Finance Receivables and Loans, Net (Commercial concentration risk) (Details) - Commercial portfolio segment	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost, finance receivables and loans, percentage	100.00%	100.00%
Real estate-backed loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost, finance receivables and loans, percentage	100.00%	100.00%
FLORIDA | Real estate-backed loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost, finance receivables and loans, percentage	13.30%	11.60%
TEXAS | Real estate-backed loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost, finance receivables and loans, percentage	13.00%	15.00%
CALIFORNIA | Real estate-backed loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost, finance receivables and loans, percentage	7.90%	7.20%
MICHIGAN | Real estate-backed loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost, finance receivables and loans, percentage	7.70%	8.20%
NEW YORK | Real estate-backed loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost, finance receivables and loans, percentage	5.60%	5.90%
NORTH CAROLINA | Real estate-backed loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost, finance receivables and loans, percentage	5.50%	4.60%
GEORGIA | Real estate-backed loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost, finance receivables and loans, percentage	3.60%	3.50%
UTAH | Real estate-backed loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost, finance receivables and loans, percentage	3.00%	2.30%
ILLINOIS | Real estate-backed loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost, finance receivables and loans, percentage	2.80%	2.40%
SOUTH CAROLINA | Real estate-backed loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost, finance receivables and loans, percentage	2.50%	2.80%
OTHER UNITED STATES | Real estate-backed loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost, finance receivables and loans, percentage	35.10%	36.50%