Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share
Net income as reported	$ 10,679	$ 9,709	$ 8,716	$ 9,346	$ 5,967	$ 8,198	$ 7,160	$ 5,848	$ 38,450	$ 27,173	$ 33,104
Impact of assumed conversions
Interest on 9% convertible trust preferred securities, net of income tax									0	66	1,015
Net income available to common shareholders and assumed conversions									$ 38,450	$ 27,239	$ 34,119
Weighted average common shares outstanding (in shares)									19,984,000	19,761,000	18,582,000
Incremental shares from assumed conversions of convertible trust preferred securities (in shares)									0	57,000	1,001,000
Additional dilutive common stock equivalents (in shares)									333,000	292,000	168,000
Weighted average diluted common shares outstanding (in shares)									20,317,000	20,110,000	19,751,000
Basic earnings per common share (in dollars per share)	$ 0.53	$ 0.49	$ 0.44	$ 0.47	$ 0.30	$ 0.41	$ 0.36	$ 0.30	$ 1.92	$ 1.38	$ 1.78
Diluted earnings per common share (in dollars per share)	$ 0.52	$ 0.48	$ 0.43	$ 0.46	$ 0.30	$ 0.41	$ 0.36	$ 0.30	$ 1.89	$ 1.35	$ 1.73
Common stock equivalents excluded from earnings per share calculations due to anti-dilutive effect (in shares)									79,670	287,546	517,694
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%	9.00%