Loans Receivable - Interest Rate Terms (Details) $ in Thousands	Sep. 30, 2021 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans, fixed-rate	$ 8,242,668
% of gross loans, fixed-rate	58.90%
Gross loans, adjustable rate	$ 5,762,202
% of gross loans, adjustable rate	41.10%
Within 1 year
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans, fixed-rate	$ 367,155
% of gross loans, fixed-rate	2.60%
Gross loans, adjustable rate	$ 4,674,668
% of gross loans, adjustable rate	33.40%
1 to 3 years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans, fixed-rate	$ 329,780
% of gross loans, fixed-rate	2.40%
Gross loans, adjustable rate	$ 296,535
% of gross loans, adjustable rate	2.10%
3 to 5 years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans, fixed-rate	$ 772,262
% of gross loans, fixed-rate	5.50%
Gross loans, adjustable rate	$ 690,120
% of gross loans, adjustable rate	4.90%
5 to 10 years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans, fixed-rate	$ 1,356,438
% of gross loans, fixed-rate	9.70%
Gross loans, adjustable rate	$ 73,214
% of gross loans, adjustable rate	0.50%
10 to 20 years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans, fixed-rate	$ 1,065,005
% of gross loans, fixed-rate	7.60%
Gross loans, adjustable rate	$ 25,400
% of gross loans, adjustable rate	0.20%
Over 20 years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans, fixed-rate	$ 4,352,028
% of gross loans, fixed-rate	31.10%
Gross loans, adjustable rate	$ 2,265
% of gross loans, adjustable rate	0.00%