Quarterly report pursuant to Section 13 or 15(d)

Net Income Per Share (Details)

v2.4.0.6
Net Income Per Share (Details) (USD $)
In Thousands, except Per Share data, unless otherwise specified
 3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Numerator [Abstract]    
Numerator for basic and diluted income per share - net income $ 10,855 $ 10,273
Denominator [Abstract]    
Denominator for basic income per share - weighted-average shares 29,511 28,692
Denominator for diluted income per share - adjusted weighted-average shares 30,264 29,363
Basic income per share (dollars per share) $ 0.37 $ 0.36
Diluted income per share (dollars per share) $ 0.36 $ 0.35
Total number anti-dilutive options and non-vested shares excluded from income per diluted share computation 166 264
Stock Option [Member]
    
Denominator [Abstract]    
Effect of dilutive stock options and non-vested shares 606 593
Total number anti-dilutive options and non-vested shares excluded from income per diluted share computation 150 189
Key Employee Performance Share Based Plan [Member]
    
Denominator [Abstract]    
Effect of dilutive stock options and non-vested shares 53 37
Total number anti-dilutive options and non-vested shares excluded from income per diluted share computation 16 14
Nonvested Shares [Member]
    
Denominator [Abstract]    
Effect of dilutive stock options and non-vested shares 94 41
Total number anti-dilutive options and non-vested shares excluded from income per diluted share computation   61