Earnings Per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Numerator and denominator of the basic and diluted earnings per common share computations
Net Income (Loss) Attributable to Parent	$ 14,378	$ 14,993	$ 14,203	$ 13,234	$ 11,662	$ 13,106	$ 13,866	$ 12,374	$ 56,808	$ 51,008	$ 43,050
Denominator for basic earnings per common share, weighted average common shares outstanding									28,183,000	27,492,000	27,455,000
Weighted average common stock equivalents									169,000	91,000	51,000
Denominator for diluted earnings per common share									28,352,000	27,583,000	27,506,000
Basic earnings per common share	$ 0.48	$ 0.54	$ 0.52	$ 0.48	$ 0.42	$ 0.48	$ 0.50	$ 0.45	$ 2.02	$ 1.86	$ 1.57
Diluted earnings per common share	$ 0.48	$ 0.53	$ 0.51	$ 0.48	$ 0.42	$ 0.48	$ 0.50	$ 0.45	$ 2.00	$ 1.85	$ 1.57
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									356,328	614,152	660,553