Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator and denominator of the basic and diluted earnings per common share computations
Numerator for both basic and diluted earnings per common share, net income	$ 25,707	$ 19,024	$ 48,969	$ 36,859
Denominator for basic earnings per common share, weighted average common shares outstanding	38,258,000	35,162,000	38,228,000	33,992,000
Weighted average common stock equivalents	342,000	235,000	332,000	235,000
Denominator for diluted earnings per common share	38,600,000	35,397,000	38,560,000	34,227,000
Basic earnings per common share (dollars per share)	$ 0.67	$ 0.54	$ 1.28	$ 1.08
Diluted earnings per common share (dollars per share)	$ 0.67	$ 0.54	$ 1.27	$ 1.08
Stock Option [Member]
Earnings Per Common Share (Textual) [Abstract]
Average number of exercisable employee stock option awards that were not included in the computation of diluted earnings per common share	0	80,700	0	100,875