Long-Term Incentive Plan and Unit Appreciation Right Activity (Parenthetical) (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Restricted phantom units | 2014 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Long-Term incentive plan, fair value per unit	$ 23.95	$ 29.52	$ 24.60	$ 29.11
Common vested unit awards the period, intrinsic values	$ 0.1	$ 0.1	$ 0.2	$ 0.1
Common unit awards outstanding, intrinsic values	$ 2.8		$ 2.8
Restricted phantom units | 2004 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Long-Term incentive plan, fair value per unit	$ 23.52	$ 30.04	$ 24.80	$ 29.02
Common vested unit awards the period, intrinsic values	$ 0.1	$ 0.1	$ 0.2	$ 0.2
Common unit awards outstanding, intrinsic values	4.9		4.9
Unit appreciation rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common unit awards outstanding, intrinsic values	$ 0.1		$ 0.1
Common unit awards outstanding, weighted average remaining contractual life			2 years 1 month 6 days