each Component of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	$ 42	$ (49)
Other comprehensive income before reclassifications	187	(89)
Amounts reclassified from accumulated other comprehensive income	(4)	(17)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(191)	71
Ending Balance	(149)	23
Income Tax Expense (Benefit)	(7)	2
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	151	86
Other comprehensive income before reclassifications	139	(73)
Amounts reclassified from accumulated other comprehensive income	(7)	(17)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(146)	56
Ending Balance	5	142
Accumulated Translation Adjustment [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(116)	(142)
Other comprehensive income before reclassifications	46	(15)
Amounts reclassified from accumulated other comprehensive income	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(46)	15
Ending Balance	(162)	(127)
Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(2)	(2)
Other comprehensive income before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income	3	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	3	0
Ending Balance	2	(2)
Other Postretirement Benefits Plan [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	8	9
Other comprehensive income before reclassifications	2	(1)
Amounts reclassified from accumulated other comprehensive income	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(2)	0
Ending Balance	6	9
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Income Tax Expense (Benefit)	1	(1)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Other Postretirement Benefits Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax	0	0
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from accumulated other comprehensive income	0	0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	0	0
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	0	0
Income Tax Expense (Benefit)	$ 0	$ 0