Share-Based and Other Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of Restricted Stock Units Valuation Assumptions

As of December 31, 2020, the estimated number of RSUs earned for the 2020 and 2019 Performance-Based RSUs and the actual number of RSUs earned for the 2018 Performance-Based RSUs was as follows:

	2020 Performance-Based RSUs	2019 Performance-Based RSUs	2018 Performance-Based RSUs
Service vesting period	January 31, 2020 - January, 2023	February 1, 2019 - January, 2022	February 14, 2018 - January, 2021
Target RSUs granted	154,267	143,396	158,205
Estimated RSUs earned (1)	142,004	220,151	229,748
Date of valuation	January 31, 2020	February 1, 2019	February 14, 2018

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(1)Estimated RSUs earned for the 2020 Performance-Based RSUs are based on the actual achievement of the 2020 FFO Performance Condition and for the 2020 Debt to EBITDA Ratio Performance Condition, assumes 100% of the target level of achievement for all participants, and target level of achievement of the 2020 Market Condition. Estimated RSUs earned for the 2019 Performance-Based RSUs are based on the actual achievement of the 2019 FFO Performance Condition and assume target level achievement of the 2019 Market Condition and maximum level of achievement of the 2019 Debt to EBITDA Ratio Performance Condition. The 2018 Performance-Based RSUs earned are based on actual performance of the 2018 Performance Conditions and the 2018 Market Condition.The total fair value of the Time-Based RSUs is based on the Company's closing share price on the NYSE on the respective fair valuation dates as detailed in the table below:

	2020 Time-Based RSU Grant		2019 Time-Based RSU Grant		December 2018 Time-Based RSU Grant		2018 Time-Based RSU Grant (1)
Service vesting period	January 31, 2020 - January 5, 2023		February 1, 2019 - January 5, 2022		December 27, 2018 - January 5, 2023		January & February 2018 - January 5, 2021
Fair value on valuation date (in millions)	$	9.0	$	10.1	$	18.5	$	8.4
Fair value per share	$	82.57	$	69.89	$	62.00	$	70.37
Date of fair valuation	January 31, 2020		February 1, 2019		December 27, 2018		January & February 2018

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(1)The 2018 Time-Based RSUs consist of 56,015 RSUs granted on January 29, 2018 at a fair value per share of $70.37 and 67,818 RSUs granted on February 14, 2018 at a fair value per share of $66.46.

Summary of Nonvested Restricted Stock

A summary of our nonvested and vested restricted stock activity for the year ended December 31, 2018 is presented below:

	Shares Granted		Shares Vested
Years ended December 31,	Nonvested Shares Issued	Weighted-Average Grant Date Fair Value Per Share	Vested Shares	Total Fair Value at Vest Date (1) (in thousands)
2018	—	—	(22,884)	1,652

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(1)    Total fair value of shares vested was calculated based on the quoted closing share price of the Company’s common stock on the NYSE on the date of vesting.

Summary of Nonvested and Vested Restricted Stock Activity

A summary of our nonvested and vested restricted stock activity for the year ended December 31, 2018 is presented below:

	Shares Granted		Shares Vested
Years ended December 31,	Nonvested Shares Issued	Weighted-Average Grant Date Fair Value Per Share	Vested Shares	Total Fair Value at Vest Date (1) (in thousands)
2018	—	—	(22,884)	1,652

_______________________

(1)    Total fair value of shares vested was calculated based on the quoted closing share price of the Company’s common stock on the NYSE on the date of vesting.

December 2018 Market-Based RSUs [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Assumptions Utilized in the Monte Carlo Simulation Pricing Models

The following table summarizes the assumptions utilized in the Monte Carlo simulation pricing models:

	December 2018 Market-Based RSU Award Fair Value Assumptions
Valuation date	December 27, 2018
Fair value per share on valuation date	$68.66
Expected share price volatility	23.0%
Risk-free interest rate	2.4%

Market measure-based Restricted Stock Units (RSUs) [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary of Restricted Stock Units Award Activity

A summary of our performance and market-measure based RSU activity from January 1, 2020 through December 31, 2020 is presented below:

	Nonvested RSUs			Vested RSUs	Total RSUs
	Amount	Weighted-Average Fair Value Per Share
Outstanding at January 1, 2020	932,675	$	71.04	36,679	969,354
Granted	154,267	85.08		38,313	192,580
Vested	(230,334)	74.71		230,334	—
Settled (1)	—	—		(259,954)	(259,954)
Issuance of dividend equivalents (2)	29,561	62.21		1,407	30,968
Forfeited	(12,460)	84.54		(4)	(12,464)
Outstanding as of December 31, 2020 (3)	873,709	$	72.06	46,775	920,484

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(1)Represents vested RSUs that were settled in shares of the Company’s common stock. Total shares settled include 125,928 shares that were tendered in accordance with the terms of the 2006 Plan to satisfy minimum statutory tax withholding requirements related to the RSUs settled. We accept the return of RSUs at the current quoted closing share price of the Company’s common stock to satisfy tax obligations.

(2)Represents the issuance of dividend equivalents earned on the underlying RSUs. The dividend equivalents vest based on terms specified under the related RSU award agreement.

(3)Outstanding RSUs as of December 31, 2020 represent the actual achievement of the FFO performance conditions and assumes target levels for the market and other performance conditions. The number of restricted stock units ultimately earned is subject to change based upon actual performance over the three-year vesting period. Dividend equivalents earned will vest along with the underlying award and are also subject to changes based on the number of RSUs ultimately earned for each underlying award.

A summary of our performance and market-measure based RSU activity for the years ended December 31, 2020, 2019 and 2018 is presented below:

	RSUs Granted			RSUs Vested
Years ended December 31,	Non-Vested RSUs Granted (1)	Weighted-Average Fair Value Per Share		Vested RSUs	Total Vest-Date Fair Value (in thousands)
2020	154,267	$	85.08	(270,054)	$	19,471
2019	231,191	71.12		(265,737)	18,703
2018	601,012	68.51		(265,918)	18,906

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(1)Non-vested RSUs granted are based on the actual achievement of the FFO performance conditions and assumes target level achievement for the market and other performance conditions.

Time-Based Restricted Stock Units (RSUs) [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary of Restricted Stock Units Award Activity

A summary of our time-based RSU activity from January 1, 2020 through December 31, 2020 is presented below:

	Nonvested RSUs			Vested RSUs	Total RSUs
	Amount	Weighted Average Fair Value Per Share
Outstanding at January 1, 2020	543,848	$	66.66	1,071,378	1,615,226
Granted	120,769	79.74		—	120,769
Vested	(173,796)	70.83		173,796	—
Settled (1)				(181,462)	(181,462)
Issuance of dividend equivalents (2)	15,523	61.80		34,812	50,335
Forfeited	(11,979)	77.58		—	(11,979)
Canceled (3)				(1,638)	(1,638)
Outstanding as of December 31, 2020	494,365	$	67.97	1,096,886	1,591,251

____________________

(1)Represents vested RSUs that were settled in shares of the Company’s common stock. Total shares settled include 67,316 shares that were tendered in accordance with the terms of the 2006 Plan to satisfy minimum statutory tax withholding requirements related to the RSUs settled. We accept the return of RSUs at the current quoted closing share price of the Company’s common stock to satisfy tax obligations.

(2)Represents the issuance of dividend equivalents earned on the underlying RSUs. The dividend equivalents vest based on terms specified under the related RSU award agreement.

(3)For shares vested but not yet settled, we accept the return of RSUs at the current quoted closing share price of the Company’s common stock to satisfy minimum statutory tax-withholding requirements related to either the settlement or vesting of RSUs in accordance with the terms of the 2006 Plan.

A summary of our time-based RSU activity for the years ended December 31, 2020, 2019 and 2018 is presented below:

	RSUs Granted			RSUs Vested
Year ended December 31,	Non-Vested RSUs Issued	Weighted-Average Grant Date Fair Value Per Share		Vested RSUs	Total Vest-Date Fair Value (1) (in thousands)
2020	120,769	$	79.74	(208,608)	$	15,066
2019	153,005	70.31		(182,219)	12,227
2018	437,216	64.21		(214,131)	14,768

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(1)    Total fair value of RSUs vested was calculated based on the quoted closing share price of the Company’s common stock on the NYSE on the day of vesting. Excludes the issuance of dividend equivalents earned on the underlying RSUs. The dividend equivalents vest based on terms specified under the related RSU award agreement.

2020, 2019, and 2018 Performance-Based RSUs [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Assumptions Utilized in the Monte Carlo Simulation Pricing Models

The following table summarizes the assumptions utilized in the Monte Carlo simulation pricing models:

	2020 Award Fair Value Assumptions	2019 Award Fair Value Assumptions	2018 Award Fair Value Assumptions
Valuation date	January 31, 2020	February 1, 2019	February 14, 2018
Fair value per share on valuation date	$84.54	$72.57	$70.08
Expected share price volatility	17.0%	19.0%	20.0%
Risk-free interest rate	1.35%	2.48%	2.37%