Share-Based Compensation - Summary of Equity Awards Authorized and Available for Future Grant and Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant [Roll Forward]
Newly authorized options (in shares)	0
Cancellation and forfeitures (in shares)	0
Plan termination (in shares)	0
Total compensation expense	$ 38	$ 28	$ 33
Income tax benefit	11	$ 9	$ 11
Unearned compensation costs related to awards granted	$ 50
Unearned compensation cost, expected to be recognized over period (years)	2 years 2 months 12 days
Maximum
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant [Roll Forward]
Unearned compensation cost, expected to be recognized over period (years)	4 years
Two Thousand Fifteen Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant [Roll Forward]
Available for future grants, beginning (in shares)	2,164,297
Equity awards granted (in shares)	(726,862)
Available for future grants, ending (in shares)	1,437,435	2,164,297
SARs
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant [Roll Forward]
Income tax benefit	$ 3	$ 1
RSA
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant [Roll Forward]
Equity awards granted (in shares)	(12,488)	(25,088)	(9,194)
Other Award Types
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares that became available under the Plan	45,781	95,210	11,618
Date Of Grant | Two Thousand Fifteen Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares that became available under the Plan	4,000,000.0