Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Interest income:
Loans receivable	$ 43,043	$ 217,774	$ 189,869	$ 164,849
Debt securities available for sale and equity securities	5,074	30,938	25,338	17,163
Debt securities held to maturity	382	8,180	7,147	68
Federal funds and interest-earning deposits	103	594	1,175	308
Federal Home Loan Bank stock dividends	567	3,597	2,761	1,838
Total interest income	49,169	261,083	226,290	184,226
Interest expense:
Deposits	7,631	61,551	39,523	25,581
Borrowings	4,609	27,161	22,733	18,865
Total interest expense	12,240	88,712	62,256	44,446
Net interest income	36,929	172,371	164,034	139,780
Provision for loan losses	3,400	4,224	6,677	6,426
Net interest income after provision for loan losses	33,529	168,147	157,357	133,354
Non-interest income:
Bank-owned life insurance	1,089	5,846	5,208	4,936
Gain (loss) on securities transactions	(60)	2,612	116	(1,689)
Change in fair value of equity securities	0	305	0	0
Gain (loss) on sale of loans	0	785	618	(380)
Other non-interest income	1,162	5,922	4,943	4,497
Total non-interest income	4,733	31,636	21,688	17,172
Non-interest expense:
Compensation and employee benefits	15,624	84,256	77,226	62,993
Occupancy	3,382	16,180	14,547	13,315
Federal deposit insurance premiums	414	895	1,893	1,652
Advertising	1,408	3,932	4,137	4,078
Professional fees	398	5,913	4,619	1,354
Data processing	595	3,001	2,600	2,244
Charitable contribution to foundation	0	0	34,767	3,603
Merger-related expenses	0	2,755	0	0
Other non-interest expense	3,780	11,769	5,597	14,207
Total non-interest expense	25,601	128,701	145,386	103,446
Income before income tax expense	12,661	71,082	33,659	47,080
Income tax expense	8,983	16,365	10,923	16,008
Net income	3,678	$ 54,717	$ 22,736	31,072
Earnings per share - basic and diluted (in dollars per share)		$ 0.49	$ 0.20
Weighted average shares outstanding - basic and diluted (in shares)		111,101,246	111,395,723
Demand deposit account fees
Non-interest income:
Revenue	960	$ 4,478	$ 3,987	3,669
Title insurance fees
Non-interest income:
Revenue	1,017	4,981	4,297	4,163
Bank Servicing
Non-interest income:
Revenue	$ 565	$ 6,707	$ 2,519	$ 1,976