Reconciliation of Benefit Obligations, Plan Assets, and Unfunded or Funded Status (Parenthetical) (Detail) - Qualified defined benefit pension plans - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Benefits paid	[1]	$ 2,055	$ 2,399
Benefit obligation released			529
Plan amendments related to the salary freeze			$ (4,578)
Estimated remaining service period of covered employees, years			10 years
Acquisition increased qualified defined benefit pension obligation		$ 30
Lump-sum settlement payments
Defined Benefit Plan Disclosure [Line Items]
Benefits paid			$ 427

[1] Benefits paid in 2014 for qualified defined benefit pension plans include $427 million in the form of lump-sum settlement payments to former employees who had not commenced receiving their vested benefit payments. The corresponding benefit obligation that was released was $529 million. The settlement payments had no impact on our 2014 FAS pension expense and CAS pension cost.