Earnings Per Common 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
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	$ 24,467	$ 16,767	$ 61,326	$ 46,816
Denominator for basic earnings per common share, weighted average common shares outstanding	38,123,000	32,762,000	35,384,000	30,896,000
Weighted average common stock equivalents	270,000	194,000	246,000	205,000
Denominator for diluted earnings per common share	38,393,000	32,956,000	35,630,000	31,101,000
Basic earnings per common share (dollars per share)	$ 0.64	$ 0.51	$ 1.73	$ 1.52
Diluted earnings per common share (dollars per share)	$ 0.64	$ 0.51	$ 1.72	$ 1.51
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	17,333	249,150	73,028	251,403