LOANS, LEASES & ALLOWANCE FOR LOAN AND LEASE LOSSES - UNPAID PRINCIPAL BALANCE FOR PERFORMING AND NONACCRUAL (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Jun. 30, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	$ 10,703,442	$ 9,449,310
Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	10,615,501	9,400,866
Nonaccrual
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	87,941	48,444
Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	4,244,563	4,281,080
Mortgage | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	4,160,533	4,235,075
Mortgage | Nonaccrual
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	84,030	46,005
Warehouse
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	474,318	301,999
Warehouse | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	474,318	301,999
Warehouse | Nonaccrual
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	0	0
Financing
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	682,477	518,560
Financing | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	682,477	518,560
Financing | Nonaccrual
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	0	0
Multifamily real estate secured - mortgage and financing
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	2,303,216	1,948,513
Multifamily real estate secured - mortgage and financing | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	2,302,686	1,946,405
Multifamily real estate secured - mortgage and financing | Nonaccrual
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	530	2,108
Commercial real estate secured - mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	371,176	326,154
Commercial real estate secured - mortgage | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	368,281	326,154
Commercial real estate secured - mortgage | Nonaccrual
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	2,895	0
Auto and RV secured
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	291,452	290,894
Auto and RV secured | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	291,250	290,779
Auto and RV secured | Nonaccrual
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	202	115
Commercial & Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	2,094,322	1,662,629
Commercial & Industrial | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	2,094,109	1,662,629
Commercial & Industrial | Nonaccrual
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	213	0
Other
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	241,918	119,481
Other | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	241,847	119,265
Other | Nonaccrual
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans and leases	$ 71	$ 216