Employee Benefit Plans (Fair Values of the Company's Pension Plan Assets by Asset Category) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Total	$ 4,839	$ 4,701
Equity Securities | U.S. | US Large Cap
Fair values of pension plan assets	278	384
Equity Securities | U.S. | US Small Cap
Fair values of pension plan assets	112	172
Equity Securities | U.S. | Treasury Stock
Fair values of pension plan assets	102	85
Equity Securities | Developed Markets | Developed Markets
Fair values of pension plan assets	795	812
Debt Securities | Cash and cash equivalents
Fair values of pension plan assets	40	115
Debt Securities | Corporate | Developed Markets
Fair values of pension plan assets	232	200
Debt Securities | Corporate | United States
Fair values of pension plan assets	1,245	881
Debt Securities | Diversified
Fair values of pension plan assets	477	698
Debt Securities | Government | Developed Markets
Fair values of pension plan assets	504	331
Debt Securities | Government | United States
Fair values of pension plan assets	265	237
Debt Securities | Other Debt Securities
Fair values of pension plan assets	175	188
Real Estate And Other
Fair values of pension plan assets	614	598
Level 1
Total	432	309
Level 1 | Equity Securities | U.S. | US Large Cap
Fair values of pension plan assets	0	6
Level 1 | Equity Securities | U.S. | US Small Cap
Fair values of pension plan assets	0	0
Level 1 | Equity Securities | U.S. | Treasury Stock
Fair values of pension plan assets	102	85
Level 1 | Equity Securities | Developed Markets | Developed Markets
Fair values of pension plan assets	107	17
Level 1 | Debt Securities | Cash and cash equivalents
Fair values of pension plan assets	0	0
Level 1 | Debt Securities | Corporate | Developed Markets
Fair values of pension plan assets	0	0
Level 1 | Debt Securities | Corporate | United States
Fair values of pension plan assets	0	0
Level 1 | Debt Securities | Diversified
Fair values of pension plan assets	0
Level 1 | Debt Securities | Government | Developed Markets
Fair values of pension plan assets	0	0
Level 1 | Debt Securities | Government | United States
Fair values of pension plan assets	223	201
Level 1 | Debt Securities | Other Debt Securities
Fair values of pension plan assets	0	0
Level 1 | Real Estate And Other
Fair values of pension plan assets	0	0
Level 2
Total	3,795	3,760
Level 2 | Equity Securities | U.S. | US Large Cap
Fair values of pension plan assets	278	378
Level 2 | Equity Securities | U.S. | US Small Cap
Fair values of pension plan assets	112	172
Level 2 | Equity Securities | U.S. | Treasury Stock
Fair values of pension plan assets	0
Level 2 | Equity Securities | Developed Markets | Developed Markets
Fair values of pension plan assets	688	795
Level 2 | Debt Securities | Cash and cash equivalents
Fair values of pension plan assets	40	115
Level 2 | Debt Securities | Corporate | Developed Markets
Fair values of pension plan assets	232	200
Level 2 | Debt Securities | Corporate | United States
Fair values of pension plan assets	1,121	750
Level 2 | Debt Securities | Diversified
Fair values of pension plan assets	477	698
Level 2 | Debt Securities | Government | Developed Markets
Fair values of pension plan assets	504	331
Level 2 | Debt Securities | Government | United States
Fair values of pension plan assets	42	36
Level 2 | Debt Securities | Other Debt Securities
Fair values of pension plan assets	153	161
Level 2 | Real Estate And Other
Fair values of pension plan assets	148	124
Level 3
Fair values of pension plan assets	612	632	519
Total	612	632
Level 3 | Equity Securities | U.S. | US Large Cap
Fair values of pension plan assets	0
Level 3 | Equity Securities | U.S. | US Small Cap
Fair values of pension plan assets	0
Level 3 | Equity Securities | U.S. | Treasury Stock
Fair values of pension plan assets	0
Level 3 | Equity Securities | Developed Markets | Developed Markets
Fair values of pension plan assets	0
Level 3 | Debt Securities | Cash and cash equivalents
Fair values of pension plan assets	0
Level 3 | Debt Securities | Corporate | Developed Markets
Fair values of pension plan assets	0
Level 3 | Debt Securities | Corporate | United States
Fair values of pension plan assets	124	131
Level 3 | Debt Securities | Diversified
Fair values of pension plan assets	0
Level 3 | Debt Securities | Government | Developed Markets
Fair values of pension plan assets	0
Level 3 | Debt Securities | Government | United States
Fair values of pension plan assets	0
Level 3 | Debt Securities | Other Debt Securities
Fair values of pension plan assets	22	27
Level 3 | Real Estate And Other
Fair values of pension plan assets	$ 466	$ 474