Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Reconciliation of the component parts of earnings per share [Abstract]
Net income	$ 12,240	$ 10,464	$ 23,187	$ 20,875
Weighted average common shares (in shares)	96,003	95,487	95,944	95,426
Stock Options (in shares)	70	93	90	70
Weighted average common shares including potential dilutive shares (in shares)	96,073	95,580	96,034	95,496
Basic EPS (in dollars per share)	$ 0.127	$ 0.110	$ 0.242	$ 0.219
Diluted EPS (in dollars per share)	$ 0.127	$ 0.109	$ 0.241	$ 0.219
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)	412	1,600	412	1,600