Schedule of Dividend Payments (Detail) - USD ($) $ in Thousands														9 Months Ended
		Oct. 02, 2019	Sep. 15, 2019	Jun. 28, 2019	Jun. 02, 2019	Mar. 29, 2019	Feb. 10, 2019	Oct. 01, 2018	Sep. 16, 2018	Jun. 29, 2018	Jun. 03, 2018	Mar. 29, 2018	Mar. 04, 2018	Sep. 30, 2019	Sep. 30, 2018
Dividends Payable [Line Items]
Approval Date			Sep. 15, 2019		Jun. 02, 2019		Feb. 10, 2019		Sep. 16, 2018		Jun. 03, 2018		Mar. 04, 2018
Record Date			Sep. 26, 2019		Jun. 21, 2019		Mar. 22, 2019		Sep. 27, 2018		Jun. 22, 2018		Mar. 21, 2018
Payment Date			Oct. 02, 2019		Jun. 28, 2019		Mar. 29, 2019		Oct. 01, 2018		Jun. 29, 2018		Mar. 29, 2018
Payment of dividends		$ 3,528		$ 3,525		$ 3,521		$ 3,504		$ 3,502		$ 3,499		$ 10,765	$ 10,656
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]													$ 191	$ 151

[1] Represents dividends declared on unvested shares, net of forfeitures.