LOANS AND LEASES AND ALLOWANCE FOR LOAN AND LEASE LOSSES - Aging of Recorded Investment in Past Due Loans and Leases (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	$ 53,471	$ 46,421
60 - 89 Days Past Due	12,672	11,914
Greater than 89 Days Past due	29,948	22,596
Total Past Due	96,091	80,931
Current	4,633,986	3,868,191
Total ending loan balances	4,730,077	3,949,122	$ 2,712,068
Single family residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	1,901,376	1,048,485
Consumer Home Equity Loan \| Green Loans (HELOC) - first liens
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	112,074	123,177
Consumer Home Equity Loan \| Green Loans (HELOC) - second liens
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	4,681	4,979
Other consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	120,015	161,939
Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	822,690	490,900	366,416
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	690,862	999,857	521,867
Multi-family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	823,415	955,683	367,364
SBA
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	52,985	36,155	25,729
Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	39,475	42,198	25,997
Lease financing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	162,504	85,749	$ 72,027
Purchased Credit Impaired
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	11,777	14,140
60 - 89 Days Past Due	5,816	3,501
Greater than 89 Days Past due	6,223	5,761
Total Past Due	23,816	23,402
Current	348,741	223,495
Total ending loan balances	372,557	246,897
Purchased Credit Impaired \| Single family residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	11,417	13,262
60 - 89 Days Past Due	5,816	3,501
Greater than 89 Days Past due	4,545	4,510
Total Past Due	21,778	21,273
Current	336,710	209,806
Total ending loan balances	358,488	231,079
Purchased Credit Impaired \| Consumer Home Equity Loan \| Green Loans (HELOC) - first liens
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	0	0
Purchased Credit Impaired \| Consumer Home Equity Loan \| Green Loans (HELOC) - second liens
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	0	0
Purchased Credit Impaired \| Other consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	0	0
Purchased Credit Impaired \| Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	0	0
60 - 89 Days Past Due	0	0
Greater than 89 Days Past due	182	0
Total Past Due	182	0
Current	274	1,134
Total ending loan balances	456	1,134
Purchased Credit Impaired \| Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	0	0
60 - 89 Days Past Due	0	0
Greater than 89 Days Past due	691	951
Total Past Due	691	951
Current	9,799	10,576
Total ending loan balances	10,490	11,527
Purchased Credit Impaired \| Multi-family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	0	0
Purchased Credit Impaired \| SBA
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	360	878
60 - 89 Days Past Due	0	0
Greater than 89 Days Past due	805	300
Total Past Due	1,165	1,178
Current	1,958	1,979
Total ending loan balances	3,123	3,157
Purchased Credit Impaired \| Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	0	0
Purchased Credit Impaired \| Lease financing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	0	0
Non-Traditional Mortgages (NTM)
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	7,708	10,562
60 - 89 Days Past Due	78	165
Greater than 89 Days Past due	3,713	2,695
Total Past Due	11,499	13,422
Current	747,779	337,153
Total ending loan balances	759,278	350,575
Non-Traditional Mortgages (NTM) \| Green Loans (HELOC) - first liens
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	754,484	345,483
Non-Traditional Mortgages (NTM) \| Green Loans (HELOC) - second liens
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	4,794	5,092
Non-Traditional Mortgages (NTM) \| Single family residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	6,776	1,415
60 - 89 Days Past Due	78	165
Greater than 89 Days Past due	3,713	2,049
Total Past Due	10,567	3,629
Current	631,843	218,677
Total ending loan balances	642,410	222,306
Non-Traditional Mortgages (NTM) \| Consumer Home Equity Loan \| Green Loans (HELOC) - first liens
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	932	8,853
60 - 89 Days Past Due	0	0
Greater than 89 Days Past due	0	437
Total Past Due	932	9,290
Current	111,142	113,887
Total ending loan balances	112,074	123,177
Non-Traditional Mortgages (NTM) \| Consumer Home Equity Loan \| Green Loans (HELOC) - second liens
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	0	294
60 - 89 Days Past Due	0	0
Greater than 89 Days Past due	0	209
Total Past Due	0	503
Current	4,681	4,476
Total ending loan balances	4,681	4,979
Non-Traditional Mortgages (NTM) \| Other consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	0	0
60 - 89 Days Past Due	0	0
Greater than 89 Days Past due	0	0
Total Past Due	0	0
Current	113	113
Total ending loan balances	113	113
Non-Traditional Mortgages (NTM) \| Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	0	0
Non-Traditional Mortgages (NTM) \| Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	0	0
Non-Traditional Mortgages (NTM) \| Multi-family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	0	0
Non-Traditional Mortgages (NTM) \| SBA
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	0	0
Non-Traditional Mortgages (NTM) \| Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	0	0
Non-Traditional Mortgages (NTM) \| Lease financing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	0	0
Traditional Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	33,986	21,719
60 - 89 Days Past Due	6,778	8,248
Greater than 89 Days Past due	20,012	14,140
Total Past Due	60,776	44,107
Current	3,537,466	3,307,543
Total ending loan balances	3,598,242	3,351,650
Traditional Loans \| Single family residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	28,045	17,185
60 - 89 Days Past Due	5,363	7,878
Greater than 89 Days Past due	16,962	10,411
Total Past Due	50,370	35,474
Current	850,108	559,626
Total ending loan balances	900,478	595,100
Traditional Loans \| Consumer Home Equity Loan \| Green Loans (HELOC) - first liens
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	0	0
Traditional Loans \| Consumer Home Equity Loan \| Green Loans (HELOC) - second liens
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending loan balances	0	0
Traditional Loans \| Other consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	36	9
60 - 89 Days Past Due	0	89
Greater than 89 Days Past due	147	5
Total Past Due	183	103
Current	119,719	161,723
Total ending loan balances	119,902	161,826
Traditional Loans \| Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	282	79
60 - 89 Days Past Due	5	37
Greater than 89 Days Past due	1,083	3,370
Total Past Due	1,370	3,486
Current	820,864	486,280
Total ending loan balances	822,234	489,766
Traditional Loans \| Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	0	2,237
60 - 89 Days Past Due	0	0
Greater than 89 Days Past due	642	0
Total Past Due	642	2,237
Current	679,730	986,093
Total ending loan balances	680,372	988,330
Traditional Loans \| Multi-family
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	0	1,072
60 - 89 Days Past Due	440	208
Greater than 89 Days Past due	0	0
Total Past Due	440	1,280
Current	822,975	954,403
Total ending loan balances	823,415	955,683
Traditional Loans \| SBA
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	166	82
60 - 89 Days Past Due	29	0
Greater than 89 Days Past due	194	254
Total Past Due	389	336
Current	49,473	32,662
Total ending loan balances	49,862	32,998
Traditional Loans \| Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	0	0
60 - 89 Days Past Due	0	0
Greater than 89 Days Past due	0	0
Total Past Due	0	0
Current	39,475	42,198
Total ending loan balances	39,475	42,198
Traditional Loans \| Lease financing
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	5,457	1,055
60 - 89 Days Past Due	941	36
Greater than 89 Days Past due	984	100
Total Past Due	7,382	1,191
Current	155,122	84,558
Total ending loan balances	$ 162,504	$ 85,749

LOANS AND LEASES AND ALLOWANCE FOR LOAN AND LEASE LOSSES - Aging of Recorded Investment in Past Due Loans and Leases (Detail) - USD ($)
$ in Thousands