Stockholders' Equity - Summary of Changes in Stockholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Shareholders Equity [Line Items]
Beginning balance, value	$ 745,108	$ 659,601
Net earnings	18,749	17,927
Dividends declared	(19,618)	(17,690)
Shares issued pursuant to dividend reinvestment, value	$ 16	$ 18
Shares issued pursuant to dividend reinvestment, shares	504	649
Stock-based compensation/settlements, value	$ 588	$ 421
Ending balance, value	744,817	680,543
ATM Program [Member]
Shareholders Equity [Line Items]
Shares issued pursuant to ATM Program, net, value	(26)	20,266
Common Stock [Member]
Shareholders Equity [Line Items]
Beginning balance, value	$ 467	$ 436
Beginning balance, shares	46,716,000	43,606,000
Shares issued pursuant to dividend reinvestment, shares		1,000
Stock-based compensation/settlements, shares	16,000	17,000
Ending balance, value	$ 467	$ 444
Ending balance, share	46,732,000	44,367,000
Common Stock [Member] | ATM Program [Member]
Shareholders Equity [Line Items]
Shares issued pursuant to ATM Program, net, value		$ 8
Shares issued pursuant to ATM Program, net, shares		743,000
Additional Paid-in-Capital [Member]
Shareholders Equity [Line Items]
Beginning balance, value	$ 818,209	$ 722,608
Shares issued pursuant to dividend reinvestment, value	16	18
Stock-based compensation/settlements, value	588	421
Ending balance, value	818,787	743,305
Additional Paid-in-Capital [Member] | ATM Program [Member]
Shareholders Equity [Line Items]
Shares issued pursuant to ATM Program, net, value	(26)	20,258
Dividends Paid in Excess of Earnings [Member]
Shareholders Equity [Line Items]
Beginning balance, value	(73,568)	(63,443)
Net earnings	18,749	17,927
Dividends declared	(19,618)	(17,690)
Ending balance, value	$ (74,437)	$ (63,206)