Non-Qualified Retirement, Savings and Investment Plans (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) plan shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($)
Compensation and Retirement Disclosure [Abstract]
Number of non-qualified retirement savings and investment plans | plan	2
Deferred compensation liability, current and long-term	$ 24.7	$ 23.0
Number of Deferred Compensation Plans | plan	2
Increase (decrease) in compensation expense	$ 2.1	(0.2)	$ 0.1
Deferred compensation plan assets	19.1	17.8
Restricted investments, current	2.2
Investment gains (losses)	$ 1.5	$ (0.5)	$ (0.4)
Deferred Compensation Arrangement with Individual, Shares Issued | shares	0	0