Derivatives and Hedging Activities (Schedule of Interest Rate Derivatives) (Details) (Derivative Financial Instruments, Liabilities [Member], Cash Flow Hedging [Member], Designated as Hedging Instrument [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2013 derivative	Dec. 31, 2012 derivative
Derivative [Line Items]
Number of Interest Rate Derivatives Held		8
Derivative, Notional Amount		$ 202,590
Swap [Member]
Derivative [Line Items]
Number of Interest Rate Derivatives Held	10	7
Derivative, Notional Amount	667,590
Notional Amount of Interest Rate Derivatives (Deprecated 2013-01-31)		152,590
Interest Rate Cap [Member]
Derivative [Line Items]
Number of Interest Rate Derivatives Held		1
Derivative, Notional Amount		$ 50,000