Real Estate Transactions	9 Months Ended
Sep. 30, 2019
Real Estate [Abstract]
Real Estate Transactions	Real Estate Transactions 2019 Real Estate Investments Cambridge Acquisition During the first quarter of 2019, the Company acquired a life science facility for $71 million and development rights at an adjacent undeveloped land parcel for consideration of up to $27 million. The existing facility and land parcel are located in Cambridge, Massachusetts. Discovery Portfolio Acquisition In April 2019, the Company acquired a portfolio of nine senior housing properties for $445 million. The properties are located across Florida, Georgia, and Texas and are operated by Discovery Senior Living, LLC. Oakmont Portfolio Acquisitions In May 2019, the Company acquired three senior housing communities for $113 million and in July 2019, the Company acquired an additional five senior housing communities for $284 million. Both portfolios were acquired from and continue to be operated by Oakmont Senior Living LLC (“Oakmont”). Each portfolio was contributed to a DownREIT joint venture in which the sellers received non-controlling interests in lieu of cash for a portion of the sales price. The Company, as the managing member, consolidates each DownREIT joint venture. As part of the May and July 2019 Oakmont transactions, the Company assumed $50 million and $112 million, respectively, of secured mortgage debt, both of which were recorded at their relative fair values through asset acquisition accounting. Sierra Point Towers Acquisition In June 2019, the Company acquired two life science buildings in South San Francisco, California adjacent to the Company’s The Shore at Sierra Point development, for $245 million. Senior Housing JV Interest Purchase (Vintage Park JV) In June 2019, the Company acquired the outstanding equity interests of a senior housing joint venture structure (which owned one senior housing facility), in which the Company previously held an unconsolidated equity investment, for $24 million. Subsequent to acquisition, the Company owned 100% of the equity. As the Company began consolidating the facility upon acquisition, it derecognized the existing investment in the joint venture structure, marked the real estate to fair value (using a relative fair value allocation), and recognized a gain on consolidation of $12 million, net of a tax impact of $1 million. The gain on consolidation is recognized within other income (expense), net and the tax impact is recognized within income tax benefit (expense). Hartwell Innovation Campus Acquisition In July 2019, the Company acquired a life science campus in the suburban Boston submarket of Lexington, Massachusetts, for $228 million. The campus is comprised of four buildings. Other During the nine months ended September 30, 2019, the Company acquired one medical office building (“MOB”) in Kansas for $15 million and one life science building in the Sorrento Mesa submarket of San Diego, California for $16 million. West Cambridge Acquisition In August 2019, the Company entered into definitive agreements to acquire one life science building, adjacent to the Company’s existing properties in Cambridge, Massachusetts, for $333 million. The Company made two nonrefundable deposits totaling $33 million upon execution of the purchase and sale agreement, which are recorded in other assets, net on the consolidated balance sheet as of September 30, 2019. The Company expects to close the transaction during the fourth quarter of 2019. SHOP Joint Venture In October 2019, the Company entered into a definitive agreement with a sovereign wealth fund to form a new joint venture that will own 19 SHOP assets operated by Brookdale. The Company will own 53.5% of the joint venture and will contribute all 19 assets with an estimated fair value of $790 million. The joint venture partner will own the other 46.5% and will contribute cash of $367 million, which will be immediately distributed to the Company. The transaction is expected to close during the fourth quarter of 2019. 2018 Real Estate Investments MSREI MOB JV In August 2018, the Company and Morgan Stanley Real Estate Investment (“MSREI”) formed a joint venture (the “MSREI JV”) to own a portfolio of MOBs for which the Company is a 51% owner and consolidates. To form the joint venture, MSREI contributed cash of $298 million and the Company contributed nine wholly-owned MOBs (the “Contributed Assets”). The Contributed Assets are primarily located in Texas and Florida and were valued at approximately $320 million at the time of contribution. The MSREI JV used substantially all of the cash contributed by MSREI to acquire an additional portfolio of 16 MOBs in Greenville, South Carolina (the “Greenville Portfolio”) for $285 million. Concurrent with acquiring the additional MOBs, the MSREI JV entered into 10-year leases with the anchor tenants in the Greenville Portfolio. The Contributed Assets are accounted for at historical depreciated cost by the Company, as the assets continue to be consolidated. The Greenville Portfolio was accounted for as an asset acquisition, which required the Company to record the individual components of the acquisition at their relative fair values. As a result, the Company recorded net real estate of $276 million and net intangible assets of $20 million during the three months ended September 30, 2018 related to the Greenville Portfolio. Additionally, during the three months ended September 30, 2018, the Company recognized a noncontrolling interest of $298 million related to the interest owned by MSREI. Refer to Note 15 for a discussion of the Company’s consolidation of the MSREI JV. Life Science JV Interest Purchase In November 2018, the Company acquired the outstanding equity interests in three life science joint ventures (which owned four buildings) for $92 million, bringing the Company’s equity ownership to 100% for all three joint ventures. As the Company began consolidating the assets upon acquisition, it derecognized the existing investment in the joint ventures, marked the real estate to fair value (using a relative fair value allocation), and recognized a gain on consolidation of $50 million within other income (expense), net. Other During the nine months ended September 30, 2018, the Company acquired development rights on a land parcel in the Boston suburb of Lexington, Massachusetts for $21 million. The Company commenced a life science development on the land in 2018. Development Activities As part of the development program with HCA Healthcare, during the nine months ended September 30, 2019, the Company commenced development on four MOBs, three of which will be on-campus. The Company’s commitments related to development and redevelopment projects increased by $56 million, to $355 million at September 30, 2019, when compared to December 31, 2018, primarily as a result of additional development and redevelopment projects. In October 2019, as part of the development program with HCA Healthcare, the Company executed development agreements for two additional on-campus MOBs. Held for Sale At September 30, 2019, 20 senior housing triple-net facilities (inclusive of 18 facilities being sold to Brookdale under the 2019 MTCA - see Note 3), 6 MOBs, 20 SHOP facilities, and 2 facilities from the other non-reportable segment were classified as held for sale, with an aggregate carrying value of $403 million, primarily comprised of real estate assets of $375 million, net of accumulated depreciation of $192 million. Liabilities of assets held for sale was primarily comprised of mortgage debt and other liabilities at September 30, 2019. At December 31, 2018, nine SHOP facilities and one undeveloped life science land parcel were classified as held for sale, with an aggregate carrying value of $108 million, primarily comprised of real estate assets of $101 million, net of accumulated depreciation of $30 million. Liabilities of assets held for sale was primarily comprised of intangible liabilities and other liabilities at December 31, 2018. 2019 Dispositions of Real Estate During the quarter ended March 31, 2019, the Company sold nine SHOP assets for $68 million, two senior housing triple-net assets for $26 million, and one undeveloped life science land parcel for $35 million, resulting in total gain on sales of $8 million. During the quarter ended June 30, 2019, the Company sold one SHOP asset for $14 million, five MOBs for $15 million, and one life science asset for $7 million, resulting in total gain on sales of $11 million. During the quarter ended September 30, 2019, the Company sold one MOB for $3 million and one SHOP asset for $7 million, resulting in no material gain or loss on sales. In October 2019, the Company sold one facility from the other non-reportable segment for $15 million. 2018 Dispositions of Real Estate Shoreline Technology Center In November 2018, the Company sold its Shoreline Technology Center life science campus located in Mountain View, California for $1.0 billion and recognized a gain on sale of $726 million. RIDEA II Sale Transaction In January 2017, the Company completed the contribution of its ownership interest in RIDEA II to an unconsolidated joint venture owned by Healthpeak and an investor group led by Columbia Pacific Advisors, LLC (“CPA”) (the “Healthpeak/CPA JV”). Also in January 2017, RIDEA II was recapitalized with $602 million of debt, of which $360 million was provided by a third-party and $242 million was provided by the Company. In return for both transaction elements, the Company received combined proceeds of $480 million from the Healthpeak/CPA JV and $242 million in loans receivable and retained an approximately 40% ownership interest in RIDEA II. This transaction resulted in the Company deconsolidating the net assets of RIDEA II and recognizing a net gain on sale of $99 million. Refer to Note 2 for the impact of adopting the Revenue ASUs on January 1, 2018 to the Company’s partial sale of RIDEA II in the first quarter of 2017. In June 2018, the Company sold its remaining 40% ownership interest in RIDEA II to an investor group led by CPA for $91 million. Additionally, CPA refinanced the Company’s $242 million of loans receivable from RIDEA II, resulting in total proceeds of $332 million. The Company no longer holds an economic interest in RIDEA II. U.K. Portfolio In June 2018, the Company entered into a joint venture with an institutional investor (the “U.K. JV”) through which the Company sold a 51% interest in substantially all United Kingdom (“U.K.”) assets previously owned by the Company (the “U.K. Portfolio”) based on a total value of £382 million ($507 million). The Company retained a 49% noncontrolling interest in the joint venture and received gross proceeds of $402 million, including proceeds from the refinancing of the Company’s previously held intercompany loans. Upon closing the U.K. JV, the Company deconsolidated the U.K. Portfolio, recognized its retained noncontrolling interest investment at fair value ($105 million) and recognized a gain on sale of $11 million, net of $17 million of cumulative foreign currency translation reclassified from other comprehensive income. The U.K. JV provides numerous mechanisms by which the joint venture partner can acquire the Company’s remaining interest in the U.K. JV. The fair value of the Company’s retained noncontrolling interest investment was based on Level 2 measurements within the fair value hierarchy. Additionally, in August 2018, the Company sold its remaining £11 million U.K. development loan at par. In October 2019, the Company entered into a definitive agreement to sell its remaining 49% interest in the U.K. JV (see Note 7). Other During the quarter ended March 31, 2018, the Company sold two SHOP assets for $35 million, resulting in total gain on sales of $21 million. During the quarter ended June 30, 2018, the Company sold eight SHOP assets for $268 million and two senior housing triple-net assets for $35 million, resulting in total gain on sales of $25 million. During the quarter ended September 30, 2018, the Company sold 4 life science assets for $269 million, 11 SHOP assets for $76 million and 2 MOBs for $21 million, resulting in total gain on sales of $95 million. During the quarter ended December 31, 2018, the Company sold two SHOP facilities for $15 million, two MOBs for $4 million, and one undeveloped land parcel for $3 million, resulting in no material gain or loss on sales. Additionally, during 2018, the Company sold 19 senior housing assets to a third-party buyer for $377 million, resulting in a gain on sale of $40 million. Impairments of Real Estate 2019 During the three months ended September 30, 2019, the Company recognized an aggregate impairment charge of $34 million related to seven SHOP assets, four senior housing triple-net assets, two MOBs, and one other non-reportable asset that are classified as held for sale. The impaired assets were written down from their aggregate carrying value of $124 million to their aggregate fair value less estimated costs to sell of $90 million. Additionally, during the three months ended September 30, 2019, the Company recognized an impairment charge of $4 million related to one MOB that it intends to demolish. The Company expects to re-purpose the land for development. During the nine months ended September 30, 2019, the Company recognized an aggregate impairment charge of $93 million in conjunction with classifying 4 senior housing triple-net assets, 15 SHOP assets, 2 MOBs, and 1 other non-reportable asset as held for sale and writing their aggregate carrying value of $288 million down to their aggregate fair value less estimated costs to sell of $195 million. During the nine months ended September 30, 2019, the Company also recognized an impairment charge of $4 million related to one MOB that it intends to demolish. Additionally, during the nine months ended September 30, 2019, the Company recognized a $5 million casualty-related gain, net of deferred tax impacts, as a result of insurance proceeds received for property damage and other associated costs related to hurricanes in 2017. The gain is recorded in other income (expense), net. Lastly, during the nine months ended September 30, 2019, the Company determined the carrying value of two MOBs that were candidates for potential future sale was no longer recoverable due to the Company’s shortened intended hold period under the held-for-use impairment model. Accordingly, the Company wrote-down the carrying amount of these two assets to their respective fair value, which resulted in an aggregate impairment charge of $9 million. The fair value of the impaired assets was based on forecasted sales prices, which are considered to be Level 3 measurements within the fair value hierarchy. Forecasted sales prices were determined using a direct capitalization model or a market approach (comparable sales model), which rely on certain assumptions by management, including: (i) property hold periods, (ii) market capitalization rates, (iii) market prices per unit, and (iv) forecasted cash flow streams (lease revenue rates, expense rates, growth rates, etc.). There are inherent uncertainties in making these assumptions. For the Company’s impairment calculations during the nine months ended September 30, 2019, the Company used a range of (i) market capitalization rates ranging from 4.97% to 8.27%, with a weighted average rate of 6.09%, and (ii) prices per unit ranging from $46,000 to $125,000, with a weighted average price of $71,000. 2018 During the three months ended September 30, 2018, in conjunction with classifying three underperforming SHOP assets as held for sale, the Company concluded that the assets were impaired and wrote-down the carrying value of the assets to their fair value less estimated costs to sell. Accordingly, the Company recognized a $5 million impairment charge during the third quarter of 2018. During the nine months ended September 30, 2018, in conjunction with classifying 16 underperforming SHOP assets and an undeveloped life science land parcel as held for sale, the Company concluded the assets were impaired and wrote-down the carrying value of the assets to their fair value less estimated costs to sell. Accordingly, the Company recognized a $19 million impairment charge during the nine months ended September 30, 2018. The fair value of the assets impaired in 2018 was based on contractual sales prices, which are considered to be Level 2 measurements within the fair value hierarchy.

Real Estate Transactions

2019 Real Estate Investments

Cambridge Acquisition

During the first quarter of 2019, the Company acquired a life science facility for $71 million and development rights at an adjacent undeveloped land parcel for consideration of up to $27 million. The existing facility and land parcel are located in Cambridge, Massachusetts.

Discovery Portfolio Acquisition

In April 2019, the Company acquired a portfolio of nine senior housing properties for $445 million. The properties are located across Florida, Georgia, and Texas and are operated by Discovery Senior Living, LLC.

Oakmont Portfolio Acquisitions

In May 2019, the Company acquired three senior housing communities for $113 million and in July 2019, the Company acquired an additional five senior housing communities for $284 million. Both portfolios were acquired from and continue to be operated by Oakmont Senior Living LLC (“Oakmont”). Each portfolio was contributed to a DownREIT joint venture in which the sellers received non-controlling interests in lieu of cash for a portion of the sales price. The Company, as the managing member, consolidates each DownREIT joint venture.

As part of the May and July 2019 Oakmont transactions, the Company assumed $50 million and $112 million, respectively, of secured mortgage debt, both of which were recorded at their relative fair values through asset acquisition accounting.

Sierra Point Towers Acquisition

In June 2019, the Company acquired two life science buildings in South San Francisco, California adjacent to the Company’s The Shore at Sierra Point development, for $245 million.

Senior Housing JV Interest Purchase (Vintage Park JV)

In June 2019, the Company acquired the outstanding equity interests of a senior housing joint venture structure (which owned one senior housing facility), in which the Company previously held an unconsolidated equity investment, for $24 million. Subsequent to acquisition, the Company owned 100% of the equity. As the Company began consolidating the facility upon acquisition, it derecognized the existing investment in the joint venture structure, marked the real estate to fair value (using a relative fair value allocation), and recognized a gain on consolidation of $12 million, net of a tax impact of $1 million. The gain on consolidation is recognized within other income (expense), net and the tax impact is recognized within income tax benefit (expense).

Hartwell Innovation Campus Acquisition

In July 2019, the Company acquired a life science campus in the suburban Boston submarket of Lexington, Massachusetts, for $228 million. The campus is comprised of four buildings.

During the nine months ended September 30, 2019, the Company acquired one medical office building (“MOB”) in Kansas for $15 million and one life science building in the Sorrento Mesa submarket of San Diego, California for $16 million.

West Cambridge Acquisition

In August 2019, the Company entered into definitive agreements to acquire one life science building, adjacent to the Company’s existing properties in Cambridge, Massachusetts, for $333 million. The Company made two nonrefundable deposits totaling $33 million upon execution of the purchase and sale agreement, which are recorded in other assets, net on the consolidated balance sheet as of September 30, 2019. The Company expects to close the transaction during the fourth quarter of 2019.

In October 2019, the Company entered into a definitive agreement with a sovereign wealth fund to form a new joint venture that will own 19 SHOP assets operated by Brookdale. The Company will own 53.5% of the joint venture and will contribute all 19 assets with an estimated fair value of $790 million. The joint venture partner will own the other 46.5% and will contribute cash of $367 million, which will be immediately distributed to the Company. The transaction is expected to close during the fourth quarter of 2019.

2018 Real Estate Investments

In August 2018, the Company and Morgan Stanley Real Estate Investment (“MSREI”) formed a joint venture (the “MSREI JV”) to own a portfolio of MOBs for which the Company is a 51% owner and consolidates. To form the joint venture, MSREI contributed cash of $298 million and the Company contributed nine wholly-owned MOBs (the “Contributed Assets”). The Contributed Assets are primarily located in Texas and Florida and were valued at approximately $320 million at the time of contribution. The MSREI JV used substantially all of the cash contributed by MSREI to acquire an additional portfolio of 16 MOBs in Greenville, South Carolina (the “Greenville Portfolio”) for $285 million. Concurrent with acquiring the additional MOBs, the MSREI JV entered into 10-year leases with the anchor tenants in the Greenville Portfolio.

The Contributed Assets are accounted for at historical depreciated cost by the Company, as the assets continue to be consolidated. The Greenville Portfolio was accounted for as an asset acquisition, which required the Company to record the individual components of the acquisition at their relative fair values. As a result, the Company recorded net real estate of $276 million and net intangible assets of $20 million during the three months ended September 30, 2018 related to the Greenville Portfolio. Additionally, during the three months ended September 30, 2018, the Company recognized a noncontrolling interest of $298 million related to the interest owned by MSREI. Refer to Note 15 for a discussion of the Company’s consolidation of the MSREI JV.

Life Science JV Interest Purchase

In November 2018, the Company acquired the outstanding equity interests in three life science joint ventures (which owned four buildings) for $92 million, bringing the Company’s equity ownership to 100% for all three joint ventures. As the Company began consolidating the assets upon acquisition, it derecognized the existing investment in the joint ventures, marked the real estate to fair value (using a relative fair value allocation), and recognized a gain on consolidation of $50 million within other income (expense), net.

During the nine months ended September 30, 2018, the Company acquired development rights on a land parcel in the Boston suburb of Lexington, Massachusetts for $21 million. The Company commenced a life science development on the land in 2018.

Development Activities

As part of the development program with HCA Healthcare, during the nine months ended September 30, 2019, the Company commenced development on four MOBs, three of which will be on-campus.

The Company’s commitments related to development and redevelopment projects increased by $56 million, to $355 million at September 30, 2019, when compared to December 31, 2018, primarily as a result of additional development and redevelopment projects.

In October 2019, as part of the development program with HCA Healthcare, the Company executed development agreements for two additional on-campus MOBs.

At September 30, 2019, 20 senior housing triple-net facilities (inclusive of 18 facilities being sold to Brookdale under the 2019 MTCA - see Note 3), 6 MOBs, 20 SHOP facilities, and 2 facilities from the other non-reportable segment were classified as held for sale, with an aggregate carrying value of $403 million, primarily comprised of real estate assets of $375 million, net of accumulated depreciation of $192 million. Liabilities of assets held for sale was primarily comprised of mortgage debt and other liabilities at September 30, 2019.

At December 31, 2018, nine SHOP facilities and one undeveloped life science land parcel were classified as held for sale, with an aggregate carrying value of $108 million, primarily comprised of real estate assets of $101 million, net of accumulated depreciation of $30 million. Liabilities of assets held for sale was primarily comprised of intangible liabilities and other liabilities at December 31, 2018.

2019 Dispositions of Real Estate

During the quarter ended March 31, 2019, the Company sold nine SHOP assets for $68 million, two senior housing triple-net assets for $26 million, and one undeveloped life science land parcel for $35 million, resulting in total gain on sales of $8 million.

During the quarter ended June 30, 2019, the Company sold one SHOP asset for $14 million, five MOBs for $15 million, and one life science asset for $7 million, resulting in total gain on sales of $11 million.

During the quarter ended September 30, 2019, the Company sold one MOB for $3 million and one SHOP asset for $7 million, resulting in no material gain or loss on sales.

In October 2019, the Company sold one facility from the other non-reportable segment for $15 million.

2018 Dispositions of Real Estate

Shoreline Technology Center

In November 2018, the Company sold its Shoreline Technology Center life science campus located in Mountain View, California for $1.0 billion and recognized a gain on sale of $726 million.

RIDEA II Sale Transaction

In January 2017, the Company completed the contribution of its ownership interest in RIDEA II to an unconsolidated joint venture owned by Healthpeak and an investor group led by Columbia Pacific Advisors, LLC (“CPA”) (the “Healthpeak/CPA JV”). Also in January 2017, RIDEA II was recapitalized with $602 million of debt, of which $360 million was provided by a third-party and $242 million was provided by the Company. In return for both transaction elements, the Company received combined proceeds of $480 million from the Healthpeak/CPA JV and $242 million in loans receivable and retained an approximately 40% ownership interest in RIDEA II. This transaction resulted in the Company deconsolidating the net assets of RIDEA II and recognizing a net gain on sale of $99 million. Refer to Note 2 for the impact of adopting the Revenue ASUs on January 1, 2018 to the Company’s partial sale of RIDEA II in the first quarter of 2017.

In June 2018, the Company sold its remaining 40% ownership interest in RIDEA II to an investor group led by CPA for $91 million. Additionally, CPA refinanced the Company’s $242 million of loans receivable from RIDEA II, resulting in total proceeds of $332 million. The Company no longer holds an economic interest in RIDEA II.

In June 2018, the Company entered into a joint venture with an institutional investor (the “U.K. JV”) through which the Company sold a 51% interest in substantially all United Kingdom (“U.K.”) assets previously owned by the Company (the “U.K. Portfolio”) based on a total value of £382 million ($507 million). The Company retained a 49% noncontrolling interest in the joint venture and received gross proceeds of $402 million, including proceeds from the refinancing of the Company’s previously held intercompany loans. Upon closing the U.K. JV, the Company deconsolidated the U.K. Portfolio, recognized its retained noncontrolling interest investment at fair value ($105 million) and recognized a gain on sale of $11 million, net of $17 million of cumulative foreign currency translation reclassified from other comprehensive income. The U.K. JV provides numerous mechanisms by which the joint venture partner can acquire the Company’s remaining interest in the U.K. JV. The fair value of the Company’s retained noncontrolling interest investment was based on Level 2 measurements within the fair value hierarchy. Additionally, in August 2018, the Company sold its remaining £11 million U.K. development loan at par.

In October 2019, the Company entered into a definitive agreement to sell its remaining 49% interest in the U.K. JV (see Note 7).

During the quarter ended March 31, 2018, the Company sold two SHOP assets for $35 million, resulting in total gain on sales of $21 million.

During the quarter ended June 30, 2018, the Company sold eight SHOP assets for $268 million and two senior housing triple-net assets for $35 million, resulting in total gain on sales of $25 million.

During the quarter ended September 30, 2018, the Company sold 4 life science assets for $269 million, 11 SHOP assets for $76 million and 2 MOBs for $21 million, resulting in total gain on sales of $95 million.

During the quarter ended December 31, 2018, the Company sold two SHOP facilities for $15 million, two MOBs for $4 million, and one undeveloped land parcel for $3 million, resulting in no material gain or loss on sales.

Additionally, during 2018, the Company sold 19 senior housing assets to a third-party buyer for $377 million, resulting in a gain on sale of $40 million.

Impairments of Real Estate

During the three months ended September 30, 2019, the Company recognized an aggregate impairment charge of $34 million related to seven SHOP assets, four senior housing triple-net assets, two MOBs, and one other non-reportable asset that are classified as held for sale. The impaired assets were written down from their aggregate carrying value of $124 million to their aggregate fair value less estimated costs to sell of $90 million. Additionally, during the three months ended September 30, 2019, the Company recognized an impairment charge of $4 million related to one MOB that it intends to demolish. The Company expects to re-purpose the land for development.

During the nine months ended September 30, 2019, the Company recognized an aggregate impairment charge of $93 million in conjunction with classifying 4 senior housing triple-net assets, 15 SHOP assets, 2 MOBs, and 1 other non-reportable asset as held for sale and writing their aggregate carrying value of $288 million down to their aggregate fair value less estimated costs to sell of $195 million. During the nine months ended September 30, 2019, the Company also recognized an impairment charge of $4 million related to one MOB that it intends to demolish.

Additionally, during the nine months ended September 30, 2019, the Company recognized a $5 million casualty-related gain, net of deferred tax impacts, as a result of insurance proceeds received for property damage and other associated costs related to hurricanes in 2017. The gain is recorded in other income (expense), net.

Lastly, during the nine months ended September 30, 2019, the Company determined the carrying value of two MOBs that were candidates for potential future sale was no longer recoverable due to the Company’s shortened intended hold period under the held-for-use impairment model. Accordingly, the Company wrote-down the carrying amount of these two assets to their respective fair value, which resulted in an aggregate impairment charge of $9 million.

The fair value of the impaired assets was based on forecasted sales prices, which are considered to be Level 3 measurements within the fair value hierarchy. Forecasted sales prices were determined using a direct capitalization model or a market approach (comparable sales model), which rely on certain assumptions by management, including: (i) property hold periods, (ii) market capitalization rates, (iii) market prices per unit, and (iv) forecasted cash flow streams (lease revenue rates, expense rates, growth rates, etc.). There are inherent uncertainties in making these assumptions. For the Company’s impairment calculations during the nine months ended September 30, 2019, the Company used a range of (i) market capitalization rates ranging from 4.97% to 8.27%, with a weighted average rate of 6.09%, and (ii) prices per unit ranging from $46,000 to $125,000, with a weighted average price of $71,000.

During the three months ended September 30, 2018, in conjunction with classifying three underperforming SHOP assets as held for sale, the Company concluded that the assets were impaired and wrote-down the carrying value of the assets to their fair value less estimated costs to sell. Accordingly, the Company recognized a $5 million impairment charge during the third quarter of 2018.

During the nine months ended September 30, 2018, in conjunction with classifying 16 underperforming SHOP assets and an undeveloped life science land parcel as held for sale, the Company concluded the assets were impaired and wrote-down the carrying value of the assets to their fair value less estimated costs to sell. Accordingly, the Company recognized a $19 million impairment charge during the nine months ended September 30, 2018.

The fair value of the assets impaired in 2018 was based on contractual sales prices, which are considered to be Level 2 measurements within the fair value hierarchy.