Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Summary of the stock-based compensation expense by instrument awarded

	Year ended December 31,
	2021		2020		2019
	(in thousands)
Performance-based RSUs	$	23,166	$	20,610	$	14,820
Time-based RSUs		10,184		9,515		6,659
Stock options		4,444		14,980		3,292
	$	37,794	$	45,105	$	24,771

Summary of valuation assumptions, stock options

	Year ended December 31,
	2021	2020	2019
Expected volatility (1)	38%	34%	30%
Expected dividends	1.4%	1.4%	0%
Risk-free interest rate	0.1% - 1.7%	0.1% - 1.5%	2.5% - 2.7%
Expected grantee forfeiture rate	0% - 6.7%	0% - 6.7%	2.3% - 22.7%

(1) Based on historical volatilities of the Company’s common stock.

Summary of Stock Option award activity

	Year ended December 31,
	2021		2020		2019
	(in thousands, except per option amounts)
Number of stock options:
Outstanding at beginning of year		4,040		3,699		3,693
Granted		249		876		344
Exercised		(377)		(530)		(317)
Forfeited		(6)		(5)		(21)
Outstanding at end of year		3,906		4,040		3,699
Weighted average exercise price per option:
Outstanding at beginning of year	$	28.01	$	18.40	$	17.81
Granted	$	58.85	$	52.00	$	22.92
Exercised	$	19.96	$	17.72	$	16.26
Forfeited	$	39.52	$	20.61	$	20.70
Outstanding at end of year	$	28.43	$	28.01	$	18.40

Following is a summary of stock options as of December 31, 2021:

Number of options exercisable at end of year (in thousands)		3,397
Weighted average exercise price per exercisable option	$	25.97
Weighted average remaining contractual term (in years):
Outstanding		5.6
Exercisable		5.1
Aggregate intrinsic value:
Outstanding (in thousands)	$	161,544
Exercisable (in thousands)	$	148,820
Expected vesting amounts:
Number of options expected to vest (in thousands)		509
Weighted average vesting period (in months)		10

Performance-based RSUs

Summary of RSU activity and compensation expense

	Year ended December 31,
	2021		2020		2019
	(in thousands, except per unit amounts)
Number of units:
Outstanding at beginning of year		1,583		1,807		1,892
Granted		310		440		682
Vested (1)		(634)		(645)		(735)
Forfeited or cancelled		(33)		(19)		(32)
Outstanding at end of year		1,226		1,583		1,807
Weighted average grant date fair value per unit:
Outstanding at beginning of year	$	27.02	$	21.67	$	14.48
Granted	$	58.85	$	35.95	$	23.11
Vested	$	24.47	$	18.16	$	11.28
Forfeited	$	36.91	$	26.71	$	21.72
Outstanding at end of year	$	36.12	$	27.02	$	21.67

(1) The actual number of performance-based RSUs vested during the years ended December 31, 2021, 2020 and 2019 was 781,000, 608,000 and 648,000 shares, respectively, which is approximately 123%, 94% and 88% of the 634,000, 645,000 and 735,000 originally granted units, respectively, due to the performance varying from the established target for the respective grant.

Following is a summary of performance-based RSUs as of December 31, 2021:

Unamortized compensation cost (in thousands)	$	20,593
Number of shares expected to vest (in thousands)		1,122
Weighted average remaining vesting period (in months)		10

Time-based RSUs

Summary of RSU activity and compensation expense

	Year ended December 31,
	2021		2020		2019
	(in thousands, except per unit amounts)
Number of units:
Outstanding at beginning of year		587		642		627
Granted		173		311		334
Vested		(312)		(357)		(300)
Forfeited		(14)		(9)		(19)
Outstanding at end of year		434		587		642
Weighted average grant date fair value per unit:
Outstanding at beginning of year	$	29.37	$	22.40	$	20.39
Granted	$	58.90	$	34.98	$	22.88
Vested	$	28.08	$	21.75	$	18.73
Forfeited	$	39.48	$	28.14	$	22.29
Outstanding at end of year	$	41.74	$	29.37	$	22.40

Following is a summary of RSUs as of December 31, 2021:

Unamortized compensation cost (in thousands)	$	4,912
Number of units expected to vest (in thousands)		401
Weighted average remaining vesting period (in months)		8