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Capital Stock - Additional Information (Detail) - USD ($)					3 Months Ended		12 Months Ended
	Feb. 07, 2020	Mar. 20, 2019	Feb. 07, 2019	Mar. 21, 2018	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2017
Class Of Stock [Line Items]
Stock repurchase authorized amount					$ 1,250,000,000
Shares repurchased and retired (in shares)					1,042,188	0
Common stock shares repurchased price per share					$ 43.18
Aggregate amount of common stock shares repurchased					$ 45,000,000
Expenses related to stock purchases					$ 21,000
Percentage Increase In Quarterly Cash Dividend	15.00%		13.00%
Quarterly dividend declared	$ 0.0975		$ 0.085		$ 0.0975	$ 0.085	$ 0.075
Annual dividend			$ 0.34				$ 0.30
Initial dividend paid		$ 18,543,000		$ 16,119,000
Dividends payable, date declared	Feb. 06, 2020		Feb. 07, 2019
Dividends paid per share		$ 0.0975		$ 0.085
Planned annual dividend	$ 0.39					$ 0.34
First Quarter Dividend
Class Of Stock [Line Items]
Dividend payment date	Mar. 18, 2020		Mar. 20, 2019
Dividends payable, date of record	Mar. 09, 2020		Mar. 08, 2019
Share Repurchase Open Market
Class Of Stock [Line Items]
Aggregate amount of common stock shares repurchased					$ 45,000,000

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