Shareholders' Equity (Details 1) (USD $)
In Thousands, except Per Share data, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Calculation of Earnings per share      
Net income $ 30,036 $ 27,638 $ 25,327
Less dividends on preferred stock and accretion of discount 0 (2,463) (3,293)
Net income available to common equity $ 30,036 $ 25,175 $ 22,034
Average common shares outstanding (in shares) 21,313 18,204 13,807
Effect of stock dividends (in shares) 0 432 1,184
Average common shares outstanding - basic (in shares) 21,313 18,636 14,991
Dilutive stock options and warrants (in shares) 2,159 2,098 1,759
Average common shares outstanding - dilutive (in shares) 23,472 20,734 16,750
Earnings per share - basic (in dollars per share) $ 1.41 $ 1.35 $ 1.47
Earnings per share - dilutive (in dollars per share) $ 1.28 $ 1.21 $ 1.32