Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share [Abstract]
Net income	$ 9,533	$ 10,296	$ 20,025	$ 20,264
Basic-weighted average shares outstanding	27,591,000	28,327,000	27,860,000	28,178,000
Effect of dilutive potential securities	392,000	345,000	398,000	399,000
Diluted- weighted average shares outstanding	27,983,000	28,672,000	28,258,000	28,577,000
Basic (per share)	$ 0.35	$ 0.36	$ 0.72	$ 0.72
Diluted (per share)	$ 0.34	$ 0.36	$ 0.71	$ 0.71
Shares excluded from computation of earnings per share	100,000	400,000	100,000	400,000