Loans Receivable - Summary of Loans Receivable - Credit Rating Equivalent (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 49,555	$ 45,821
Lending Commitments	91,150	93,920
Loans Receivable And Related Lending Commitments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	46,467	43,700
Lending Commitments	91,155	93,919
Total	137,622	137,619
Loans Receivable And Related Lending Commitments [Member] | Investment-Grade [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	19,155	19,459
Lending Commitments	65,819	64,898
Total	84,974	84,357
Loans Receivable And Related Lending Commitments [Member] | Non-Investment-Grade [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	27,312	24,241
Lending Commitments	25,336	29,021
Total	$ 52,648	$ 53,262