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Cash and Cash Equivalents - Annual Yield Rates of Bank Deposits, Commercial Paper, Negotiable Certificates of Deposit and Time Deposits and Repurchase Agreements Collateralized by Bonds (Detail) | Dec. 31, 2020 | Dec. 31, 2019
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Bank deposits [Member] | Bottom of range [Member] |  |
Disclosure of cash and cash equivalents [Line Items] |  |
Yield rate | 0.00% | 0.00%
Bank deposits [Member] | Top of Range [Member] |  |
Disclosure of cash and cash equivalents [Line Items] |  |
Yield rate | 0.40% | 0.74%
Commercial paper [Member] | Bottom of range [Member] |  |
Disclosure of cash and cash equivalents [Line Items] |  |
Yield rate | 0.14% | 0.47%
Commercial paper [Member] | Top of Range [Member] |  |
Disclosure of cash and cash equivalents [Line Items] |  |
Yield rate | 0.26% | 0.54%
Negotiable certificates of deposit [Member] | Bottom of range [Member] |  |
Disclosure of cash and cash equivalents [Line Items] |  |
Yield rate | 0.24% | 0.58%
Negotiable certificates of deposit [Member] | Top of Range [Member] |  |
Disclosure of cash and cash equivalents [Line Items] |  |
Yield rate | 0.30% | 0.60%
Time deposits [Member] | Bottom of range [Member] |  |
Disclosure of cash and cash equivalents [Line Items] |  |
Yield rate | 0.10% | 0.09%
Time deposits [Member] | Top of Range [Member] |  |
Disclosure of cash and cash equivalents [Line Items] |  |
Yield rate | 3.60% | 4.40%
Repurchase agreements collateralized by bonds [Member] |  |
Disclosure of cash and cash equivalents [Line Items] |  |
Yield rate |  | 1.90%

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