Dividends (Detail) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Dividend Declared [Line Items]
Amount per Share of Common Stock		$ 0.36	$ 1.36
Total Dividends	[1]	$ 42,567	$ 159,951
First Quarter Dividend
Dividend Declared [Line Items]
Declaration Date		Feb. 21, 2020	Feb. 23, 2019
Record Date		Mar. 06, 2020	Mar. 08, 2019
Payable Date		Mar. 20, 2020	Mar. 22, 2019
Amount per Share of Common Stock		$ 0.36	$ 0.34
Total Dividends	[1]	$ 42,567	$ 39,905
Second Quarter Dividend
Dividend Declared [Line Items]
Declaration Date			May 24, 2019
Record Date			Jun. 10, 2019
Payable Date			Jun. 24, 2019
Amount per Share of Common Stock			$ 0.34
Total Dividends	[1]		$ 40,012
Third Quarter Dividend
Dividend Declared [Line Items]
Declaration Date			Aug. 16, 2019
Record Date			Sep. 04, 2019
Payable Date			Sep. 18, 2019
Amount per Share of Common Stock			$ 0.34
Total Dividends	[1]		$ 40,020
Fourth Quarter Dividend
Dividend Declared [Line Items]
Declaration Date			Nov. 22, 2019
Record Date			Dec. 04, 2019
Payable Date			Dec. 18, 2019
Amount per Share of Common Stock			$ 0.34
Total Dividends	[1]		$ 40,014

[1] Of the dividends recorded during 2019, 2020 and 2021, $670, $256 and $(4), respectively, were related to outstanding restricted stock units and will not be paid until such units vest. See Note 17.