Loans Receivable and Allowance for Loan Losses - Credit Quality Tables for Loans Receivable Portfolio (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	$ 5,453,145	$ 4,311,661
Pass/Satisfactory
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	5,294,352	4,124,027
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	24,506	34,558
Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	17,089	21,912
Performing
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	107,945	119,239
Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	9,253	11,925
Multi-family
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	2,909,439	2,208,405
Multi-family | Pass/Satisfactory
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	2,907,362	2,206,776
Multi-family | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	661	0
Multi-family | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	1,416	1,629
Multi-family | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Multi-family | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Commercial and industrial (including owner occupied commercial real estate)
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	803,159	549,935
Commercial and industrial (including owner occupied commercial real estate) | Pass/Satisfactory
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	784,892	531,790
Commercial and industrial (including owner occupied commercial real estate) | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	14,052	14,565
Commercial and industrial (including owner occupied commercial real estate) | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	4,215	3,580
Commercial and industrial (including owner occupied commercial real estate) | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Commercial and industrial (including owner occupied commercial real estate) | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Commercial real estate - owner occupied
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	308,241	235,734
Commercial real estate - owner occupied | Pass/Satisfactory
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	295,762	217,356
Commercial real estate - owner occupied | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	7,840	13,056
Commercial real estate - owner occupied | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	4,639	5,322
Commercial real estate - owner occupied | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Commercial real estate - owner occupied | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Commercial real estate non-owner occupied
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	956,255	839,310
Commercial real estate non-owner occupied | Pass/Satisfactory
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	950,886	829,238
Commercial real estate non-owner occupied | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	1,671	6,694
Commercial real estate non-owner occupied | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	3,698	3,378
Commercial real estate non-owner occupied | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Commercial real estate non-owner occupied | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Construction
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	87,240	49,718
Construction | Pass/Satisfactory
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	87,240	44,642
Construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	5,076
Construction | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Construction | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	271,613	297,395
Residential Real Estate | Pass/Satisfactory
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	268,210	294,225
Residential Real Estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	282	243
Residential Real Estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	3,121	2,927
Residential Real Estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Residential Real Estate | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Manufactured Housing
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	113,490	126,731
Manufactured Housing | Pass/Satisfactory
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Manufactured Housing | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Manufactured Housing | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Manufactured Housing | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	104,484	115,088
Manufactured Housing | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	9,006	11,643
Other Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	3,708	4,433
Other Consumer | Pass/Satisfactory
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Other Consumer | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Other Consumer | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Other Consumer | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	3,461	4,151
Other Consumer | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	$ 247	$ 282