Share and Unit-Based Plans:

Under the Long-Term Incentive Plan ("LTIP"), each award recipient is issued a form of units ("LTIP Units") in the Operating Partnership. Upon the occurrence of specified events and subject to the satisfaction of applicable vesting conditions, LTIP Units (after conversion into OP Units) are ultimately redeemable for common stock of the Company, or cash at the Company's option, on a one-unit for one-share basis. LTIP Units receive cash dividends based on the dividend amount paid on the common stock of the Company. The LTIP may include both market-indexed awards and service-based awards.

The market-indexed LTIP Units vest over the service period of the award based on the percentile ranking of the Company in terms of total return to the stockholders (the "Total Return") per common stock share relative to the Total Return of a group of peer REITs, as measured at the end of the measurement period.

During the three months ended March 31, 2018, the Company granted the following LTIP Units:



Grant Date	Units	Type	Fair Value per LTIP Unit		Vest Date
1/1/2018	65,466	Service-based	$	65.68	12/31/2020
1/1/2018	291,326	Market-indexed	$	44.28	12/31/2020
1/29/2018	13,632	Service-based	$	66.02	2/1/2022
1/29/2018	1,893	Service-based	$	66.02	12/31/2020
1/29/2018	7,775	Market-indexed	$	48.23	12/31/2020
3/2/2018	99,407	Service-based	$	59.04	3/2/2018
	479,499

The fair value of the marked-indexed LTIP Units granted on January 1, 2018 were estimated on the date of grant using a Monte Carlo Simulation model that assumed a risk free interest rate of 1.98% and an expected volatility of 23.38%. The fair value of the marked-indexed LTIP Units granted on January 29, 2018 were estimated on the date of grant using a Monte Carlo Simulation model that assumed a risk free interest rate of 2.25% and an expected volatility of 23.86%.

The following summarizes the compensation cost under the share and unit-based plans:



	For the Three Months Ended March 31,
	2018		2017
LTIP Units	$	10,108	$	14,381
Stock units	3,230		2,612
Stock options	31		4
Phantom stock units	243		177
	$	13,612	$	17,174

The Company capitalized share and unit-based compensation costs of $2,609 and $3,369 for the three months ended March 31, 2018 and 2017, respectively. Unrecognized compensation costs of share and unit-based plans at March 31, 2018 consisted of $14,647 from LTIP Units, $6,981 from stock units, $146 from stock options and $278 from phantom stock units.

The following table summarizes the activity of the non-vested LTIP Units, phantom stock units and stock units:



	LTIP Units				Phantom Stock Units				Stock Units
	Units		Value(1)		Units		Value(1)		Units		Value(1)
Balance at January 1, 2018	636,632		$	52.36	4,054		$	79.82	151,355		$	73.32
Granted	479,499		51.03		4,366		63.03		82,782		59.00
Vested	(99,407	)	59.04		(3,639	)	70.71		(102,596	)	73.42
Forfeited	—		—		(790	)	80.20		—		—
Balance at March 31, 2018	1,016,724		$	51.08	3,991		$	69.67	131,541		$	64.24


(1) Value represents the weighted average grant date fair value.

The following table summarizes the activity of the stock appreciations rights ("SARs") and stock options outstanding:



	SARs				Stock Options
	Units		Value(1)		Units	Value(1)
Balance at January 1, 2018	235,439		$	53.83	35,565	$	57.32
Granted	—		—		—	—
Exercised	(225,439	)	53.95		—	—
Balance at March 31, 2018	10,000		$	51.70	35,565	$	57.32


(1) Value represents the weighted average exercise price.