Consolidation of a Real Estate Development Company - Revenues, Expenses and Net Losses Recognized in the Partnership's Consolidated Statement of Operations Related to Urbplan (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue of a consolidated real estate VIE:
Revenue of a consolidated real estate VIE:	$ 86.8	$ 70.2	$ 7.5
Interest and other expenses of a consolidated real estate VIE:
Interest and other expenses of a consolidated real estate VIE:	144.6	175.3	33.8
Urbplan
Revenue of a consolidated real estate VIE:
Land development services	80.0	56.4	0.4
Investment income	6.8	13.8	7.1
Revenue of a consolidated real estate VIE:	86.8	70.2	7.5
Interest and other expenses of a consolidated real estate VIE:
Costs of services rendered	48.5	41.9	0.0
Interest expense	40.9	37.2	12.9
Change in fair value of loans payable	9.2	47.1	13.0
Compensation and benefits	10.7	11.2	2.7
G&A and other expenses	35.3	37.9	5.2
Interest and other expenses of a consolidated real estate VIE:	$ 144.6	$ 175.3	$ 33.8