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Comprehensive Income - Schedule of Changes in Balances of Each Component of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | ---
Jun. 30, 2020 | Jun. 30, 2019 | Jun. 30, 2020 | Jun. 30, 2019 | Dec. 31, 2019 | Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |
Accumulated Other Comprehensive Income (Loss), Restated |  |  |  |  | $ 42 | $ (49)
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets |  |  |  |  | 0 | 0
Changes In Accumulated Other Comprehensive Income [Roll Forward] |  |  |  |  |  |
Beginning Balance | $ (149) | $ 23 | $ 42 | $ (49) |  |
Other comprehensive income before reclassifications | (111) | (33) | 75 | (121) |  |
Amounts reclassified from accumulated other comprehensive income | (11) | (36) | (15) | (53) |  |
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent | 100 | (3) | (90) | 68 |  |
Ending Balance | (48) | 19 | (48) | 19 |  |
Income Tax Expense (Benefit) | 2 | 28 | (4) | 30 |  |
Unrealized Gains (Losses) on Available-for-Sale Securities [Member] |  |  |  |  |  |
Changes In Accumulated Other Comprehensive Income [Roll Forward] |  |  |  |  |  |
Beginning Balance | 5 | 142 | 151 | 86 |  |
Other comprehensive income before reclassifications | (114) | (51) | 25 | (124) |  |
Amounts reclassified from accumulated other comprehensive income | (10) | (36) | (17) | (53) |  |
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent | 104 | 15 | (42) | 71 |  |
Ending Balance | 109 | 157 | 109 | 157 |  |
Accumulated Translation Adjustment [Member] |  |  |  |  |  |
Changes In Accumulated Other Comprehensive Income [Roll Forward] |  |  |  |  |  |
Beginning Balance | (162) | (127) | (116) | (142) |  |
Other comprehensive income before reclassifications | 2 | 19 | 48 | 4 |  |
Amounts reclassified from accumulated other comprehensive income | 0 | 0 | 0 | 0 |  |
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent | (2) | (19) | (48) | (4) |  |
Ending Balance | (164) | (145) | (164) | (145) |  |
Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member] |  |  |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets |  |  |  |  | $ 0 | $ 0
Changes In Accumulated Other Comprehensive Income [Roll Forward] |  |  |  |  |  |
Beginning Balance | 2 | (2) | (2) | (2) |  |
Other comprehensive income before reclassifications | 0 | 0 | 0 | 0 |  |
Amounts reclassified from accumulated other comprehensive income | (1) | 0 | 2 | 0 |  |
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent | (1) | 0 | 2 | 0 |  |
Ending Balance | 0 | (2) | 0 | (2) |  |
Other Postretirement Benefits Plan [Member] |  |  |  |  |  |
Changes In Accumulated Other Comprehensive Income [Roll Forward] |  |  |  |  |  |
Beginning Balance | 6 | 9 | 8 | 9 |  |
Other comprehensive income before reclassifications | 0 | 0 | 2 | (1) |  |
Amounts reclassified from accumulated other comprehensive income | 0 | 0 | 0 | (1) |  |
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent | 0 | 0 | (2) | 0 |  |
Ending Balance | 6 | 9 | 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 | 5 | 1 | 5 |  |
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member] |  |  |  |  |  |
Changes In Accumulated Other Comprehensive Income [Roll Forward] |  |  |  |  |  |
Income Tax Expense (Benefit) |  |  | 0 |  |  |
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 | 0 | 0 |  |
Changes In Accumulated Other Comprehensive Income [Roll Forward] |  |  |  |  |  |
Amounts reclassified from accumulated other comprehensive income | 0 | 0 | 0 | (1) |  |
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax | 0 | 0 | 0 | 0 |  |
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest | 0 | 0 | 0 | (1) |  |
Income Tax Expense (Benefit) | $ 0 | $ 0 | $ 0 | $ 0 |  |

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