Earnings Per Common Share (Computation Of Basic And Diluted Net Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share [Abstract]
Net income	$ 12,798		$ 11,517		$ 11,320		$ 8,579		$ 10,565		$ 9,996		$ 9,828		$ 7,767		$ 44,214	$ 38,156	$ 34,441
Basic earnings per common share, Income (Numerator)																	44,214	38,156	34,441
Basic earnings per common share, Shares (Denominator)																	67,511	66,637	65,917
Basic earnings per common share (dollars per share)	$ 0.19	[1]	$ 0.17	[1]	$ 0.17	[1]	$ 0.13	[1]	$ 0.16	[1]	$ 0.15	[1]	$ 0.15	[1]	$ 0.12	[1]	$ 0.65	$ 0.57	$ 0.52
Effect of dilutive securities, Options, Shares																	974	948	1,091
Effect of dilutive securities, Options, (dollars per share)																	$ 0.00	$ (0.01)	$ (0.01)
Diluted earnings per common share, Income (Numerator)																	$ 44,214	$ 38,156	$ 34,441
Diluted earnings per common share, Shares (Denominator)																	68,485	67,585	67,008
Diluted earnings per common share (dollars per share)	$ 0.19	[1]	$ 0.17	[1]	$ 0.17	[1]	$ 0.13	[1]	$ 0.16	[1]	$ 0.15	[1]	$ 0.15	[1]	$ 0.12	[1]	$ 0.65	$ 0.56	$ 0.51
Options outstanding to purchase common stock excluded from computation of diluted earnings per common share																	576	510	1,037

[1] Year-to-date earnings and cash dividends per common share amounts may differ from the sum of quarterly amounts due to rounding.