Acquisitions (Details Textual) (USD $) In Millions, unless otherwise specified	9 Months Ended			0 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2012 Newmark [Member]	Oct. 14, 2011 Newmark [Member]	Sep. 30, 2012 Newmark [Member] Affiliated company of Newmark [Member]	Oct. 14, 2011 Newmark [Member] Class A Common stock [Member]	Sep. 30, 2012 Grubb & Ellis Company [Member]	Sep. 30, 2012 Grubb & Ellis Company [Member]	Apr. 13, 2012 Grubb & Ellis Company [Member]
Acquisitions (Textual) [Abstract]
Total consideration transferred		$ 90.1	$ 2.1				$ 47.1
Goodwill related to acquisition of Newmark		59.5	1.8
Consideration transferred of Class A common stock				4.83
Performance period for contingent consideration				5 years
Estimated fair value of contingent consideration				26.8
Additional noncontrolling interests purchased	6.9
Pre-bankruptcy senior secured debt							30.0
Prepetition Debt							25.6
Debtor-in-possession term loans							5.5
Cash paid to the bankruptcy estate							16.0
Direct costs incurred		3.2					2.8
Revenues subsequent to acquisition of Grubb & Ellis					$ 62.6	$ 128.3