Derivatives (Details) (USD $)	3 Months Ended
	Mar. 31, 2012 derivatives	Mar. 31, 2011	Jun. 30, 2011 Treasury Locks [Member] derivatives
Schedule of Trading Securities and Other Trading Assets [Line Items]
Number Of Interest Rate Derivatives Terminated			2
Notional amount of interest rate hedges terminated			$ 150,000,000
Treasury locks designated as cash flow hedges, fair value			5,300,000
Treasury locks designated as cash flow hedges, other comprehensive income			5,218,000
Fair value of interest rate hedges recognized in other comprehensive income	5,868,000
Interest rate hedges gain reclassified as reduction to interest expense	56,000	43,000
Interest rate hedges gain (loss) to be reclassified into interest expense over next 12 months	$ 235,000
Number of Interest Rate Derivatives Held	0