Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Reconciliation of the component parts of earnings per share [Abstract]
Net income	$ 14,667	$ 14,558	$ 15,405	$ 14,808	$ 29,225	$ 30,213
Weighted average common shares (in shares)	96,822		96,449		96,784	96,401
Stock Options (in shares)	69		131		73	134
Weighted average common shares including potential dilutive shares (in shares)	96,891		96,580		96,857	96,535
Basic EPS (in dollars per share)	$ 0.152		$ 0.160		$ 0.302	$ 0.313
Diluted EPS (in dollars per share)	$ 0.151		$ 0.160		$ 0.302	$ 0.313
Stock Options [Member]
Antidilutive Securities [Abstract]
Antidilutive stock options excluded from diluted earnings per share (in shares)	0		0		0	0