Long-Term Incentive Plans	3 Months Ended
Mar. 31, 2018
Long-Term Incentive Plans
Long-Term Incentive Plans	(3) Long-Term Incentive Plans As of March 31, 2018, IDR LLC had 98,600 Series B Units authorized and outstanding that entitle the holders to receive up to 6% of the amount of the distributions that Antero Midstream makes on its IDRs in excess of $7.5 million per quarter, subject to certain vesting conditions. Series B Units issued to common law employees of AMGP, including officers of AMGP and Antero Resources employees who provide services directly to AMGP, are classified as equity awards. Series B Units issued to Antero Resources employees who are not common law employees of AMGP are classified as liability awards. IDR LLC has granted 92,000 Series B Units that are equity classified awards and 8,000 Series B Units that are liability classified awards. As of March 31, 2018, 500 Series B Units that were equity classified awards have been forfeited, and 900 Series B Units that were liability classified awards have been forfeited. The Series B Units vest ratably over a three year period. As of March 31, 2018, 32,875 Series B Units have vested. The holders of vested Series B Units have the right to convert the units to common shares with a value equal to their pro rata share of up to 6% of any increase in our equity value in excess of $2.0 billion. In no event will the aggregate number of newly issued common shares exceed 6% of the total number of our issued and outstanding common shares. For equity classified awards, we recognize expense for the grant date fair value of the awards over the vesting period of the awards. Forfeitures are accounted for as they occur by reversing expense previously recognized for awards that were forfeited during the period. The grant date fair value of the Series B Unit awards was estimated using a Monte Carlo simulation using various assumptions including a floor equity value of $2.0 billion, expected volatility of 43% based on historical volatility of a peer group of publicly traded partnerships, a risk free rate of 2.45%, and expected IDR distributions based on internal estimates discounted based on a weighted average cost of capital assumption of 7.25%. Based on these assumptions, the estimated value of each Series B Unit was $999 when they were issued. The fair value measurement is based on significant inputs not observable in the market and thus represents a Level 3 measurement within the fair value hierarchy. For liability classified awards, we recognize expense for the fair value of the awards over the vesting period of the awards. Forfeitures are accounted for as they occur by reversing expense previously recognized for awards that were forfeited during the period. We update our assumptions each reporting period based on new developments and adjust such amounts to fair value based on revised assumptions, if applicable, over the vesting period. At March 31, 2018, the fair value of the liability classified Series B Unit awards was estimated using a Monte Carlo simulation using various assumptions including an equity value of $3.0 billion, expected volatility of 38% based on historical volatility of a peer group of publicly traded partnerships, a risk free rate of 2.70%, and expected IDR distributions based on internal estimates discounted based on a weighted average cost of capital assumption of 7.25%. Based on these assumptions, the estimated value of each Series B Unit at March 31, 2018 was $1,574. The fair value measurement is based on significant inputs not observable in the market and thus represents a Level 3 measurement within the fair value hierarchy. We recognized expense of $8.4 million, of which $7.6 million was for equity classified awards and $0.8 million was for liability classified awards, during the three months ended March 31, 2018. We recognized expense of $8.3 million, of which $7.7 million was for equity classified awards and $0.6 million was for liability classified awards, during the three months ended March 31, 2017. As of March 31, 2018, there was $59.3 million of unamortized compensation expense related to nonvested Series B Units that is expected to be recognized over the next 1.75 years. On April 17, 2017, we also adopted the Antero Midstream GP LP Long-Term Incentive Plan (“2017 LTIP”), pursuant to which certain non-employee directors of our general partner and certain officers, employees and consultants of Antero Resources are eligible to receive awards representing equity interests in AMGP. An aggregate of 930,851 common shares may be delivered pursuant to awards under the 2017 LTIP, subject to customary adjustments. As of March 31, 2018, 19,486 common shares have been granted. We recognized zero and $0.2 million in expense related to these grants in the three months ended March 31, 2017 and 2018, respectively. As of March 31, 2018, 911,365 common shares remain available for grant under the 2017 LTIP.

(3) Long-Term Incentive Plans

As of March 31, 2018, IDR LLC had 98,600 Series B Units authorized and outstanding that entitle the holders to receive up to 6% of the amount of the distributions that Antero Midstream makes on its IDRs in excess of $7.5 million per quarter, subject to certain vesting conditions. Series B Units issued to common law employees of AMGP, including officers of AMGP and Antero Resources employees who provide services directly to AMGP, are classified as equity awards. Series B Units issued to Antero Resources employees who are not common law employees of AMGP are classified as liability awards. IDR LLC has granted 92,000 Series B Units that are equity classified awards and 8,000 Series B Units that are liability classified awards. As of March 31, 2018, 500 Series B Units that were equity classified awards have been forfeited, and 900 Series B Units that were liability classified awards have been forfeited. The Series B Units vest ratably over a three year period. As of March 31, 2018, 32,875 Series B Units have vested. The holders of vested Series B Units have the right to convert the units to common shares with a value equal to their pro rata share of up to 6% of any increase in our equity value in excess of $2.0 billion. In no event will the aggregate number of newly issued common shares exceed 6% of the total number of our issued and outstanding common shares.

For equity classified awards, we recognize expense for the grant date fair value of the awards over the vesting period of the awards. Forfeitures are accounted for as they occur by reversing expense previously recognized for awards that were forfeited during the period. The grant date fair value of the Series B Unit awards was estimated using a Monte Carlo simulation using various assumptions including a floor equity value of $2.0 billion, expected volatility of 43% based on historical volatility of a peer group of publicly traded partnerships, a risk free rate of 2.45%, and expected IDR distributions based on internal estimates discounted based on a weighted average cost of capital assumption of 7.25%. Based on these assumptions, the estimated value of each Series B Unit was $999 when they were issued. The fair value measurement is based on significant inputs not observable in the market and thus represents a Level 3 measurement within the fair value hierarchy.

For liability classified awards, we recognize expense for the fair value of the awards over the vesting period of the awards. Forfeitures are accounted for as they occur by reversing expense previously recognized for awards that were forfeited during the period. We update our assumptions each reporting period based on new developments and adjust such amounts to fair value based on revised assumptions, if applicable, over the vesting period. At March 31, 2018, the fair value of the liability classified Series B Unit awards was estimated using a Monte Carlo simulation using various assumptions including an equity value of $3.0 billion, expected volatility of 38% based on historical volatility of a peer group of publicly traded partnerships, a risk free rate of 2.70%, and expected IDR distributions based on internal estimates discounted based on a weighted average cost of capital assumption of 7.25%. Based on these assumptions, the estimated value of each Series B Unit at March 31, 2018 was $1,574. The fair value measurement is based on significant inputs not observable in the market and thus represents a Level 3 measurement within the fair value hierarchy.

We recognized expense of $8.4 million, of which $7.6 million was for equity classified awards and $0.8 million was for liability classified awards, during the three months ended March 31, 2018. We recognized expense of $8.3 million, of which $7.7 million was for equity classified awards and $0.6 million was for liability classified awards, during the three months ended March 31, 2017. As of March 31, 2018, there was $59.3 million of unamortized compensation expense related to nonvested Series B Units that is expected to be recognized over the next 1.75 years.

On April 17, 2017, we also adopted the Antero Midstream GP LP Long-Term Incentive Plan (“2017 LTIP”), pursuant to which certain non-employee directors of our general partner and certain officers, employees and consultants of Antero Resources are eligible to receive awards representing equity interests in AMGP. An aggregate of 930,851 common shares may be delivered pursuant to awards under the 2017 LTIP, subject to customary adjustments. As of March 31, 2018, 19,486 common shares have been granted. We recognized zero and $0.2 million in expense related to these grants in the three months ended March 31, 2017 and 2018, respectively. As of March 31, 2018, 911,365 common shares remain available for grant under the 2017 LTIP.