Derivative Financial Instruments - Information about Interest Rate Swap Agreements (Detail) - Fixed Rate Long-Term Borrowings [Member] - Fair Value Hedges [Member] - USD ($)	9 Months Ended	12 Months Ended
Sep. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Notional Amount	$ 1,400,000,000	$ 1,400,000,000
Average Maturity (in years)	1 year 10 months 24 days	2 years 8 months 12 days
Weighted-Average Rate, Fixed	4.42%	4.42%
Weighted-Average Rate, Variable	1.29%	1.19%

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

+ Details

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- Definition

Average fixed interest rate related to the group of interest rate derivatives.

+ References

No definition available.

+ Details

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- Definition

Average remaining period until maturity of the derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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- Definition

Average variable interest rate related to the group of interest rate derivatives.

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Details

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- Details

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