Operating Segments and Related Disclosures - Schedule of Selected Financial Information for Each Reportable Segment (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net Sales:
Net sales	$ 492.0	$ 405.3
Reconciliation of segment performance to income before income taxes:
Segment performance	39.6	34.4
Interest expense	(8.1)	(7.4)
Interest income	1.6	0.5
Stock-based compensation expense	(1.5)	(6.8)
Unusual items	0.0	(0.4)
Income before income taxes	18.7	9.2
Operating Segments
Reconciliation of segment performance to income before income taxes:
Segment performance	34.9	35.5
Operating Segments | Aerospace and Defense
Net Sales:
Net sales	490.4	403.7
Segment Performance:
Operating profit	36.6	38.2
Environmental remediation provision adjustments	(1.3)	(0.6)
Retirement benefits, net	(1.0)	(3.5)
Reconciliation of segment performance to income before income taxes:
Segment performance	34.3	34.7
Unusual items	0.0	0.6
Operating Segments | Real Estate
Net Sales:
Net sales	1.6	1.6
Reconciliation of segment performance to income before income taxes:
Segment performance	0.6	0.8
Segment Reconciling Items
Reconciliation of segment performance to income before income taxes:
Interest expense	(8.1)	(7.4)
Interest income	1.6	0.5
Stock-based compensation expense	(1.5)	(6.8)
Unusual items	0.0	(1.0)
Corporate, Non-Segment
Segment Performance:
Retirement benefits, net	(3.3)	(5.0)
Reconciliation of segment performance to income before income taxes:
Corporate and other expense, net	$ (4.9)	$ (6.6)