Earnings Per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
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	$ 16,767	$ 14,993	$ 46,816	$ 42,430
Denominator for basic earnings per common share, weighted average common shares outstanding	32,762,000	27,870,000	30,896,000	27,642,000
Weighted average common stock equivalents	194,000	167,000	205,000	144,000
Denominator for diluted earnings per common share	32,956,000	28,037,000	31,101,000	27,786,000
Basic earnings per common share (dollars per share)	$ 0.51	$ 0.54	$ 1.52	$ 1.54
Diluted earnings per common share (dollars per share)	$ 0.51	$ 0.53	$ 1.51	$ 1.53
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	249,150	308,009	251,403	377,847