Long-Term Incentive Employee Compensation Outstanding RSUs, Cash Settled RSUs and PSUs (Detail) - shares shares in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Equity settled RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity and Cash settled shares	0.7	0.7	0.7
Cash settled RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity and Cash settled shares	0.1	0.1	0.1
PSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity and Cash settled shares	0.3	0.5	0.3