Capital Structure (Details) - Common Stock - USD ($) $ in Millions			1 Months Ended			12 Months Ended
	Oct. 24, 2014	Mar. 25, 2014	Nov. 30, 2018	Dec. 31, 2016	Oct. 31, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Feb. 21, 2014
Class of Stock [Line Items]
Repurchase program, authorized amount	$ 40.0	$ 20.0	$ 75.0		$ 50.0	$ 0.0			$ 10.0
Share repurchase program, increase in shares authorized	$ 20.0	$ 10.0	$ 15.0	$ 10.0	$ 10.0
Repurchases of common stock, shares						440,286	27,599	905,403
Stock repurchased during period, value						$ 4.1