Stock Buy Back Plans - Schedule of Number of Shares Purchased and Maximum Value of Shares that May Yet Be Purchased Under the Plan (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Jul. 31, 2019	Jun. 30, 2019	Dec. 31, 2019	Nov. 30, 2019	Oct. 31, 2019	Sep. 30, 2019	Aug. 31, 2019	May 31, 2019	Apr. 30, 2019	Mar. 31, 2019	Feb. 28, 2019	Jan. 31, 2019
Equity Class Of Treasury Stock [Line Items]
Total Number of Shares Purchased	444,509	181,811	626,320
Average Price Paid Per Share	$ 39.85	$ 40.06	$ 39.91
Maximum Value of Shares that May Yet Be Purchased Under the Plan	$ 75,002	$ 92,717	$ 75,002	$ 75,002	$ 75,002	$ 75,002	$ 75,002	$ 100,000	$ 100,000	$ 100,000	$ 100,000	$ 100,000
Publicly Announced Plan [Member]
Equity Class Of Treasury Stock [Line Items]
Total Number of Shares Purchased	444,509	181,811	626,320