Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Oct. 01, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenue	$ 485.8	$ 446.6	$ 464.6	$ 410.3	$ 474.7	$ 446.0	$ 452.2	$ 397.2	$ 1,807.3	$ 1,770.1	$ 1,590.2
Retained earnings	599.5				531.0				599.5	531.0		$ 531.2
Receivables from long-term manufacturing contracts	181.1				120.3				181.1	120.3		122.2
Inventories	176.6				172.5				176.6	172.5		170.9
Deferred income taxes	73.6				76.4				73.6	76.4		76.5
Cost of Goods and Services Sold									1,184.3	1,128.0	999.4
Gross profit	166.7	$ 148.4	$ 160.9	$ 147.0	163.8	$ 163.5	$ 168.6	$ 146.2	623.0	642.1	590.8
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest									176.7	146.5	188.3
Consolidated net income									126.2	81.2	$ 128.4
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenue									1,807.3
Retained earnings	599.3				531.0				599.3	531.0
Receivables from long-term manufacturing contracts	179.2				120.3				179.2	120.3
Inventories	178.3				172.5				178.3	172.5
Deferred income taxes	73.6				$ 76.4				73.6	$ 76.4
Cost of Goods and Services Sold									1,184.3
Gross profit									623.0
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest									176.7
Consolidated net income									126.2
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenue									0.0
Retained earnings	(0.2)								(0.2)			0.2
Receivables from long-term manufacturing contracts	(1.9)								(1.9)			1.9
Inventories	1.7								1.7			(1.6)
Deferred income taxes	$ 0.0								0.0			$ 0.1
Cost of Goods and Services Sold									0.0
Gross profit									0.0
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest									0.0
Consolidated net income									$ 0.0