Partners' Capital - Cash Distributions to Unitholders (Details) - USD ($) $ / shares in Units, $ in Millions	May 03, 2018	Jan. 31, 2018	Nov. 02, 2017	Aug. 02, 2017	May 03, 2017
Partners' Capital
Cash distribution declared	$ 16.5	$ 16.3	$ 16.2	$ 15.0	$ 14.6
Cash distribution declared (in dollars per unit)	$ 0.6250	$ 0.6200	$ 0.6150	$ 0.5700	$ 0.5550
Incentive distribution paid	$ 1.3	$ 1.1	$ 1.1	$ 0.7	$ 0.5