Fair Value Measurements - Schedule of Reconciliation of Level 3 Investments Securities (Parenthetical) (Detail) $ in Millions |
Sep. 30, 2017
USD ($)
Security
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Dec. 31, 2016
USD ($)
Security
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|---|---|---|
| Fair Value Disclosures [Abstract] | ||
| Investment grade rated debt held for more than 12 months | $ 10 | $ 10 |
| Securities in unrealized loss position | $ 1 | $ 1 |
| Securities in unrealized loss position | Security | 0 | 0 |
| X | ||||||||||
- Definition Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
- Definition This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for twelve months or longer. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
- Definition Number of investment positions in available-for-sale investments in a continuous unrealized loss position for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
- References No definition available.
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