Deferred Compensation Retirement Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012	Dec. 31, 2009	Dec. 31, 2012 Chairman Of The Board And Chief Executive Officer [Member]	Dec. 31, 2011 Chairman Of The Board And Chief Executive Officer [Member]	Dec. 31, 2008 Chairman Of The Board And Chief Executive Officer [Member]	Dec. 31, 2012 President And Chief Operating Officer [Member]	Dec. 31, 2011 President And Chief Operating Officer [Member]	Dec. 31, 2008 President And Chief Operating Officer [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Annual retirement benefit					$ 1,333,333		$ 1,000,000	$ 1,214,333		$ 881,000
Retirement benefit biannual increase			333,333
Annual retirement benefit, maximum annual benefit						2,000,000			1,881,000
Discount rate used in present value calculation	5.50%	5.50%
Annual retirement benefit, accrued expense liability	$ 3,200,000	$ 3,200,000		$ 2,500,000