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Capital Stock - Summary of Normal Course Issuer Bids (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020
Schedule Of Share Repurchase Programs [Line Items] |  |
Shares purchased | 5,992,323 | 5,077,882
Cash amount | $ 517 | $ 203
2019 Bid [Member] |  |
Schedule Of Share Repurchase Programs [Line Items] |  |
Shares purchased | 0 | 5,077,882
Cash amount | $ 0 | $ 203
2020 Bid [Member] |  |
Schedule Of Share Repurchase Programs [Line Items] |  |
Shares purchased | 3,318,523 | 0
Cash amount | $ 301 | $ 0
2021 Bid [Member] |  |
Schedule Of Share Repurchase Programs [Line Items] |  |
Shares purchased | 2,673,800 | 0
Cash amount | $ 216 | $ 0

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