Balance Sheet Accounts - Narrative (Details) shares in Millions, $ in Millions	1 Months Ended		3 Months Ended		12 Months Ended
	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014	Mar. 31, 2016 USD ($) action shares	Feb. 28, 2015 USD ($)	Nov. 30, 2014 USD ($) shares	Nov. 30, 2015 USD ($) shares
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Current and noncurrent Rocketdyne Business integration costs	$ 33.1		$ 30.6			$ 34.3
Savings to restructuring cost ratio		2
Number of actions to be completed | action			2
Redeemable common stock, shares outstanding, less than (in shares) | shares	0.1		0.1			0.1
Realized gains (losses) and interest	$ 0.4		$ (0.1)	$ (0.7)
Number of common shares repurchased (in shares) | shares					3.5
Purchase of treasury stock					$ 64.5