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
Reconciliation of the component parts of earnings per share [Abstract]
Net income	$ 14,708	$ 14,667	$ 14,558	$ 15,199	$ 15,405	$ 14,808	$ 43,933	$ 45,412
Weighted average common shares (in shares)	96,907			96,555			96,825	96,453
Stock Options (in shares)	70			134			72	134
Weighted average common shares including potential dilutive shares (in shares)	96,977			96,689			96,897	96,587
Basic EPS (in dollars per share)	$ 0.152			$ 0.157			$ 0.454	$ 0.471
Diluted EPS (in dollars per share)	$ 0.152			$ 0.157			$ 0.453	$ 0.470
Stock Options [Member]
Antidilutive Securities [Abstract]
Number of antidilutive stock options excluded from diluted earnings per share (in shares)	0			0			0	0