Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Oct. 02, 2017
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 97.5	$ 84.6	$ 96.1	$ 119.0	$ 93.4	$ 90.2	$ 126.7	$ 108.0	$ 397.2	$ 418.3	$ 581.7
Gross margin	39.4	27.2	43.5	46.6	48.2	32.8	102.7	43.1	156.7	226.8	325.8
Net earnings	$ 49.4	$ 22.8	$ 39.5	$ 42.2	$ 44.1	$ 28.8	$ 98.7	$ 37.7	$ 153.9	$ 209.3	$ 306.9
Net earnings per Common Unit (in dollars per unit)	$ 1.44	$ 0.92	$ 1.48	$ 2.10	$ 1.85	$ 1.04	$ 3.22	$ 1.44	$ 5.93	$ 7.56	$ 10.06
Gain on sale of equity method investment									$ (14.3)	$ 0.0	$ 0.0
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Oklahoma CO2 Partnership [Member]
Gain on sale of equity method investment	$ (14.3)
Partnership equity interest (as a percent)												50.00%