Loans and finance receivables - Schedule of manufactured housing loan balances before discounts and allowances designated as performing or non-performing by year of loan origination (Detail) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and financing receivables by origination year, Total	$ 18,867	$ 18,199
Manufactured Housing Loan Balances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and financing receivables by origination year, 2020	1,409
Loans and financing receivables by origination year, 2019	2,722
Loans and financing receivables by origination year, 2018	2,089
Loans and financing receivables by origination year, 2017	1,556
Loans and financing receivables by origination year, 2016	1,391
Loans and financing receivables by origination year, Prior	7,524
Loans and financing receivables by origination year, Total	16,691
Performing [Member] | Manufactured Housing Loan Balances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and financing receivables by origination year, 2020	1,401
Loans and financing receivables by origination year, 2019	2,719
Loans and financing receivables by origination year, 2018	2,081
Loans and financing receivables by origination year, 2017	1,547
Loans and financing receivables by origination year, 2016	1,375
Loans and financing receivables by origination year, Prior	7,445
Loans and financing receivables by origination year, Total	16,568
Non-Performing [Member] | Manufactured Housing Loan Balances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and financing receivables by origination year, 2020	8
Loans and financing receivables by origination year, 2019	3
Loans and financing receivables by origination year, 2018	8
Loans and financing receivables by origination year, 2017	9
Loans and financing receivables by origination year, 2016	16
Loans and financing receivables by origination year, Prior	79
Loans and financing receivables by origination year, Total	$ 123