Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Basic and Diluted Earnings:
Net income	$ 19,792	$ 18,610	$ 18,817	$ 20,303	$ 20,203	$ 16,251	$ 57,219	$ 56,757
Basic weighted-average shares outstanding (in shares)	33,773			35,114			33,732	35,066
Add: Stock awards (in shares)	128			174			146	175
Diluted weighted-average shares outstanding (in shares)	33,901			35,288			33,878	35,241
Basic Earnings Per Share:
Earnings per common share - basic (in dollars per share)	$ 0.59			$ 0.58			$ 1.70	$ 1.62
Diluted Earnings Per Share:
Earnings per common share - diluted (in dollars per share)	$ 0.58			$ 0.58			$ 1.69	$ 1.61
Antidilutive securities excluded from calculating earnings
Number of antidilutive options (in shares)	477			497			482	310