Derivative Instruments (Details) (USD $)	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011	Dec. 31, 2011
Derivative [Line Items]
Fair value of effective cash flow hedges	$ (5,300,000)			$ (5,500,000)
Ineffective portion of cash flow hedges	0		0
Reclassified as increase to interest expense	3,300,000
Notional Amount	177,265,000			246,973,000
Fair Value at Significant Other Observable Inputs (Level 2)	(5,322,000)			(5,484,000)
EUR [Member]
Derivative [Line Items]
Exchange rate	1.33			1.30
GBP [Member]
Derivative [Line Items]
Exchange rate	1.60			1.55
Swap 1 [Member]
Derivative [Line Items]
Notional Amount	68,554,000	[1]		66,563,000	[1]
Type of Derivative	Swap	[1]
Strike Rate	$ 2.980	[1]
Effective Date	Apr. 06, 2009	[1]
Expiration Date	Nov. 30, 2013	[1]
Fair Value at Significant Other Observable Inputs (Level 2)	(2,215,000)	[1]		(2,363,000)	[1]
Swap 2 [Member]
Derivative [Line Items]
Notional Amount	13,655,000	[2]		13,319,000	[2]
Type of Derivative	Swap	[2]
Strike Rate	$ 3.981	[2]
Effective Date	May 17, 2006	[2]
Expiration Date	Jul. 18, 2013	[2]
Fair Value at Significant Other Observable Inputs (Level 2)	(558,000)	[2]		(583,000)	[2]
Swap 3 [Member]
Derivative [Line Items]
Notional Amount	9,880,000	[2]		9,636,000	[2]
Type of Derivative	Swap	[2]
Strike Rate	$ 4.070	[2]
Effective Date	Jun. 23, 2006	[2]
Expiration Date	Jul. 18, 2013	[2]
Fair Value at Significant Other Observable Inputs (Level 2)	(415,000)	[2]		(435,000)	[2]
Swap 4 [Member]
Derivative [Line Items]
Notional Amount	8,695,000	[2]		8,480,000	[2]
Type of Derivative	Swap	[2]
Strike Rate	$ 3.989	[2]
Effective Date	Jul. 27, 2006	[2]
Expiration Date	Oct. 18, 2013	[2]
Fair Value at Significant Other Observable Inputs (Level 2)	(421,000)	[2]		(432,000)	[2]
Swap 5 [Member]
Derivative [Line Items]
Notional Amount				39,483,000	[2],[3]
Type of Derivative	Swap	[2],[3]
Strike Rate	$ 3.776	[2],[3]
Effective Date	Dec. 05, 2006	[2],[3]
Expiration Date	Jan. 18, 2012	[2],[3]
Fair Value at Significant Other Observable Inputs (Level 2)				(41,000)	[2],[3]
Swap 6 [Member]
Derivative [Line Items]
Notional Amount				33,946,000	[2],[3]
Type of Derivative	Swap	[2],[3]
Strike Rate	$ 4.000	[2],[3]
Effective Date	Dec. 20, 2006	[2],[3]
Expiration Date	Jan. 18, 2012	[2],[3]
Fair Value at Significant Other Observable Inputs (Level 2)				(38,000)	[2],[3]
Swap 7 [Member]
Derivative [Line Items]
Notional Amount	40,029,000	[2]		38,883,000	[2]
Type of Derivative	Swap	[2]
Strike Rate	$ 2.703	[2]
Effective Date	Dec. 03, 2009	[2]
Expiration Date	Sep. 04, 2014	[2]
Fair Value at Significant Other Observable Inputs (Level 2)	(1,713,000)	[2]		(1,592,000)	[2]
Cap 1 [Member]
Derivative [Line Items]
Notional Amount	15,952,000			16,163,000
Type of Derivative	Cap
Strike Rate	$ 4.000
Effective Date	Jun. 24, 2009
Expiration Date	Jun. 25, 2012	[4]
Cap 2 [Member]
Derivative [Line Items]
Notional Amount	$ 20,500,000			$ 20,500,000
Type of Derivative	Cap
Strike Rate	$ 4.000
Effective Date	Aug. 04, 2010
Expiration Date	Jun. 15, 2013

[1] Translation to U.S. dollars is based on exchange rate of $1.60 to £1.00 as of March 31, 2012 and $1.55 to £1.00 as of December 31, 2011.

[2] Translation to U.S. dollars is based on exchange rate of $1.33 to €1.00 as of March 31, 2012 and $1.30 to €1.00 as of December 31, 2011.

[3] The swap agreements were terminated as the mortgage loans were paid in full at maturity in January 2012.

[4] This cap agreement was terminated on April 27, 2012 as the mortgage loan was paid in full on April 26, 2012.