Long-Term Debt - Summary of Debt, Textual (Detail)	Dec. 31, 2020 USD ($)
Public | 3.80% Senior Notes 11/25/2025 | Senior Bonds
Debt Instrument [Line Items]
Senior notes, issued at par percentage	99.975%
Revolving Credit Facility | Nonpublic
Debt Instrument [Line Items]
Aggregate maximum borrowing capacity	$ 500,000,000
Line of credit facility maximum borrowing capacity increased amount subject to obtaining commitments	$ 750,000,000