Consolidation of a Real Estate Development Company - Assets and Liabilities Recognized in the Partnership's Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Millions	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Receivables and inventory of a consolidated real estate VIE:
Receivables and inventory of a consolidated real estate VIE	$ 167.2		$ 145.4
Other assets of a consolidated real estate VIE:
Other assets of a consolidated real estate VIE	33.0		31.5
Other liabilities of a consolidated real estate VIE:
Principal amount	145.3		144.4
Partnership
Receivables and inventory of a consolidated real estate VIE:
Customer and other receivables	107.2		99.4
Inventory costs in excess of billings and advances	60.0		46.0
Receivables and inventory of a consolidated real estate VIE	167.2		145.4
Other assets of a consolidated real estate VIE:
Restricted investments	12.2		12.7
Fixed assets, net	0.2		0.2
Deferred tax assets	4.0		9.1
Other assets	16.6		9.5
Other assets of a consolidated real estate VIE	33.0		31.5
Loans payable of a consolidated real estate VIE at fair value (principal amount of $145.3 million and $144.4 million as of June 30, 2017 and December 31, 2016, respectively)	72.6		79.4
Other liabilities of a consolidated real estate VIE:
Accounts payable	14.0		14.6
Other liabilities	159.4		109.9
Other liabilities of a consolidated real estate VIE	$ 173.4		124.5
Loans Payable of a consolidated real estate VIE | Partnership
Other liabilities of a consolidated real estate VIE:
Principal amount		$ 145.3	$ 144.4