Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended					65 Months Ended
	Aug. 31, 2018	Feb. 28, 2018	Aug. 31, 2017	Mar. 31, 2017	Feb. 28, 2017	Sep. 30, 2018	May 31, 2018
Share repurchase plan
Aggregate purchase price up to which shares can be acquired under share repurchase program	$ 20.0				$ 5.0		$ 5.0
Number of shares purchased and cancelled under the share repurchase program	335,705			216,350
Amount paid for shares purchased and cancelled under share repurchase program	$ 8.5			$ 5.0
Amount paid for shares purchased and cancelled under share repurchase program (per share)	$ 25.26			$ 23.10
LTR Plan
Common Stock
Shares of common stock issued under the long-term incentive plan		71,757			65,429
Amount received in exchange for shares of common stock under a long term incentive plan		$ 1.5			$ 1.1
Percentage of average market closing prices used in determining number of common stock that could be purchased by participants		75.00%			75.00%
Equity Plan
Common Stock
Shares of common stock issued as a part of quarterly compensation of non-employee members of the Board of Directors	10,092	10,062	11,448		11,784
Equity Plan | Restricted Stock Units
Common Stock
Granted, Units						379,912
Accrued dividend equivalent units						4,472