Loans Receivable and Allowance for Loan Losses - Financing Receivable Credit Quality Indicators (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 12,273,265	$ 12,097,906
Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans		10,199,858
Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans		1,898,048
Real estate-Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	52,437	51,197
Real estate-Residential | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans		44,612
Real estate-Residential | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans		6,585
Real estate-Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	8,316,382	8,395,327
Real estate-Commercial | Legacy | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Loans		1,863,928
Real estate-Commercial | Legacy | Hotel & Motel
Financing Receivable, Credit Quality Indicator [Line Items]
Loans		1,427,150
Real estate-Commercial | Legacy | Gas Station & Car Wash
Financing Receivable, Credit Quality Indicator [Line Items]
Loans		819,565
Real estate-Commercial | Legacy | Mixed Use
Financing Receivable, Credit Quality Indicator [Line Items]
Loans		535,793
Real estate-Commercial | Legacy | Industrial & Warehouse
Financing Receivable, Credit Quality Indicator [Line Items]
Loans		751,233
Real estate-Commercial | Legacy | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans		1,396,952
Real estate-Commercial | Acquired | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Loans		505,957
Real estate-Commercial | Acquired | Hotel & Motel
Financing Receivable, Credit Quality Indicator [Line Items]
Loans		207,040
Real estate-Commercial | Acquired | Gas Station & Car Wash
Financing Receivable, Credit Quality Indicator [Line Items]
Loans		155,008
Real estate-Commercial | Acquired | Mixed Use
Financing Receivable, Credit Quality Indicator [Line Items]
Loans		89,237
Real estate-Commercial | Acquired | Industrial & Warehouse
Financing Receivable, Credit Quality Indicator [Line Items]
Loans		199,319
Real estate-Commercial | Acquired | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans		444,145
Real estate-Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	296,146	275,076
Real estate-Construction | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans		238,135
Real estate-Construction | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans		36,941
Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	8,664,965	8,721,600
Real Estate | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	7,482,747	7,077,368
Real Estate | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,182,218	1,644,232
Commercial Business
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,558,351	2,127,630
Commercial Business | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,498,788	2,017,691
Commercial Business | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	59,563	109,939
Trade Finance
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	160,859	197,190
Trade Finance | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	160,859	194,066
Trade Finance | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	3,124
Consumer and Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	889,090	1,051,486
Consumer and Other | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	845,263	910,733
Consumer and Other | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	43,827	140,753
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	11,872,522	11,616,490
Pass | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	10,702,893	9,884,742
Pass | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,169,629	1,731,748
Pass | Real estate-Residential | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	48,414	44,066
Pass | Real estate-Residential | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	3,563	5,812
Pass | Real estate-Commercial | Legacy | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,884,336	1,815,170
Pass | Real estate-Commercial | Legacy | Hotel & Motel
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,482,398	1,389,349
Pass | Real estate-Commercial | Legacy | Gas Station & Car Wash
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	738,988	814,291
Pass | Real estate-Commercial | Legacy | Mixed Use
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	634,186	510,021
Pass | Real estate-Commercial | Legacy | Industrial & Warehouse
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	834,514	711,236
Pass | Real estate-Commercial | Legacy | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,386,594	1,326,795
Pass | Real estate-Commercial | Acquired | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	322,519	483,939
Pass | Real estate-Commercial | Acquired | Hotel & Motel
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	147,647	186,761
Pass | Real estate-Commercial | Acquired | Gas Station & Car Wash
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	92,852	148,702
Pass | Real estate-Commercial | Acquired | Mixed Use
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	65,268	77,100
Pass | Real estate-Commercial | Acquired | Industrial & Warehouse
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	138,928	171,574
Pass | Real estate-Commercial | Acquired | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	311,674	402,247
Pass | Real estate-Construction | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	253,765	227,231
Pass | Real estate-Construction | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	29,058
Pass | Commercial Business | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,435,892	1,944,783
Pass | Commercial Business | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	45,185	89,611
Pass | Trade Finance | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	160,859	191,508
Pass | Trade Finance | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Pass | Consumer and Other | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	842,947	910,292
Pass | Consumer and Other | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	41,993	136,944
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	141,452	163,089
Special Mention | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	120,620	121,622
Special Mention | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	20,832	41,467
Special Mention | Real estate-Residential | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Special Mention | Real estate-Residential | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	393
Special Mention | Real estate-Commercial | Legacy | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	29,478	18,072
Special Mention | Real estate-Commercial | Legacy | Hotel & Motel
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,237	21,932
Special Mention | Real estate-Commercial | Legacy | Gas Station & Car Wash
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,707	2,810
Special Mention | Real estate-Commercial | Legacy | Mixed Use
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,974	12,480
Special Mention | Real estate-Commercial | Legacy | Industrial & Warehouse
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	7,641	1,665
Special Mention | Real estate-Commercial | Legacy | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	15,625	35,539
Special Mention | Real estate-Commercial | Acquired | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	3,442	4,651
Special Mention | Real estate-Commercial | Acquired | Hotel & Motel
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	158	807
Special Mention | Real estate-Commercial | Acquired | Gas Station & Car Wash
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	454	274
Special Mention | Real estate-Commercial | Acquired | Mixed Use
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,932	3,986
Special Mention | Real estate-Commercial | Acquired | Industrial & Warehouse
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	4,039	9,451
Special Mention | Real estate-Commercial | Acquired | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	9,791	12,902
Special Mention | Real estate-Construction | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	24,641	10,904
Special Mention | Real estate-Construction | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	7,883
Special Mention | Commercial Business | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	38,160	18,220
Special Mention | Commercial Business | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	7	1,083
Special Mention | Trade Finance | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Special Mention | Trade Finance | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Special Mention | Consumer and Other | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	157	0
Special Mention | Consumer and Other | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	9	37
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	259,278	317,915
Substandard | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	164,131	193,494
Substandard | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	95,147	124,421
Substandard | Real estate-Residential | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	143	546
Substandard | Real estate-Residential | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	317	380
Substandard | Real estate-Commercial | Legacy | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	38,164	30,686
Substandard | Real estate-Commercial | Legacy | Hotel & Motel
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	20,864	15,869
Substandard | Real estate-Commercial | Legacy | Gas Station & Car Wash
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	4,560	2,464
Substandard | Real estate-Commercial | Legacy | Mixed Use
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	8,211	13,292
Substandard | Real estate-Commercial | Legacy | Industrial & Warehouse
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	35,739	38,332
Substandard | Real estate-Commercial | Legacy | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	21,994	34,618
Substandard | Real estate-Commercial | Acquired | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	10,597	17,332
Substandard | Real estate-Commercial | Acquired | Hotel & Motel
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	11,294	19,472
Substandard | Real estate-Commercial | Acquired | Gas Station & Car Wash
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,953	6,032
Substandard | Real estate-Commercial | Acquired | Mixed Use
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	8,144	8,151
Substandard | Real estate-Commercial | Acquired | Industrial & Warehouse
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	10,015	18,071
Substandard | Real estate-Commercial | Acquired | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	25,466	28,996
Substandard | Real estate-Construction | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	7,574	0
Substandard | Real estate-Construction | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	10,165	0
Substandard | Commercial Business | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	24,723	54,688
Substandard | Commercial Business | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	14,371	19,237
Substandard | Trade Finance | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	2,558
Substandard | Trade Finance | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	3,124
Substandard | Consumer and Other | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,159	441
Substandard | Consumer and Other | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,825	3,626
Doubtful/ Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	13	412
Doubtful/ Loss | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	13	0
Doubtful/ Loss | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	412
Doubtful/ Loss | Real estate-Residential | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful/ Loss | Real estate-Residential | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful/ Loss | Real estate-Commercial | Legacy | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful/ Loss | Real estate-Commercial | Legacy | Hotel & Motel
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful/ Loss | Real estate-Commercial | Legacy | Gas Station & Car Wash
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful/ Loss | Real estate-Commercial | Legacy | Mixed Use
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful/ Loss | Real estate-Commercial | Legacy | Industrial & Warehouse
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful/ Loss | Real estate-Commercial | Legacy | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful/ Loss | Real estate-Commercial | Acquired | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	35
Doubtful/ Loss | Real estate-Commercial | Acquired | Hotel & Motel
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful/ Loss | Real estate-Commercial | Acquired | Gas Station & Car Wash
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful/ Loss | Real estate-Commercial | Acquired | Mixed Use
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful/ Loss | Real estate-Commercial | Acquired | Industrial & Warehouse
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	223
Doubtful/ Loss | Real estate-Commercial | Acquired | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful/ Loss | Real estate-Construction | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful/ Loss | Real estate-Construction | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful/ Loss | Commercial Business | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	13	0
Doubtful/ Loss | Commercial Business | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	8
Doubtful/ Loss | Trade Finance | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful/ Loss | Trade Finance | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful/ Loss | Consumer and Other | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful/ Loss | Consumer and Other | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	$ 146
Non Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	12,273,265
Non Pass | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	10,987,657
Non Pass | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,285,608
Non Pass | Real estate-Residential | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	48,557
Non Pass | Real estate-Residential | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	3,880
Non Pass | Real estate-Commercial | Legacy | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,951,978
Non Pass | Real estate-Commercial | Legacy | Hotel & Motel
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,504,499
Non Pass | Real estate-Commercial | Legacy | Gas Station & Car Wash
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	745,255
Non Pass | Real estate-Commercial | Legacy | Mixed Use
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	644,371
Non Pass | Real estate-Commercial | Legacy | Industrial & Warehouse
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	877,894
Non Pass | Real estate-Commercial | Legacy | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,424,213
Non Pass | Real estate-Commercial | Acquired | Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	336,558
Non Pass | Real estate-Commercial | Acquired | Hotel & Motel
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	159,099
Non Pass | Real estate-Commercial | Acquired | Gas Station & Car Wash
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	96,259
Non Pass | Real estate-Commercial | Acquired | Mixed Use
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	76,344
Non Pass | Real estate-Commercial | Acquired | Industrial & Warehouse
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	152,982
Non Pass | Real estate-Commercial | Acquired | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	346,931
Non Pass | Real estate-Construction | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	285,980
Non Pass | Real estate-Construction | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	10,165
Non Pass | Commercial Business | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,498,788
Non Pass | Commercial Business | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	59,563
Non Pass | Trade Finance | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	160,859
Non Pass | Trade Finance | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0
Non Pass | Consumer and Other | Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	845,263
Non Pass | Consumer and Other | Acquired
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 43,827