Activity Related to "Senior, mezzanine, and other loans" Notes Receivable Reserve (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	$ 50	$ 90	$ 79
Reversals			(2)
Write-offs		(45)
Transfers and other	5	5	13
Ending balance	$ 55	$ 50	$ 90