Derivative Instruments (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Derivative [Line Items]
Fair value measurements on a recurring basis using significant unobservable inputs (Level 3)	$ 0		$ 0
Lender accelerated indebtedness repayment threshold amount	75,000,000
Fair value of effective cash flow hedges	100,000		(8,700,000)
Ineffective portion of cash flow hedges	0		0		0
Interest Expense	189,399,000		157,108,000		149,350,000
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedge Adjustments [Member]
Derivative [Line Items]
Interest Expense	3,100,000
Swap 1 [Member]
Derivative [Line Items]
Notional Amount	410,905,000	[1]	410,905,000	[1]
Type of Derivative	Swap
Strike Rate	0.717%
Fair Value at Significant Other Observable Inputs (Level 2)	(76,000)		(3,642,000)
Swap 2 [Member]
Derivative [Line Items]
Notional Amount	150,040,000	[2]	155,099,000	[2]
Type of Derivative	Swap
Strike Rate	0.925%
Effective Date	Jul. 17, 2012
Expiration Date	Apr. 18, 2017
Fair Value at Significant Other Observable Inputs (Level 2)	131,000		(1,131,000)
Swap 3 [Member]
Derivative [Line Items]
Notional Amount			69,612,000	[3]
Type of Derivative	Swap
Strike Rate	2.98%
Effective Date	Apr. 06, 2009
Expiration Date	Nov. 30, 2013	[4]
Fair Value at Significant Other Observable Inputs (Level 2)			(1,552,000)
Swap 4 [Member]
Derivative [Line Items]
Notional Amount			39,579,000	[5]
Type of Derivative	Swap
Strike Rate	2.703%
Effective Date	Dec. 03, 2009
Expiration Date	Sep. 04, 2014	[6]
Fair Value at Significant Other Observable Inputs (Level 2)			(1,617,000)
Swap 5 [Member]
Derivative [Line Items]
Notional Amount			13,335,000	[5]
Type of Derivative	Swap
Strike Rate	3.981%
Effective Date	May 17, 2006
Expiration Date	Jul. 18, 2013	[7]
Fair Value at Significant Other Observable Inputs (Level 2)			(275,000)
Swap 6 [Member]
Derivative [Line Items]
Notional Amount			9,649,000	[5]
Type of Derivative	Swap
Strike Rate	4.07%
Effective Date	Jun. 23, 2006
Expiration Date	Jul. 18, 2013	[7]
Fair Value at Significant Other Observable Inputs (Level 2)			(203,000)
Swap 7 [Member]
Derivative [Line Items]
Notional Amount			8,492,000	[5]
Type of Derivative	Swap
Strike Rate	3.989%
Effective Date	Jul. 27, 2006
Expiration Date	Oct. 18, 2013
Fair Value at Significant Other Observable Inputs (Level 2)			(255,000)
Cap 1 [Member]
Derivative [Line Items]
Notional Amount	560,945,000		706,671,000
Fair Value at Significant Other Observable Inputs (Level 2)	$ 55,000		$ (8,675,000)
SGD [Member]
Derivative [Line Items]
Exchange rate	0.79		0.82
GBP [Member]
Derivative [Line Items]
Exchange rate			1.63
EUR [Member]
Derivative [Line Items]
Exchange rate			1.32

[1] Represents the U.S. dollar tranche of the unsecured term loan.

[2] Represents a portion of the Singapore dollar tranche of the unsecured term loan. Translation to U.S. dollars is based on exchange rate of $0.79 to 1.00 SGD as of December 31, 2013 and $0.82 to 1.00 SGD as of December 31, 2012.

[3] Translation to U.S. dollars is based on exchange rate of $1.63 to £1.00 as of December 31, 2012.

[4] The swap agreement was terminated as the mortgage loan was paid in full in October 2013.

[5] Translation to U.S. dollars is based on exchange rate of $1.32 to €1.00 as of December 31, 2012.

[6] The swap agreement was terminated as the mortgage loan was paid in full in June 2013.

[7] The swap agreements were terminated as the mortgage loans were paid in full in July 2013.