Stock-Based Compensation - Performance Based Units Earned under Long-Term Incentive Plan (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Earned (in dollars per share)		$ 33.27	$ 36.08
Earned (in dollars per share)		$ 33.27	$ 36.08
Weighted average grant-date fair value of shares vested	$ 1,611	$ 1,073	$ 1,821
Performance stock units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning Balance (in shares)	59,335
Earned (in shares)	92,816
Vested (in shares)	(51,147)
Canceled (in shares)	(20,064)
Accrued dividend equivalents (in shares)	1,014
Ending Balance (in shares)	81,954	59,335
Vested but not released (in shares)	49,376
Outstanding (in shares)	131,330
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Beginning Balance (in dollars per share)	$ 33.79
Earned (in dollars per share)	27.35
Vested (in dollars per share)	31.50
Canceled (in dollars per share)	29.33
Accrued dividend equivalents (in dollars per share)	33.85
Ending Balance (in dollars per share)	29.02	$ 33.79
Vested but not released (in dollars per share)	31.39
Outstanding (in dollars per share)	$ 29.91
Aggregate intrinsic value of shares outstanding	$ 3,928
Weighted-average remaining contractual term of shares outstanding	11 months
Earned (in dollars per share)	$ 27.35