Earnings per Share - Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share, Basic and Diluted [Abstract]
Net income	$ 18,119	$ 17,662	$ 21,042	$ 50,209
Net income allocated to unvested restricted stock awards	(23)	(58)	(29)	(186)
Net income allocated to common shares	$ 18,096	$ 17,604	$ 21,013	$ 50,023
Weighted average shares outstanding	29,227	29,306	29,233	29,290
Average unvested restricted stock awards	(38)	(95)	(47)	(111)
Denominator for basic earnings per share—weighted-average shares outstanding	29,189	29,211	29,186	29,179
Effect of dilutive securities—employee stock options and restricted stock units	28	74	32	64
Denominator for diluted earnings per share—adjusted weighted-average shares outstanding	29,217	29,285	29,218	29,243
Basic earnings per share	$ 0.62	$ 0.60	$ 0.72	$ 1.71
Diluted earnings per share	$ 0.62	$ 0.60	$ 0.72	$ 1.71
Average antidilutive options and restricted stock units excluded from computation of diluted earnings per share	526	323	509	326