Loans and finance receivables - Summary of performing and non-performing home loans before discounts and allowances by year of loan origination (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and financing receivables by origination year, Total	$ 20,436	$ 18,199
Manufactured Housing Loan Balances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and financing receivables by origination year, 2020	4,433
Loans and financing receivables by origination year, 2019	2,542
Loans and financing receivables by origination year, 2018	1,935
Loans and financing receivables by origination year, 2017	1,431
Loans and financing receivables by origination year, 2016	1,283
Loans and financing receivables by origination year, Prior	6,688
Loans and financing receivables by origination year, Total	18,312
Performing [Member] | Manufactured Housing Loan Balances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and financing receivables by origination year, 2020	4,430
Loans and financing receivables by origination year, 2019	2,537
Loans and financing receivables by origination year, 2018	1,928
Loans and financing receivables by origination year, 2017	1,424
Loans and financing receivables by origination year, 2016	1,276
Loans and financing receivables by origination year, Prior	6,645
Loans and financing receivables by origination year, Total	18,240
Non-Performing [Member] | Manufactured Housing Loan Balances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and financing receivables by origination year, 2020	3
Loans and financing receivables by origination year, 2019	5
Loans and financing receivables by origination year, 2018	7
Loans and financing receivables by origination year, 2017	7
Loans and financing receivables by origination year, 2016	7
Loans and financing receivables by origination year, Prior	43
Loans and financing receivables by origination year, Total	$ 72