Loans - Aging of Loan Portfolio (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Other information concerning the credit quality
Total	$ 13,236,433	$ 8,722,311
Investor loans secured by real estate
Other information concerning the credit quality
Total	8,225,765	4,153,084
Investor loans secured by real estate | CRE non-owner-occupied
Other information concerning the credit quality
Total	2,675,085	2,070,141
Investor loans secured by real estate | Multifamily
Other information concerning the credit quality
Total	5,171,356	1,575,726
Investor loans secured by real estate | Construction and land
Other information concerning the credit quality
Total	321,993	438,786
Investor loans secured by real estate | SBA secured by real estate
Other information concerning the credit quality
Total	57,331	68,431
Business loans secured by real estate
Other information concerning the credit quality
Total	2,541,577	2,288,175
Business loans secured by real estate | SBA secured by real estate
Other information concerning the credit quality
Total	79,595	88,381
Business loans secured by real estate | CRE owner-occupied
Other information concerning the credit quality
Total	2,114,050	1,846,554
Business loans secured by real estate | Franchise real estate secured
Other information concerning the credit quality
Total	347,932	353,240
Commercial loans
Other information concerning the credit quality
Total	2,229,588	1,975,053
Commercial loans | Commercial and industrial
Other information concerning the credit quality
Total	1,768,834	1,393,270
Commercial loans | Franchise non-real estate secured
Other information concerning the credit quality
Total	444,797	564,357
Commercial loans | SBA non-real estate secured
Other information concerning the credit quality
Total	15,957	17,426
Retail loans
Other information concerning the credit quality
Total	239,503	305,999
Retail loans | Single family residential
Other information concerning the credit quality
Total	232,574	255,024
Retail loans | Consumer
Other information concerning the credit quality
Total	6,929	50,975
Current
Other information concerning the credit quality
Current	13,223,111	8,703,209
Current | Investor loans secured by real estate
Other information concerning the credit quality
Current	8,223,750	4,150,427
Current | Investor loans secured by real estate | CRE non-owner-occupied
Other information concerning the credit quality
Current	2,674,328	2,067,874
Current | Investor loans secured by real estate | Multifamily
Other information concerning the credit quality
Current	5,171,355	1,575,726
Current | Investor loans secured by real estate | Construction and land
Other information concerning the credit quality
Current	321,993	438,786
Current | Investor loans secured by real estate | SBA secured by real estate
Other information concerning the credit quality
Current	56,074	68,041
Current | Business loans secured by real estate
Other information concerning the credit quality
Current	2,534,714	2,286,409
Current | Business loans secured by real estate | SBA secured by real estate
Other information concerning the credit quality
Current	78,036	86,946
Current | Business loans secured by real estate | CRE owner-occupied
Other information concerning the credit quality
Current	2,108,746	1,846,223
Current | Business loans secured by real estate | Franchise real estate secured
Other information concerning the credit quality
Current	347,932	353,240
Current | Commercial loans
Other information concerning the credit quality
Current	2,225,160	1,960,382
Current | Commercial loans | Commercial and industrial
Other information concerning the credit quality
Current	1,765,451	1,389,026
Current | Commercial loans | Franchise non-real estate secured
Other information concerning the credit quality
Current	444,797	555,215
Current | Commercial loans | SBA non-real estate secured
Other information concerning the credit quality
Current	14,912	16,141
Current | Retail loans
Other information concerning the credit quality
Current	239,487	305,991
Current | Retail loans | Single family residential
Other information concerning the credit quality
Current	232,559	255,024
Current | Retail loans | Consumer
Other information concerning the credit quality
Current	6,928	50,967
30-59
Other information concerning the credit quality
Days Past Due	1,269	2,104
30-59 | Investor loans secured by real estate
Other information concerning the credit quality
Days Past Due	1	1,179
30-59 | Investor loans secured by real estate | CRE non-owner-occupied
Other information concerning the credit quality
Days Past Due	0	1,179
30-59 | Investor loans secured by real estate | Multifamily
Other information concerning the credit quality
Days Past Due	1	0
30-59 | Investor loans secured by real estate | Construction and land
Other information concerning the credit quality
Days Past Due	0	0
30-59 | Investor loans secured by real estate | SBA secured by real estate
Other information concerning the credit quality
Days Past Due	0	0
30-59 | Business loans secured by real estate
Other information concerning the credit quality
Days Past Due	486	331
30-59 | Business loans secured by real estate | SBA secured by real estate
Other information concerning the credit quality
Days Past Due	486	0
30-59 | Business loans secured by real estate | CRE owner-occupied
Other information concerning the credit quality
Days Past Due	0	331
30-59 | Business loans secured by real estate | Franchise real estate secured
Other information concerning the credit quality
Days Past Due	0	0
30-59 | Commercial loans
Other information concerning the credit quality
Days Past Due	766	589
30-59 | Commercial loans | Commercial and industrial
Other information concerning the credit quality
Days Past Due	428	422
30-59 | Commercial loans | Franchise non-real estate secured
Other information concerning the credit quality
Days Past Due	0	0
30-59 | Commercial loans | SBA non-real estate secured
Other information concerning the credit quality
Days Past Due	338	167
30-59 | Retail loans
Other information concerning the credit quality
Days Past Due	16	5
30-59 | Retail loans | Single family residential
Other information concerning the credit quality
Days Past Due	15	0
30-59 | Retail loans | Consumer
Other information concerning the credit quality
Days Past Due	1	5
60-89
Other information concerning the credit quality
Days Past Due	57	10,559
60-89 | Investor loans secured by real estate
Other information concerning the credit quality
Days Past Due	0	0
60-89 | Investor loans secured by real estate | CRE non-owner-occupied
Other information concerning the credit quality
Days Past Due	0	0
60-89 | Investor loans secured by real estate | Multifamily
Other information concerning the credit quality
Days Past Due	0	0
60-89 | Investor loans secured by real estate | Construction and land
Other information concerning the credit quality
Days Past Due	0	0
60-89 | Investor loans secured by real estate | SBA secured by real estate
Other information concerning the credit quality
Days Past Due	0	0
60-89 | Business loans secured by real estate
Other information concerning the credit quality
Days Past Due	0	589
60-89 | Business loans secured by real estate | SBA secured by real estate
Other information concerning the credit quality
Days Past Due	0	589
60-89 | Business loans secured by real estate | CRE owner-occupied
Other information concerning the credit quality
Days Past Due	0	0
60-89 | Business loans secured by real estate | Franchise real estate secured
Other information concerning the credit quality
Days Past Due	0	0
60-89 | Commercial loans
Other information concerning the credit quality
Days Past Due	57	9,968
60-89 | Commercial loans | Commercial and industrial
Other information concerning the credit quality
Days Past Due	57	826
60-89 | Commercial loans | Franchise non-real estate secured
Other information concerning the credit quality
Days Past Due	0	9,142
60-89 | Commercial loans | SBA non-real estate secured
Other information concerning the credit quality
Days Past Due	0	0
60-89 | Retail loans
Other information concerning the credit quality
Days Past Due	0	2
60-89 | Retail loans | Single family residential
Other information concerning the credit quality
Days Past Due	0	0
60-89 | Retail loans | Consumer
Other information concerning the credit quality
Days Past Due	0	2
90+
Other information concerning the credit quality
Days Past Due	11,996	6,439
90+ | Investor loans secured by real estate
Other information concerning the credit quality
Days Past Due	2,014	1,478
90+ | Investor loans secured by real estate | CRE non-owner-occupied
Other information concerning the credit quality
Days Past Due	757	1,088
90+ | Investor loans secured by real estate | Multifamily
Other information concerning the credit quality
Days Past Due	0	0
90+ | Investor loans secured by real estate | Construction and land
Other information concerning the credit quality
Days Past Due	0	0
90+ | Investor loans secured by real estate | SBA secured by real estate
Other information concerning the credit quality
Days Past Due	1,257	390
90+ | Business loans secured by real estate
Other information concerning the credit quality
Days Past Due	6,377	846
90+ | Business loans secured by real estate | SBA secured by real estate
Other information concerning the credit quality
Days Past Due	1,073	846
90+ | Business loans secured by real estate | CRE owner-occupied
Other information concerning the credit quality
Days Past Due	5,304	0
90+ | Business loans secured by real estate | Franchise real estate secured
Other information concerning the credit quality
Days Past Due	0	0
90+ | Commercial loans
Other information concerning the credit quality
Days Past Due	3,605	4,114
90+ | Commercial loans | Commercial and industrial
Other information concerning the credit quality
Days Past Due	2,898	2,996
90+ | Commercial loans | Franchise non-real estate secured
Other information concerning the credit quality
Days Past Due	0	0
90+ | Commercial loans | SBA non-real estate secured
Other information concerning the credit quality
Days Past Due	707	1,118
90+ | Retail loans
Other information concerning the credit quality
Days Past Due	0	1
90+ | Retail loans | Single family residential
Other information concerning the credit quality
Days Past Due	0	0
90+ | Retail loans | Consumer
Other information concerning the credit quality
Days Past Due	$ 0	$ 1