Netting Arrangements for Certain Financial Instruments and Securities Financing Activities - Information on Company's Accounting Netting Adjustments and Items Not Offset in Consolidated Balance Sheet Liabilities But Available for Offset in Event of Default (Parenthetical) (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Offsetting [Abstract]
Cash collateral netted against derivative liabilities	$ 793	$ 641
Derivative liabilities not subject to netting arrangements	$ 1,500	$ 576

Netting Arrangements for Certain Financial Instruments and Securities Financing Activities - Information on Company's Accounting Netting Adjustments and Items Not Offset in Consolidated Balance Sheet Liabilities But Available for Offset in Event of Default (Parenthetical) (Detail) - USD ($)
$ in Millions

Mar. 31, 2016

Dec. 31, 2015

Cash collateral netted against derivative liabilities

$ 793

$ 641

Derivative liabilities not subject to netting arrangements

$ 1,500

$ 576