Retirement Plans - Rate and standard deviation assumptions - (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pension:
Employee savings plan/ 401(K) plan	$ 1.8	$ 1.4	$ 3.4	$ 2.8