Stock-Based Compensation	9 Months Ended
Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	6. STOCK-BASED COMPENSATION Stock-based compensation plans are designed to promote stock ownership in NW Natural, and after October 1, 2018, NW Holdings, by employees and officers of NW Natural and certain approved affiliates. These compensation plans include a Long Term Incentive Plan (LTIP), an Employee Stock Purchase Plan (ESPP), and a Restated Stock Option Plan. For additional information on stock-based compensation plans, see Note 6 in the 2017 Form 10-K and the updates provided below. Long Term Incentive Plan Performance Shares LTIP performance shares incorporate a combination of market, performance, and service-based factors. During the nine months ended September 30, 2018, no performance-based shares were granted under the LTIP for accounting purposes. In February 2018, the 2018 LTIP was awarded to participants; however, the agreement allows for one of the performance factors to remain variable until the first quarter of the third year of the award period. As the performance factor will not be approved until the first quarter of 2020, there is not a mutual understanding of the award’s key terms and conditions between NW Natural and the participants as of September 30, 2018, and therefore, no expense was recognized for the 2018 award. NW Natural will calculate the grant date fair value and recognize expense once the final performance factor has been approved. For the 2018 LTIP, award share payouts range from a threshold of 0% to a maximum of 200% based on achievement of pre-established goals. The performance criteria for the 2018 performance shares consists of a three-year Return on Invested Capital (ROIC) threshold that must be satisfied and a cumulative EPS factor, which can be modified by a total shareholder return factor (TSR modifier) relative to the performance of the Russell 2500 Utilities Index over the three-year performance period. If the target was achieved for the 2018 award, NW Holdings would grant 34,702 shares in the first quarter of 2020. As of September 30, 2018, there was $1.3 million of unrecognized compensation cost associated with the 2016 and 2017 LTIP grants, which is expected to be recognized through 2019. Restricted Stock Units During the nine months ended September 30, 2018, 31,490 RSUs were granted under the LTIP with a weighted-average grant date fair value of $57.37 per share. Generally, the RSUs awarded are forfeitable and include a performance-based threshold as well as a vesting period of four years from the grant date. Generally, an RSU obligates us, upon vesting, to issue the RSU holder one share of common stock plus a cash payment equal to the total amount of dividends paid per share between the grant date and vesting date of that portion of the RSU. The fair value of an RSU is equal to the closing market price of common stock on the grant date. As of September 30, 2018, there was $3.4 million of unrecognized compensation cost from grants of RSUs, which is expected to be recognized over a period extending through 2023.

6. STOCK-BASED COMPENSATION

Stock-based compensation plans are designed to promote stock ownership in NW Natural, and after October 1, 2018, NW Holdings, by employees and officers of NW Natural and certain approved affiliates. These compensation plans include a Long Term Incentive Plan (LTIP), an Employee Stock Purchase Plan (ESPP), and a Restated Stock Option Plan. For additional information on stock-based compensation plans, see Note 6 in the 2017 Form 10-K and the updates provided below.

Long Term Incentive Plan

Performance Shares

LTIP performance shares incorporate a combination of market, performance, and service-based factors. During the nine months ended September 30, 2018, no performance-based shares were granted under the LTIP for accounting purposes. In February 2018, the 2018 LTIP was awarded to participants; however, the agreement allows for one of the performance factors to remain variable until the first quarter of the third year of the award period. As the performance factor will not be approved until the first quarter of 2020, there is not a mutual understanding of the award’s key terms and conditions between NW Natural and the participants as of September 30, 2018, and therefore, no expense was recognized for the 2018 award. NW Natural will calculate the grant date fair value and recognize expense once the final performance factor has been approved.

For the 2018 LTIP, award share payouts range from a threshold of 0% to a maximum of 200% based on achievement of pre-established goals. The performance criteria for the 2018 performance shares consists of a three-year Return on Invested Capital (ROIC) threshold that must be satisfied and a cumulative EPS factor, which can be modified by a total shareholder return factor (TSR modifier) relative to the performance of the Russell 2500 Utilities Index over the three-year performance period. If the target was achieved for the 2018 award, NW Holdings would grant 34,702 shares in the first quarter of 2020.

As of September 30, 2018, there was $1.3 million of unrecognized compensation cost associated with the 2016 and 2017 LTIP grants, which is expected to be recognized through 2019.

Restricted Stock Units

During the nine months ended September 30, 2018, 31,490 RSUs were granted under the LTIP with a weighted-average grant date fair value of $57.37 per share. Generally, the RSUs awarded are forfeitable and include a performance-based threshold as well as a vesting period of four years from the grant date. Generally, an RSU obligates us, upon vesting, to issue the RSU holder one share of common stock plus a cash payment equal to the total amount of dividends paid per share between the grant date and vesting date of that portion of the RSU. The fair value of an RSU is equal to the closing market price of common stock on the grant date. As of September 30, 2018, there was $3.4 million of unrecognized compensation cost from grants of RSUs, which is expected to be recognized over a period extending through 2023.