LOANS, LEASES & ALLOWANCE FOR LOANS AND LEASE LOSSES - PERFORMING AND NONPERFORMING BY CLASS AND SOURCE (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Jun. 30, 2015
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	$ 6,102,666	$ 5,001,271
Performing
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	6,078,694	4,970,440
Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	23,972	30,831
Mortgage
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	3,541,663	2,980,795
Mortgage | Performing
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	3,523,089	2,957,953
Mortgage | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	18,574	22,842
Multifamily real estate secured
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	1,276,934	1,185,531
Multifamily real estate secured | Performing
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	1,272,206	1,180,132
Multifamily real estate secured | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	4,728	5,399
Commercial real estate secured
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	98,791	61,403
Commercial real estate secured | Performing
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	98,419	59,275
Commercial real estate secured | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	372	2,128
In-house originated | Mortgage
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	3,461,213	2,885,604
In-house originated | Mortgage | Performing
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	3,448,448	2,869,119
In-house originated | Mortgage | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	12,765	16,485
In-house originated | Multifamily real estate secured
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	1,166,521	1,051,696
In-house originated | Multifamily real estate secured | Performing
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	1,163,275	1,048,266
In-house originated | Multifamily real estate secured | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	3,246	3,430
In-house originated | Commercial real estate secured
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	86,227	46,577
In-house originated | Commercial real estate secured | Performing
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	86,227	46,577
In-house originated | Commercial real estate secured | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	0	0
Purchased | Mortgage
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	80,450	95,191
Purchased | Mortgage | Performing
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	74,641	88,834
Purchased | Mortgage | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	5,809	6,357
Purchased | Multifamily real estate secured
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	110,413	133,835
Purchased | Multifamily real estate secured | Performing
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	108,931	131,866
Purchased | Multifamily real estate secured | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	1,482	1,969
Purchased | Commercial real estate secured
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	12,564	14,826
Purchased | Commercial real estate secured | Performing
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	12,192	12,698
Purchased | Commercial real estate secured | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Total gross loans and leases	$ 372	$ 2,128