Share-Based Compensation - Schedule of Information with Respect to all Outstanding Restricted Stock (Detail) - Restricted Stock Units [Member] - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019		Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Beginning balance of Outstanding, Units	1,921,192	2,017,477	[1]	1,453,823
Granted, Units	534,471	427,488		1,397,644
Vested, Units	(242,515)	(500,818)		(709,132)
Forfeited, Units	(67,098)	(22,955)		(124,858)
Ending balance of Outstanding, Units	2,146,050	1,921,192		2,017,477	[1]
Beginning balance of Outstanding, Weighted Average Grant-Date Fair Value Per Unit	$ 16.34	$ 12.70	[1]	$ 5.32
Granted, Weighted Average Grant-Date Fair Value Per Unit	15.45	21.31		12.91
Vested, Weighted Average Grant-Date Fair Value Per Unit	11.02	6.14		4.97
Forfeited, Weighted Average Grant-Date Fair Value Per Unit	17.18	11.42		7.14
Ending balance of Outstanding, Weighted Average Grant-Date Fair Value Per Unit	$ 16.70	$ 16.34		$ 12.70	[1]

[1] The weighted average grant-date fair value per unit as of December 31, 2018 reflects an adjusted fair value per unit from $10.59 to $12.70 due to the modification of grants approved by the Board of Directors during 2019 for our performance-based awards granted on December 14, 2018.