LOANS, LEASES & ALLOWANCE FOR LOAN AND LEASE LOSSES - ALLOWANCE FOR CREDIT LOSS NARRATIVE (Details) $ in Thousands	6 Months Ended
	Dec. 31, 2017 USD ($) class	Jun. 30, 2017 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	$ 7,939,074	$ 7,420,868
Number of classes loans are divided for LTV analysis | class	2
Auto and RV secured
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	$ 189,405
Auto and RV secured | FICO greater than or equal to 770
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	94,210
Auto and RV secured | FICO 715 - 769
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	64,411
Auto and RV secured | FICO 700 - 714
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	15,736
Auto and RV secured | FICO 660 - 699
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	13,520
Auto and RV secured | FICO less than 660
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	1,528
Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	3,954,404	3,878,377
Mortgage | LTV less than or equal to 60%
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	2,303,779
Mortgage | LTV 61% - 70%
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	1,317,002
Mortgage | LTV 71% - 80%
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	333,428
Mortgage | LTV greater than 80%
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	195
Multifamily real estate secured
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	1,695,450	$ 1,615,149
Multifamily real estate secured | LTV greater than 80%
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	0
Multifamily real estate secured | LTV less than or equal to 55%
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	886,901
Multifamily real estate secured | LTV 56% - 65%
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	520,878
Multifamily real estate secured | LTV 66% - 75%
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	278,070
Multifamily real estate secured | LTV 76% - 80%
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	9,601
Commercial Real Estate and Land Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	176,147
Commercial Real Estate and Land Loan [Member] | LTV 61% - 70%
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	46,635
Commercial Real Estate and Land Loan [Member] | LTV 71% - 80%
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	10,174
Commercial Real Estate and Land Loan [Member] | LTV less than or equal to 50%
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	80,086
Commercial Real Estate and Land Loan [Member] | LTV 51% - 60%
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and leases collectively evaluated for impairment	$ 39,252