Stockholders' Equity (Details) - USD ($)	1 Months Ended	3 Months Ended
	May 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	May 31, 2015	May 31, 2014
Stockholders' equity
Common stock, outstanding shares (in shares)		16,787,202		16,771,000
2016 Stock Purchase Plan
Stockholders' equity
Period over which repurchases allowed under the plan	12 months
Common stock purchased under the stock purchase plan (in shares)		85,354	0
Cost of shares of common stock acquired		$ 6,800,000	$ 0
2016 Stock Purchase Plan | Maximum
Stockholders' equity
Authorized amount of repurchase under the stock purchase plan (up to)	$ 25,000,000
2015 Stock Purchase Plan
Stockholders' equity
Common stock purchased under the stock purchase plan (in shares)		0	93,600
Cost of shares of common stock acquired		$ 0	$ 5,200,000
2015 Stock Purchase Plan | Maximum
Stockholders' equity
Authorized amount of repurchase under the stock purchase plan (up to)					$ 25,000,000
Stock Purchase 2014 Plan
Stockholders' equity
Authorized amount of repurchase under the stock purchase plan (up to)						$ 25,000,000