Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reconciliation of the component parts of earnings per share [Abstract]
Net income	$ 10,464	$ 10,727	$ 20,875	$ 21,442
Weighted average common shares (in shares)	95,487	95,056	95,426	95,002
Stock Options (in shares)	93	134	70	130
Weighted average common shares including potential dilutive shares (in shares)	95,580	95,190	95,496	95,132
Basic EPS (in dollars per share)	$ 0.110	$ 0.113	$ 0.219	$ 0.226
Diluted EPS (in dollars per share)	$ 0.109	$ 0.113	$ 0.219	$ 0.225
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)	1,600	1,400	1,600	1,400