Derivative Financial Instruments - Credit-Risk Related Contingent Features (Detail) $ in Millions	Mar. 31, 2016 USD ($)
S&P Long Term Rating A plus [Member]
Credit Derivatives [Line Items]
Total Credit Rating Scenario of Derivatives	$ 35
S&P Long Term Rating A [Member]
Credit Derivatives [Line Items]
Total Credit Rating Scenario of Derivatives	45
Moody's Long Term Rating Aa3 [Member]
Credit Derivatives [Line Items]
Total Credit Rating Scenario of Derivatives	0
Moody's Long Term Rating A1 [Member]
Credit Derivatives [Line Items]
Total Credit Rating Scenario of Derivatives	$ 35