Derivative Financial Instruments (Schedule of interest rate derivatives designated as cash flow hedges) (Details) (Designated as Hedging Instrument [Member], Cash Flow Hedging [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2014 Derivative	Dec. 31, 2013 Derivative
Other Assets [Member] | Interest rate swap [Member]
Derivative [Line Items]
Number of Instruments, Other assets	0	8
Notional Amount, Other assets	$ 0	$ 200,000
Fair Value, Other assets	0	3,027
Other Assets [Member] | Interest rate cap [Member]
Derivative [Line Items]
Number of Instruments, Other assets	6	2
Notional Amount, Other assets	150,000	50,000
Fair Value, Other assets	4,481	3,554
Other Liabilities [Member] | Interest rate swap [Member]
Derivative [Line Items]
Number of Instruments, Other liabilities	10	5
Notional Amount, Other liabilities	250,000	125,000
Fair Value, Other liabilities	$ (4,598)	$ (622)