Annual report pursuant to Section 13 and 15(d)

Acquisition - Additional Information (Detail)

v3.8.0.1
Acquisition - Additional Information (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Oct. 27, 2016
Aug. 31, 2014
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Business Acquisition [Line Items]          
Goodwill     $ 11,031 $ 11,031  
Banc of California Leases Acquisition [Member]          
Business Acquisition [Line Items]          
Cash consideration paid $ 240,800        
Other tangible and intangible assets acquired 12,600        
Goodwill 11,000        
Central Bancorp, Inc [Member]          
Business Acquisition [Line Items]          
Intangible asset amortization period   10 years      
Core deposit intangible   $ 2,200      
Amortization expense of core deposit intangible     280 326 $ 379
Certificates of deposit   11,300      
Amortization of certificates of deposit     473 2,700 5,600
Discount on subordinated debentures   $ 8,300      
Amortization of subordinated debentures     $ 329 $ 275 $ 176
Lease Intangible Asset [Member] | Banc of California Leases Acquisition [Member]          
Business Acquisition [Line Items]          
Estimated fair value of acquired intangibles 228,200        
Third Party Originators Intangible [Member]          
Business Acquisition [Line Items]          
Intangible asset amortization period     7 years    
Third Party Originators Intangible [Member] | Banc of California Leases Acquisition [Member]          
Business Acquisition [Line Items]          
Estimated fair value of acquired intangibles $ 483        
Intangible asset amortization period 7 years