Schedule of Net Periodic Benefit Costs (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Qualified defined benefit pension plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	[1]	$ 875	$ 903	$ 1,142
Interest cost	[1]	1,791	1,912	1,800
Expected return on plan assets	[1]	(2,734)	(2,693)	(2,485)
Recognized net actuarial losses	[1]	1,599	1,173	1,410
Amortization of net prior service (credit) cost	[1]	(389)	(151)	81
Total net periodic benefit cost	[1],[2]	1,142	1,144	1,948
Retiree medical and life insurance plans
Defined Benefit Plan Disclosure [Line Items]
Service cost		21	22	27
Interest cost		110	123	116
Expected return on plan assets		(147)	(146)	(145)
Recognized net actuarial losses		43	23	44
Amortization of net prior service (credit) cost		4	4	(17)
Total net periodic benefit cost		$ 31	$ 26	$ 25

[1] Total net periodic benefit cost associated with our qualified defined benefit plans represents pension expense calculated in accordance with GAAP (FAS pension expense). We are required to calculate pension expense in accordance with both GAAP and CAS rules, each of which results in a different calculated amount of pension expense. The CAS pension cost is recovered through the pricing of our products and services on U.S. Government contracts and, therefore, is recognized in net sales and cost of sales for products and services. We include the difference between FAS pension expense and CAS pension cost, referred to as the FAS/CAS pension adjustment, as a component of other unallocated, net on our Statements of Earnings. The FAS/CAS pension adjustment, which was income of $471 million in 2015; income of $376 million in 2014; and expense of $482 million in 2013, effectively adjusts the amount of CAS pension cost in the business segment operating profit so that pension expense recorded on our Statements of Earnings is equal to FAS pension expense.

[2] FAS pension expense in 2015 and 2014 was less than in 2013 primarily due to the June 2014 plan amendments to certain of our defined benefit pension plans to freeze future retirement benefits, partially offset by the impact of using new longevity assumptions (Note 11).