Consolidated Statements of Changes in Stockholders' Equity Statement - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income	Noncontrolling Interest [Member]
Beginning balance at Dec. 31, 2018	$ 889,312	$ 28	$ 495,366	$ 393,918	$ 0	$ 0
Beginning balance (in shares) at Dec. 31, 2018		28,404,316
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	5,873			5,873
Share-based compensation	870		886	(16)
Issuance of restricted and deferred stock units	(132)		(132)
Issuance of restricted and deferred stock units (in shares)		14,312
Employee stock purchase plan	811		811
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs	(10)		(10)
Employee stock purchase plan (in shares)		15,932
Dividends paid	(8,528)			(8,528)
Ending balance at Mar. 31, 2019	888,293	$ 28	496,921	391,344	0	0
Ending balance (in shares) at Mar. 31, 2019		28,434,560
Beginning balance at Dec. 31, 2018	889,312	$ 28	495,366	393,918	0	0
Beginning balance (in shares) at Dec. 31, 2018		28,404,316
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	19,635
Ending balance at Jun. 30, 2019	893,995	$ 28	497,633	396,334	0	0
Ending balance (in shares) at Jun. 30, 2019		28,442,139
Beginning balance at Mar. 31, 2019	888,293	$ 28	496,921	391,344	0	0
Beginning balance (in shares) at Mar. 31, 2019		28,434,560
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	13,762			13,538		224
Distribution to noncontrolling interest	(224)					(224)
Share-based compensation	702		718	(16)
Issuance of restricted and deferred stock units	(6)		(6)
Issuance of restricted and deferred stock units (in shares)		7,579
Dividends paid	(8,532)			(8,532)
Ending balance at Jun. 30, 2019	893,995	$ 28	497,633	396,334	0	0
Ending balance (in shares) at Jun. 30, 2019		28,442,139
Beginning balance at Dec. 31, 2019	$ 889,984	$ 28	506,639	383,191	126	0
Beginning balance (in shares) at Dec. 31, 2019	28,456,508	28,456,508
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 2,417			2,417
Unrealized Gain (Loss) on Investments	(135)				(135)
Share-based compensation	208		251	(43)
Issuance of restricted and deferred stock units	(785)		(785)
Issuance of restricted and deferred stock units (in shares)		25,781
Employee stock purchase plan	970		970
Employee stock purchase plan (in shares)		15,552
Dividends paid	(9,118)			(9,118)
Ending balance at Mar. 31, 2020	883,541	$ 28	507,075	376,447	(9)	0
Ending balance (in shares) at Mar. 31, 2020		28,497,841
Beginning balance at Dec. 31, 2019	$ 889,984	$ 28	506,639	383,191	126	0
Beginning balance (in shares) at Dec. 31, 2019	28,456,508	28,456,508
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 22,138
Ending balance at Jun. 30, 2020	$ 895,131	$ 29	508,098	387,003	1	0
Ending balance (in shares) at Jun. 30, 2020	28,516,705	28,516,705
Beginning balance at Mar. 31, 2020	$ 883,541	$ 28	507,075	376,447	(9)	0
Beginning balance (in shares) at Mar. 31, 2020		28,497,841
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	19,721			19,721		0
Unrealized Gain (Loss) on Investments	10				10
Share-based compensation	966		1,009	(43)
Issuance of restricted and deferred stock units	15	$ 1	14
Issuance of restricted and deferred stock units (in shares)		18,864
Dividends paid	(9,122)			(9,122)
Ending balance at Jun. 30, 2020	$ 895,131	$ 29	$ 508,098	$ 387,003	$ 1	$ 0
Ending balance (in shares) at Jun. 30, 2020	28,516,705	28,516,705