Significant Accounting Policies - Additional Information (Details) - USD ($)		1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 07, 2021	Apr. 30, 2021	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Accounting Policies [Abstract]
Impairment of fixed asset impairment charges			$ 0		$ 2,000,000.0
Common stock, shares authorized (in shares)			32,000,000		32,000,000		32,000,000
Common stock, par value (in dollars per share)			$ 0.01		$ 0.01		$ 0.01
Common stock, shares issued (in shares)			24,621,111		24,621,111		24,418,939
Common stock, shares outstanding (in shares)			24,621,111		24,621,111		24,418,939
Preferred stock, shares authorized (in shares)			8,000,000		8,000,000		8,000,000
Issued shares of preferred stock			0		0		0
Outstanding shares of preferred stock			0		0		0
Common stock dividends declared (in dollars per share)		$ 0.60	$ 0.60	$ 0.60	$ 1.20	$ 1.20
Common stock dividends paid (in dollars per share)	$ 0.60
Accumulated other comprehensive income net of tax			$ 30,823,000		$ 30,823,000		$ 48,880,000
Tax from unrealized gains and losses on marketable securities					300,000		$ 300,000
Reclassifications from AOCI			$ 0	$ 25,000	$ 0	$ 25,000
Reclassifications from AOCI, tax				$ 10,000		$ 10,000