Restructuring Charges - Schedule of Resctucturing Charges (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Restructuring Cost and Reserve [Line Items]
Total expected restructuring charges		$ 410		$ 410
Restructuring charges		112	$ 0	363	$ 0
General and Administrative Expense [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges		112		363
Cash Severance [Member]
Restructuring Cost and Reserve [Line Items]
Total expected restructuring charges		154		154
Cash Severance [Member] | General and Administrative Expense [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges		5		151
Retirement Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Total expected restructuring charges	[1]	219		219
Retirement Benefits [Member] | General and Administrative Expense [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	[1]	102		178
Share-based Compensation [Member]
Restructuring Cost and Reserve [Line Items]
Total expected restructuring charges		37		37
Share-based Compensation [Member] | General and Administrative Expense [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges		5		34
Amount to be Recognized in 2017 [Member] | Retirement Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Total expected restructuring charges		$ 17		$ 17

[1] Includes termination benefits, curtailments, and settlements. See Note 13—Pension Plans and Other Postretirement Benefits.