Amounts Recognized for Pension and Postretirement Benefits in Other Comprehensive Income (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Compensation and Retirement Disclosure [Abstract]
Amortization of prior service cost included in net periodic pension and postretirement cost, Before-tax amount	$ 0	$ (1)
Amortization of actuarial loss included in net periodic pension and postretirement cost, Before-tax amount	4	6
Other comprehensive income - pension benefits, Before-tax amount	4	5
Amortization of prior service cost included in net periodic pension and postretirement cost, Tax Benefit	0	0
Amortization of actuarial loss included in net periodic pension and postretirement cost, Tax Benefit	(1)	(1)
Other comprehensive - pension benefits, Tax Benefit	(1)	(1)
Amortization of prior service cost included in net periodic pension and postretirement cost, Net-of-tax Amount	0	(1)
Amortization of actuarial loss included in net periodic pension and postretirement cost, Net-of-tax Amount	3	5
Other comprehensive income - pension benefits, Net-of-tax Amount	$ 3	$ 4