Stock-Based Compensation - Performance Based Units Earned under Long-Term Incentive Plan (Detail) - Performance stock units - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning Balance (in shares)	32,071
Earned (in shares)	69,938
Vested (in shares)	(30,705)
Canceled (in shares)	(12,472)
Accrued dividend equivalents (in shares)	503
Ending Balance (in shares)	59,335	32,071
Vested but not released (in shares)	22,529
Outstanding (in shares)	81,864
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)	$ 27.79
Earned (in dollars per share)	33.27	$ 36.08	$ 38.23
Vested (in dollars per share)	34.93
Canceled (in dollars per share)	34.35
Accrued dividend equivalents (in dollars per share)	36.13
Ending Balance (in dollars per share)	33.79	27.79
Vested but not released (in dollars per share)	34.31
Outstanding (in dollars per share)	$ 33.93
Aggregate intrinsic value of shares outstanding	$ 2,778
Weighted-average remaining contractual term of shares outstanding	12 months
Earned (in dollars per share)	$ 33.27	$ 36.08	$ 38.23
Weighted average grant-date fair value of shares vested	$ 1,073	$ 1,821	$ 4,213