Stockholders' Equity - Additional Information (Detail) - USD ($)	1 Months Ended			3 Months Ended												12 Months Ended
	Jan. 31, 2021	Jan. 31, 2019	Sep. 30, 2017	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Common stock, shares authorized				110,000,000				110,000,000								110,000,000	110,000,000
Common stock entitles																one
Cash dividends declared per common share				$ 0.60	$ 0.60	$ 0.60	$ 0.60	$ 0.51	$ 0.51	$ 0.51	$ 0.51	$ 0.42	$ 0.42	$ 0.42	$ 0.42	$ 2.40	$ 2.04	$ 1.68
Share Repurchase Program [Member]
Class of Stock [Line Items]
Shares repurchase program period		2 years	15 months
Shares repurchase program authorized		$ 100,000,000.0	$ 100,000,000.0
Commencement date		2019-04	2017-10
Share Repurchase Program [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Shares repurchase program authorized	$ 100,000,000
Commencement date	2021-04
Common Stock Non-Voting [Member]
Class of Stock [Line Items]
Common stock, shares authorized				10,000,000				10,000,000								10,000,000	10,000,000
Common Stock Voting [Member]
Class of Stock [Line Items]
Common stock, shares authorized				110,000,000				110,000,000								110,000,000	110,000,000