Derivatives and Hedging Activity (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2011
Outstanding interest rate derivatives designated as hedging instruments
Number of derivative instruments designated as hedging instruments	19
Outstanding interest rate derivatives not designated as hedging instrument
Number of derivative instruments not designated as hedging instruments	19
Interest rate swaps [Member]
Outstanding interest rate derivatives designated as hedging instruments
Number of derivative instruments designated as hedging instruments	16
Notional amount of derivative instruments designated as hedging instruments	$ 633,287
Outstanding interest rate derivatives not designated as hedging instrument
Number of derivative instruments not designated as hedging instruments	16
Interest rate caps [Member]
Outstanding interest rate derivatives designated as hedging instruments
Number of derivative instruments designated as hedging instruments	3
Notional amount of derivative instruments designated as hedging instruments	137,004
Outstanding interest rate derivatives not designated as hedging instrument
Number of derivative instruments not designated as hedging instruments	3
Notional amount of derivative instruments not designated as hedging instruments	$ 309,984