Operating Segments and Related Disclosures - Schedule of Selected Financial Information for Each Reportable Segment (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net Sales:
Net sales	$ 476.1	$ 491.7
Segment Performance:
Unusual items	0.0	(0.3)
Reconciliation of segment performance to income before income taxes:
Segment performance	57.1	63.3
Interest expense	(8.4)	(9.0)
Interest income	3.2	4.0
Stock-based compensation	(2.4)	(5.3)
Income before income taxes	42.7	51.8
Operating Segments
Net Sales:
Net sales	476.1	491.7
Reconciliation of segment performance to income before income taxes:
Segment performance	57.2	70.2
Operating Segments | Aerospace and Defense
Net Sales:
Net sales	474.4	490.0
Segment Performance:
Operating profit	52.6	64.9
Environmental remediation provision adjustments	0.5	(0.3)
Retirement benefits, net	4.7	5.4
Unusual items	0.0	(0.3)
Reconciliation of segment performance to income before income taxes:
Segment performance	57.8	69.7
Operating Segments | Real Estate
Net Sales:
Net sales	1.7	1.7
Reconciliation of segment performance to income before income taxes:
Segment performance	(0.6)	0.5
Segment Reconciling Items
Reconciliation of segment performance to income before income taxes:
Interest expense	(8.4)	(9.0)
Interest income	3.2	4.0
Stock-based compensation	(2.4)	(5.3)
Corporate, Non-Segment
Segment Performance:
Retirement benefits, net	(2.0)	(1.8)
Reconciliation of segment performance to income before income taxes:
Corporate and other	$ (4.9)	$ (6.3)