Real Estate Investments Real Estate Investments, Business Combinations (Details) (USD $) In Thousands, unless otherwise specified	0 Months Ended
	Dec. 19, 2013
One and Two Commerce Square [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	$ 255,705
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	85,036
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other	(8,637)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	332,104
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt	(238,082)
Business Combination, return of capital on equity method investment	(30,424)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other	10,423
Business Combination, Total Cash Payment at Settlement	73,075
In-place lease value [Member] | One and Two Commerce Square [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	80,916
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	7 years 10 months 24 days
Above Market Leases [Member] | One and Two Commerce Square [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	4,120
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	6 years 10 months 24 days
Finite-Lived Intangible Assets [Member] | One and Two Commerce Square [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	85,036
Below market leases acquired [Member] | One and Two Commerce Square [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	(8,637)
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	6 years 6 months
Subsidiaries [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value	$ (946)