Share-Based Compensation - Schedule of Restricted Stock Units to be Settled in Cash (Detail) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Beginning balance of Outstanding, Restricted Stock Units to be Settled in Cash	81,508	212,794	471,728
Restricted Stock Units to be Settled in Cash, Vested	(81,508)	(129,116)	(214,192)
Restricted Stock Units to be Settled in Cash, Forfeited		(2,170)	(44,742)
Ending balance of Outstanding, Restricted Stock Units to be Settled in Cash		81,508	212,794