Loans Receivable and Allowance for Loan Losses - Loans by Type and Performance Status (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	$ 11,954	$ 12,969
Non-Accrual	10,771	11,733
Current	5,387,940	4,230,342
Purchased Credit Impaired Loans	42,480	56,617
Total Loans	$ 5,453,145	4,311,661
Due days for loan payments (days)	30 days
Delinquent period (days)	90 days
Multi-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	$ 0	0
Non-Accrual	0	0
Current	2,905,789	2,204,059
Purchased Credit Impaired Loans	3,650	4,346
Total Loans	2,909,439	2,208,405
Commercial and industrial (including owner occupied commercial real estate)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	39	884
Non-Accrual	1,973	2,513
Current	799,595	543,245
Purchased Credit Impaired Loans	1,552	3,293
Total Loans	803,159	549,935
Commercial real estate - owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	268	0
Non-Accrual	2,700	2,514
Current	292,312	217,187
Purchased Credit Impaired Loans	12,961	16,033
Total Loans	308,241	235,734
Commercial real estate non-owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	1,997	0
Non-Accrual	1,307	1,460
Current	940,895	822,046
Purchased Credit Impaired Loans	12,056	15,804
Total Loans	956,255	839,310
Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	0	0
Non-Accrual	0	2,325
Current	87,006	44,483
Purchased Credit Impaired Loans	234	2,910
Total Loans	87,240	49,718
Residential Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	2,986	1,226
Non-Accrual	2,202	1,855
Current	257,984	284,347
Purchased Credit Impaired Loans	8,441	9,967
Total Loans	271,613	297,395
Manufactured Housing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	6,557	10,712
Non-Accrual	2,449	931
Current	101,132	111,072
Purchased Credit Impaired Loans	3,352	4,016
Total Loans	113,490	126,731
Other Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	107	147
Non-Accrual	140	135
Current	3,227	3,903
Purchased Credit Impaired Loans	234	248
Total Loans	3,708	4,433
30 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	9,149	8,581
30 to 89 Days Past Due | Multi-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	0	0
30 to 89 Days Past Due | Commercial and industrial (including owner occupied commercial real estate)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	39	884
30 to 89 Days Past Due | Commercial real estate - owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	268	0
30 to 89 Days Past Due | Commercial real estate non-owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	1,997	0
30 to 89 Days Past Due | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	0	0
30 to 89 Days Past Due | Residential Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	2,986	1,226
30 to 89 Days Past Due | Manufactured Housing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	3,752	6,324
30 to 89 Days Past Due | Other Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	107	147
90 Days Or More Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	2,805	4,388
90 Days Or More Days Past Due | Multi-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	0	0
90 Days Or More Days Past Due | Commercial and industrial (including owner occupied commercial real estate)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	0	0
90 Days Or More Days Past Due | Commercial real estate - owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	0	0
90 Days Or More Days Past Due | Commercial real estate non-owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	0	0
90 Days Or More Days Past Due | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	0	0
90 Days Or More Days Past Due | Residential Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	0	0
90 Days Or More Days Past Due | Manufactured Housing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	2,805	4,388
90 Days Or More Days Past Due | Other Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due Still Accruing	$ 0	$ 0