Financial Instruments: Derivatives and Hedging (Details) (USD $)	1 Months Ended	12 Months Ended
	Mar. 31, 2010 y	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Financial Instruments: Derivatives and Hedging
Loss from settlement of hedges included in accumulated other comprehensive loss		$ 18,000,000
Share of joint venture accumulated other comprehensive loss		17,400,000
Net loss on forward swaps	19,500,000
Amortization period of the loss from the settlement of the hedges (in years)	10
Accumulated Other Comprehensive Loss relating to derivatives		35,400,000	32,300,000
Estimated current balance held in accumulated other comprehensive income to be reclassified into earnings within the next 12 months		1,700,000
Amount of (Loss) or Gain Recognized in Other Comprehensive Loss (Effective Portion) on derivatives qualifying as hedges		(16,049,000)	(17,619,000)	(15,560,000)
Amount of (Loss) or Gain Reclassified from Accumulated Other Comprehensive Loss into Interest Expense/ Equity in net income of unconsolidated joint ventures (Effective Portion) on derivatives qualifying as hedges		(12,625,000)	(12,661,000)	(12,293,000)
Amount of (Loss) or Gain Recognized in Interest Expense/Equity in Net Income of Unconsolidated Joint Ventures (Ineffective Portion) on derivatives qualifying as hedges		(16,000)	(1,329,000)	(1,000)
Amount of (Loss) or Gain Recognized in Interest Expense/Equity in Net Income of Unconsolidated Joint Ventures (Ineffective Portion) on derivatives not qualifying as hedges		(82,000)
Interest Rate Cap expiring in February, 2012
Financial Instruments: Derivatives and Hedging
Notional Value		110,180,000
Strike Rate (as a percent)		6.00%
Interest Rate Cap expiring in January, 2012
Financial Instruments: Derivatives and Hedging
Notional Value		139,672,000
Strike Rate (as a percent)		5.00%
Interest Rate Swap
Financial Instruments: Derivatives and Hedging
Notional Value		30,000,000
Strike Rate (as a percent)		2.295%
Currency Hedge
Financial Instruments: Derivatives and Hedging
Notional Value		20,748,000
Strike Rate		1.55185
Level 2
Financial Instruments: Derivatives and Hedging
Fair Value		1,900,000
Level 2 | Interest Rate Swap
Financial Instruments: Derivatives and Hedging
Fair Value		(1,716,000)
Level 2 | Currency Hedge
Financial Instruments: Derivatives and Hedging
Fair Value		$ (151,000)