Commitment and Contingencies	3 Months Ended
Mar. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and contingencies	8. Commitments and Contingencies Contingencies The Company records accruals for loss contingencies to the extent that the Company concludes it is probable that a liability has been incurred and the amount of the related loss can be reasonably estimated. The Company evaluates, on a quarterly basis, developments in legal proceedings and other matters that could cause a change in the potential amount of the liability recorded or of the range of potential losses disclosed. Additionally, the Company records receivables from third-party insurers when recovery has been determined to be probable. This includes instances when the Company’s third-party insurers have agreed to reimburse certain legal defense costs incurred with the applicable law firms by the Company. Appeal of USPTO Decision In March 2009, the Company received a final rejection in one of the Company’s original patent applications pertaining to certain limited methods of use claims for NK-92 from the U.S. Patent and Trademark Office (the USPTO), but the USPTO allowed claims on all of the other proposed claims, including other methods of use. The Company appealed this decision with the USPTO Board of Appeals and, in the fall of 2013, the Board of Appeals reversed the Examiner’s rejection of the claim to certain limited methods of use with NK-92, but affirmed the Examiner’s rejection of the remaining patent claims. In December 2013, the Company brought an action in the U.S. District Court for the Eastern District of Virginia to review the decision of the USPTO as the Company disagreed with the decision as to the certain limited non-allowed claims. On September 2, 2015, the U.S. District Court granted the USPTO’s motion for summary judgment. On September 24, 2015, the Company filed a notice of appeal to the United States Court of Appeals for the Federal Circuit. In September 2015, the USPTO filed a Motion for Expenses seeking $0.1 million for attorney’s fees and the USPTO’s expert witness fees. In February 2016, the U.S. District Court denied the USPTO’s Motion for Expenses for attorney’s fees and granted Director’s Motion for Expenses for the USPTO’s expert witness fees. The USPTO filed a notice of appeal on April 5, 2016. In May 2017, the Federal Circuit affirmed the U.S. District Court’s summary judgment ruling. The formal mandate was issued on June 26, 2017. In June 2017, the Federal Circuit reversed the U.S. District Court and remanded the case for the U.S. District Court to enter an award of $0.1 million in favor of the USPTO. On August 31, 2017, a majority of active Federal Circuit judges voted to vacate the June 2017 decision and hear the case en banc sua sponte. The USPTO filed its opening brief on November 15, 2017. The Company filed its opening brief on January 16, 2018. The USPTO filed its reply brief on January 31, 2018. Oral argument was heard on March 8, 2018. Based on the information available at present, the Company cannot reasonably estimate a range of loss for this action beyond the attorney and expert witness fees. Accordingly, the awarded fees have been accrued, but no liability associated with this action beyond the fees has been accrued. The Company is expensing legal costs associated with defending this litigation as the costs are incurred. Securities Litigation In March 2016, a putative securities class action complaint captioned Sudunagunta v. NantKwest, Inc., et al., No. 16-cv-01947 was filed in federal district court for the Central District of California related to the Company’s restatement of certain interim financial statements for the periods ended June 30, 2015 and September 30, 2015. A number of similar putative class actions were filed in federal and state court in California. The actions originally filed in state court were removed to federal court, and the various related actions have been consolidated. Plaintiffs assert causes of action for alleged violations of Sections 11 and 15 of the Securities Act of 1933 and Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 and Rule 10b-5 promulgated thereunder. Plaintiffs seek unspecified damages, costs and attorneys’ fees, and equitable/injunctive or other relief on behalf of putative classes of persons who purchased or acquired the Company’s securities during various time periods from July 28, 2015 through March 11, 2016. In September 2017, the court denied defendants' motion to dismiss the third amended consolidated complaint. A trial date has been set for August 2019. Management intends to vigorously defend these proceedings. At this time, the Company cannot predict how the Court will rule on the merits of the claims and/or the scope of the potential loss in the event of an adverse outcome. Therefore, based on the information available at present, the Company cannot reasonably estimate a range of loss for this action. Should the Company ultimately be found liable, the liability could have a material adverse effect on the Company’s results of operations for the period or periods in which it is incurred. On September 6, 2016, a putative shareholder derivative complaint captioned Bushansky v. Soon-Shiong, et al., No. 37-2016-00030867-CU-SL-CTL was filed in California Superior Court, San Diego County also related to the Company’s restatement of certain interim financial statements. The complaint named as defendants the Company’s directors and outside auditor at the time of the IPO. The Company is named solely as a nominal defendant. The complaint alleges the directors breached their fiduciary duties to the Company and wasted corporate assets, and that the outside auditors committed malpractice. The complaint seeks, on behalf of the Company, unspecified damages, the return of directors’ salaries for unspecified periods, and injunctive relief. At this time, the Company cannot predict how the Court will rule on the merits of the claims and/or the scope of the potential loss in the event of an adverse outcome. In April 2017, the court entered a written order of dismissal after granting the Company’s motion to dismiss the California complaint based on a corporate charter provision specifying a Delaware forum. Plaintiffs have filed a notice of appeal. Should the Company ultimately be found liable, the liability could have a material adverse effect on the Company’s results of operations for the period or periods in which it is incurred. In October 2017, the first of two putative stockholder derivative complaints was filed in the Delaware Court of Chancery. The Delaware actions have been consolidated as In re NantKwest, Inc. Derivative Litigation, Cons. C.A. No. 2017-0774- VCL. A consolidated complaint was filed asserting that various of the Company's current and former directors and officers breached their fiduciary duties to the Company based on factual allegations similar to those in the Sudunagunta and Bushansky actions. The complaint seeks damages and other relief on behalf of the Company, which is named solely as a nominal defendant. On February 5, 2018, the defendants filed a motion to dismiss the consolidated complaint. At this time, the Company cannot predict how the Court will rule on the merits of the claims and/or the scope of the potential loss in the event of an adverse outcome. Therefore, based on the information available at present, the Company cannot reasonably estimate a range of loss for this action. Should the Company ultimately be found liable, the liability could have a material adverse effect on the Company’s results of operations for the period or periods in which it is incurred. Insurance Recoveries The Company has reflected its right to insurance recoveries, limited to the extent of incurred or probable losses, as a receivable when such recoveries have been agreed to with its third-party insurers and receipt is deemed probable. This includes instances where the Company’s third-party insurers have agreed to reimburse certain legal defense costs incurred with applicable law firms by the Company. The amount of such receivable recorded at March 31, 2018 was $1.6 million included in prepaid expenses and current assets on the Company’s condensed consolidated balance sheet. Contractual Obligations - Leases The Company leases: (i) office space in Cardiff-by-the-Sea, California; (ii) a research facility in Woburn, Massachusetts; (iii) a research facility and office space in San Diego, California; (iv) research and manufacturing space in Culver City, California, from a related party (Note 9); and (v) a research and manufacturing facility in El Segundo, California, also from a related party (Note 9). The Company recognizes rent expense under its operating leases on a straight-line basis. Rent expense for the three months ended March 31, 2018 and 2017 was $0.7 million for both periods. Build-to-suit Lease In September 2016, the Company entered into a lease agreement with 605 Doug St, LLC, a related party (Note 9), for approximately 24,250 square feet in El Segundo, California, which is to be converted to a research and development laboratory and a current Good Manufacturing Practices (cGMP) manufacturing facility. The lease runs from July 2016 through July 2023. The Company has the option to extend the lease for an additional three year term through July 2026. The monthly rent is $0.1 million with annual increases of 3% beginning in July 2017. During the construction period, the Company records the rent payments as (1) a reduction of the build-to-suit lease liability; (2) deferred rent; and (3) rent expense on the imputed cost to lease the underlying land of the facility, which is considered an operating lease. For the three months ended March 31, 2018 and 2017, the Company recorded $0.1 million for both periods in rent expense, which is recorded in research and development expense on the condensed consolidated statement of operations. The Company is responsible for costs to build out the facility and has incurred costs of approximately $30.1 million as of March 31, 2018, which is reflected in construction in progress as part of property, plant and equipment, net on the condensed consolidated balance sheet. Additionally, in order for the facility to meet the Company's research and development laboratory and cGMP specifications, the Company started to make certain structural changes to the facility as part of the conversion. As a result of these changes, the Company concluded that it is the “deemed owner” of the building (for accounting purposes only) during the construction period. Accordingly, the Company recorded a non-cash build-to-suit lease asset of $5.1 million, representing its estimate of the fair market value of the building, and a corresponding construction build-to-suit lease liability, recorded as a component of other current and non-current liabilities on the condensed consolidated balance sheet as of March 31, 2018. Upon completion of construction of this facility, the Company evaluates the de-recognition of the asset and liability under the provisions of ASC 840-40 Leases - Sale-Leaseback Transactions. However, if the Company does not comply with the provisions needed for sale-leaseback accounting, the lease will be accounted for as a financing obligation and lease payments will be attributed to (1) a reduction of the principal financing obligation; (2) imputed interest expense; and (3) land lease expense (which is considered an operating lease and a component of research and development expenses) representing an imputed cost to lease the underlying land of the facility. In addition, the underlying building asset will be depreciated over the building's estimated useful life which is estimated at 39 years. At the conclusion of the lease term, the Company would de-recognize both the net book values of the asset and financing obligation. Financing Lease Obligation In November 2015, the Company entered into a facility license agreement with NantWorks LLC (NantWorks) (Note 9) for approximately 9,500 square feet of office space in Culver City, California, which has been converted to a research and development laboratory and a cGMP manufacturing facility. The license was effective in May 2015 and extends through December 2020. The Company has the option to extend the license through December 2023. The monthly license fee is $47,000 with annual increases of 3% beginning in January 2017. The Company records the rent payments as (1) a reduction of the financing obligation; (2) imputed interest expense; and (3) rent expense on the imputed cost to lease the underlying land of the facility, which is considered an operating lease. For the three months ended March 31, 2018 and 2017, the Company recorded $47,000 for both periods in rent expense, which is reflected in research and development expense in the condensed consolidated statement of operations. Under the facility license agreement, the Company was responsible for costs to build out the laboratory and manufacturing facility space and incurred costs of approximately $3.5 million. The Company concluded that it was the “deemed owner” of the building (for accounting purposes only) during the construction period. The Company recorded the build out costs as an asset with a corresponding build-to-suit liability, which was recorded as a component of other current and non-current liabilities in the condensed consolidated balance sheet while the building was under construction. Upon completion of construction of this building in August 2016, the Company evaluated the de-recognition of the asset and liability under the provisions of ASC 840-40, Leases – Sale-Leaseback Transactions. The Company determined that the lease does not meet the criteria for sale-leaseback accounting treatment, due to the continuing involvement in the project resulting from the significant collateral the Company provided to the landlord in the form of building improvements. As a result, the building is being accounted for as a financing obligation. The underlying assets of $4.3 million are depreciated over the building’s estimated useful life, which is 39 years. At the conclusion of the lease term, the Company will de-recognize both the net book values of the assets and financing obligation. Commitments The Company did not enter into any significant contracts during the three months ended March 31, 2018 other than those disclosed in this document.

8. Commitments and Contingencies

Contingencies

The Company records accruals for loss contingencies to the extent that the Company concludes it is probable that a liability has been incurred and the amount of the related loss can be reasonably estimated. The Company evaluates, on a quarterly basis, developments in legal proceedings and other matters that could cause a change in the potential amount of the liability recorded or of the range of potential losses disclosed. Additionally, the Company records receivables from third-party insurers when recovery has been determined to be probable. This includes instances when the Company’s third-party insurers have agreed to reimburse certain legal defense costs incurred with the applicable law firms by the Company.

Appeal of USPTO Decision

In March 2009, the Company received a final rejection in one of the Company’s original patent applications pertaining to certain limited methods of use claims for NK-92 from the U.S. Patent and Trademark Office (the USPTO), but the USPTO allowed claims on all of the other proposed claims, including other methods of use. The Company appealed this decision with the USPTO Board of Appeals and, in the fall of 2013, the Board of Appeals reversed the Examiner’s rejection of the claim to certain limited methods of use with NK-92, but affirmed the Examiner’s rejection of the remaining patent claims. In December 2013, the Company brought an action in the U.S. District Court for the Eastern District of Virginia to review the decision of the USPTO as the Company disagreed with the decision as to the certain limited non-allowed claims. On September 2, 2015, the U.S. District Court granted the USPTO’s motion for summary judgment. On September 24, 2015, the Company filed a notice of appeal to the United States Court of Appeals for the Federal Circuit. In September 2015, the USPTO filed a Motion for Expenses seeking $0.1 million for attorney’s fees and the USPTO’s expert witness fees. In February 2016, the U.S. District Court denied the USPTO’s Motion for Expenses for attorney’s fees and granted Director’s Motion for Expenses for the USPTO’s expert witness fees. The USPTO filed a notice of appeal on April 5, 2016. In May 2017, the Federal Circuit affirmed the U.S. District Court’s summary judgment ruling. The formal mandate was issued on June 26, 2017. In June 2017, the Federal Circuit reversed the U.S. District Court and remanded the case for the U.S. District Court to enter an award of $0.1 million in favor of the USPTO. On August 31, 2017, a majority of active Federal Circuit judges voted to vacate the June 2017 decision and hear the case en banc sua sponte. The USPTO filed its opening brief on November 15, 2017. The Company filed its opening brief on January 16, 2018. The USPTO filed its reply brief on January 31, 2018. Oral argument was heard on March 8, 2018. Based on the information available at present, the Company cannot reasonably estimate a range of loss for this action beyond the attorney and expert witness fees. Accordingly, the awarded fees have been accrued, but no liability associated with this action beyond the fees has been accrued. The Company is expensing legal costs associated with defending this litigation as the costs are incurred.

Securities Litigation

In March 2016, a putative securities class action complaint captioned Sudunagunta v. NantKwest, Inc., et al., No. 16-cv-01947 was filed in federal district court for the Central District of California related to the Company’s restatement of certain interim financial statements for the periods ended June 30, 2015 and September 30, 2015. A number of similar putative class actions were filed in federal and state court in California. The actions originally filed in state court were removed to federal court, and the various related actions have been consolidated. Plaintiffs assert causes of action for alleged violations of Sections 11 and 15 of the Securities Act of 1933 and Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 and Rule 10b-5 promulgated thereunder. Plaintiffs seek unspecified damages, costs and attorneys’ fees, and equitable/injunctive or other relief on behalf of putative classes of persons who purchased or acquired the Company’s securities during various time periods from July 28, 2015 through March 11, 2016. In September 2017, the court denied defendants' motion to dismiss the third amended consolidated complaint. A trial date has been set for August 2019. Management intends to vigorously defend these proceedings. At this time, the Company cannot predict how the Court will rule on the merits of the claims and/or the scope of the potential loss in the event of an adverse outcome. Therefore, based on the information available at present, the Company cannot reasonably estimate a range of loss for this action. Should the Company ultimately be found liable, the liability could have a material adverse effect on the Company’s results of operations for the period or periods in which it is incurred.

On September 6, 2016, a putative shareholder derivative complaint captioned Bushansky v. Soon-Shiong, et al., No. 37-2016-00030867-CU-SL-CTL was filed in California Superior Court, San Diego County also related to the Company’s restatement of certain interim financial statements. The complaint named as defendants the Company’s directors and outside auditor at the time of the IPO. The Company is named solely as a nominal defendant. The complaint alleges the directors breached their fiduciary duties to the Company and wasted corporate assets, and that the outside auditors committed malpractice. The complaint seeks, on behalf of the Company, unspecified damages, the return of directors’ salaries for unspecified periods, and injunctive relief. At this time, the Company cannot predict how the Court will rule on the merits of the claims and/or the scope of the potential loss in the event of an adverse outcome. In April 2017, the court entered a written order of dismissal after granting the Company’s motion to dismiss the California complaint based on a corporate charter provision specifying a Delaware forum. Plaintiffs have filed a notice of appeal. Should the Company ultimately be found liable, the liability could have a material adverse effect on the Company’s results of operations for the period or periods in which it is incurred.

In October 2017, the first of two putative stockholder derivative complaints was filed in the Delaware Court of Chancery. The Delaware actions have been consolidated as In re NantKwest, Inc. Derivative Litigation, Cons. C.A. No. 2017-0774- VCL. A consolidated complaint was filed asserting that various of the Company's current and former directors and officers breached their fiduciary duties to the Company based on factual allegations similar to those in the Sudunagunta and Bushansky actions. The complaint seeks damages and other relief on behalf of the Company, which is named solely as a nominal defendant. On February 5, 2018, the defendants filed a motion to dismiss the consolidated complaint. At this time, the Company cannot predict how the Court will rule on the merits of the claims and/or the scope of the potential loss in the event of an adverse outcome. Therefore, based on the information available at present, the Company cannot reasonably estimate a range of loss for this action. Should the Company ultimately be found liable, the liability could have a material adverse effect on the Company’s results of operations for the period or periods in which it is incurred.

Insurance Recoveries

The Company has reflected its right to insurance recoveries, limited to the extent of incurred or probable losses, as a receivable when such recoveries have been agreed to with its third-party insurers and receipt is deemed probable. This includes instances where the Company’s third-party insurers have agreed to reimburse certain legal defense costs incurred with applicable law firms by the Company. The amount of such receivable recorded at March 31, 2018 was $1.6 million included in prepaid expenses and current assets on the Company’s condensed consolidated balance sheet.

Contractual Obligations - Leases

The Company leases: (i) office space in Cardiff-by-the-Sea, California; (ii) a research facility in Woburn, Massachusetts; (iii) a research facility and office space in San Diego, California; (iv) research and manufacturing space in Culver City, California, from a related party (Note 9); and (v) a research and manufacturing facility in El Segundo, California, also from a related party (Note 9).

The Company recognizes rent expense under its operating leases on a straight-line basis. Rent expense for the three months ended March 31, 2018 and 2017 was $0.7 million for both periods.

Build-to-suit Lease

In September 2016, the Company entered into a lease agreement with 605 Doug St, LLC, a related party (Note 9), for approximately 24,250 square feet in El Segundo, California, which is to be converted to a research and development laboratory and a current Good Manufacturing Practices (cGMP) manufacturing facility. The lease runs from July 2016 through July 2023. The Company has the option to extend the lease for an additional three year term through July 2026. The monthly rent is $0.1 million with annual increases of 3% beginning in July 2017. During the construction period, the Company records the rent payments as (1) a reduction of the build-to-suit lease liability; (2) deferred rent; and (3) rent expense on the imputed cost to lease the underlying land of the facility, which is considered an operating lease. For the three months ended March 31, 2018 and 2017, the Company recorded $0.1 million for both periods in rent expense, which is recorded in research and development expense on the condensed consolidated statement of operations.

The Company is responsible for costs to build out the facility and has incurred costs of approximately $30.1 million as of March 31, 2018, which is reflected in construction in progress as part of property, plant and equipment, net on the condensed consolidated balance sheet. Additionally, in order for the facility to meet the Company's research and development laboratory and cGMP specifications, the Company started to make certain structural changes to the facility as part of the conversion. As a result of these changes, the Company concluded that it is the “deemed owner” of the building (for accounting purposes only) during the construction period. Accordingly, the Company recorded a non-cash build-to-suit lease asset of $5.1 million, representing its estimate of the fair market value of the building, and a corresponding construction build-to-suit lease liability, recorded as a component of other current and non-current liabilities on the condensed consolidated balance sheet as of March 31, 2018.

Upon completion of construction of this facility, the Company evaluates the de-recognition of the asset and liability under the provisions of ASC 840-40 Leases - Sale-Leaseback Transactions. However, if the Company does not comply with the provisions needed for sale-leaseback accounting, the lease will be accounted for as a financing obligation and lease payments will be attributed to (1) a reduction of the principal financing obligation; (2) imputed interest expense; and (3) land lease expense (which is considered an operating lease and a component of research and development expenses) representing an imputed cost to lease the underlying land of the facility. In addition, the underlying building asset will be depreciated over the building's estimated useful life which is estimated at 39 years. At the conclusion of the lease term, the Company would de-recognize both the net book values of the asset and financing obligation.

Financing Lease Obligation

In November 2015, the Company entered into a facility license agreement with NantWorks LLC (NantWorks) (Note 9) for approximately 9,500 square feet of office space in Culver City, California, which has been converted to a research and development laboratory and a cGMP manufacturing facility. The license was effective in May 2015 and extends through December 2020. The Company has the option to extend the license through December 2023. The monthly license fee is $47,000 with annual increases of 3% beginning in January 2017. The Company records the rent payments as (1) a reduction of the financing obligation; (2) imputed interest expense; and (3) rent expense on the imputed cost to lease the underlying land of the facility, which is considered an operating lease. For the three months ended March 31, 2018 and 2017, the Company recorded $47,000 for both periods in rent expense, which is reflected in research and development expense in the condensed consolidated statement of operations.

Under the facility license agreement, the Company was responsible for costs to build out the laboratory and manufacturing facility space and incurred costs of approximately $3.5 million. The Company concluded that it was the “deemed owner” of the building (for accounting purposes only) during the construction period. The Company recorded the build out costs as an asset with a corresponding build-to-suit liability, which was recorded as a component of other current and non-current liabilities in the condensed consolidated balance sheet while the building was under construction.

Upon completion of construction of this building in August 2016, the Company evaluated the de-recognition of the asset and liability under the provisions of ASC 840-40, Leases – Sale-Leaseback Transactions. The Company determined that the lease does not meet the criteria for sale-leaseback accounting treatment, due to the continuing involvement in the project resulting from the significant collateral the Company provided to the landlord in the form of building improvements. As a result, the building is being accounted for as a financing obligation. The underlying assets of $4.3 million are depreciated over the building’s estimated useful life, which is 39 years. At the conclusion of the lease term, the Company will de-recognize both the net book values of the assets and financing obligation.

Commitments

The Company did not enter into any significant contracts during the three months ended March 31, 2018 other than those disclosed in this document.