Summary of Stock Appreciation Rights Activity (Detail) - Stock Appreciation Rights [Member] - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Grants outstanding at beginning of the period	100,000	100,000	100,000
Shares, Exercised	(100,000)
Shares, Grants outstanding at end of the period		100,000	100,000
Shares, Grants exercisable at end of the period		100,000	100,000
Shares, Grants vested and expected to vest at end of the period		100,000	100,000
Weighted Average Exercise Price per Share, Grants outstanding at beginning of the period	$ 23.85	$ 23.85	$ 23.85
Weighted Average Exercise Price per Share, Exercised	$ (23.85)
Weighted Average Exercise Price per Share, Grants outstanding at end of the period		23.85	23.85
Weighted Average Exercise Price per Share, Grants exercisable at end of the period		23.85	23.85
Weighted Average Exercise Price per Share, Grants vested and expected to vest at end of the period		$ 23.85	$ 23.85