Other Liabilities - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Other Liabilities [Line Items]
Deferred gains on sale of assets included in accrued expenses and other liabilities	$ 1,381		$ 1,381		$ 1,412
Amortization of deferred gains	21	$ 22	42	$ 44
SPG [Member]
Other Liabilities [Line Items]
Total actuarial liability	1,239		1,239		1,219
Accrued expenses	$ 506		$ 506		$ 491