Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share
Net income as reported	$ 9,709	$ 8,198	$ 27,771	$ 21,206
Impact of assumed conversions
Interest on 9% convertible trust preferred securities, net of income tax	0	0	0	66
Net income available to common shareholders and assumed conversions	$ 9,709	$ 8,198	$ 27,771	$ 21,272
Weighted average common shares outstanding (in shares)	19,995,000	19,838,000	19,970,000	19,729,000
Incremental shares from assumed conversions of convertible trust preferred securities (in shares)	0	0	0	76,000
Additional dilutive common stock equivalents (in shares)	266,000	142,000	266,000	165,000
Weighted average diluted common shares outstanding (in shares)	20,261,000	19,980,000	20,236,000	19,970,000
Basic earnings per common share (in dollars per share)	$ 0.49	$ 0.41	$ 1.39	$ 1.07
Diluted earnings per common share (in dollars per share)	$ 0.48	$ 0.41	$ 1.37	$ 1.07
Common stock equivalents excluded from earnings per share calculations due to anti-dilutive effect (in shares)	80,220	289,286	88,040	289,407
Convertible Debt Securities
Debt Instrument, Interest Rate, Stated Percentage [Abstract]
Convertible trust preferred securities, interest rate, stated percentage	9.00%	9.00%	9.00%	9.00%