(8)Equity-Based Compensation

The Partnership’s general and administrative expenses include equity-based compensation costs allocated to it by Antero Resources for grants made pursuant to Antero Resources’ long‑term incentive plan and the Midstream LTIP. Equity‑based compensation expense allocated to the Partnership was $7.2 million and $4.5 million for the three months ended September 30, 2017 and 2018, respectively, and $20.4 million and $16.6 million for the nine months ended September 30, 2017 and 2018, respectively. These expenses were allocated to the Partnership based on its proportionate share of Antero Resources’ labor costs. Antero Resources has unamortized expense totaling approximately $79 million as of September 30, 2018 related to its various equity-based compensation plans, which includes the Midstream LTIP. A portion of this will be allocated to the Partnership as it is amortized over the remaining service period of the related awards. The Partnership does not reimburse Antero Resources for noncash equity compensation allocated to it for awards issued under the Antero Resources long-term incentive plan or the Midstream LTIP.

Midstream LTIP

The Partnership’s general partner manages its operations and activities, and Antero Resources employs the personnel who provide support to the Partnership’s operations. The general partner has adopted the Midstream LTIP, pursuant to which non‑employee directors of the general partner and certain officers, employees and consultants of the general partner and its affiliates are eligible to receive awards representing limited partner interests in the Partnership. An aggregate of 10,000,000 common units may be delivered pursuant to awards under the Midstream LTIP, subject to customary adjustments. A total of 7,752,232 common units are available for future grant under the Midstream LTIP as of September 30, 2018. Restricted units and phantom units granted under the Midstream LTIP vest subject to the satisfaction of service requirements, upon the completion of which common units in the Partnership are delivered to the holder of the restricted units or phantom units. Phantom units also contain distribution equivalent rights, which entitle the holder of vested common units to receive a “catch up” payment equal to common unit distributions paid during the vesting period of the phantom unit award. Compensation related to each restricted unit and phantom unit award is recognized on a straight-line basis over the requisite service period of the entire award. The grant date fair values of these awards are determined based on the closing price of the Partnership’s common units on the date of grant. These units are accounted for as if they are distributed by the Partnership to Antero Resources. Antero Resources recognizes compensation expense for the units awarded and a portion of that expense is allocated to the Partnership. Antero Resources allocates equity-based compensation expense to the Partnership based on our proportionate share of Antero Resources’ labor costs. The Partnership’s portion of the equity-based compensation expense is included in general and administrative expenses, and recorded as a credit to the applicable classes of partners’ capital.

A summary of restricted unit and phantom unit awards activity during the nine months ended September 30, 2018 is as follows:


		Weighted average		Aggregate
	Number of	grant date		intrinsic value
	units	fair value		(in thousands)
Total awarded and unvested—December 31, 2017	1,042,963	$	28.69	$	30,288
Granted	247,692	$	25.84
Vested	(144,620)	$	30.17
Forfeited	(93,419)	$	28.64
Total awarded and unvested—September 30, 2018	1,052,616	$	28.15	$	30,168

Intrinsic values are based on the closing price of the Partnership’s common units on the referenced dates. Midstream LTIP unamortized expense of $16.3 million at September 30, 2018, is expected to be recognized over a weighted average period of approximately 2.5 years and the Partnership’s proportionate share will be allocated to it as it is recognized.