Real Estate Intangibles (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Intangible Assets:
Gross historical cost	$ 1,066,625,000	$ 1,070,754,000
Accumulated amortization	649,362,000	571,008,000
Net book value	417,263,000	499,746,000
Weighted-average amortization period in years	17 years 4 months	16 years 8 months
Intangible Liabilities:
Gross historical cost	85,830,000	85,871,000
Accumulated amortization	36,086,000	34,434,000
Net book value	49,744,000	51,437,000
Weighted-average amortization period in years	14 years 4 months	14 years 4 months
Estimated Aggregate Amortization Expense For Acquired Lease Intangibles Expected To Be Recognized [Line Items]
Totals	417,263,000	499,746,000
Intangible Liability [Member]
Estimated Aggregate Amortization Expense For Acquired Lease Intangibles Expected To Be Recognized [Line Items]
2014	3,319,000
2015	6,144,000
2016	5,230,000
2017	4,936,000
2018	4,609,000
Thereafter	25,506,000
Intangible Asset [Member]
Estimated Aggregate Amortization Expense For Acquired Lease Intangibles Expected To Be Recognized [Line Items]
2014	131,571,000
2015	60,803,000
2016	27,796,000
2017	21,181,000
2018	18,396,000
Thereafter	157,517,000
In place lease intangibles [Member]
Intangible Assets:
Gross historical cost	930,686,000	937,357,000
Above market tenant leases [Member]
Intangible Assets:
Gross historical cost	57,910,000	55,939,000
Below market ground leases [Member]
Intangible Assets:
Gross historical cost	59,165,000	59,165,000
Lease commissions [Member]
Intangible Assets:
Gross historical cost	18,864,000	18,293,000
Below market tenant leases [Member]
Intangible Liabilities:
Gross historical cost	76,340,000	76,381,000
Above market ground leases [Member]
Intangible Liabilities:
Gross historical cost	$ 9,490,000	$ 9,490,000