Loans and Allowance for Credit Losses on Loans - Amortized cost basis and ACL (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Mar. 31, 2022
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	$ 7,070,677
Allowance for credit losses on loans	37,474	$ 32,102
Collateral Dependent Loans
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	42,585
Allowance for credit losses on loans	309
Real Estate
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	37,405
Accounts Receivable Or Equipment
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	4,935
Other Collateralized Assets
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	245
Mortgage warehouse lines of credit
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	900,585
Allowance for credit losses on loans	2,422	1,941
Residential real estate
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	876,652
Allowance for credit losses on loans	4,910	4,547
Residential real estate | Collateral Dependent Loans
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	359
Allowance for credit losses on loans	29
Residential real estate | Real Estate
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	353
Residential real estate | Other Collateralized Assets
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	6
Multi-family financing
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	3,236,917
Allowance for credit losses on loans	16,364	15,131
Multi-family financing | Collateral Dependent Loans
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	36,760
Allowance for credit losses on loans	187
Multi-family financing | Real Estate
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	36,760
Healthcare financing
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	1,262,424
Allowance for credit losses on loans	7,936	5,618
Commercial and commercial real estate
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	695,158
Allowance for credit losses on loans	5,195	4,102
Commercial and commercial real estate | Collateral Dependent Loans
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	5,305
Allowance for credit losses on loans	92
Commercial and commercial real estate | Real Estate
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	134
Commercial and commercial real estate | Accounts Receivable Or Equipment
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	4,935
Commercial and commercial real estate | Other Collateralized Assets
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	236
Agricultural production and real estate
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	90,070
Allowance for credit losses on loans	551	597
Agricultural production and real estate | Collateral Dependent Loans
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	158
Allowance for credit losses on loans	1
Agricultural production and real estate | Real Estate
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	158
Consumer and margin loans
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	8,871
Allowance for credit losses on loans	96	$ 166
Consumer and margin loans | Collateral Dependent Loans
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	3
Consumer and margin loans | Other Collateralized Assets
Loans and Allowance for Credit Losses on Loans
Amortized Cost Basis	$ 3