Operating Segments and Related Disclosures - Schedule of Selected Financial Information for Each Reportable Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Net Sales:
Net sales	$ 467.2	$ 459.6	$ 959.2	$ 864.9
Reconciliation of segment performance to income before income taxes:
Segment performance	68.0	61.5	107.6	95.9
Interest expense	(8.3)	(7.8)	(16.4)	(15.2)
Interest income	2.0	0.8	3.6	1.3
Stock-based compensation expense	(5.2)	(3.4)	(6.7)	(10.2)
Unusual items	0.0	1.3	0.0	0.9
Income before income taxes	47.3	36.2	66.0	45.4
Operating Segments
Net Sales:
Net sales	467.2	459.6	959.2	864.9
Reconciliation of segment performance to income before income taxes:
Segment performance	67.9	57.0	102.8	92.5
Operating Segments | Aerospace and Defense
Net Sales:
Net sales	465.6	458.0	956.0	861.7
Segment Performance:
Operating profit	69.5	58.8	106.1	97.0
Environmental remediation provision adjustments	(1.0)	(0.5)	(2.3)	(1.1)
Retirement benefits, net	(1.2)	(3.4)	(2.2)	(6.9)
Reconciliation of segment performance to income before income taxes:
Segment performance	67.3	56.2	101.6	90.9
Unusual items	0.0	1.3	0.0	1.9
Operating Segments | Real Estate
Net Sales:
Net sales	1.6	1.6	3.2	3.2
Reconciliation of segment performance to income before income taxes:
Segment performance	0.6	0.8	1.2	1.6
Segment Reconciling Items
Reconciliation of segment performance to income before income taxes:
Interest expense	(8.3)	(7.8)	(16.4)	(15.2)
Interest income	2.0	0.8	3.6	1.3
Stock-based compensation expense	(5.2)	(3.4)	(6.7)	(10.2)
Unusual items	0.0	0.0	0.0	(1.0)
Corporate, Non-Segment
Segment Performance:
Retirement benefits, net	(3.3)	(5.0)	(6.6)	(10.0)
Reconciliation of segment performance to income before income taxes:
Corporate and other expense, net	$ (5.8)	$ (5.4)	$ (10.7)	$ (12.0)