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	Sep. 30, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and financing receivables by origination year, Total	$ 21,685	$ 20,436
Manufactured Housing Loan Balances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and financing receivables by origination year, 2021	3,796
Loans and financing receivables by origination year, 2020	3,267
Loans and financing receivables by origination year, 2019	2,314
Loans and financing receivables by origination year, 2018	1,754
Loans and financing receivables by origination year, 2017	1,305
Loans and financing receivables by origination year, Prior	7,166
Loans and financing receivables by origination year, Total	19,602
Performing [Member] | Manufactured Housing Loan Balances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and financing receivables by origination year, 2021	3,794
Loans and financing receivables by origination year, 2020	3,264
Loans and financing receivables by origination year, 2019	2,308
Loans and financing receivables by origination year, 2018	1,748
Loans and financing receivables by origination year, 2017	1,300
Loans and financing receivables by origination year, Prior	7,126
Loans and financing receivables by origination year, Total	19,540
Non-Performing [Member] | Manufactured Housing Loan Balances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and financing receivables by origination year, 2021	2
Loans and financing receivables by origination year, 2020	3
Loans and financing receivables by origination year, 2019	6
Loans and financing receivables by origination year, 2018	6
Loans and financing receivables by origination year, 2017	5
Loans and financing receivables by origination year, Prior	40
Loans and financing receivables by origination year, Total	$ 62