Annual report pursuant to Section 13 and 15(d)

Shareholders' Equity, Stock Options and Net Income per Share - Net Income per Share (Details)

v2.4.0.6
Shareholders' Equity, Stock Options and Net Income per Share - Net Income per Share (Details) (USD $)
In Thousands, except Per Share data, unless otherwise specified
 3 Months Ended 12 Months Ended
Dec. 31, 2012
Sep. 30, 2012
Jun. 30, 2012
Mar. 31, 2012
Dec. 31, 2011
Sep. 30, 2011
Jun. 30, 2011
Mar. 31, 2011
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]                      
Numerator for basic and diluted income per share - net income $ 15,961 $ 12,267 $ 14,167 $ 10,273 $ 14,449 $ 12,912 $ 11,969 $ 7,869 $ 52,668 $ 47,199 $ 32,036
Denominator for basic income per share - weighted-average shares                 28,967 29,052 28,984
Denominator for diluted income per share - adjusted weighted-average shares                 29,536 29,435 29,111
Basic net income per share $ 0.55 $ 0.42 $ 0.49 $ 0.36 $ 0.51 $ 0.44 $ 0.41 $ 0.27 $ 1.82 $ 1.62 $ 1.11
Diluted net income per share $ 0.54 $ 0.41 $ 0.48 $ 0.35 $ 0.50 $ 0.44 $ 0.40 $ 0.27 $ 1.78 $ 1.60 $ 1.10
Total number anti-dilutive options and non-vested shares excluded from income per diluted share computation                 248 649 3,174
Stock Option [Member]
                      
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]                      
Weighted Average Number Diluted Shares Outstanding Adjustment                 492 333 127
Total number anti-dilutive options and non-vested shares excluded from income per diluted share computation                 226 649 3,174
Key Employee Performance Share Based Plan [Member]
                      
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]                      
Weighted Average Number Diluted Shares Outstanding Adjustment                 41 25  
Total number anti-dilutive options and non-vested shares excluded from income per diluted share computation                 22    
Nonvested Shares and Deferred Stock Units [Member]
                      
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]                      
Weighted Average Number Diluted Shares Outstanding Adjustment                 36 25