Real Estate Intangibles (Details) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Intangible Assets:
Gross historical cost	$ 1,084,703,000	$ 1,070,754,000
Accumulated amortization	713,334,000	571,008,000
Net book value	371,369,000	499,746,000
Weighted-average amortization period in years	17 years 11 months	16 years 8 months
Intangible Liabilities:
Gross historical cost	85,369,000	85,871,000
Accumulated amortization	37,425,000	34,434,000
Net book value	47,944,000	51,437,000
Weighted-average amortization period in years	13 years 1 month	14 years 4 months
Estimated Aggregate Amortization Expense For Acquired Lease Intangibles Expected To Be Recognized [Line Items]
Totals	371,369,000	499,746,000
Intangible Liability [Member]
Estimated Aggregate Amortization Expense For Acquired Lease Intangibles Expected To Be Recognized [Line Items]
2014	3,421,000
2015	5,994,000
2016	5,580,000
2017	5,115,000
2018	4,729,000
Thereafter	23,105,000
Intangible Asset [Member]
Estimated Aggregate Amortization Expense For Acquired Lease Intangibles Expected To Be Recognized [Line Items]
2014	77,024,000
2015	64,525,000
2016	30,515,000
2017	22,266,000
2018	19,317,000
Thereafter	157,722,000
In place lease intangibles [Member]
Intangible Assets:
Gross historical cost	947,616,000	937,357,000
Above market tenant leases [Member]
Intangible Assets:
Gross historical cost	58,735,000	55,939,000
Below market ground leases [Member]
Intangible Assets:
Gross historical cost	60,088,000	59,165,000
Lease commissions [Member]
Intangible Assets:
Gross historical cost	18,264,000	18,293,000
Below market tenant leases [Member]
Intangible Liabilities:
Gross historical cost	78,723,000	76,381,000
Above market ground leases [Member]
Intangible Liabilities:
Gross historical cost	$ 6,646,000	$ 9,490,000