Fair Value Measurements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	9 Months Ended
	Jun. 30, 2012	Sep. 30, 2012	Sep. 30, 2011 Property acre
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest income		$ 0.6	$ 0.5
Other income related to contract termination	0.8	0.8
Number of homes to be disposed of			4
Number of homes to be disposed of, parcel of land in acres			53
Carrying amount of long-lived assets written down to fair value			4.6
Long-lived assets, fair value			2.9
Impairment of long-lived assets			1.7
Impaired predevelopment costs			$ 0.8