Debt Obligations - Consolidated Debt Obligations Outstanding (Parenthetical) (Details) - One Commerce Square [Member] - Secured Debt [Member] - USD ($) $ in Millions		3 Months Ended
	Dec. 29, 2015	Mar. 31, 2017		Dec. 31, 2015
Debt Instrument [Line Items]
Debt instrument increase in principal	$ 130.0
Debt instrument maturity date		Apr. 05, 2023
Effective interest rate		3.64%	[1]	3.64%

[1] This loan was assumed upon acquisition of the related properties on December 19, 2013. On December 29, 2015, the Company refinanced the debt increasing the principal balance to $130.0 million and extended the term of the scheduled maturity from January 6, 2016 to April 5, 2023.  The effective interest rate as of December 31, 2015 was 3.64%.  A default under this loan will also constitute a default under the loan outstanding on Two Commerce Square. This loan is also secured by a lien on Two Commerce Square.