Loans Receivable, Net - Allowance for Loan Losses and Recorded Investment in Loans by Portfolio Segment and Based on Impairment Method Excluding PCI Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 16,852	$ 16,577
Initial allowance for credit losses on PCD loans	2,639
Credit loss expense	57,402	1,636
Charge-offs	(20,184)	(2,804)
Recoveries	1,325	1,443
Balance at end of period	60,735	16,852
Ending allowance balance attributed to loans
Individually evaluated for impairment				$ 476
Collectively evaluated for impairment				16,376
Total ending allowance balance	16,852	16,852	$ 60,735	16,852
Loans
Loans individually evaluated for impairment				26,510
Loans collectively evaluated for impairment				6,174,877
Total ending loan balance			7,756,106	6,201,387
Cumulative Effect, Period of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	2,701
Balance at end of period		2,701
Ending allowance balance attributed to loans
Total ending allowance balance	2,701	2,701		2,701
Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	1,458	1,609
Initial allowance for credit losses on PCD loans	1,221
Credit loss expense	1,039	(311)
Charge-offs	(890)	0
Recoveries	146	160
Balance at end of period	5,390	1,458
Ending allowance balance attributed to loans
Individually evaluated for impairment				0
Collectively evaluated for impairment				1,458
Total ending allowance balance	5,390	1,609	5,390	1,458
Loans
Loans individually evaluated for impairment				243
Loans collectively evaluated for impairment				395,848
Total ending loan balance			470,656	396,091
Commercial and industrial | Cumulative Effect, Period of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	2,416
Balance at end of period		2,416
Ending allowance balance attributed to loans
Total ending allowance balance	2,416	2,416		2,416
Commercial real estate – owner occupied
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	2,893	2,277
Initial allowance for credit losses on PCD loans	26
Credit loss expense	15,007	947
Charge-offs	(1,769)	(663)
Recoveries	6	332
Balance at end of period	15,054	2,893
Ending allowance balance attributed to loans
Individually evaluated for impairment				474
Collectively evaluated for impairment				2,419
Total ending allowance balance	2,893	2,893	15,054	2,893
Loans
Loans individually evaluated for impairment				6,163
Loans collectively evaluated for impairment				785,778
Total ending loan balance			1,145,065	791,941
Commercial real estate – owner occupied | Cumulative Effect, Period of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	(1,109)
Balance at end of period		(1,109)
Ending allowance balance attributed to loans
Total ending allowance balance	(1,109)	(1,109)		(1,109)
Commercial Real Estate - Investor
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	9,883	8,770
Initial allowance for credit losses on PCD loans	260
Credit loss expense	34,935	638
Charge-offs	(13,081)	(236)
Recoveries	101	711
Balance at end of period	26,703	9,883
Ending allowance balance attributed to loans
Individually evaluated for impairment				0
Collectively evaluated for impairment				9,883
Total ending allowance balance	9,883	9,883	26,703	9,883
Loans
Loans individually evaluated for impairment				5,584
Loans collectively evaluated for impairment				2,279,114
Total ending loan balance			3,491,464	2,284,698
Commercial Real Estate - Investor | Cumulative Effect, Period of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	(5,395)
Balance at end of period		(5,395)
Ending allowance balance attributed to loans
Total ending allowance balance	(5,395)	(5,395)		(5,395)
Residential real estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	2,002	2,413
Initial allowance for credit losses on PCD loans	109
Credit loss expense	8,191	792
Charge-offs	(3,200)	(1,299)
Recoveries	883	96
Balance at end of period	11,818	2,002
Ending allowance balance attributed to loans
Individually evaluated for impairment				0
Collectively evaluated for impairment				2,002
Total ending allowance balance	11,818	2,413	11,818	2,002
Loans
Loans individually evaluated for impairment				11,009
Loans collectively evaluated for impairment				2,309,812
Total ending loan balance			2,309,459	2,320,821
Residential real estate | Cumulative Effect, Period of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	3,833
Balance at end of period		3,833
Ending allowance balance attributed to loans
Total ending allowance balance	3,833	3,833		3,833
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	591	486
Initial allowance for credit losses on PCD loans	1,023
Credit loss expense	(1,770)	567
Charge-offs	(1,244)	(606)
Recoveries	189	144
Balance at end of period	1,770	591
Ending allowance balance attributed to loans
Individually evaluated for impairment				2
Collectively evaluated for impairment				589
Total ending allowance balance	1,770	486	1,770	591
Loans
Loans individually evaluated for impairment				3,511
Loans collectively evaluated for impairment				404,325
Total ending loan balance			339,462	407,836
Consumer | Cumulative Effect, Period of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	2,981
Balance at end of period		2,981
Ending allowance balance attributed to loans
Total ending allowance balance	2,981	2,981		2,981
Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	25	1,022
Initial allowance for credit losses on PCD loans	0
Credit loss expense	0	(997)
Charge-offs	0	0
Recoveries	0	0
Balance at end of period	0	25
Ending allowance balance attributed to loans
Individually evaluated for impairment				0
Collectively evaluated for impairment				25
Total ending allowance balance	25	25	$ 0	25
Loans
Loans individually evaluated for impairment				0
Loans collectively evaluated for impairment				0
Total ending loan balance				0
Unallocated | Cumulative Effect, Period of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	(25)
Balance at end of period		(25)
Ending allowance balance attributed to loans
Total ending allowance balance	$ (25)	$ (25)		$ (25)