Benefit Plans - Summary of Company's Restricted Stock Units Activity (Detail) - Restricted Stock Units [Member] - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Beginning Balance	225,970	196,248	139,510
Number of Shares, granted	116,326	126,540	83,440
Number of Shares, vested	(116,242)	(89,225)	(25,862)
Number of Shares, cancelled/forfeited/expired	(8,646)	(7,593)	(840)
Number of Shares, Ending Balance	217,408	225,970	196,248
Weighted-Average Grant Date Fair Value, Beginning Balance	$ 57.06	$ 50.68	$ 44.73
Weighted-Average Grant Date Fair Value, granted	72.75	50.99	59.98
Weighted-Average Grant Date Fair Value, vested	53.32	43.42	48.31
Weighted-Average Grant Date Fair Value, cancelled/forfeited/expired	52.78	57.93	59.84
Weighted-Average Grant Date Fair Value, Ending Balance	$ 67.63	$ 57.06	$ 50.68
Aggregate Intrinsic Value	$ 17.4