Stockholders' Equity - Summary of Changes in Stockholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Shareholders Equity [Line Items]
Beginning balance, value	$ 757,067	$ 685,766	$ 745,108	$ 659,601
Net earnings	13,302	14,011	62,731	44,828
Dividends declared	(19,619)	(18,043)	(58,856)	(53,518)
Shares issued pursuant to dividend reinvestment, value	14	23	$ 44	$ 59
Shares issued pursuant to dividend reinvestment, shares			1,512	1,996
Stock-based compensation/settlements, value	1,227	1,037	$ 3,047	$ 2,246
Ending balance, value	751,927	702,224	751,927	702,224
ATM Program [Member]
Shareholders Equity [Line Items]
Shares issued pursuant to ATM Program, net, value	(64)	19,430	(147)	49,008
Common Stock [Member]
Shareholders Equity [Line Items]
Beginning balance, value	$ 467	$ 447	$ 467	$ 436
Beginning balance, shares	46,733,000	44,703,000	46,716,000	43,606,000
Shares issued pursuant to dividend reinvestment, shares	1,000		2,000	1,000
Stock-based compensation/settlements, value				$ 1
Stock-based compensation/settlements, shares			16,000	64,000
Ending balance, value	$ 467	$ 453	$ 467	$ 453
Ending balance, share	46,734,000	45,339,000	46,734,000	45,339,000
Common Stock [Member] | ATM Program [Member]
Shareholders Equity [Line Items]
Shares issued pursuant to ATM Program, net, value		$ 6		$ 16
Shares issued pursuant to ATM Program, net, shares		636,000		1,668,000
Additional Paid-in-Capital [Member]
Shareholders Equity [Line Items]
Beginning balance, value	$ 819,976	$ 753,420	$ 818,209	$ 722,608
Shares issued pursuant to dividend reinvestment, value	14	23	44	59
Stock-based compensation/settlements, value	1,227	1,037	3,047	2,245
Ending balance, value	821,153	773,904	821,153	773,904
Additional Paid-in-Capital [Member] | ATM Program [Member]
Shareholders Equity [Line Items]
Shares issued pursuant to ATM Program, net, value	(64)	19,424	(147)	48,992
Dividends Paid in Excess of Earnings [Member]
Shareholders Equity [Line Items]
Beginning balance, value	(63,376)	(68,101)	(73,568)	(63,443)
Net earnings	13,302	14,011	62,731	44,828
Dividends declared	(19,619)	(18,043)	(58,856)	(53,518)
Ending balance, value	$ (69,693)	$ (72,133)	$ (69,693)	$ (72,133)