Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Summary of Stock Option Activity

A summary of stock option activity is as follows:

Options	Number of Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value as of December 31, 2019
Outstanding at December 31, 2016	510,574		$	30.60
Exercised	(38,418	)	32.94
Outstanding at December 31, 2017	472,156		$	30.41
Exercised	(54,575	)	21.45
Outstanding at December 31, 2018	417,581		$	31.58
Exercised	(211,057	)	14.65
Outstanding at December 31, 2019	206,524		$	48.88	3.43	$11,719
Vested and Expected to Vest	206,460		$	48.87	3.43	$11,717
Ending Exercisable	197,576		$	47.20	3.30	$11,543

Schedule of Stock Options Outstanding and Exercisable

A summary of stock options outstanding and exercisable as of December 31, 2019, is as follows:

	Options Outstanding				Options Exercisable
Exercise Price	Shares	Weighted Average Remaining Contractual Life	Weighted Average Exercise Price		Shares	Weighted Average Exercise Price
$12.21 - $12.21	77,400	0.18	$	12.21	77,400	$	12.21
$38.40 - $38.40	8,085	3.14	38.40		8,085	38.40
$47.50 - $47.50	9,800	4.13	47.50		9,800	47.50
$65.36 - $65.36	15,647	5.15	65.36		15,647	65.36
$65.45 - $65.45	11,960	5.13	65.45		11,960	64.45
$73.52 - $73.52	50,000	5.58	73.52		50,000	73.52
$85.99 - $85.99	33,632	6.15	85.99		24,684	85.99
	206,524	3.42	$	48.88	197,576	$	47.20

Summary of Company's Employee and Director Share Grant Activity

A summary of the Company’s employee and director share grant activity is as follows:

Restricted Stock Grants	Shares		Weighted-Average Grant-Date Fair Value
Unreleased at December 31, 2016	299,585		$	70.57
Granted	95,392		74.49
Released	(120,323	)	63.95
Cancelled	(8,179	)	77.25
Unreleased at December 31, 2017	266,475		$	74.76
Granted	85,066		86.14
Released	(116,656	)	72.38
Cancelled	(11,771	)	80.96
Unreleased at December 31, 2018	223,114		$	80.02
Granted	109,081		101.52
Released	(110,724	)	79.58
Cancelled	(8,863	)	90.11
Unreleased at December 31, 2019	212,608		$	90.85

Schedule of Nonvested Performance-based Units Activity

A summary of the PSU activity is as follows:

Performance-Based Stock Units	Units	Weighted-Average Grant-Date Fair Value
Unvested at December 31, 2016	—	$	—
Granted	30,071	83.84
Unvested at December 31, 2017	30,071	$	83.84
Granted	28,735	96.19
Unvested at December 31, 2018	58,806	$	89.87
Granted	49,334	103.18
Unvested at December 31, 2019	108,140	$	95.94

Schedule of Weighted Average Assumptions Used to Estimate Fair Value of Awards

A Monte Carlo simulation model was used to calculate the fair value of the TSR Target portion of the PSUs, using the following assumptions:

	For the Year Ended December 31,
	2019	2018	2017
Intrinsic value	$6,211	$5,321	$2,630
Risk-free rate	2.53%	2.37%	1.62%
Volatility	20.7%	22.6%	21.4%
Expected term (in years)	2.8	2.9	2.8
Dividend yield	—%	—%	—%
Unrecognized compensation cost	$4,315	$2,739	$1,681
Term over which compensation cost recognized	3	3	3