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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Net Sales:
Net sales	$ 485.0	$ 467.2	$ 976.7	$ 959.2
Segment Performance:
Unusual items	0.0	0.0	(0.3)	0.0
Reconciliation of segment performance to income before income taxes:
Segment performance	71.1	68.0	134.4	107.6
Interest expense	(9.2)	(8.3)	(18.2)	(16.4)
Interest income	4.0	2.0	8.0	3.6
Stock-based compensation	(10.2)	(5.2)	(15.5)	(6.7)
Income before income taxes	59.4	47.3	111.2	66.0
Operating Segments
Net Sales:
Net sales	485.0	467.2	976.7	959.2
Reconciliation of segment performance to income before income taxes:
Segment performance	82.8	67.9	153.0	102.8
Operating Segments | Aerospace and Defense
Net Sales:
Net sales	483.1	465.6	973.1	956.0
Segment Performance:
Operating profit	77.1	69.5	142.0	106.1
Environmental remediation provision adjustments	(0.4)	(1.0)	(0.7)	(2.3)
Retirement benefits, net	5.5	(1.2)	10.9	(2.2)
Unusual items	0.0	0.0	(0.3)	0.0
Reconciliation of segment performance to income before income taxes:
Segment performance	82.2	67.3	151.9	101.6
Operating Segments | Real Estate
Net Sales:
Net sales	1.9	1.6	3.6	3.2
Reconciliation of segment performance to income before income taxes:
Segment performance	0.6	0.6	1.1	1.2
Segment Reconciling Items
Reconciliation of segment performance to income before income taxes:
Interest expense	(9.2)	(8.3)	(18.2)	(16.4)
Interest income	4.0	2.0	8.0	3.6
Stock-based compensation	(10.2)	(5.2)	(15.5)	(6.7)
Corporate, Non-Segment
Segment Performance:
Retirement benefits, net	(1.8)	(3.3)	(3.6)	(6.6)
Reconciliation of segment performance to income before income taxes:
Corporate and other	$ (6.2)	$ (5.8)	$ (12.5)	$ (10.7)