Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Reconciliation of the component parts of earnings per share [Abstract]
Net income	$ 12,596	$ 10,930	$ 35,783	$ 31,803
Weighted average common shares (in shares)	96,102	95,603	95,997	95,486
Stock Options (in shares)	103	119	94	86
Weighted average common shares including potential dilutive shares (in shares)	96,205	95,722	96,091	95,572
Basic EPS (in dollars per share)	$ 0.131	$ 0.114	$ 0.373	$ 0.333
Diluted EPS (in dollars per share)	$ 0.131	$ 0.114	$ 0.372	$ 0.333
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of antidilutive stock options excluded from diluted earnings per share (in shares)	995	1,600	1,400	1,600