Annual report pursuant to Section 13 and 15(d)

Stock Based Compensation - Status of Unvested Shares of Stock Issued to Employees and Directors (Detail)

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Stock Based Compensation - Status of Unvested Shares of Stock Issued to Employees and Directors (Detail) - $ / shares
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]      
Unvested at beginning of year, Non-vested Shares 154,770 147,723 145,004
Granted, Non-vested Shares 55,433 60,288 57,849
Vested, Non-vested Shares (60,716) (45,767) (52,938)
Forfeited, Non-vested Shares 0 (7,474) (2,192)
Unvested at end of year, Non-vested Shares 149,487 154,770 147,723
Unvested at beginning of year, Weighted average grant date fair value $ 66.62 $ 63.07 $ 60.19
Granted, Weighted average grant date fair value 114.61 71.70 67.33
Vested, Weighted average grant date fair value 67.14 63.10 59.89
Forfeited, Weighted average grant date fair value 0 59.06 61.84
Unvested at end of year, Weighted average grant date fair value $ 84.21 $ 66.62 $ 63.07