Retirement Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
401 (k) Plan [Member]
Defined Contribution Plans [Line Items]
Contribution to plan	$ 2.6	$ 2.5	$ 2.3
SERP [Member]
Defined Contribution Plans [Line Items]
Liability due to participants	$ 2.7	$ 2.7