Pension and Other Postretirement Benefits - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Employer matching contribution (percent)	6.00%
Defined contribution plan expense	$ 4	$ 5	$ 6
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension expense	21	17	18
Supplemental Employee Retirement Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	38	43
Pension expense	7	5	7
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension expense	$ (7)	2	7
Decrease in postemployment benefit liability		(46)
Amortization period of change in postemployement obligation	7 years
Expected pension benefits in 2017	$ 9
Funded status of postretirement benefit plans	$ 91	100	173
Health care cost trend rate assumed, participants under 65	6.90%
Health care cost trend rate assumed, participants over 65	8.30%
Ultimate health care cost trend rate	4.50%
Year that rate reaches ultimate trend rate	2027
Gain from curtailment	$ (5)	$ 0	$ 0