Real Estate Transactions	3 Months Ended
Mar. 31, 2018
Real Estate [Abstract]
Real Estate Transactions	Real Estate Transactions Dispositions of Real Estate Held for Sale At March 31, 2018, seven SHOP facilities, two senior housing triple-net facilities and four life science facilities were classified as held for sale, with an aggregate carrying value of $436 million, primarily comprised of real estate assets of $410 million, net of accumulated depreciation of $98 million. At December 31, 2017, two senior housing triple-net facilities, four life science facilities and six SHOP facilities were classified as held for sale, with an aggregate carrying value of $417 million, primarily comprised of real estate assets of $393 million, net of accumulated depreciation of $93 million. Liabilities of assets held for sale is primarily comprised of intangible and other liabilities at both March 31, 2018 and December 31, 2017. RIDEA II Sale Transaction In January 2017, the Company completed the contribution of its ownership interest in RIDEA II to an unconsolidated JV owned by HCP and an investor group led by Columbia Pacific Advisors, LLC (“CPA”) (“HCP/CPA PropCo” and “HCP/CPA OpCo,” together, the “HCP/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 HCP. In return for both transaction elements, the Company received combined proceeds of $480 million from the HCP/CPA JV and $242 million in loan receivables and retained an approximately 40% ownership interest in RIDEA II (the note receivable and 40% ownership interest are herein referred to as the “RIDEA II Investments”). This transaction resulted in the Company deconsolidating the net assets of RIDEA II and recognizing a net gain on sale of $99 million. The RIDEA II Investments are currently recognized and accounted for as equity method investments. 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. On November 1, 2017, the Company entered into a definitive agreement with an investor group led by CPA to sell its remaining 40% ownership interest in RIDEA II for $91 million. The Company expects the transaction to close in the second quarter of 2018. CPA has also agreed to cause refinancing of the Company’s $242 million loan receivables from RIDEA II within one year following the close of the transaction. U.K. Portfolio On May 1, 2018, the Company entered into definitive agreements with an institutional investor to create a joint venture (the “U.K. JV”) through which the Company will sell a 51% interest in all United Kingdom (“U.K.”) assets owned by the Company (“the U.K. Portfolio”) based on a total value of £394 million. The Company will retain a 49% noncontrolling interest in the joint venture. Upon closing the U.K. JV, the Company expects to deconsolidate the U.K. Portfolio and recognize a gain on deconsolidation. 2018 Dispositions In January 2018, the Company sold two SHOP assets for $35 million, resulting in gain on sales of $21 million. In April 2018, the Company sold four SHOP assets and two senior housing triple-net assets for $265 million. 2017 Dispositions (Three months ended March 31, 2017) In January 2017, the Company sold four life science facilities in Salt Lake City, Utah for $76 million, resulting in a net gain on sale of $45 million. In March 2017, the Company sold 64 senior housing triple-net assets, previously under triple-net leases with Brookdale, for $1.125 billion to affiliates of Blackstone Real Estate Partners VIII, L.P., resulting in a net gain on sale of $170 million. Investments in Real Estate During the three months ended March 31, 2018, the Company acquired development rights on a land parcel in the Boston suburb of Lexington, Massachusetts for $21 million. The Company will commence a life science development on the land in 2018. There were no new real estate investments made during the three months ended March 31, 2017.

Real Estate Transactions

Dispositions of Real Estate

Held for Sale

At March 31, 2018, seven SHOP facilities, two senior housing triple-net facilities and four life science facilities were classified as held for sale, with an aggregate carrying value of $436 million, primarily comprised of real estate assets of $410 million, net of accumulated depreciation of $98 million. At December 31, 2017, two senior housing triple-net facilities, four life science facilities and six SHOP facilities were classified as held for sale, with an aggregate carrying value of $417 million, primarily comprised of real estate assets of $393 million, net of accumulated depreciation of $93 million. Liabilities of assets held for sale is primarily comprised of intangible and other liabilities at both March 31, 2018 and December 31, 2017.

RIDEA II Sale Transaction

In January 2017, the Company completed the contribution of its ownership interest in RIDEA II to an unconsolidated JV owned by HCP and an investor group led by Columbia Pacific Advisors, LLC (“CPA”) (“HCP/CPA PropCo” and “HCP/CPA OpCo,” together, the “HCP/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 HCP. In return for both transaction elements, the Company received combined proceeds of $480 million from the HCP/CPA JV and $242 million in loan receivables and retained an approximately 40% ownership interest in RIDEA II (the note receivable and 40% ownership interest are herein referred to as the “RIDEA II Investments”). This transaction resulted in the Company deconsolidating the net assets of RIDEA II and recognizing a net gain on sale of $99 million. The RIDEA II Investments are currently recognized and accounted for as equity method investments. 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.

On November 1, 2017, the Company entered into a definitive agreement with an investor group led by CPA to sell its remaining 40% ownership interest in RIDEA II for $91 million. The Company expects the transaction to close in the second quarter of 2018. CPA has also agreed to cause refinancing of the Company’s $242 million loan receivables from RIDEA II within one year following the close of the transaction.

U.K. Portfolio

On May 1, 2018, the Company entered into definitive agreements with an institutional investor to create a joint venture (the “U.K. JV”) through which the Company will sell a 51% interest in all United Kingdom (“U.K.”) assets owned by the Company (“the U.K. Portfolio”) based on a total value of £394 million. The Company will retain a 49% noncontrolling interest in the joint venture. Upon closing the U.K. JV, the Company expects to deconsolidate the U.K. Portfolio and recognize a gain on deconsolidation.

2018 Dispositions

In January 2018, the Company sold two SHOP assets for $35 million, resulting in gain on sales of $21 million.

In April 2018, the Company sold four SHOP assets and two senior housing triple-net assets for $265 million.

2017 Dispositions (Three months ended March 31, 2017)

In January 2017, the Company sold four life science facilities in Salt Lake City, Utah for $76 million, resulting in a net gain on sale of $45 million.

In March 2017, the Company sold 64 senior housing triple-net assets, previously under triple-net leases with Brookdale, for $1.125 billion to affiliates of Blackstone Real Estate Partners VIII, L.P., resulting in a net gain on sale of $170 million.

Investments in Real Estate

During the three months ended March 31, 2018, the Company acquired development rights on a land parcel in the Boston suburb of Lexington, Massachusetts for $21 million. The Company will commence a life science development on the land in 2018.

There were no new real estate investments made during the three months ended March 31, 2017.