Earnings Per Common 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
Numerator and denominator of the basic and diluted earnings per common share computations
Net Income (Loss) Attributable to Parent	$ 25,504	$ 24,467	$ 19,024	$ 17,835	$ 15,305	$ 16,767	$ 16,236	$ 13,813	$ 86,830	$ 62,121	$ 56,808
Denominator for basic earnings per common share, weighted average common shares outstanding											28,183,000
Weighted average common stock equivalents									272,000	221,000	169,000
Denominator for diluted earnings per common share									36,353,000	31,588,000	28,352,000
Basic earnings per common share	$ 0.67	$ 0.64	$ 0.54	$ 0.54	$ 0.47	$ 0.51	$ 0.54	$ 0.46	$ 2.41	$ 1.98	$ 2.02
Diluted earnings per common share	$ 0.66	$ 0.64	$ 0.54	$ 0.54	$ 0.46	$ 0.51	$ 0.54	$ 0.46	$ 2.39	$ 1.97	$ 2.00
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									54,771	240,165	356,328