Notes Payable - Components of Notes Payable (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Jun. 16, 2021	Mar. 17, 2021	Nov. 05, 2015
Series B senior notes [Member] | 3.68% Series B senior notes due in 2021 [Member]
Debt Instrument [Line Items]
Senior Notes, interest rate		3.68%
Senior Notes, year of maturity		2021
Series C senior notes [Member] | 3.84% Series C senior notes due in 2022 [Member]
Debt Instrument [Line Items]
Senior Notes, interest rate	3.84%	3.84%			3.84%
Senior Notes, year of maturity	2022	2022
Series E senior notes [Member] | 2.35% Series E senior notes due in 2026 [Member]
Debt Instrument [Line Items]
Senior Notes, interest rate	2.35%		2.35%
Senior Notes, year of maturity	2026
Series D senior notes [Member] | 2.57% Series D senior notes due in 2028 [Member]
Debt Instrument [Line Items]
Senior Notes, interest rate	2.57%			2.57%
Senior Notes, year of maturity	2028