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	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Dec. 31, 2019
Allowance for credit losses on loans
Balance at beginning of period	$ 38,509	$ 16,135	$ 16,852	$ 16,577
Credit loss (benefit) expense	32,836		50,075
Initial allowance for credit losses on PCD loans			2,639
Credit loss (benefit) expense	35,714	305	55,332	1,281
Charge-offs	(15,411)	(353)	(16,964)	(2,359)
Recoveries	416	549	1,047	1,137
Balance at end of period	56,350	16,636	56,350	16,636
Ending allowance balance attributed to loans
Individually evaluated for impairment						$ 476
Collectively evaluated for impairment						16,376
Total ending allowance balance	38,509	16,636	16,852	16,636	$ 56,350	16,852
Loans
Loans individually evaluated for impairment						26,510
Loans collectively evaluated for impairment						6,174,877
Total					8,000,978	6,201,387
Cumulative Effect, Period Of Adoption, Adjustment
Allowance for credit losses on loans
Balance at beginning of period			2,701
Ending allowance balance attributed to loans
Total ending allowance balance			2,701			2,701
Commercial and industrial
Allowance for credit losses on loans
Balance at beginning of period	4,979	1,639	1,458	1,609
Credit loss (benefit) expense	(106)		(275)
Initial allowance for credit losses on PCD loans			1,221
Credit loss (benefit) expense		(352)		(406)
Charge-offs	(575)	0	(575)	0
Recoveries	29	49	82	133
Balance at end of period	4,327	1,336	4,327	1,336
Ending allowance balance attributed to loans
Individually evaluated for impairment						0
Collectively evaluated for impairment						1,458
Total ending allowance balance	4,327	1,336	1,458	1,609	4,327	1,458
Loans
Loans individually evaluated for impairment						243
Loans collectively evaluated for impairment						395,848
Total					599,188	396,091
Commercial and industrial | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for credit losses on loans
Balance at beginning of period			2,416
Ending allowance balance attributed to loans
Total ending allowance balance			2,416			2,416
Commercial real estate – owner occupied
Allowance for credit losses on loans
Balance at beginning of period	2,765	2,868	2,893	2,277
Credit loss (benefit) expense	5,166		6,120
Initial allowance for credit losses on PCD loans			26
Credit loss (benefit) expense		80		1,192
Charge-offs	(2,252)	(142)	(2,253)	(663)
Recoveries	2	114	4	114
Balance at end of period	5,681	2,920	5,681	2,920
Ending allowance balance attributed to loans
Individually evaluated for impairment						474
Collectively evaluated for impairment						2,419
Total ending allowance balance	5,681	2,920	2,893	2,277	5,681	2,893
Loans
Loans individually evaluated for impairment						6,163
Loans collectively evaluated for impairment						785,778
Total					1,176,529	791,941
Commercial real estate – owner occupied | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for credit losses on loans
Balance at beginning of period			(1,109)
Ending allowance balance attributed to loans
Total ending allowance balance			(1,109)			(1,109)
Commercial Real Estate – Investor
Allowance for credit losses on loans
Balance at beginning of period	8,860	8,406	9,883	8,770
Credit loss (benefit) expense	30,131		34,208
Initial allowance for credit losses on PCD loans			260
Credit loss (benefit) expense		711		26
Charge-offs	(12,037)	(57)	(12,062)	(143)
Recoveries	32	292	92	699
Balance at end of period	26,986	9,352	26,986	9,352
Ending allowance balance attributed to loans
Individually evaluated for impairment						0
Collectively evaluated for impairment						9,883
Total ending allowance balance	26,986	9,352	9,883	9,352	26,986	9,883
Loans
Loans individually evaluated for impairment						5,584
Loans collectively evaluated for impairment						2,279,114
Total					3,453,276	2,284,698
Commercial Real Estate – Investor | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for credit losses on loans
Balance at beginning of period			(5,395)
Ending allowance balance attributed to loans
Total ending allowance balance			(5,395)			(5,395)
Residential Real Estate
Allowance for credit losses on loans
Balance at beginning of period	17,685	1,966	2,002	2,413
Credit loss (benefit) expense	(1,891)		10,749
Initial allowance for credit losses on PCD loans			109
Credit loss (benefit) expense		193		899
Charge-offs	(6)	(27)	(1,351)	(1,221)
Recoveries	320	39	766	80
Balance at end of period	16,108	2,171	16,108	2,171
Ending allowance balance attributed to loans
Individually evaluated for impairment						0
Collectively evaluated for impairment						2,002
Total ending allowance balance	16,108	2,171	2,002	2,413	16,108	2,002
Loans
Loans individually evaluated for impairment						11,009
Loans collectively evaluated for impairment						2,309,812
Total					2,407,178	2,320,821
Residential Real Estate | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for credit losses on loans
Balance at beginning of period			3,833
Ending allowance balance attributed to loans
Total ending allowance balance			3,833			3,833
Consumer
Allowance for credit losses on loans
Balance at beginning of period	4,220	512	591	486
Credit loss (benefit) expense	(464)		(727)
Initial allowance for credit losses on PCD loans			1,023
Credit loss (benefit) expense		10		185
Charge-offs	(541)	(127)	(723)	(332)
Recoveries	33	55	103	111
Balance at end of period	3,248	450	3,248	450
Ending allowance balance attributed to loans
Individually evaluated for impairment						2
Collectively evaluated for impairment						589
Total ending allowance balance	3,248	450	3,248	486	3,248	591
Loans
Loans individually evaluated for impairment						3,511
Loans collectively evaluated for impairment						404,325
Total					364,807	407,836
Consumer | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for credit losses on loans
Balance at beginning of period			2,981
Ending allowance balance attributed to loans
Total ending allowance balance			2,981			2,981
Unallocated
Allowance for credit losses on loans
Balance at beginning of period	0	744	25	1,022
Credit loss (benefit) expense	0		0
Initial allowance for credit losses on PCD loans			0
Credit loss (benefit) expense		(337)		(615)
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Balance at end of period	0	407	0	407
Ending allowance balance attributed to loans
Individually evaluated for impairment						0
Collectively evaluated for impairment						25
Total ending allowance balance	$ 0	$ 407	0	$ 1,022	$ 0	25
Loans
Loans individually evaluated for impairment						0
Loans collectively evaluated for impairment						0
Total						0
Unallocated | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for credit losses on loans
Balance at beginning of period			(25)
Ending allowance balance attributed to loans
Total ending allowance balance			$ (25)			$ (25)