Schedule II - Condensed Financial Information of Registrant, Statements of Cash Flows (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
	Aug. 12, 2019	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net income		$ 17,853	$ 12,976	$ 13,767	$ 18,720	$ 4,448	$ 11,940	$ 10,112	$ 7,287	$ 63,316	$ 33,787	$ 24,901
Adjustments to reconcile net income to net cash used in operating activities:
Deferred tax (benefit) expense										(125)	(3,230)	1,065
Stock compensation expense										2,742	1,597	652
Dividends received from subsidiary										5,000	11,500	4,500
Net cash provided by (used in) operating activities										178,357	103,980	77,398
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net cash provided by (used in) investing activities										(230,793)	(106,540)	(42,432)
Financing activities:
Proceeds from Issuance of Common Stock	$ 65,900									65,879	0	0
Common stock issued, stock options exercised										2,750	1,808	1,077
Payroll taxes withheld and remitted on share-based payments										(617)	0	0
Dividends paid										(6,929)	(5,906)	(5,039)
Proceeds from credit facility										17,300	0	0
Debt issuance costs										(628)	0	0
Net cash provided by (used in) financing activities										77,755	(4,098)	(3,971)
Net change in cash and cash equivalents										25,319	(6,658)	30,995
Cash and cash equivalents at beginning of period					75,089				81,747	75,089	81,747	50,752
Cash and cash equivalents at end of period		100,408				75,089				100,408	75,089	81,747
Parent Company [Member]
Operating activities:
Net income										63,316	33,787	24,901
Adjustments to reconcile net income to net cash used in operating activities:
Deferred tax (benefit) expense										(150)	(170)	429
Stock compensation expense										2,742	1,597	652
Equity in undistributed earnings of subsidiaries										(61,315)	(33,469)	(25,303)
Changes in operating assets and liabilities										(14,247)	(633)	(1,583)
Dividends received from subsidiary										5,000	11,500	4,500
Net cash provided by (used in) operating activities										(4,654)	12,612	3,596
Net Cash Provided by (Used in) Investing Activities [Abstract]
Contribution to subsidiary										(68,391)	0	0
Net cash provided by (used in) investing activities										(68,391)	0	0
Financing activities:
Proceeds from Issuance of Common Stock										65,879	0	0
Common stock issued, stock options exercised										2,750	1,808	1,077
Payroll taxes withheld and remitted on share-based payments										(617)	0	0
Dividends paid										(6,929)	(5,906)	(5,039)
Proceeds from credit facility										17,300	0	0
Debt issuance costs										(628)
Net cash provided by (used in) financing activities										77,755	(4,098)	(3,962)
Net change in cash and cash equivalents										4,710	8,514	(366)
Cash and cash equivalents at beginning of period					$ 10,016				$ 1,502	10,016	1,502	1,868
Cash and cash equivalents at end of period		$ 14,726				$ 10,016				$ 14,726	$ 10,016	$ 1,502