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Stockholders' Equity - Additional Information (Detail) - USD ($) |  |  |  | 1 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | --- | --- | ---
Jul. 31, 2025 | Mar. 01, 2024 | Mar. 01, 2023 | Jul. 31, 2024 | Feb. 28, 2023 | Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023 | Dec. 31, 2023
Shareholders Equity [Line Items] |  |  |  |  |  |  |  |  |  |
Payment of regular quarterly dividend |  |  |  |  |  |  |  | $ 74,800,000 | $ 63,800,000 |
Regular quarterly dividends paid per share |  |  |  |  |  |  |  | $ 1.35 | $ 1.29 |
Shares issued pursuant to dividend reinvestment, shares |  |  |  |  |  |  |  | 1,643 | 1,178 |
Shares issued pursuant to dividend reinvestment, value |  |  |  |  |  | $ 16,000 | $ 12,000 | $ 46,000 | $ 40,000 |
Proceeds from issuance of common stock under the dividend reinvestment plan |  |  |  |  |  |  |  | 46,000 | 40,000 |
Stock based compensation expense |  |  |  |  |  |  |  | $ 4,500,000 | $ 4,200,000 |
Common Stock [Member] |  |  |  |  |  |  |  |  |  |
Shareholders Equity [Line Items] |  |  |  |  |  |  |  |  |  |
Shares issued pursuant to Offering/Program net, shares |  |  |  |  |  |  | 2,200,000 |  | 2,200,000 |
Shares issued pursuant to dividend reinvestment, shares |  |  |  |  |  | 1,000 | 1,000 | 1,000 | 1,000 |
July 2024 Forward Offering [Member] |  |  |  |  |  |  |  |  |  |
Shareholders Equity [Line Items] |  |  |  |  |  |  |  |  |  |
Number of shares settled under forward provisions |  |  |  |  |  | 0 |  | 0 |  |
July 2024 Forward Offering [Member] | Scenario Forecast [Member] |  |  |  |  |  |  |  |  |  |
Shareholders Equity [Line Items] |  |  |  |  |  |  |  |  |  |
Proceeds from issuance of common stock, net | $ 121,100,000 |  |  |  |  |  |  |  |  |
February 2023 Forward Offering [Member] |  |  |  |  |  |  |  |  |  |
Shareholders Equity [Line Items] |  |  |  |  |  |  |  |  |  |
Proceeds from issuance of common stock, net |  |  |  |  |  |  | $ 71,500,000 |  |  | $ 112,100,000
Number of shares settled under forward provisions |  |  |  |  |  |  | 2,200,000 |  |  | 3,500,000
Follow-on Public Offering [Member] | July 2024 Forward Offering [Member] | Common Stock [Member] |  |  |  |  |  |  |  |  |  |
Shareholders Equity [Line Items] |  |  |  |  |  |  |  |  |  |
Shares issued pursuant to Offering/Program net, shares |  |  |  | 4,000,000 |  |  |  |  |  |
Follow-on Public Offering [Member] | February 2023 Forward Offering [Member] | Common Stock [Member] |  |  |  |  |  |  |  |  |  |
Shareholders Equity [Line Items] |  |  |  |  |  |  |  |  |  |
Shares issued pursuant to Offering/Program net, shares |  |  |  |  | 3,500,000 |  |  |  |  |
ATM Program [Member] |  |  |  |  |  |  |  |  |  |
Shareholders Equity [Line Items] |  |  |  |  |  |  |  |  |  |
Proceeds from issuance of common stock, net |  |  |  |  |  | $ 23,900,000 |  | $ 31,100,000 | $ 114,100,000 |
Number of shares allowed for sale under forward provisions |  |  |  |  |  |  |  | 400,000 | 200,000 |
Sale of common stock average gross offering price per share |  |  |  |  |  | $ 27.98 | $ 34.97 | $ 27.98 | $ 34.97 |
Number of shares settled under forward provisions |  |  |  |  |  | 800,000 |  | 1,000,000 | 3,700,000 |
ATM Program [Member] | Common Stock [Member] |  |  |  |  |  |  |  |  |  |
Shareholders Equity [Line Items] |  |  |  |  |  |  |  |  |  |
Shares issued pursuant to Offering/Program net, shares |  |  |  |  |  | 831,000 |  | 1,049,000 | 3,721,000 |
Number of shares allowed for sale under forward provisions |  |  |  |  |  |  |  | 400,000 |  |
ATM Program [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |
Shareholders Equity [Line Items] |  |  |  |  |  |  |  |  |  |
Aggregate sales price |  |  |  |  | $ 350,000,000 |  |  |  |  |
ATM Direct Issuances [Member] | Common Stock [Member] |  |  |  |  |  |  |  |  |  |
Shareholders Equity [Line Items] |  |  |  |  |  |  |  |  |  |
Shares issued pursuant to Offering/Program net, shares |  |  |  |  |  | 0 | 0 | 0 | 0 |
Amended and Restated 2004 Omnibus Incentive Compensation Plan [Member] | Restricted Stock Units [Member] |  |  |  |  |  |  |  |  |  |
Shareholders Equity [Line Items] |  |  |  |  |  |  |  |  |  |
Granted, Number of RSUs Outstanding |  | 271,250 | 253,075 |  |  |  |  |  |  |

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