Risk Management and Use of Derivative Financial Instruments (Details 7) In Thousands, unless otherwise specified		9 Months Ended
	Sep. 30, 2013 USD ($)	Sep. 30, 2013 Designated as hedging Foreign currency collars September 2011 Euro USD ($)	Sep. 30, 2013 Designated as hedging Foreign currency collars September 2011 Euro EUR (€)	Sep. 30, 2013 Designated as hedging Foreign currency collars Minimum September 2011 Euro	Sep. 30, 2013 Designated as hedging Foreign currency collars Maximum September 2011 Euro	Sep. 30, 2013 Designated as hedging Foreign currency contract January 2013 Euro USD ($)	Sep. 30, 2013 Designated as hedging Foreign currency contract January 2013 Euro EUR (€)	Sep. 30, 2013 Designated as hedging Foreign currency contract May 2012 Euro USD ($)	Sep. 30, 2013 Designated as hedging Foreign currency contract May 2012 Euro EUR (€)	Sep. 30, 2013 Designated as hedging Foreign currency contract June 2013 Euro USD ($)	Sep. 30, 2013 Designated as hedging Foreign currency contract June 2013 Euro EUR (€)	Sep. 30, 2013 Designated as hedging Foreign currency contract July 2013 Euro USD ($)	Sep. 30, 2013 Designated as hedging Foreign currency contract July 2013 Euro EUR (€)	Sep. 30, 2013 Designated as hedging Foreign currency contract August 2013 Euro USD ($)	Sep. 30, 2013 Designated as hedging Foreign currency contract August 2013 Euro EUR (€)	Sep. 30, 2013 Designated as hedging Foreign currency contract September 2011 Euro USD ($)	Sep. 30, 2013 Designated as hedging Foreign currency contract September 2011 Euro EUR (€)	Sep. 30, 2013 Designated as hedging Foreign currency contract September 2013 Euro USD ($)	Sep. 30, 2013 Designated as hedging Foreign currency contract September 2013 Euro EUR (€)	Sep. 30, 2013 Designated as hedging Foreign currency contract December 2012 Euro USD ($)	Sep. 30, 2013 Designated as hedging Foreign currency contract December 2012 Euro EUR (€)	Sep. 30, 2013 Designated as hedging Foreign currency contract December 2012 Yen USD ($)	Sep. 30, 2013 Designated as hedging Foreign currency contract December 2012 Yen JPY (¥)	Sep. 30, 2013 Designated as hedging Foreign currency contract Minimum January 2013 Euro	Sep. 30, 2013 Designated as hedging Foreign currency contract Minimum May 2012 Euro	Sep. 30, 2013 Designated as hedging Foreign currency contract Minimum June 2013 Euro	Sep. 30, 2013 Designated as hedging Foreign currency contract Minimum August 2013 Euro	Sep. 30, 2013 Designated as hedging Foreign currency contract Minimum September 2011 Euro	Sep. 30, 2013 Designated as hedging Foreign currency contract Minimum September 2013 Euro	Sep. 30, 2013 Designated as hedging Foreign currency contract Minimum December 2012 Euro	Sep. 30, 2013 Designated as hedging Foreign currency contract Minimum December 2012 Yen	Sep. 30, 2013 Designated as hedging Foreign currency contract Maximum January 2013 Euro	Sep. 30, 2013 Designated as hedging Foreign currency contract Maximum May 2012 Euro	Sep. 30, 2013 Designated as hedging Foreign currency contract Maximum June 2013 Euro	Sep. 30, 2013 Designated as hedging Foreign currency contract Maximum August 2013 Euro	Sep. 30, 2013 Designated as hedging Foreign currency contract Maximum September 2011 Euro	Sep. 30, 2013 Designated as hedging Foreign currency contract Maximum September 2013 Euro	Sep. 30, 2013 Designated as hedging Foreign currency contract Maximum December 2012 Euro	Sep. 30, 2013 Designated as hedging Foreign currency contract Maximum December 2012 Yen	Sep. 30, 2013 Not designated Foreign currency contract December 2012 Yen USD ($)	Sep. 30, 2013 Not designated Foreign currency contract December 2012 Yen JPY (¥)
Derivative Instrument Detail
Derivative notional amount			€ 20,444				€ 11,342		€ 56,700		€ 11,400		€ 45,000		€ 12,000		€ 18,500		€ 11,800		€ 17,100		¥ 776,666																		¥ 610,129
Derivative, floor price		1.40	1.40			1.34	1.34	1.28	1.28	1.35	1.35	1.33	1.33	1.38	1.38	1.34	1.34	1.41	1.41	1.34	1.34	0.0122	0.0122																	0.0128	0.0128
Derivative, cap price		1.42	1.42					1.29	1.29							1.35	1.35					0.0128	0.0128
Effective date		Sep. 01, 2011	Sep. 01, 2011			Jan. 01, 2013	Jan. 01, 2013	May 01, 2012	May 01, 2012	Jun. 01, 2013	Jun. 01, 2013	Jul. 01, 2013	Jul. 01, 2013	Aug. 01, 2013	Aug. 01, 2013	Sep. 01, 2011	Sep. 01, 2011	Sep. 01, 2013	Sep. 01, 2013	Dec. 01, 2012	Dec. 01, 2012	Dec. 01, 2012	Dec. 01, 2012																	Dec. 01, 2012	Dec. 01, 2012
Expiration date				Dec. 01, 2013	Sep. 01, 2014							Jul. 01, 2015	Jul. 01, 2015											Sep. 01, 2015	Dec. 01, 2014	Jun. 01, 2018	Dec. 01, 2018	Mar. 01, 2014	Jun. 01, 2019	Sep. 01, 2017	Dec. 01, 2013	Mar. 01, 2016	Jun. 01, 2017	Sep. 01, 2018	Mar. 01, 2019	Mar. 01, 2015	Sep. 01, 2019	Mar. 01, 2018	Dec. 01, 2017	Dec. 01, 2017	Dec. 01, 2017
Fair value, foreign currency derivatives	$ (3,336)	$ 1,041				$ (184)		$ (3,967)		$ (423)		$ (1,301)		$ (231)		$ (210)		$ (51)		$ (610)		$ 1,524																		$ 1,076