Selected Consolidated Quarterly Financial Data - Summary of Consolidated Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 92,562	$ 92,962	$ 95,877	$ 98,207	$ 77,075	$ 76,887	$ 78,410	$ 76,422	$ 379,608	$ 308,794	$ 276,654
Interest expense	14,711	16,174	17,210	18,562	13,721	13,495	13,573	12,034	66,657	52,823	36,152
Net interest income	77,851	76,788	78,667	79,645	63,354	63,392	64,837	64,388	312,951	255,971	240,502
Credit loss expense	4,072	35,714	9,649	9,969	355	305	356	620	59,404	1,636	3,490
Net interest income after credit loss expense	73,779	41,074	69,018	69,676	62,999	63,087	64,481	63,768	253,547	254,335	237,012
Other income	11,032	11,755	11,282	13,542	11,231	11,543	9,879	9,512
Net gain on equity investments	24,487	(3,576)	148	155					21,214	267	(199)
Gain On Sale PPP Loans	5,101	0	0	0
Operating expenses (excluding FHLB advance prepayment fees, branch consolidation and merger related expenses)	53,053	52,801	51,075	51,675	43,589	40,884	43,289	41,827
FHLB advance prepayment fees	13,333	0	924	0					14,257		0
Branch consolidation expenses	3,336	830	863	2,594					7,623	9,050	3,151
Merger related expenses	1,194	3,156	3,070	8,527					15,947	10,503	26,911
Merger related and branch consolidation expenses					4,010	2,473	7,626	5,444
Income before provision for income taxes	43,483	(7,534)	24,516	20,577	26,631	31,273	23,445	26,009	81,042	107,358	85,502
Provision for income taxes	10,419	(2,608)	5,878	4,044	3,181	6,302	4,465	4,836	17,733	18,784	13,570
Net income	33,064	(4,926)	18,638	16,533	$ 23,450	$ 24,971	$ 18,980	$ 21,173	63,309	88,574	71,932
Net income (loss) available to common stockholders	$ 32,060	$ (6,019)	$ 18,638	$ 16,533					$ 61,212	$ 88,574	$ 71,932
Basic earnings per share (in dollars per share)	$ 0.53	$ (0.10)	$ 0.31	$ 0.28	$ 0.47	$ 0.50	$ 0.37	$ 0.43	$ 1.02	$ 1.77	$ 1.54
Diluted earnings per share (in dollars per share)	$ 0.54	$ (0.10)	$ 0.31	$ 0.27	$ 0.47	$ 0.49	$ 0.37	$ 0.42	$ 1.02	$ 1.75	$ 1.51