Share-Based Compensation and Other Employee Benefit Plans - Activity Related to Stock Options (Detail) - Stock Option Awards - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of shares
Balance at beginning of the period (in shares)	714,420	686,366	721,538
Granted (in shares)	127,090	97,620	80,557
Exercised (in shares)	(122,143)	(42,047)	(85,221)
Forfeited or expired (in shares)	(13,570)	(27,519)	(30,508)
Balance at end of the period (in shares)	705,797	714,420	686,366
Exercisable at period end (in shares)	463,595	501,815	455,010
Weighted Average Exercise Price
Balance at beginning of the period (in usd per share)	$ 61.41	$ 58.24	$ 55.38
Granted (in usd per share)	70.34	82.02	84.78
Exercised (in usd per share)	54.39	53.07	55.45
Forfeited or expired (in usd per share)	72.52	68.30	68.46
Balance at end of the period (in usd per share)	64.02	61.41	58.24
Exercisable at period end (in usd per share)	$ 59.13	$ 56.75	$ 55.77
Aggregate Intrinsic Value (Dollars in thousands)
Exercised	$ 2,575	$ 1,242	$ 2,098
Balance at end of period	8,926
Exercisable at period end	$ 7,796
Weighted Average Remaining Contract Life (in years)
Weighted average remaining contract life at period end	5 years 4 months 24 days
Exercisable at period end	3 years 10 months 24 days