Stock-based Compensation (Tables)

9 Months Ended

Sep. 30, 2021

Share-based Payment Arrangement [Abstract]

Estimated Fair Value of Stock Option Grants

The fair value of stock option awards granted during the thirty-nine weeks ended September 30, 2021 was estimated using the Black-Scholes-Merton option pricing model with the following weighted-average assumptions:

	Thirty-nine Weeks Ended
	September 30, 2021
Weighted average fair value per stock option	$	41.75
Risk-free interest rate	0.8%
Expected volatility	48.1%
Expected life (in years)	5.4
Dividend yield	—%

Stock Option Activity

The table below summarizes stock option activity for the thirty-nine weeks ended September 30, 2021:

	Options	Weighted Average Exercise Price
Outstanding at January 1, 2021	3,740,604	$	20.72
Granted	66,505	95.68
Exercised	(1,071,838)	10.98
Forfeited or expired	(48,988)	39.03
Outstanding at September 30, 2021	2,686,283	$	26.13
Vested and exercisable at September 30, 2021	1,689,127	$	17.80

Restricted Stock Unit Activity

The following table summarizes restricted stock unit activity during the thirty-nine weeks ended September 30, 2021:

	Restricted Stock Units
Unvested at January 1, 2021	128,220
Granted	123,362
Vested	(26,968)
Forfeited	(12,472)
Unvested at September 30, 2021	212,142

Restricted Stock Award Activity

The following table summarizes restricted stock award activity during the thirty-nine weeks ended September 30, 2021:

	Restricted Stock Awards
	Service-based	Performance-based	Total Stock Return (TSR)
Unvested at January 1, 2021	131,844	160,315	104,456
Granted	28,814	—	—
Vested	(13,555)	—	—
Forfeited	(2,508)	—	—
Unvested at September 30, 2021	144,595	160,315	104,456