Equity Investments in Unconsolidated Joint Ventures - Debt Outstanding of Unconsolidated Entities (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended					6 Months Ended									3 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014 Minimum	Jun. 30, 2014 Maximum	Jun. 30, 2014 Ramco 450 Venture LLC	Jun. 30, 2014 Ramco 450 Venture LLC Minimum	Jun. 30, 2014 Ramco 450 Venture LLC Maximum	Jun. 30, 2014 Ramco/Lion Venture LP	Mar. 31, 2014 Ramco 191 LLC	Jun. 30, 2014 Unconsolidated joint ventures	Jun. 30, 2014 Unconsolidated joint ventures Ramco 450 Venture LLC		Jun. 30, 2014 Unconsolidated joint ventures Ramco/Lion Venture LP		Mar. 31, 2014 Olentangy Plaza Ramco 450 Venture LLC	Mar. 31, 2014 Olentangy Plaza Ramco-Gershenson Properties Trust Ramco 450 Venture LLC
Debt Instrument [Line Items]
Total mortgage debt	$ 301,029	$ 333,049								$ 170,842	$ 140,597	[1]	$ 30,245	[2]
Unamortized premium	(2,826)	(3,174)								(150)
Total mortgage debt	170,692	178,708								170,692
Mortgage debt interest rate, minimum						1.90%
Mortgage debt interest rate, maximum							5.80%
Mortgage debt interest rate								5.00%
Equity Method Investment, Ownership Percentage			7.00%	30.00%	20.00%			30.00%	20.00%
Repayments of long-term debt	$ 0														$ 7,500	$ 1,500

[1] Maturities range from October 2015 to September 2023 with interest rates ranging from 1.9% to 5.8%

[2] Balance relates to Millennium Park’s mortgage loan which has a maturity date of October 2015 with a 5.0% interest rate.