Components of Calculation of Basic and Diluted Earnings Per Share (Detail) - USD ($) shares in Thousands, $ in Thousands		4 Months Ended	12 Months Ended
		Dec. 31, 2016	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net loss attributable to common shareholders		$ 224,785	$ (310,557)	$ 70,589	$ 224,785
Weighted-average shares – basic		15,059	15,176	15,110	15,059
Effect of dilutive securities	[1]	233	0	16
Weighted average shares outstanding – diluted		15,292	15,176	15,126	15,292
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			100

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