Deconsolidation of a Real Estate Development Company - Assets and Liabilities Recognized in the Partnership's Consolidated Balance Sheet Related to Urbplan (Additional Information) (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Other liabilities of a real estate VIE:
Principal amount of loans payable	$ 0.0	$ 144.4
Partnership
Receivables and inventory of a real estate VIE:
Customer and other receivables		99.4
Inventory costs in excess of billings and advances		46.0
Receivables and inventory of a real estate VIE:		145.4
Other assets of a real estate VIE:
Restricted investments		12.7
Fixed assets, net		0.2
Deferred tax assets		9.1
Other assets		9.5
Other assets of a real estate VIE:		31.5
Loans payable of a real estate VIE, at fair value (principal amount of $144.4 million as of December 31, 2016)		79.4
Other liabilities of a real estate VIE:
Accounts payable		14.6
Other liabilities		109.9
Other liabilities of a real estate VIE:		124.5
Loans Payable of a real estate VIE | Partnership
Other liabilities of a real estate VIE:
Principal amount of loans payable		$ 144.4