Debt and Credit Arrangements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Long Term Debt	$ 3,300	$ 3,575
Interest rate of capital securities through April 14, 2017	6.375%
Interest rate on capital securities after April 14, 2017, plus three-month LIBOR rate	2.25%
Consecutive years payment of interest may be deferred on capital securities	10 years
Interest costs incurred	213	224	245
Interest paid	213	220	244
Maximum unsecured borrowings permitted under credit agreement	500	500
Maximum facility amount permitted to request an increase in the credit available	750
6.375% capital securities due March 29, 2067 [Member]
Debt Instrument [Line Items]
Long Term Debt	1,000	1,000
Interest rate of capital securities through April 14, 2017	6.375%
6.8% debentures due November 15, 2031 [Member]
Debt Instrument [Line Items]
Long Term Debt	$ 200	$ 200
Interest rate due on notes and debentures	6.80%