The domestic federal statutory tax rate applicable under enacted tax laws to the Company's pretax income from continuing operations for the period. The "statutory" tax rate is the regular tax rate if there are alternative tax systems.

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Income Taxes Income Taxes-Reconciliation (Details) (USD $) In Thousands, 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
Income Tax Disclosure [Abstract]
Statutory federal income tax rate									35.00%	35.00%	35.00%
Increase (reduction) in income tax resulting from:
Income tax expense at statutory rate									$ 14,670	$ 13,080	$ 2,239
Tax-exempt income, net									(853)	(717)	(527)
State and local income taxes, net									1,232	994	67
Non-deductible expenses									326	335	292
Federal income tax credits									(883)	(749)	(749)
Change in estimated rate for deferred taxes									0	(1,180)	0
Other, net									(874)	186	(499)
Total income tax expense (benefit)	$ 1,874	$ 4,167	$ 4,517	$ 3,060	$ 2,316	$ 3,289	$ 4,350	$ 1,994	$ 13,618	$ 11,949	$ 823