Risk Management and Use of Derivative Financial Instruments (Details 4) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Amount of Gain (Loss) Recognized in Income on Derivatives
Derivatives not in cash flow hedging relationships, gain (loss), net	$ (960)	$ (84)	$ 904	$ (63)
Interest rate swap | Interest expense
Amount of Gain (Loss) Recognized in Income on Derivatives
Derivatives not in cash flow hedging relationships, gain (loss), net	(50)	(18)	154	5
Put option | Other income and expense
Amount of Gain (Loss) Recognized in Income on Derivatives
Derivatives not in cash flow hedging relationships, gain (loss), net	0	0	0	(2)
Stock warrants | Other income and expense
Amount of Gain (Loss) Recognized in Income on Derivatives
Derivatives not in cash flow hedging relationships, gain (loss), net	66	(66)	231	(66)
Foreign currency forward | Other income and expense
Amount of Gain (Loss) Recognized in Income on Derivatives
Derivatives not in cash flow hedging relationships, gain (loss), net	59	0	822	0
Embedded derivatives | Other income and expense
Amount of Gain (Loss) Recognized in Income on Derivatives
Derivatives not in cash flow hedging relationships, gain (loss), net	(1,093)	0	(540)	0
Swaption | Other income and expense
Amount of Gain (Loss) Recognized in Income on Derivatives
Derivatives not in cash flow hedging relationships, gain (loss), net	$ 58	$ 0	$ 237	$ 0