Recent Transactions - Equity Transactions - Schedule of Equity Distribution Declared (Detail) - USD ($) $ / shares in Units, $ in Thousands  | 
9 Months Ended | |
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Sep. 30, 2019  | 
Sep. 30, 2018  | 
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| Schedule Of Equity [Line Items] | ||
| Cash Distributed (in thousands) | $ 5,160 | $ 5,104 | 
| Dividend Payment One [Member] | ||
| Schedule Of Equity [Line Items] | ||
| Announcement Date | Sep. 11, 2019 | |
| Record Date | Sep. 23, 2019 | |
| Payment Date | Sep. 30, 2019 | |
| Amount Per Share | $ 0.0650 | |
| Cash Distributed (in thousands) | $ 1,730 | |
| Dividend Payment Two [Member] | ||
| Schedule Of Equity [Line Items] | ||
| Announcement Date | May 14, 2019 | |
| Record Date | Jun. 14, 2019 | |
| Payment Date | Jun. 28, 2019 | |
| Amount Per Share | $ 0.0650 | |
| Cash Distributed (in thousands) | $ 1,728 | |
| Dividend Payment Three [Member] | ||
| Schedule Of Equity [Line Items] | ||
| Announcement Date | Mar. 07, 2019 | |
| Record Date | Mar. 19, 2019 | |
| Payment Date | Mar. 29, 2019 | |
| Amount Per Share | $ 0.0650 | |
| Cash Distributed (in thousands) | $ 1,702 | |
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- Definition Schedule of equity. No definition available. 
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- Definition Date the declared dividend will be paid, in CCYY-MM-DD format. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition The per share amount of a dividend declared, but not paid, as of the financial reporting date. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Date the dividend to be paid was declared, in CCYY-MM-DD format. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Date the holder must own the stock to be entitled to the dividend, in CCYY-MM-DD format. No definition available. 
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- Definition Amount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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