Risk Management and Use of Derivative Financial Instruments (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net
Derivatives not in cash flow hedging relationships, gain (loss), net	$ 3,362	$ (857)	$ 234
Embedded derivatives | Other income and expense
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net
Derivatives not in cash flow hedging relationships, gain (loss), net	1,159	(1,141)	0
Foreign currency forward | Other income and expense
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net
Derivatives not in cash flow hedging relationships, gain (loss), net	1,266	254	432
Put option | Other income and expense
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net
Derivatives not in cash flow hedging relationships, gain (loss), net	0	(2)	0
Stock warrants | Other income and expense
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net
Derivatives not in cash flow hedging relationships, gain (loss), net	297	66	(198)
Swaption | Other income and expense
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net
Derivatives not in cash flow hedging relationships, gain (loss), net	428	0	0
Interest rate swap | Interest Expense
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net
Derivatives not in cash flow hedging relationships, gain (loss), net	$ 212	$ (34)	$ 0