Share Repurchases Transactions and Other Comprehensive Loss - Components of Accumulated Other Comprehensive Loss (Parenthetical) (Detail) $ in Millions	9 Months Ended
Sep. 30, 2018 USD ($)
Equity [Abstract]
Unrealized losses on available-for-sale securities, tax benefit portion	$ 1
Defined benefit plans, Expense (income) reclassified into operations from other comprehensive income, Income tax benefit	3
Defined benefit plans, Expense (income) reclassified into operations from other comprehensive income, net of Income taxes	1
Change in fair value of derivative instruments, change in fair value of derivative instruments, income taxes	$ 4

Other Comprehensive Income Loss Reclassification Adjustment Net Of Tax

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- Definition

Amount of tax (expense) benefit for reclassification adjustment from accumulated other comprehensive (income) loss of defined benefit plan.

+ References

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Amount of tax expense (benefit), before reclassification adjustments, related to increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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Amount of tax expense (benefit) before reclassification adjustments of unrealized holding gain (loss) on available-for-sale securities.

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