Performance restricted stock units granted in 2021 include a market condition which is the Company’s total shareholder return relative to its peer group ("Relative TSR") over the performance period. Relative TSR is calculated in accordance with the terms of the applicable award agreement. If performance goals are achieved, these awards will cliff vest at the end of a three-year performance period within a range of 0% to 200% of target. Performance restricted stock units granted in 2021 were share-settled awards.

The fair value of performance restricted stock units granted in 2021 was measured on the grant date using a Monte Carlo simulation model.


			Six months ended June 30,			2021

			Expected volatility			32.99%
			Expected term (in years)			3.0
			Expected dividend yield			n/a
			Risk-free interest rate			0.17%

Beginning share price: The beginning share price is based on the average closing share price over the 10 trading days preceding and including the start of the performance period.

Ending share price: The ending share price is based on the average closing share price over the 10 trading days preceding and including the end of the performance period.

Expected dividend yield: The expected dividend yield is not applicable to the performance restricted stock units as dividends are paid at the end of the vesting period and do not affect the value of the performance restricted stock units.

Risk-free interest rate: The risk free rate is estimated based on the yield on a U.S. treasury zero-coupon bond issued with a remaining term equal to the vesting period of the performance restricted stock units.

Compensation expense associated with performance restricted stock units granted in 2021 is determined on the grant date based on the fair value calculated by the Monte Carlo simulation model. The fair value of these awards is recognized on a straight-line basis over the requisite service period.

Performance restricted stock units granted in 2020 and 2019 include a market condition which is the Company’s total shareholder return relative to its peer group ("Relative TSR") over the performance period. Relative TSR is calculated in accordance with the terms of the applicable award agreement. If performance goals are achieved, these awards will cliff vest at the end of a three-year performance period within a range of 75% to 125% of target. Performance restricted stock units granted in 2020 and 2019 were share-settled awards.

Compensation expense associated with performance restricted stock units granted in 2020 and 2019 is determined based on market value of the Company's common shares measured at the grant date. The fair value of these awards is recognized on a straight-line basis over the requisite service period and is subject to periodic adjustment based on the achievement of established performance criteria during the performance period.

Performance restricted stock units granted in 2018 included a performance condition which was growth in the Company’s book value per diluted common share adjusted for dividends over three years compared to its peer group. Growth in book value per diluted common share adjusted for dividends was calculated in accordance with the terms of the applicable award agreements. Where performance goals were achieved, these awards cliff vested at the end of a three-year performance period within a range of 0% to 200% of target. Performance restricted stock units granted in 2018 were share-settled awards.

Compensation expense associated with performance restricted stock units granted in 2018 was determined based on market value of the Company's common shares measured at the grant date. The fair value of these awards was recognized on a straight-line basis over the requisite service period and was subject to periodic adjustment based on the achievement of established performance criteria during the performance period.

The following table provides an activity summary of the Company's share-settled restricted stock units for the six months ended June 30, 2021:


	Share-Settled Performance Restricted Stock Units			Share-Settled Service Restricted Stock Units
	Number of restricted stock units	Weighted average grant date fair value		Number of restricted stock units	Weighted average grant date fair value

Non-vested restricted stock units - beginning of period	289	$	55.92	1,501	$	56.50
Granted	122	49.04		1,192	47.95
Vested	(66)	48.89		(546)	56.45
Forfeited	(4)	62.26		(58)	56.10
Non-vested restricted stock units - end of period	341	$	54.74	2,089	$	51.65

The following table provides an activity summary of the Company's cash-settled restricted stock units for the six months ended June 30, 2021:


												Cash-Settled Service Restricted Stock Units
												Number of restricted stock units

			Non-vested restricted stock units - beginning of period									471
			Granted									—
			Vested									(223)
			Forfeited									(17)
			Non-vested restricted stock units - end of period									231

The following table provides additional information related to share-based compensation:


Six months ended June 30,	2021		2020

Share-based compensation expense(1)	$	25,080	$	25,410
Tax benefits associated with share-based compensation expense	$	4,075	$	3,995
Liability for cash-settled restricted stock units(2)	$	5,804	$	7,675
Fair value of restricted stock units vested(3)	$	41,671	$	46,490
Unrecognized share-based compensation expense	$	107,267	$	98,005
Expected weighted average period associated with the recognition of unrecognized share-based compensation expense	2.8 years		2.7 years