Long-Term Incentive Employee Compensation Summary of Stock Options by Exercise Price (Detail) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding Number	1.7	1.9	2.7	4.3
Options Outstanding Weighted-Average Remaining Contractual Life (In Years)	6 years 6 months
Options Outstanding Aggregate Intrinsic Value	$ 18.7
Options Exercisable Number	1.1	1.1	1.5
Options Exercisable Weighted-Average Remaining Contractual Life (In Years)	5 years 8 months
Options Exercisable Aggregate Intrinsic Value	$ 16.8
$12.39 Exercise Price
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding Number	0.1
Options Outstanding Weighted-Average Remaining Contractual Life (In Years)	2 months
Options Outstanding Aggregate Intrinsic Value	$ 0.6
Options Exercisable Number	0.1
Options Exercisable Weighted-Average Remaining Contractual Life (In Years)	2 months
Options Exercisable Aggregate Intrinsic Value	$ 0.6
$19.97 Exercise Price
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding Number	0.1
Options Outstanding Weighted-Average Remaining Contractual Life (In Years)	4 years 2 months
Options Outstanding Aggregate Intrinsic Value	$ 1.3
Options Exercisable Number	0.1
Options Exercisable Weighted-Average Remaining Contractual Life (In Years)	4 years 2 months
Options Exercisable Aggregate Intrinsic Value	$ 1.3
$20.28 Exercise Price
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding Number	0.4
Options Outstanding Weighted-Average Remaining Contractual Life (In Years)	5 years 11 months
Options Outstanding Aggregate Intrinsic Value	$ 7.1
Options Exercisable Number	0.4
Options Exercisable Weighted-Average Remaining Contractual Life (In Years)	5 years 11 months
Options Exercisable Aggregate Intrinsic Value	$ 7.1
$21.53 Exercise Price
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding Number	0.2
Options Outstanding Weighted-Average Remaining Contractual Life (In Years)	5 years 2 months
Options Outstanding Aggregate Intrinsic Value	$ 3.7
Options Exercisable Number	0.2
Options Exercisable Weighted-Average Remaining Contractual Life (In Years)	5 years 2 months
Options Exercisable Aggregate Intrinsic Value	$ 3.7
$22.80 Exercise Price
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding Number	0.3
Options Outstanding Weighted-Average Remaining Contractual Life (In Years)	6 years 2 months
Options Outstanding Aggregate Intrinsic Value	$ 3.6
Options Exercisable Number	0.2
Options Exercisable Weighted-Average Remaining Contractual Life (In Years)	6 years 2 months
Options Exercisable Aggregate Intrinsic Value	$ 3.6
$26.76 Exercise Price
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding Number	0.2
Options Outstanding Weighted-Average Remaining Contractual Life (In Years)	7 years 2 months
Options Outstanding Aggregate Intrinsic Value	$ 2.4
Options Exercisable Number	0.1
Options Exercisable Weighted-Average Remaining Contractual Life (In Years)	7 years 2 months
Options Exercisable Aggregate Intrinsic Value	$ 0.5
$41.52 Exercise Price
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding Number	0.2
Options Outstanding Weighted-Average Remaining Contractual Life (In Years)	9 years 2 months
Options Outstanding Aggregate Intrinsic Value	$ 0.0
$43.52 Exercise Price
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding Number	0.2
Options Outstanding Weighted-Average Remaining Contractual Life (In Years)	8 years 2 months
Options Outstanding Aggregate Intrinsic Value	$ 0.0