Dividends - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended		8 Months Ended
	Oct. 11, 2018	Jul. 18, 2018	Jun. 29, 2018	Sep. 09, 2018	Sep. 10, 2017	Sep. 09, 2018	Sep. 10, 2017	Dec. 31, 2017	[1]
Dividends Payable [Line Items]
Dividends paid per share			$ 0.55
Record date of dividend		Sep. 14, 2018	Jun. 15, 2018
Dividends declared per share		$ 0.55		$ 0.55	$ 0.46	$ 1.65	$ 1.38
Common stock dividends accrued				$ 23,265		$ 23,265		$ 536
Dividend declared date		Jul. 18, 2018
Dividend payable date		Sep. 28, 2018
Subsequent Event [Member]
Dividends Payable [Line Items]
Record date of dividend	Dec. 14, 2018
Dividends declared per share	$ 0.55
Dividend declared date	Oct. 11, 2018
Dividend payable date	Dec. 28, 2018

[1] Note: The balance sheet at December 31, 2017 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by accounting principles generally accepted in the United States for complete financial statements.