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Schedule of Dividends & Distributions Declared (Detail) - USD ($) $ in Thousands													9 Months Ended
		Sep. 13, 2020	Jun. 30, 2020	Jun. 07, 2020	Mar. 31, 2020	Feb. 09, 2020	Oct. 02, 2019	Sep. 15, 2019	Jun. 28, 2019	Jun. 02, 2019	Mar. 29, 2019	Feb. 10, 2019	Sep. 30, 2020	Sep. 30, 2019
Dividends Payable [Line Items]
Approval Date		Sep. 13, 2020		Jun. 07, 2020		Feb. 09, 2020		Sep. 15, 2019		Jun. 02, 2019		Feb. 10, 2019
Record Date		Sep. 25, 2020		Jun. 23, 2020		Mar. 24, 2020		Sep. 26, 2019		Jun. 21, 2019		Mar. 22, 2019
Payment Date		Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020		Oct. 02, 2019		Jun. 28, 2019		Mar. 29, 2019
Payment of dividends		$ 3,552	$ 3,545		$ 3,539		$ 3,528		$ 3,525		$ 3,521		$ 10,973	$ 10,765
Unvested Shares, Net of Forfeitures
Dividends Payable [Line Items]
Approval Date													Various	Various
Record Date													Various	Various
Payment Date													Various	Various
Payment of dividends	[1]												$ 337	$ 191
[1] Represents dividends declared on unvested shares, net of forfeitures.

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-Publisher FASB
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