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Accounting Policies - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Significant Accounting Policies [Line Items] |  |  |  |
Cumulative effect of accounting change | $ (5,012) | $ (6,789) | $ (6,269) | $ (4,972)
Operating lease liability | 136 | 159 |  |
Operating lease right-of-use asset | 118 | 139 |  |
Deferred rent and lease incentives | $ 18 | $ 20 |  |
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List] | Other liabilities | Other liabilities |  |
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration] | Other assets | Other assets |  |
Weighted average common shares adjustment related to stock-based compensation | 500,000 | 500,000 | 1,100,000 |
Anti-dilutive potential common shares related to stock-based compensation plans | 0 | 0 | 0 |
Maturities of short term investments | 3 months |  |  |
AOCI attributable to parent |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |
Cumulative effect of accounting change | $ (119) | $ (1,273) | $ (863) | (48)
Retained Earnings |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |
Cumulative effect of accounting change | $ (3,478) | $ (4,149) | (4,009) | $ (3,588)
Cumulative effect, period of adoption, adjustment |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |
Cumulative effect of accounting change |  |  | (7) |
Cumulative effect, period of adoption, adjustment | Retained Earnings |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |
Cumulative effect of accounting change |  |  | (7) |
Accounting Standards Update 2016-13 | Cumulative effect, period of adoption, adjustment | Retained Earnings |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |
Cumulative effect of accounting change |  |  | $ (7) |

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