Derivative and Hedging Activities - Schedule of Interest Rate Derivatives (Details) (Interest Rate Swap (EUR), Swap, Designated as Hedging Instrument, USD $) In Thousands, unless otherwise specified	Dec. 31, 2014 derivative	Dec. 31, 2013 derivative
Derivative [Line Items]
Number of Instruments	30	7
Notional Amount	$ 654,224	$ 35,465
GBP-USD Forwards
Derivative [Line Items]
Number of Instruments	20	7
Notional Amount	371,225	35,465
EUR-USD Forwards
Derivative [Line Items]
Number of Instruments	10	0
Notional Amount	$ 282,999	$ 0