Derivative Financial Instruments - Credit-Risk Related Contingent Features (Detail) $ in Millions	Jun. 30, 2015 USD ($)
S&P Long Term Ratings A [Member]
Credit Derivatives [Line Items]
Total Credit Rating Scenario of Derivatives	$ 59
S&P Long Term Ratings A [Member]
Credit Derivatives [Line Items]
Total Credit Rating Scenario of Derivatives	97
Moody's Long Term Ratings A2 [Member]
Credit Derivatives [Line Items]
Total Credit Rating Scenario of Derivatives	0
Moody's Long Term Ratings A3 [Member]
Credit Derivatives [Line Items]
Total Credit Rating Scenario of Derivatives	$ 59