Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share
Net income as reported	$ 11,832	$ 9,709	$ 35,209	$ 27,771
Impact of assumed conversions
Weighted average common shares outstanding (in shares)	19,997,000	19,995,000	20,002,000	19,970,000
Additional dilutive common stock equivalents (in shares)	227,000	266,000	229,000	266,000
Weighted average diluted common shares outstanding (in shares)	20,224,000	20,261,000	20,231,000	20,236,000
Basic earnings per common share (in dollars per share)	$ 0.59	$ 0.49	$ 1.76	$ 1.39
Diluted earnings per common share (in dollars per share)	$ 0.59	$ 0.48	$ 1.74	$ 1.37
Common stock equivalents excluded from earnings per share calculations due to anti-dilutive effect (in shares)	0	80,220	2,900	88,040
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%