Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended				12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock Repurchase Program
Total Shares Repurchased					500,000	500,000	400,000
Shares Repurchased Under Board Authorization					286,696	885,285	1,336,132
Total cost (in dollars)					$ 5.8	$ 16.9	$ 22.1
Average share price (in dollars per share)					$ 20.28	$ 19.13	$ 16.55
Shares withheld for net settlements of share-based awards, shares					504,037	531,346	391,195
Dividend Program
Dividend declared (in dollars per share)	$ 0.07	$ 0.07	$ 0.07	$ 0.07
Dividend paid (in dollars per share)	$ 0.07	$ 0.07	$ 0.07	$ 0.07
Aggregate cash dividends					$ 9.2
Aggregate stock dividends					$ 0.1
October 2014
Stock Repurchase Program
Number of shares authorized to repurchase by Board (in shares)	4,000,000				4,000,000
Total Shares Repurchased					3,700,000
Shares remaining under Board Authorization	300,000				300,000
Shares Repurchased Under Board Authorization					300,000	900,000	1,300,000
February 2018
Stock Repurchase Program
Number of shares authorized to repurchase by Board (in shares)	4,000,000				4,000,000
Shares remaining under Board Authorization	4,000,000				4,000,000