Tiaa Real Estate Account 10-K 14 Mar 19 2018 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Jun. 30, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	TIAA REAL ESTATE ACCOUNT
Document Type	10-K
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding (in shares)	0
Entity Public Float		$ 0
Amendment Flag	false
Entity Central Index Key	0000946155
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	No
Entity Smaller Reporting Company	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY

AUDITED CONSOLIDATED STATEMENTS

AUDITED CONSOLIDATED STATEMENTS OF ASSETS AND LIABILITIES - USD ($) shares in Millions, $ in Millions		Dec. 31, 2018	Dec. 31, 2017
Investments, at fair value:
Real estate properties (cost: $12,687.8 and $12,972.5)		$ 15,531.1	$ 15,742.7
Real estate joint ventures and limited partnerships (cost: $5,207.8 and $4,675.3)		6,532.5	6,003
Marketable securities:
Real estate related (cost: $1,274.7 and $991.0)	[1]	1,415.1	1,238
Other (cost: $4,088.9 and $3,888.1)		4,088.7	3,887.5
Loans receivable (cost: $910.6 and $296.7)		913	298.8
Total investments (cost: $24,169.8 and $22,823.6)		28,480.4	27,170
Cash and cash equivalents		3.8	11.7
Due from investment manager		2.2	1
Other	[2]	331.8	270.9
TOTAL ASSETS		28,818.2	27,453.6
LIABILITIES
Mortgage loans payable, at fair value (principal outstanding: $2,688.1 and $2,238.6)		2,608	2,238.3
Accrued real estate property expenses		222.4	199.1
Payable for collateral for securities loaned		68.8	18.5
Other		76.4	55.1
TOTAL LIABILITIES		2,975.6	2,511
COMMITMENTS AND CONTINGENCIES
NET ASSETS
Accumulation Fund		25,320.1	24,430.8
Annuity Fund		522.5	511.8
TOTAL NET ASSETS		$ 25,842.6	$ 24,942.6
NUMBER OF ACCUMULATION UNITS OUTSTANDING (in shares)		60.7	61.3
NET ASSET VALUE, PER ACCUMULATION UNIT (in dollars per share)		$ 417.416	$ 398.329
[1]	Includes securities loaned of $67.4 million at December 31, 2018 and $18.1 million at December 31, 2017.
[2]	Includes cash collateral for securities loaned of $68.8 million at December 31, 2018 and $18.5 million at December 31, 2017.

AUDITED CONSOLIDATED STATEMEN_2

AUDITED CONSOLIDATED STATEMENTS OF ASSETS AND LIABILITIES (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Securities loaned	$ 67.4	$ 18.1
Collateral for securities loaned	68.8	18.5
Real estate properties at cost	12,687.8	12,972.5
Real estate joint ventures and limited partnerships at cost	5,207.8	4,675.3
Real estate related marketable securities at cost	1,274.7	991
Other marketable securities at cost	4,088.9	3,888.1
Loan Receivable at cost	910.6	296.7
Cost of total investments	24,169.8	22,823.6
Principal outstanding on mortgage loans payable	$ 2,688.1	$ 2,238.6

AUDITED CONSOLIDATED STATEMEN_3

AUDITED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Real estate income, net
Rental income	$ 1,083.2	$ 1,059.6	$ 1,009
Real estate property level expenses and taxes:
Operating expenses	228.6	221.2	218.1
Real estate taxes	178.9	166.7	158.7
Interest expense	113.9	89.7	85.8
Total real estate property level expenses and taxes	521.4	477.6	462.6
Real estate income, net	561.8	582	546.4
Income from real estate joint ventures and limited partnerships	204.7	214.1	161.8
Interest	120.4	54.1	26.4
Dividends	50.8	26.3	32.5
TOTAL INVESTMENT INCOME	937.7	876.5	767.1
Expenses
Investment management charges	62.1	72	72.6
Administrative charges	50.9	59.3	62.1
Distribution charges	28	25.7	27.7
Mortality and expense risk charges	1.3	1.2	1.2
Liquidity guarantee charges	50.5	47	38.4
TOTAL EXPENSES	192.8	205.2	202
INVESTMENT INCOME, NET	744.9	671.3	565.1
Net realized gain (loss) on investments
Real estate properties	242.7	42	(6.2)
Real estate joint ventures and limited partnerships	75.9	(21.9)	0.6
Marketable securities	12.8	17.6	25.6
Mortgage loans payable	(0.4)	0	0
Net realized gain on investments	331	37.7	20
Net change in unrealized appreciation (depreciation) on
Real estate properties	73.1	135.5	317.5
Real estate joint ventures and limited partnerships	55.5	146.8	236.9
Marketable securities	(103)	50	30
Loans receivable	0.3	1.2	0.3
Mortgage loans payable	79.8	15.9	15.1
Net change in unrealized appreciation on investments and mortgage loans payable	105.7	349.4	599.8
NET REALIZED AND UNREALIZED GAIN ON INVESTMENTS AND MORTGAGE LOANS PAYABLE	436.7	387.1	619.8
NET INCREASE IN NET ASSETS RESULTING FROM OPERATIONS	$ 1,181.6	$ 1,058.4	$ 1,184.9

AUDITED CONSOLIDATED STATEMEN_4

AUDITED CONSOLIDATED STATEMENTS OF CHANGES IN NET ASSETS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
FROM OPERATIONS
Investment income, net	$ 744.9	$ 671.3	$ 565.1
Net realized gain on investments	331	37.7	20
Net change in unrealized appreciation on investments and mortgage loans payable	105.7	349.4	599.8
NET INCREASE IN NET ASSETS RESULTING FROM OPERATIONS	1,181.6	1,058.4	1,184.9
FROM PARTICIPANT TRANSACTIONS
Premiums	2,637.4	2,561.7	3,064.2
Annuity payments	(45)	(43.4)	(41)
Withdrawals and death benefits	(2,874)	(2,938.8)	(2,263.4)
NET (DECREASE) INCREASE IN NET ASSETS RESULTING FROM PARTICIPANT TRANSACTIONS	(281.6)	(420.5)	759.8
NET INCREASE IN NET ASSETS	900	637.9	1,944.7
NET ASSETS
Beginning of period	24,942.6	24,304.7	22,360
End of period	$ 25,842.6	$ 24,942.6	$ 24,304.7

AUDITED CONSOLIDATED STATEMEN_5

AUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net increase in net assets resulting from operations		$ 1,181.6	$ 1,058.4	$ 1,184.9
Adjustments to reconcile net changes in net assets resulting from operations to net cash provided by (used in) operating activities:
Net realized gain on investments		(331)	(37.7)	(20)
Net change in unrealized appreciation on investments and mortgage loans payable		(105.7)	(349.4)	(599.8)
Purchase of real estate properties		(786.3)	(538.2)	(623.9)
Capital improvements on real estate properties		(228.6)	(130.1)	(157.2)
Proceeds from sale of real estate properties		1,462.7	525.5	251.1
Purchases of long term investments		(1,422.2)	(592)	(1,379.4)
Proceeds from long term investments		756.4	385.3	68.3
Purchases and originations of loans receivable		(939.2)	(1.9)	(194.8)
Proceeds from sales of loans receivable		257.3	0	0
Proceeds from payoffs of loans receivable		68	0	0
(Increase) decrease in other investments		(200.8)	165.9	153.6
Change in due (from) to investment manager		(1.2)	4.9	(0.2)
(Increase) decrease in other assets		(59.7)	58.2	(107.5)
Increase (decrease) in other liabilities		63	(72.6)	122.3
NET CASH (USED IN) PROVIDED BY OPERATING ACTIVITIES		(285.7)	476.3	(1,302.6)
CASH FLOWS FROM FINANCING ACTIVITIES
Mortgage loan proceeds received		712.8	0	563.5
Payments of mortgage loans		(152.2)	(50.6)	(34.7)
Premiums		2,637.4	2,561.7	3,064.2
Annuity payments		(45)	(43.4)	(41)
Withdrawals and death benefits		(2,874)	(2,938.8)	(2,263.4)
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES		279	(471.1)	1,288.6
CASH, CASH EQUIVALENTS AND RESTRICTED CASH
Beginning of period cash, cash equivalents and restricted cash		54	48.8	62.8
Net (decrease) increase in cash, cash equivalents and restricted cash		(6.7)	5.2	(14)
End of period cash, cash equivalents and restricted cash		47.3	54	48.8
SUPPLEMENTAL DISCLOSURES
Cash paid for interest		108.7	89.9	84.2
Debt assumed as part of a real estate acquisition		105.1	17.7	24
Loan assignment as part of a real estate disposition		216.5	45	0
Stock consideration received from the merger of marketable securities		6.1	0	0
Cash and cash equivalents		3.8	11.7	3
Restricted cash	[1]	43.5	42.3	45.8
End of period cash, cash equivalents and restricted cash		$ 47.3	$ 54	$ 48.8
[1]	Restricted cash is included within other assets on the Account's Consolidated Statements of Assets and Liabilities.

Organization and Significant Ac

Organization and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Organization and Significant Accounting Policies	Organization and Significant Accounting Policies Business: The TIAA Real Estate Account (“Account”) is an insurance separate account of Teachers Insurance and Annuity Association of America (“TIAA”) and was established by resolution of TIAA’s Board of Trustees (the “Board”) on February 22, 1995, under the insurance laws of the State of New York, for the purpose of funding variable annuity contracts issued by TIAA. The Account offers individual and group accumulating annuity contracts (with contributions made on a pre-tax or after-tax basis), as well as individual lifetime and term-certain variable payout annuity contracts (including the payment of death benefits to beneficiaries). Investors are entitled to transfer funds to or from the Account, and make withdrawals from the Account on a daily basis, under certain circumstances. Funds invested in the Account for each category of contract are expressed in terms of units, and unit values will fluctuate depending on the Account’s performance. The investment objective of the Account is to seek favorable long-term returns primarily through rental income and appreciation of a diversified portfolio of directly held, private real estate investments and real estate-related investments while offering investors guaranteed, daily liquidity. The Account holds real estate properties directly and through subsidiaries wholly-owned by TIAA for the sole benefit of the Account. The Account also holds limited interests in real estate joint ventures and limited partnerships, as well as investments in loans receivable with commercial real estate properties as underlying collateral. Additionally, the Account invests in real estate-related and non-real estate-related publicly traded securities, cash and other instruments to maintain adequate liquidity levels for operating expenses, capital expenditures and to fund benefit payments (withdrawals, transfers and related transactions). The Consolidated Financial Statements were prepared in accordance with accounting principles generally accepted in the United States of America, which requires the use of estimates made by management. Actual results may vary from those estimates and such differences may be material. The following is a summary of the significant accounting policies of the Account. Basis of Presentation: The accompanying Consolidated Financial Statements include the Account and those subsidiaries wholly-owned by TIAA for the benefit of the Account. All significant intercompany accounts and transactions between the Account and such subsidiaries have been eliminated. The Accumulation Unit Value (“AUV”) used for financial reporting purposes may differ from the AUV used for processing transactions. The AUV used for financial reporting purposes includes security and participant transactions effective through the period end date to which this report relates. Total return is computed based on the AUV used for processing transactions. Determination of Investments at Fair Value: The Account reports all investments at fair value in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 946, Financial Services—Investment Companies. Further in accordance with the adoption of the fair value option allowed under ASC 825, Financial Instruments , and at the election of Account management, mortgage loans payable are reported at fair value. The FASB has defined fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. The following is a description of the valuation methodologies used to determine the fair value of the Account’s investments and investment related mortgage loans payable. Valuation of Real Estate Properties —Investments in real estate properties are stated at fair value, as determined in accordance with policies and procedures reviewed by the Investment Committee of the Board and in accordance with the responsibilities of the Board as a whole. Accordingly, the Account does not record depreciation. Determination of fair value involves significant levels of judgment because the actual fair value of real estate can be determined only by negotiation between the parties in a sales transaction. The Account’s primary objective when valuing its real estate investments will be to produce a valuation that represents a reasonable estimate of the fair value of its investments. Implicit in the Account’s definition of fair value are the consummation of a sale as of a specified date and the passing of title from seller to buyer under conditions whereby: • Buyer and seller are typically motivated; • Both parties are well informed or well advised, and acting in what they consider their best interests; • A reasonable time is allowed for exposure in the open market; • Payment is made in terms of cash or in terms of financial arrangements comparable thereto; and • The price represents the normal consideration for the property sold unaffected by special or creative financing or sales concessions granted by anyone associated with the sale. Property and investment values are affected by, among other things, the availability of capital, occupancy rates, rental rates, and interest and inflation rates. As a result, determining real estate and investment values involves many assumptions. Key inputs and assumptions include rental income and expense amounts, related rental income and expense growth rates, capital expenditures, discount rates and capitalization rates. Valuation techniques include discounted cash flow analysis, prevailing market capitalization rates or multiples applied to earnings from the property, analysis of recent comparable sales transactions, actual sale negotiations and bona fide purchase offers received from third parties. Amounts ultimately realized from each investment may vary significantly from the fair value presented. Real estate properties owned by the Account are initially valued based on an independent third party appraisal, as reviewed by TIAA’s internal appraisal staff and as applicable by the Account’s independent fiduciary at the time of the closing of the purchase. Such initial valuation may result in a potential unrealized gain or loss reflecting the difference between an investment’s fair value (i.e., exit price) and its cost basis (which is inclusive of transaction costs). Subsequently, each property is appraised each quarter by an independent third party appraiser, reviewed by TIAA’s internal appraisal staff and as applicable the Account’s independent fiduciary. In general, the Account obtains appraisals of its real estate properties spread out throughout the quarter, which is intended to result in appraisal adjustments, and thus, adjustments to the valuations of its holdings (to the extent such adjustments are made) that happen regularly throughout each quarter and not on one specific day or month in each period. Further, management reserves the right to order an appraisal and/or conduct another valuation outside of the normal quarterly process when facts or circumstances at a specific property change. For example, under certain circumstances a valuation adjustment could be made when the account receives a bona fide bid for the sale of a property held within the Account or one of the Account’s joint ventures. Adjustments may be made for events or circumstances indicating an impairment of a tenant’s ability to pay amounts due to the Account under a lease (including due to a bankruptcy filing of that tenant). Alternatively, adjustments may be made to reflect the execution or renewal of a significant lease. Also, adjustments may be made to reflect factors (such as sales values for comparable properties or local employment rate) bearing uniquely on a particular region in which the Account holds properties. TIAA’s internal appraisal staff oversees the entire appraisal process, in conjunction with the Account’s independent fiduciary (the independent fiduciary is more fully described in the following paragraph). Any differences in the conclusions of TIAA’s internal appraisal staff and the independent appraiser will be reviewed by the independent fiduciary, which will make a final determination on the matter (which may include ordering a subsequent independent appraisal). The independent fiduciary, RERC, LLC, has been appointed by a special subcommittee of the Investment Committee of the Board to, among other things, oversee the appraisal process. The independent fiduciary must approve all independent appraisers used by the Account. All appraisals are performed in accordance with Uniform Standards of Professional Appraisal Practices, the real estate appraisal industry standards created by The Appraisal Foundation. Real estate appraisals are estimates of property values based on a professional’s opinion. Appraisals of properties held outside of the U.S. are performed in accordance with industry standards commonly applied in the applicable jurisdiction. These independent appraisers are always expected to be MAI-designated members of the Appraisal Institute (or its European equivalent, Royal Institute of Chartered Surveyors) and state certified appraisers from national or regional firms with relevant property type experience and market knowledge. Under the Account’s current procedures, each independent appraisal firm will be rotated off of a particular property at least every three years, although such appraisal firm may perform appraisals of other Account properties subsequent to such rotation. Also, the independent fiduciary can require additional appraisals if factors or events have occurred that could materially change a property’s value (including those identified above) and such change is not reflected in the quarterly valuation review, or otherwise to ensure that the Account is valued appropriately. The independent fiduciary must also approve any valuation change of real estate-related assets where a property’s value changed by more than 6% from the most recent independent annual appraisal, or if the value of the Account would change by more than 4% within any calendar quarter or more than 2% since the prior calendar month. When a real estate property is subject to a mortgage, the property is valued independently of the mortgage and the property and mortgage fair values are reported separately (see Valuation of Loans Payable ). The independent fiduciary reviews and approves all mortgage valuation adjustments before such adjustments are recorded by the Account. The Account continues to use the revised value for each real estate property and mortgage loan payable to calculate the Account’s daily net asset value until the next valuation review or appraisal. Valuation of Real Estate Joint Ventures —Real estate joint ventures are stated at the fair value of the Account’s ownership interests of the underlying entities. The Account’s ownership interests are valued based on the fair value of the underlying real estate, any related mortgage loans payable, and other factors, such as ownership percentage, ownership rights, buy/sell agreements, distribution provisions and capital call obligations. Upon the disposition of all real estate investments by an investee entity, the Account will continue to state its equity in the remaining net assets of the investee entity during the wind down period, if any, which occurs prior to the dissolution of the investee entity. Valuation of Real Estate Limited Partnerships —Limited partnership interests are stated at the fair value of the Account’s ownership in the partnership. Management uses net asset value information provided by limited partners as a practical expedient to estimate fair value. The Account receives estimates from limited partners on a quarterly basis, and audited information is provided annually. Upon receipt of the information, management reviews and concludes on whether the net asset values provided are an appropriate representation of the fair value of the Account's interests in the limited partnerships and makes valuation adjustments as necessary. Valuation of limited partnerships proceeds under the direction of the Investment Committee of the Board and in accordance with the responsibilities of the Board as a whole. Valuation of Marketable Securities —Equity securities listed or traded on any national market or exchange are valued at the last sale price as of the close of the principal securities market or exchange on which such securities are traded or, if there is no sale, at the mean of the last bid and asked prices on such market or exchange, exclusive of transaction costs. Valuation of Debt Securities —Debt securities with readily available market quotations, other than money market instruments, are generally valued at the most recent bid price or the equivalent quoted yield for such securities (or those of comparable maturity, quality and type). Debt securities for which market quotations are not readily available, are valued at fair value as determined by management and the Investment Committee of the Board and in accordance with the responsibilities of the Board as a whole. Short-term investments are valued in the same manner as debt securities, as described above. Money market instruments are valued at amortized cost, which approximates fair value. Valuation of Loans Receivable (i.e. the Account as a creditor) —Loans receivable are stated at fair value and are initially valued at the face amount of the loan funding. Subsequently, loans receivable are valued at least quarterly by TIAA’s internal valuation department based on market factors, such as market interest rates and spreads for comparable loans, the liquidity for loans of similar characteristics, the performance of the underlying collateral (such as the loan-to-value ratio and the cash flow of the underlying collateral) and the credit quality of the counterparty. The independent fiduciary reviews and approves all loan receivable valuation adjustments before such adjustments are recorded by the Account. The Account continues to use the revised value for each loan receivable to calculate the Account’s daily net asset value until the next valuation review. Valuation of Loans Payable (i.e. the Account as a debtor) —Mortgage or other loans payable are stated at fair value. The estimated fair value of mortgage loans payable is generally based on the amount at which the liability could be transferred in a current transaction, exclusive of transaction costs. Fair values are estimated based on market factors, such as market interest rates and spreads on comparable loans, the liquidity for mortgage loans of similar characteristics, the performance of the underlying collateral (such as the loan-to-value ratio and the cash flow of the underlying collateral), the maturity date of the loan, the return demands of the market, and the credit quality of the Account. Different assumptions or changes in future market conditions could significantly affect estimated fair values. At times, the Account may assume debt in connection with the purchase of real estate (including under the Account's Line of Credit or additional credit facilities). See Note 5 — Assets and Liabilities Measured at Fair Value on a Recurring Basis for further discussion and disclosure regarding the determination of the fair value of the Account’s investments. Accumulation and Annuity Funds: The accumulation fund represents the net assets attributable to participants in the accumulation phase of their investment (“Accumulation Fund”). The annuity fund represents the net assets attributable to the participants currently receiving annuity payments (“Annuity Fund”). The net increase or decrease in net assets from investment operations is apportioned between the accounts based upon their relative daily net asset values. Once an Account participant begins receiving lifetime annuity income benefits, payment levels cannot be reduced as a result of the Account’s actual mortality experience. In addition, the contracts pursuant to which the Account is offered are required to stipulate the maximum expense charge for all Account level expenses that can be assessed, which is not to exceed 2.5% of average net assets per year. The Account pays a fee to TIAA to assume mortality and expense risks. Accounting for Investments: The investments held by the Account are accounted for as follows: Real Estate Properties —Rent from real estate properties consists of all amounts earned under tenant operating leases, including base rent, recoveries of real estate taxes and other expenses and charges for miscellaneous services provided to tenants. Rental income is recognized in accordance with the billing terms of the lease agreements. The Account bears the direct expenses of the real estate properties owned. These expenses include, but are not limited to, fees to local property management companies, property taxes, utilities, maintenance, repairs, insurance, and other operating and administrative costs. An estimate of the net operating income earned from each real estate property is accrued by the Account on a daily basis and such estimates are adjusted when actual operating results are determined. Real Estate Joint Ventures —The Account has limited ownership interests in various real estate joint ventures (collectively, the “joint ventures”). The Account records its contributions as increases to its investments in the joint ventures, and distributions from the joint ventures are treated as income within income from real estate joint ventures and limited partnerships in the Account’s Consolidated Statements of Operations. Distributions that are identified as returns of capital are recorded as a reduction to the cost basis of the investment, whereas distributions identified as capital gains or losses are recorded as realized gains or losses. Income distributions from the joint ventures are recorded based on the Account’s proportional interest of the income distributed by the joint ventures. Income earned but not yet distributed to the Account by the joint ventures is recorded as unrealized gains and losses. Limited Partnerships —The Account has limited ownership interests in various private real estate funds (primarily limited partnerships) and a private real estate investment trust (collectively, the “limited partnerships”). The Account records its contributions as increases to the investments, and distributions from the investments are treated as income within income from real estate joint ventures and limited partnerships in the Account’s Consolidated Statements of Operations. Distributions that are identified as returns of capital are recorded as a reduction to the cost basis of the investment, whereas distributions identified as capital gains or losses are recorded as realized gains or losses. Unrealized gains and losses are recorded based upon the changes in the net asset values of the limited partnerships as determined from the financial statements of the limited partnerships when received by the Account. Prior to the receipt of the financial statements from the limited partnerships, the Account estimates the value of its interest using information provided by the limited partners. Changes in value based on such estimates are recorded by the Account as unrealized gains and losses. Marketable Securities —Transactions in marketable securities are accounted for as of the date the securities are purchased or sold (trade date). Interest income is recorded as earned. Dividend income is recorded on the ex-dividend date within dividend income. Dividends that are identified as returns of capital are recorded as a reduction to the cost basis of the investment, whereas dividends identified as capital gains or losses are recorded as realized gains or losses. Realized gains and losses on securities transactions are accounted for on the specific identification method. Loans Receivable —The Account may originate, purchase or sell loans collateralized by real estate. The cost basis of originated loans is comprised of the principal balance and direct costs incurred that represent a component of loan’s reported fair value. The cost basis of purchased loans consists of the purchase price of the loan and additional direct costs incurred that represent a component of the loan’s reported fair value. Additional costs incurred by the Account to originate or purchase loans that do not represent a component of a loan’s fair value are recorded as expenses in the period incurred. Nonrefundable origination fees paid by borrowers are recognized as interest income once all activities required to execute the loan are completed. Prepayment fees received from the payoff of loans in advance of their maturity date are recognized as interest income on the date the payoff occurs. Interest income from loans in accrual status is recognized based on the current coupon rate of the loans. Interest income accruals are suspended when a loan becomes a non-performing loan, defined as a loan more than ninety days in arrears or at any point when management believes the full collection of principal is doubtful. Interest income on non-performing loans is recognized only as cash payments are received. Loans can be rehabilitated to normal accrual status once all past due interest has been collected and management believes the full collection of principal is likely. Realized and Unrealized Gains and Losses —Realized gains and losses are recorded at the time an investment is sold or a distribution is received in relation to an investment sale from a joint venture or limited partnership. Real estate and loan receivable transactions are accounted for as of the date on which the purchase or sale transactions close (settlement date). The Account recognizes a realized gain on the sale of an investment to the extent that the contract sales price exceeds the cost-to-date of the investment being sold. A realized loss occurs when the cost-to-date exceeds the sales price. Realized gains and losses from partial sales of non-financial assets are recognized in accordance with ASC 610-20 - Gains and Losses from the Derecognition of Nonfinancial Assets . Realized gains and losses from the sale of financial assets are recognized in accordance with ASC 860 - Transfers and Servicing . Unrealized gains and losses are recorded as the fair values of the Account’s investments are adjusted, and as discussed within the Real Estate Joint Ventures, Limited Partnerships and Loans Receivable sections above. Net Assets —The Account’s net assets as of the close of each valuation day are valued by taking the sum of: • the value of the Account’s cash; cash equivalents, and short-term and other debt instruments; • the value of the Account’s other securities and other non-real estate assets; • the value of the individual real properties (based on the most recent valuation of that property) and other real estate-related investments owned by the Account; • an estimate of the net operating income accrued by the Account from its properties, other real estate-related investments and non-real estate-related investments (including short-term marketable securities) since the end of the prior valuation day; and • actual net operating income earned from the Account’s properties, other real estate-related investments and non-real estate-related investments (but only to the extent any such item of income differs from the estimated income accrued for on such investments), and then reducing the sum by liabilities held within the Account, including the daily investment management fee, administration and distribution fees, mortality and expense fee, liquidity guarantee fee, and certain other expenses attributable to operating the Account. Daily estimates of net operating income are adjusted to reflect actual net operating income on a monthly basis, at which time such adjustments (if any) are reflected in the Account’s unit value. After the end of every quarter, the Account reconciles the amount of expenses deducted from the Account (which is established in order to approximate the costs that the Account will incur) with the expenses the Account actually incurred. If there is a difference, the Account adds it to or deducts it from the Account in equal daily installments over the remaining days of the following quarter. Material differences may be repaid in the current calendar quarter. The Account’s at-cost deductions are based on projections of Account assets and overall expenses, and the size of any adjusting payments will be directly affected by the difference between management’s projections and the Account’s actual assets or expenses. Cash and Cash Equivalents: Cash and cash equivalents are balances held by the Account in bank deposit accounts which, at times, exceed federally insured limits. The Account’s management monitors these balances to mitigate the exposure of risk due to concentration and has not experienced any losses from such concentration. Other Assets and Other Liabilities: Other assets and other liabilities consist of operating assets and liabilities utilized and held at each individual real estate property investment. Other assets consist of, amongst other items, cash, tenant receivables and prepaid expenses; whereas other liabilities primarily consist of security deposits. Other assets also include cash collateral held for securities on loan. Federal Income Taxes: Based on provisions of the Internal Revenue Code, Section 817, the Account is taxed as a segregated asset account of TIAA and as such, the Account incurs no material federal income tax attributable to the net investment activity of the Account. The Account’s federal income tax return is generally subject to examination for a period of three years after filed. State and local tax returns may be subject to examination for an additional period of time depending on the jurisdiction. Management has analyzed the Account’s tax positions taken for all open federal income tax years and has concluded that no provision for federal income tax is required in the Account’s Consolidated Financial Statements. Restricted Cash: The Account held restricted cash in escrow accounts for security deposits, as required by certain states, as well as property taxes, insurance, and various other property related matters as required by certain creditors related to outstanding mortgage loans payable collateralized by certain real estate investments. These amounts are recorded within other assets on the Consolidated Statements of Assets and Liabilities. See Note 9—Mortgage Loans Payable for additional information regarding the Account’s outstanding mortgage loans payable. Changes in Net Assets: Premiums include premiums paid by existing accumulation unit holders in the Account and transfers into the Account. Withdrawals and death benefits include withdrawals out of the Account which include transfers out of the Account and required minimum distributions. Due to/from Investment Manager: Due to/from investment manager represents amounts that are to be paid or received by TIAA on behalf of the Account. Amounts generally are paid or received by the Account within one or two business days and no interest is contractually charged on these amounts. Securities Lending: The Account may lend securities to qualified borrowers to earn additional income. The Account receives cash collateral against the loaned securities and maintains cash collateral in an amount not less than 100% of the market value of loaned securities during the period of the loan; any additional collateral required due to changes in security values is delivered to the Account the next business day. Cash collateral received by the Account is invested exclusively in an interest-bearing deposit account. The value of the loaned securities and the liability to return the cash collateral received are reflected in the Consolidated Statements of Assets and Liabilities. When loaning securities, the Account retains the benefits of owning the securities, including the economic equivalent of dividends or interest generated by the securities. All income generated by the securities lending program is reflected within interest income on the Consolidated Statements of Operations. As of December 31, 2018 and 2017, securities lending transactions are for real-estate related equity securities, and the resulting loans are continuous, can be recalled at any time, and have no set maturity. Securities lending income recognized by the Account consists of interest earned on cash collateral and lending fees, net of any rebates to the borrower and compensation to the agent. Such income is reflected within interest income on the Consolidated Statements of Operations. In lending its securities, the Account bears the market risk with respect to the investment of collateral and the risk that the agent may default on its contractual obligations to the Account. The agent bears the risk that the borrower may default on its obligation to return the loaned securities as the agent is contractually obligated to indemnify the Account if at the time of a default by a borrower some or all of the loan securities have not been returned. New Accounting Pronouncements In May 2014, the FASB issued Accounting Standard Update 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”). ASU 2014-09 supersedes all existing revenue recognition guidance and establishes a five-step model to measure and recognize revenue. ASU 2014-09 was effective for fiscal years beginning after December 15, 2017 and the Account adopted this guidance as of January 1, 2018 utilizing the modified retrospective adoption approach. Under this approach, ASU 2014-09 was applied to all contracts that were not completed as of the date of adoption. Based on the Accounts implementation procedures, the adoption of ASU 2014-09 had an immaterial impact to the Account. In February 2016, the FASB issued Accounting Standards Update 2016-02 Leases (Topic 842) (“ASU 2016-02”) which will supersede Topic 840, Leases. This ASU applies to all entities that enter into a lease. Lessees will be required to report assets and liabilities that arise from leases. Lessor accounting is expected to remain unchanged; however, certain refinements were made to conform with the recently issued revenue recognition guidance in ASU 2014-09, specifically related to the allocation and recognition of contract consideration earned from lease and non-lease revenue components. The ASU contains certain practical expedients, which the Account plans to elect. The Account is electing the transition package of practical expedients permitted within the new standard. This practical expedient permits the Account to carryforward the historical lease classification and not to reassess initial direct costs for any existing leases. Further, the Account will initially apply the new lease requirements at the effective date of January 1, 2019, and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. In addition, the Account plans to elect the practical expedient that allows lessors to avoid separating lease and non-lease components within a contract if certain criteria are met. The lessor’s practical expedient election would be limited to circumstances in which (i) the timing and pattern of revenue recognition are the same for the non-lease component and the related lease component and (ii) the combined single lease component would be classified as an operating lease. This practical expedient would allow the Account the ability to combine the lease and non-lease components if the underlying asset meets the two criteria above. This ASU is effective for public business entities for fiscal years beginning after December 15, 2018, including all interim periods within those fiscal years. Management has completed its initial scoping for the adoption of the ASU 2016-02 and does not expect the adoption of such guidance to materially impact the Account. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement: Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurements. ASU 2018-13 modifies the disclosures required for fair value measurements. This guidance is effective for fiscal years beginning after December 15, 2019. Management is currently evaluating the impact of this guidance but does not expect it to materially impact the Account's Notes to the Consolidated Financial Statements.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Investment management, administrative and distribution services are provided to the Account at cost by TIAA. Services provided at cost are paid by the Account on a daily basis based upon projected expenses to be provided to the Account. Payments are adjusted periodically to ensure daily payments are as close as possible to the Account’s actual expenses incurred. Differences between actual expenses and the amounts paid by the Account are reconciled and adjusted quarterly. Investment management services for the Account are provided by TIAA officers, under the direction and control of the Board, pursuant to investment management procedures adopted by TIAA for the Account. TIAA’s investment management decisions for the Account are subject to review by the Account’s independent fiduciary. TIAA also provides various portfolio accounting and related services for the Account. The Account is a party to the Distribution Agreement for the Contracts Funded by the TIAA Real Estate Account (the “Distribution Agreement”), dated January 1, 2008, by and among TIAA, for itself and on behalf of the Account, and TIAA-CREF Individual and Institutional Services, LLC (“Services”), a wholly-owned subsidiary of TIAA, a registered broker-dealer and a member of the Financial Industry Regulatory Authority. Pursuant to the Distribution Agreement, Services performs distribution services for the Account which include, among other things, (i) distribution of annuity contracts issued by TIAA and funded by the Account, (ii) advising existing annuity contract owners in connection with their accumulations and (iii) helping employers implement and manage retirement plans. In addition, TIAA performs administrative functions for the Account, which include, among other things, (i) maintaining accounting records and performing accounting services, (ii) receiving and allocating premiums, (iii) calculating and making annuity payments, (iv) processing withdrawal requests, (v) providing regulatory compliance and reporting services, (vi) maintaining the Account’s records of contract ownership and (vii) otherwise assisting generally in all aspects of the Account’s operations. Both distribution services (pursuant to the Distribution Agreement) and administrative services are provided to the Account by Services and TIAA, as applicable, on an at cost basis.The Distribution Agreement is terminable by either party upon 60 days written notice and terminates automatically upon any assignment thereof. In addition to providing the services described above, TIAA charges the Account fees to bear certain mortality and expense risks, and risks with providing the liquidity guarantee. These fees are charged as a percentage of the net assets of the Account. Rates for these fees are established annually. Once an Account participant begins receiving lifetime annuity income benefits, payment levels cannot be reduced as a result of the Account’s actual mortality experience. As such, mortality and expense risk expenses are contractual charges for TIAA’s assumption of this risk. The liquidity guarantee ensures that sufficient funds are available to meet participant transfer and cash withdrawal requests in the event that the Account’s cash flows and liquid investments are insufficient to fund such requests. Expenses for the services and fees described above are identified as such in the accompanying Consolidated Statements of Operations and are further identified as "Expenses" in Note 11—Financial Highlights. The independent fiduciary, which has the right to adjust the trigger point, has established the trigger point at 45% of the outstanding accumulation units and it will continue to monitor TIAA’s ownership interest in the Account and provide further recommendations as necessary.

Concentration Risk

Concentration Risk	12 Months Ended
	Dec. 31, 2018
Risks and Uncertainties [Abstract]
Concentration Risk	Concentration Risk Concentration risk may arise when a number of properties are located in a similar geographic region such that the economic conditions of that region could impact tenants’ obligations to meet their contractual obligations or cause the values of individual properties to decline. Additionally, concentrations of risk may arise if any one tenant comprises a significant amount of the Account's rent, or if tenants are concentrated in a particular industry. As of December 31, 2018 , the Account had no significant concentrations of tenants as no single tenant had annual contract rent that made up more than 3% of the rental income of the Account. Moreover, the Account's tenants have no notable concentration present in any one industry. There are no significant lease expirations scheduled to occur over the next twelve months. The Account’s wholly-owned real estate investments and investments in joint ventures are located in the United States. The following table represents the diversification of the Account’s portfolio by region and property type as of December 31, 2018 : Diversification by Fair Value (1) West East South Midwest Total Office 13.9 % 19.0 % 5.3 % — % 38.2 % Apartment 9.6 % 7.5 % 6.6 % 1.0 % 24.7 % Retail 7.7 % 3.1 % 7.9 % 0.8 % 19.5 % Industrial 8.3 % 1.3 % 4.2 % 0.5 % 14.3 % Other (2) 0.6 % 2.5 % 0.1 % 0.1 % 3.3 % Total 40.1 % 33.4 % 24.1 % 2.4 % 100.0 % (1) Wholly-owned properties are represented at fair value and gross of any debt, while joint venture properties are represented at the net equity value. (2) Represents interests in Storage Portfolio investments, a fee interest encumbered by a ground lease real estate investment and land. Properties in the “West” region are located in: AK, AZ, CA, CO, HI, ID, MT, NM, NV, OR, UT, WA, WY Properties in the “East” region are located in: CT, DC, DE, KY, MA, MD, ME, NC, NH, NJ, NY, PA, RI, SC, VA, VT, WV Properties in the “South” region are located in: AL, AR, FL, GA, LA, MS, OK, TN, TX Properties in the “Midwest” region are located in: IA, IL, IN, KS, MI, MN, MO, ND, NE, OH, SD, WI

Leases

Leases	12 Months Ended
	Dec. 31, 2018
Leases, Operating [Abstract]
Leases	Leases The Account’s wholly-owned real estate properties are leased to tenants under operating lease agreements which expire on various dates through 2090. Aggregate minimum annual rentals for wholly-owned real estate investments owned by the Account through the non-cancelable lease term, excluding short-term residential leases, are as follows (millions): Years Ending December 31, 2019 $ 535.2 2020 497.7 2021 431.5 2022 366.9 2023 307.8 Thereafter 2,701.8 Total $ 4,840.9 Certain leases provide for additional rental amounts based upon the recovery of actual operating expenses in excess of specified base amounts, sales volume or contractual increases as defined in the lease agreement. These contractual contingent rentals are not included in the table above.

Assets and Liabilities Measured

Assets and Liabilities Measured at Fair Value on a Recurring Basis	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Assets and Liabilities Measured at Fair Value on a Recurring Basis	Assets and Liabilities Measured at Fair Value on a Recurring Basis Valuation Hierarchy: The Account’s fair value measurements are grouped categorically into three levels, as defined by the FASB. The levels are defined as follows: • Level 1 fair value inputs are quoted prices for identical items in active, liquid and visible markets such as stock exchanges. • Level 2 fair value inputs are observable information for similar items in active or inactive markets, and appropriately consider counterparty creditworthiness in the valuations. • Level 3 fair value inputs reflect our best estimate of inputs and assumptions market participants would use in pricing an asset or liability at the measurement date. The inputs are unobservable in the market and significant to the valuation estimate. An investment’s categorization within the valuation hierarchy described above is based upon the lowest level of input that is significant to the fair value measurement. Limited partnership investments are excluded from the valuation hierarchy, as these investments are fair valued using their net asset value as a practical expedient since market quotations or values from independent pricing services are not readily available. See Note 1 - Organization and Significant Accounting Policies for further discussion regarding the use of a practical expedient for the valuation of limited partnerships. The Account’s determination of fair value is based upon quoted market prices, where available. If listed prices or quotes are not available, fair value is based upon vendor-provided, evaluated prices or internally developed models that primarily use market-based or independently sourced market data, including interest rate yield curves, market spreads, and currency rates. Valuation adjustments will be made to reflect changes in credit quality, counterparty’s creditworthiness, the Account’s creditworthiness, liquidity, and other observable and unobservable inputs that are applied consistently over time. The methods described above are considered to produce fair values that represent an estimate by management of what an unaffiliated buyer in the marketplace would pay to purchase the asset or would receive to transfer the liability. Since fair value calculations involve significant professional judgment in the application of both observable and unobservable attributes, actual realizable values or future fair values may differ from amounts reported. Furthermore, while the Account believes its valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments, while reasonable, could result in different estimates of fair value at the reporting date. As discussed in Note 1 — Organization and Significant Accounting Policies in more detail, the Account generally obtains independent third party appraisals on a quarterly basis; there may be circumstances in the interim in which the true realizable value of a property is not reflected in the Account’s daily net asset value calculation or in the Account’s periodic Consolidated Financial Statements. This disparity may be more apparent when the commercial and/or residential real estate markets experience an overall and possibly dramatic decline (or increase) in property values in a relatively short period of time between appraisals. The following tables show the major categories of assets and liabilities measured at fair value on a recurring basis as of December 31, 2018 and 2017 , using unadjusted quoted prices in active markets for identical assets (Level 1); significant other observable inputs (Level 2); significant unobservable inputs (Level 3); and Practical Expedient (millions): Description Level 1: Quoted Prices in Active Markets for Identical Assets Level 2: Significant Other Observable Inputs Level 3: Significant Unobservable Inputs Fair Value Using Practical Expedient Total at December 31, 2018 Real estate properties $ — $ — $ 15,531.1 $ — $ 15,531.1 Real estate joint ventures — — 6,356.6 — 6,356.6 Limited partnerships — — — 175.9 175.9 Marketable securities: Real estate-related 1,415.1 — — — 1,415.1 Government agency notes — 2,050.7 — — 2,050.7 United States Treasury securities — 2,038.0 — — 2,038.0 Loans receivable — — 913.0 — 913.0 Total Investments at $ 1,415.1 $ 4,088.7 $ 22,800.7 $ 175.9 $ 28,480.4 Mortgage loans payable $ — $ — $ (2,608.0 ) $ — $ (2,608.0 ) Description Level 1: Quoted Prices in Active Markets for Identical Assets Level 2: Significant Other Observable Inputs Level 3: Significant Unobservable Inputs Fair Value Using Practical Expedient Total at December 31, 2017 Real estate properties $ — $ — $ 15,742.7 $ — $ 15,742.7 Real estate joint ventures — — 5,860.6 — 5,860.6 Limited partnerships — — — 142.4 142.4 Marketable securities: Real estate-related 1,238.0 — — — 1,238.0 Government agency notes — 2,872.3 — — 2,872.3 United States Treasury securities — 1,015.2 — — 1,015.2 Loans receivable — — 298.8 — 298.8 Total Investments at $ 1,238.0 $ 3,887.5 $ 21,902.1 $ 142.4 $ 27,170.0 Mortgage loans payable $ — $ — $ (2,238.3 ) $ — $ (2,238.3 ) The following tables show the reconciliation of the beginning and ending balances for assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) during the years ended December 31, 2018 and 2017 (millions): Real Estate Properties Real Estate Joint Ventures Loans Receivable Total Level 3 Investments Mortgage Loans Payable For the year ended December 31, 2018 Beginning balance January 1, 2018 $ 15,742.7 $ 5,860.6 $ 298.8 $ 21,902.1 $ (2,238.3 ) Total realized and unrealized gains included in changes in net assets 315.8 116.3 0.3 432.4 79.4 Purchases (1) 1,151.8 941.5 939.2 3,032.5 (817.9 ) Sales (1,679.2 ) — (257.3 ) (1,936.5 ) — Settlements (2) — (561.8 ) (68.0 ) (629.8 ) 368.8 Ending balance December 31, 2018 $ 15,531.1 $ 6,356.6 $ 913.0 $ 22,800.7 $ (2,608.0 ) Real Estate Properties Real Estate Joint Ventures Loans Receivable Total Level 3 Investments Mortgage Loans Payable For the year ended December 31, 2017 Beginning balance January 1, 2017 $ 15,452.8 $ 5,622.4 $ 295.7 $ 21,370.9 $ (2,332.1 ) Total realized and unrealized gains included in changes in net assets 177.5 123.5 1.2 302.2 15.9 Purchases (1) 682.9 419.0 1.9 1,103.8 (17.7 ) Sales (570.5 ) — — (570.5 ) — Settlements (2) — (304.3 ) — (304.3 ) 95.6 Ending balance December 31, 2017 $ 15,742.7 $ 5,860.6 $ 298.8 $ 21,902.1 $ (2,238.3 ) (1) Includes purchases, contributions for joint ventures, capital expenditures, lending for loans receivable and assumption of mortgage loans payable. (2) Includes operating income for real estate joint ventures net of distributions, principal payments and payoffs of loans receivable, and principal payments and extinguishment of mortgage loans payable. The following table shows quantitative information about unobservable inputs related to the Level 3 fair value measurements as of December 31, 2018 . Type Asset Class Valuation Technique(s) Unobservable Inputs Range (Weighted Average) Real Estate Properties and Joint Ventures Office Income Approach—Discounted Cash Flow Discount Rate 5.5%–8.6% (6.5%) Terminal Capitalization Rate 4.0%–7.5% (5.4%) Income Approach—Direct Capitalization Overall Capitalization Rate 4.0%–7.0% (4.8%) Industrial Income Approach—Discounted Cash Flow Discount Rate 5.3%–8.9% (6.8%) Terminal Capitalization Rate 4.4%–7.3% (5.5%) Income Approach—Direct Capitalization Overall Capitalization Rate 4.0%–7.0% (4.9%) Residential Income Approach—Discounted Cash Flow Discount Rate 5.5%–7.8% (6.5%) Terminal Capitalization Rate 3.8%–6.8% (5.0%) Income Approach—Direct Capitalization Overall Capitalization Rate 3.3%–6.0% (4.5%) Retail Income Approach—Discounted Cash Flow Discount Rate 5.0%–10.7% (6.4%) Terminal Capitalization Rate 4.3%–9.0% (5.3%) Income Approach—Direct Capitalization Overall Capitalization Rate 3.3%–8.5% (4.7%) Mortgage Loans Payable Office and Industrial Discounted Cash Flow Loan-to-Value Ratio 36.4%–67.8% (47.6%) Equivalency Rate 3.9%–6.2% (4.6%) Net Present Value Loan-to-Value Ratio 36.4%–67.8% (47.6%) Weighted Average Cost of Capital Risk Premium Multiple 1.2–1.4 (1.3) Residential Discounted Cash Flow Loan-to-Value Ratio 31.9%–63.6% (48.1%) Equivalency Rate 3.4%–4.6% (4.1%) Net Present Value Loan-to-Value Ratio 31.9%–63.6% (48.1%) Weighted Average Cost of Capital Risk Premium Multiple 1.1–1.4 (1.2) Retail Discounted Cash Flow Loan-to-Value Ratio 31.9%–55.3% (39.3%) Equivalency Rate 4.3%–5.3% (4.5%) Net Present Value Loan-to-Value Ratio 31.9%–55.3% (39.3%) Weighted Average Cost of Capital Risk Premium Multiple 1.1–1.3 (1.2) Loans Receivable Residential, Industrial, Office, Retail and Storage Discounted Cash Flow Loan-to-Value Ratio 70.8%-79.2% (75.6%) Equivalency Rate 6.0%-8.3% (6.9%) The following table shows quantitative information about unobservable inputs related to the Level 3 fair value measurements as of December 31, 2017. Type Asset Class Valuation Technique(s) Unobservable Inputs Range (Weighted Average) Real Estate Properties and Joint Ventures Office Income Approach—Discounted Cash Flow Discount Rate 5.5%–8.0% (6.5%) Terminal Capitalization Rate 4.5%–7.0% (5.5%) Income Approach—Direct Capitalization Overall Capitalization Rate 3.8%–7.0% (4.8%) Industrial Income Approach—Discounted Cash Flow Discount Rate 5.5%–8.9% (6.8%) Terminal Capitalization Rate 4.5%–8.3% (5.5%) Income Approach—Direct Capitalization Overall Capitalization Rate 4.0%–7.5% (5.0%) Residential Income Approach—Discounted Cash Flow Discount Rate 5.0%–8.0% (6.1%) Terminal Capitalization Rate 3.5%–6.5% (4.8%) Income Approach—Direct Capitalization Overall Capitalization Rate 3.3%–6.0% (4.3%) Retail Income Approach—Discounted Cash Flow Discount Rate 5.0%–10.5% (6.4%) Terminal Capitalization Rate 4.3%–8.8% (5.2%) Income Approach—Direct Capitalization Overall Capitalization Rate 3.8%–8.8% (4.7%) Mortgage Loans Payable Office and Industrial Discounted Cash Flow Loan-to-Value Ratio 37.7%–69.5% (45.6%) Equivalency Rate 3.7%–5.2% (3.9%) Net Present Value Loan-to-Value Ratio 37.7%–69.5% (45.6%) Weighted Average Cost of Capital Risk Premium Multiple 1.2–1.5 (1.3) Residential Discounted Cash Flow Loan-to-Value Ratio 28.1%–64.2% (38.6%) Equivalency Rate 3.3%–3.6% (3.4%) Net Present Value Loan-to-Value Ratio 28.1%–64.2% (38.6%) Weighted Average Cost of Capital Risk Premium Multiple 1.1–1.5 (1.3) Retail Discounted Cash Flow Loan-to-Value Ratio 17.9%–56.0% (32.7%) Equivalency Rate 3.1%–4.4% (3.8%) Net Present Value Loan-to-Value Ratio 17.9%–56.0% (32.7%) Weighted Average Cost of Capital Risk Premium Multiple 1.1–1.4 (1.2) Loans Receivable Office, Retail and Storage Discounted Cash Flow Loan-to-Value Ratio 59.4%-77.3% (75.1%) Equivalency Rate 4.2%-8.3% (6.2%) Real Estate Properties and Joint Ventures: The significant unobservable inputs used in the fair value measurement of the Account’s real estate property and joint venture investments are the selection of certain investment rates (Discount Rate, Terminal Capitalization Rate, and Overall Capitalization Rate). Significant increases (decreases) in any of those inputs in isolation would result in significantly lower (higher) fair value measurements, respectively. Mortgage Loans Payable: The significant unobservable inputs used in the fair value measurement of the Account’s mortgage loans payable are the loan-to-value ratios and the selection of certain credit spreads and weighted average cost of capital risk premiums. Significant increases (decreases) in any of those inputs in isolation would result in a significantly lower (higher) fair value, respectively. Loans Receivable: The significant unobservable inputs used in the fair value measurement of the Account’s loans receivable are the loan-to-value ratios and the selection of certain credit spreads. Significant increases (decreases) in any of those inputs in isolation would result in a significantly lower (higher) fair value, respectively. During the years ended December 31, 2018 and 2017 there were no transfers between Levels 1, 2 or 3. The amount of total net unrealized gains included in changes in net assets attributable to the change in net unrealized gains relating to Level 3 investments and mortgage loans payable using significant unobservable inputs still held as of the reporting date is as follows (millions): Real Estate Properties Real Estate Joint Ventures Loans Receivable Total Level 3 Investments Mortgage Loans Payable For the year ended December 31, 2018 $ 282.6 $ 80.8 $ 0.3 $ 363.7 $ 86.2 For the year ended December 31, 2017 $ 185.1 $ 125.2 $ 1.2 $ 311.5 $ 15.9

Investments in Joint Ventures

Investments in Joint Ventures	12 Months Ended
	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Investments in Joint Ventures	Investments in Joint Ventures The Account owns interests in several real estate properties through joint ventures and receives distributions and allocations of profits and losses from the joint ventures based on the Account’s ownership interest in those investments. Several of these joint ventures have mortgage loans payable collateralized by the properties owned by the aforementioned joint ventures. At December 31, 2018 , the Account held investments in joint ventures with ownership interest percentages that ranged from 33.3% to 97.0% . Certain joint ventures are subject to adjusted distribution percentages when earnings in the investment reach a pre-determined threshold. A condensed summary of the financial position and results of operations of the combined joint ventures is shown below (millions): December 31, 2018 2017 Assets Real estate properties, at fair value $ 16,134.1 $ 14,240.8 Other assets 460.3 337.1 Total assets $ 16,594.4 $ 14,577.9 Liabilities & Equity Mortgage notes payable and other obligations, at fair value $ 5,035.3 $ 3,995.7 Other liabilities 262.5 150.7 Total liabilities 5,297.8 4,146.4 Total equity 11,296.6 10,431.5 Total liabilities and equity $ 16,594.4 $ 14,577.9 Years ended December 31, 2018 2017 2016 Operating Revenue and Expenses Revenues $ 950.6 $ 869.2 $ 714.6 Expenses 487.1 426.9 365.0 Excess of revenues over expenses $ 463.5 $ 442.3 $ 349.6

Investments in Limited Partners

Investments in Limited Partnerships	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Investments in Limited Partnerships	Investments in Limited Partnerships The Account invests in limited partnerships and limited liability companies that own real estate properties. The Account receives distributions from these investments based on the Account’s ownership interest percentage. At December 31, 2018 , the Account held ownership interest percentages that ranged from 1.7% to 90.0% . As of December 31, 2018 and 2017 , the fair value of the Account’s ownership interest in limited partnerships was $175.9 million and $142.4 million , respectively. Clarion Gables Multi-Family Trust LP allows redemptions with an advanced notice of three months or more. Redemptions are funded using the partnership’s available cash, which may not immediately be in excess of the redemption amount, and may not be sufficient to fund the redemption amount for several months. The general partner has sole discretion in identifying how much cash is available to process redemptions. The partnership allows the Account to sell its interest in the partnership, subject to the consent and approval of the general partner. Taconic New York City GP Fund, LP prohibits redemptions in the partnership prior to liquidation. Liquidation of the partnership is estimated to begin no earlier than 2024. The partnership allows the Account to sell its interest in the partnership, subject to the consent and approval of the general partner. LCS SHIP Venture I, LLC prohibits redemptions prior to liquidation. The Account is generally not permitted to sell or transfer its interest in the company without consent of the manager.

Loans Receivable

Loans Receivable	12 Months Ended
	Dec. 31, 2018
Receivables [Abstract]
Loans Receivable	Loans Receivable The Account’s loan receivable portfolio is comprised of mezzanine loans secured by the borrower’s direct and indirect interest in commercial real estate. Mezzanine loans are subordinate to first mortgages on the underlying real estate collateral. The following property types represent the underlying real estate collateral for the Account's mezzanine loans: December 31, 2018 2017 Fair Value % Fair Value % Office $ 512.1 56.2 % $ 227.0 76.0 % Industrial 176.4 19.3 % — — % Retail 101.6 11.1 % 34.2 11.4 % Storage 63.2 6.9 % 37.6 12.6 % Apartments 59.7 6.5 % — — % $ 913.0 100.0 % $ 298.8 100.0 % The Account monitors the risk profile of the loan receivable portfolio with the assistance of a third-party rating service that models the loans and assigns risk ratings based on inputs such as loan-to-value ratios, yields, credit quality of the borrowers, property types of the collateral, geographic and local market dynamics, physical condition of the collateral, and the underlying structure of the loans. Ratings for the loans are updated monthly. Ratings range from AAA to C, with a AAA designation representing debt with the lowest level of credit risk and C representing a high likelihood of default or principal loss. Mezzanine debt in good health is typically reflective of a risk rating in the B range (e.g., BBB, BB, B), as these ratings reflect borrowers having adequate financial resources to service their financial commitments, but also acknowledging that adverse economic conditions, should they occur, would likely impede on a borrowers' ability to pay. The following table presents the fair values of the Account's loan portfolio based on the risk ratings as of December 31, 2018, listed in order of the strength of the risk rating (from strongest to weakest): Number of Loans Fair Value % BBB 3 $ 175.0 19.2 % BB 5 561.5 61.5 % B 5 170.2 18.6 % NR 1 1 6.3 0.7 % 14 $ 913.0 100.0 % (1) " NR" designates loans not assigned an internal credit rating. As of December 31, 2018, this is representative of one loan collateralized by an interest in a joint venture invested in real estate. The loan is scheduled to mature on July 12, 2019. Management expects all principal and interest owed to the Account for this loan to be collected in full. The Account has zero loans in non-performing status as of December, 31, 2018.

Mortgage Loans Payable

Mortgage Loans Payable	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Mortgage Loans Payable	Mortgage Loans Payable At December 31, 2018 and 2017, the Account had outstanding mortgage loans payable secured by the following properties (millions): Property Interest Rate and Payment Frequency (2) Principal Amounts Outstanding as of December 31, Maturity 2018 2017 Mass Court (1) 2.88% paid monthly $ 90.2 $ 92.1 September 1, 2019 Red Canyon at Palomino Park (4) 5.34% paid monthly 27.1 27.1 August 1, 2020 Green River at Palomino Park (4) 5.34% paid monthly 33.2 33.2 August 1, 2020 Blue Ridge at Palomino Park (4) 5.34% paid monthly 33.4 33.4 August 1, 2020 Ashford Meadows Apartments 5.17% paid monthly 44.6 44.6 August 1, 2020 The Knoll (1) 3.98% paid monthly 16.9 17.5 December 5, 2020 The Corner 4.66% paid monthly — 105.0 June 1, 2021 Ascent at Windward 3.51% paid monthly 34.6 — January 1, 2022 The Palatine (1) 4.25% paid monthly 77.4 78.8 January 10, 2022 The Forum at Carlsbad (1) 4.25% paid monthly 87.3 88.9 March 1, 2022 Fusion 1560 3.42% paid monthly 37.4 — June 10, 2022 The Colorado (1) 3.69% paid monthly 89.9 91.7 November 1, 2022 The Legacy at Westwood (1) 3.69% paid monthly 45.8 46.7 November 1, 2022 Regents Court (1) 3.69% paid monthly 38.8 39.6 November 1, 2022 Fourth & Madison (1) 3.75% paid monthly 198.2 200.0 June 1, 2023 Fourth & Madison 4.17% paid monthly 90.0 — June 1, 2023 1001 Pennsylvania Avenue (1) 3.70% paid monthly 327.0 330.0 June 1, 2023 Biltmore at Midtown 3.94% paid monthly 36.4 — July 5, 2023 Cherry Knoll 3.78% paid monthly 35.3 — July 5, 2023 Lofts at SoDo 3.94% paid monthly 35.1 — July 5, 2023 1401 H Street, NW 3.65% paid monthly 115.0 115.0 November 5, 2024 Circa Green Lake 3.71% paid monthly 52.0 — March 5, 2025 Union - South Lake Union 3.66% paid monthly 57.0 — March 5, 2025 Holly Street Village 3.65% paid monthly 81.0 — May 1, 2025 Township Apartments 3.65% paid monthly 49.0 — May 1, 2025 32 South State Street 4.48% paid monthly 24.0 24.0 June 6, 2025 780 Third Avenue 3.55% paid monthly 150.0 150.0 August 1, 2025 Property Interest Rate and Payment Frequency (2) Principal Amounts Outstanding as of December 31, Maturity 2018 2017 780 Third Avenue 3.55% paid monthly $ 20.0 $ 20.0 August 1, 2025 701 Brickell Avenue 3.66% paid monthly 184.0 184.0 April 1, 2026 55 Second Street (5) 3.74% paid monthly 137.5 137.5 October 1, 2026 1900 K Street, NW 3.93% paid monthly 163.0 163.0 April 1, 2028 501 Boylston Street (6) 3.70% paid monthly — 216.5 April 1, 2028 99 High Street 3.90% paid monthly 277.0 — March 1, 2030 Total Principal Outstanding $ 2,688.1 $ 2,238.6 Fair Value Adjustment (3) (80.1 ) (0.3 ) Total Mortgage Loans Payable $ 2,608.0 $ 2,238.3 (1) The mortgage is adjusted monthly for principal payments. (2) Interest rates are fixed. Some mortgages held by the Account are structured to begin principal and interest payments after an initial interest only period. (3) The fair value adjustment consists of the difference (positive or negative) between the principal amount of the outstanding debt and the fair value of the outstanding debt. See Note 1—Organization and Significant Accounting Policies. (4) Represents mortgage loans on these individual properties which are held within the Palomino Park portfolio. (5) This mortgage is comprised of three individual loans, all with equal recourse, interest and maturity. The principal balances by loan are $79.0 million , $45.0 million , and $13.5 million . (6) On August 21, 2018, the Account sold a 49.9% interest in the property and transferred the remaining 50.1% to a joint venture investment. The debt was assumed by the buyer and new joint venture, respectively. Principal payment schedule on mortgage loans payable as of December 31, 2018 was as follows (millions): Amount 2019 $ 107.2 2020 171.7 2021 20.0 2022 407.7 2023 686.4 Thereafter 1,295.1 Total maturities $ 2,688.1 Line of Credit On September 20, 2018, the Account entered into a $500.0 million unsecured revolving credit agreement (“Line of Credit”) syndicated across four national banks (“Lenders”), with each Lender providing a $125.0 million commitment. Access to the Line of Credit expires on September 20, 2021, with an option to extend the Line of Credit for two consecutive twelve terms at the Account’s election. The Account may request an additional $250.0 million in commitments from the Lenders at any time; however, this request is subject to approval at the sole discretion of the Lenders and is not a guarantee that an expansion beyond the original $500.0 million commitment will be granted. Draws against the Line of Credit can take the form of Eurodollar Loans or Alternate Base Rate Loans (“ABR Loans”). Eurodollar Loans and ABR Loans both require a minimum funding of $5.0 million . The Account is charged a fee of 0.20% per annum on any unused portion of the Line of Credit. Eurodollar Loans are issued for a term of twelve months or less and bear interest during the period (“Interest Period”) at a rate equal to the Adjusted London Interbank Offer Rate (“Adjusted LIBOR”) plus a spread ranging between 0.85% - 1.05% per annum (the “Applicable Rate”), with the spread dependent upon the leverage ratio of the Account. The Adjusted LIBOR Rate is calculated by multiplying the Statutory Reserve Rate, as determined by the Federal Reserve Board for Eurodollar liabilities, by the LIBOR rate, as determined by the Intercontinental Exchange on the date of issuance that corresponds to the length of the Interest Period of the Eurodollar Loan. The Account may prepay Eurodollar Loans at any time during the life of the loan without penalty. The Account is limited to five active Eurodollar Loans through the Line of Credit; however, the Account may retire and initiate new Eurodollar Loans without restriction so long as the total number of loans in active status never exceeds the limit. ABR Loans are issued for a specific length of time and bear interest at a rate equal to the highest rate among the following calculations plus the Applicable Rate: a) the Prime Rate on the date of issuance, with the Prime Rate being defined as the rate of interest last quoted by the Wall Street Journal as the Prime Rate; b) the Federal Reserve Bank of New York (“NYFRB”) Rate as provided by the NYFRB on the date of issuance plus 0.5% ; or c) the Adjusted LIBOR Rate plus 1.0% . The Account may prepay ABR Loans at any time during the life of the loan without penalty. As of December 31, 2018, the Account had zero active loans outstanding on the Line of Credit. The Account is in compliance with all covenants required by the Line of Credit.

Line of Credit

Line of Credit	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Line of Credit	Mortgage Loans Payable At December 31, 2018 and 2017, the Account had outstanding mortgage loans payable secured by the following properties (millions): Property Interest Rate and Payment Frequency (2) Principal Amounts Outstanding as of December 31, Maturity 2018 2017 Mass Court (1) 2.88% paid monthly $ 90.2 $ 92.1 September 1, 2019 Red Canyon at Palomino Park (4) 5.34% paid monthly 27.1 27.1 August 1, 2020 Green River at Palomino Park (4) 5.34% paid monthly 33.2 33.2 August 1, 2020 Blue Ridge at Palomino Park (4) 5.34% paid monthly 33.4 33.4 August 1, 2020 Ashford Meadows Apartments 5.17% paid monthly 44.6 44.6 August 1, 2020 The Knoll (1) 3.98% paid monthly 16.9 17.5 December 5, 2020 The Corner 4.66% paid monthly — 105.0 June 1, 2021 Ascent at Windward 3.51% paid monthly 34.6 — January 1, 2022 The Palatine (1) 4.25% paid monthly 77.4 78.8 January 10, 2022 The Forum at Carlsbad (1) 4.25% paid monthly 87.3 88.9 March 1, 2022 Fusion 1560 3.42% paid monthly 37.4 — June 10, 2022 The Colorado (1) 3.69% paid monthly 89.9 91.7 November 1, 2022 The Legacy at Westwood (1) 3.69% paid monthly 45.8 46.7 November 1, 2022 Regents Court (1) 3.69% paid monthly 38.8 39.6 November 1, 2022 Fourth & Madison (1) 3.75% paid monthly 198.2 200.0 June 1, 2023 Fourth & Madison 4.17% paid monthly 90.0 — June 1, 2023 1001 Pennsylvania Avenue (1) 3.70% paid monthly 327.0 330.0 June 1, 2023 Biltmore at Midtown 3.94% paid monthly 36.4 — July 5, 2023 Cherry Knoll 3.78% paid monthly 35.3 — July 5, 2023 Lofts at SoDo 3.94% paid monthly 35.1 — July 5, 2023 1401 H Street, NW 3.65% paid monthly 115.0 115.0 November 5, 2024 Circa Green Lake 3.71% paid monthly 52.0 — March 5, 2025 Union - South Lake Union 3.66% paid monthly 57.0 — March 5, 2025 Holly Street Village 3.65% paid monthly 81.0 — May 1, 2025 Township Apartments 3.65% paid monthly 49.0 — May 1, 2025 32 South State Street 4.48% paid monthly 24.0 24.0 June 6, 2025 780 Third Avenue 3.55% paid monthly 150.0 150.0 August 1, 2025 Property Interest Rate and Payment Frequency (2) Principal Amounts Outstanding as of December 31, Maturity 2018 2017 780 Third Avenue 3.55% paid monthly $ 20.0 $ 20.0 August 1, 2025 701 Brickell Avenue 3.66% paid monthly 184.0 184.0 April 1, 2026 55 Second Street (5) 3.74% paid monthly 137.5 137.5 October 1, 2026 1900 K Street, NW 3.93% paid monthly 163.0 163.0 April 1, 2028 501 Boylston Street (6) 3.70% paid monthly — 216.5 April 1, 2028 99 High Street 3.90% paid monthly 277.0 — March 1, 2030 Total Principal Outstanding $ 2,688.1 $ 2,238.6 Fair Value Adjustment (3) (80.1 ) (0.3 ) Total Mortgage Loans Payable $ 2,608.0 $ 2,238.3 (1) The mortgage is adjusted monthly for principal payments. (2) Interest rates are fixed. Some mortgages held by the Account are structured to begin principal and interest payments after an initial interest only period. (3) The fair value adjustment consists of the difference (positive or negative) between the principal amount of the outstanding debt and the fair value of the outstanding debt. See Note 1—Organization and Significant Accounting Policies. (4) Represents mortgage loans on these individual properties which are held within the Palomino Park portfolio. (5) This mortgage is comprised of three individual loans, all with equal recourse, interest and maturity. The principal balances by loan are $79.0 million , $45.0 million , and $13.5 million . (6) On August 21, 2018, the Account sold a 49.9% interest in the property and transferred the remaining 50.1% to a joint venture investment. The debt was assumed by the buyer and new joint venture, respectively. Principal payment schedule on mortgage loans payable as of December 31, 2018 was as follows (millions): Amount 2019 $ 107.2 2020 171.7 2021 20.0 2022 407.7 2023 686.4 Thereafter 1,295.1 Total maturities $ 2,688.1 Line of Credit On September 20, 2018, the Account entered into a $500.0 million unsecured revolving credit agreement (“Line of Credit”) syndicated across four national banks (“Lenders”), with each Lender providing a $125.0 million commitment. Access to the Line of Credit expires on September 20, 2021, with an option to extend the Line of Credit for two consecutive twelve terms at the Account’s election. The Account may request an additional $250.0 million in commitments from the Lenders at any time; however, this request is subject to approval at the sole discretion of the Lenders and is not a guarantee that an expansion beyond the original $500.0 million commitment will be granted. Draws against the Line of Credit can take the form of Eurodollar Loans or Alternate Base Rate Loans (“ABR Loans”). Eurodollar Loans and ABR Loans both require a minimum funding of $5.0 million . The Account is charged a fee of 0.20% per annum on any unused portion of the Line of Credit. Eurodollar Loans are issued for a term of twelve months or less and bear interest during the period (“Interest Period”) at a rate equal to the Adjusted London Interbank Offer Rate (“Adjusted LIBOR”) plus a spread ranging between 0.85% - 1.05% per annum (the “Applicable Rate”), with the spread dependent upon the leverage ratio of the Account. The Adjusted LIBOR Rate is calculated by multiplying the Statutory Reserve Rate, as determined by the Federal Reserve Board for Eurodollar liabilities, by the LIBOR rate, as determined by the Intercontinental Exchange on the date of issuance that corresponds to the length of the Interest Period of the Eurodollar Loan. The Account may prepay Eurodollar Loans at any time during the life of the loan without penalty. The Account is limited to five active Eurodollar Loans through the Line of Credit; however, the Account may retire and initiate new Eurodollar Loans without restriction so long as the total number of loans in active status never exceeds the limit. ABR Loans are issued for a specific length of time and bear interest at a rate equal to the highest rate among the following calculations plus the Applicable Rate: a) the Prime Rate on the date of issuance, with the Prime Rate being defined as the rate of interest last quoted by the Wall Street Journal as the Prime Rate; b) the Federal Reserve Bank of New York (“NYFRB”) Rate as provided by the NYFRB on the date of issuance plus 0.5% ; or c) the Adjusted LIBOR Rate plus 1.0% . The Account may prepay ABR Loans at any time during the life of the loan without penalty. As of December 31, 2018, the Account had zero active loans outstanding on the Line of Credit. The Account is in compliance with all covenants required by the Line of Credit.

Financial Highlights

Financial Highlights	12 Months Ended
	Dec. 31, 2018
Condensed Financial Information Disclosure [Abstract]
Financial Highlights	Financial Highlights Selected condensed financial information for an Accumulation Unit of the Account is presented below. Per Accumulation Unit data is calculated on average units outstanding. Years ended December 31, 2018 2017 2016 2015 2014 Per Accumulation Unit Data: Rental income $ 17.757 $ 17.132 $ 16.433 $ 15.538 $ 15.862 Real estate property level expenses and taxes 8.548 7.722 7.534 7.319 7.788 Real estate income, net 9.209 9.410 8.899 8.219 8.074 Other income 6.162 4.762 3.594 3.342 3.459 Total income 15.371 14.172 12.493 11.561 11.533 Expense charges (1) 3.161 3.318 3.290 3.092 2.880 Investment income, net 12.210 10.854 9.203 8.469 8.653 Net realized and unrealized gain on investments and mortgage loans payable 6.877 5.839 9.660 18.911 27.868 Net increase in Accumulation Unit Value 19.087 16.693 18.863 27.380 36.521 Accumulation Unit Value: Beginning of period 398.329 381.636 362.773 335.393 298.872 End of period $ 417.416 $ 398.329 $ 381.636 $ 362.773 $ 335.393 Total return 4.79 % 4.37 % 5.20 % 8.16 % 12.22 % Ratios to Average net Assets: Expenses (1) 0.76 % 0.83 % 0.86 % 0.86 % 0.89 % Investment income, net 2.95 % 2.72 % 2.41 % 2.37 % 2.68 % Portfolio turnover rate: Real estate properties (2) 11.8 % 2.7 % 1.3 % 5.7 % 6.5 % Marketable securities (3) 5.1 % 5.7 % 3.5 % 10.0 % 15.9 % Accumulation Units outstanding at end of period (millions): 60.7 61.3 62.4 60.4 57.9 Net assets end of period (millions) $ 25,842.6 $ 24,942.6 $ 24,304.7 $ 22,360.0 $ 19,829.0 (1) Expense charges per Accumulation Unit and the Ratio of Expenses to average net assets reflect the year to date Account level expenses and exclude real estate property level expenses which are included in real estate income, net. (2) Real estate investment portfolio turnover rate is calculated by dividing the lesser of purchases or sales of real estate property investments (including contributions to, or return of capital distributions received from, existing joint venture and limited partnership investments) by the average value of the portfolio of real estate investments held during the period. (3) Marketable securities portfolio turnover rate is calculated by dividing the lesser of purchases or sales of securities, excluding securities having maturity dates at acquisition of one year or less, by the average value of the portfolio securities held during the period.

Accumulation Units

Accumulation Units	12 Months Ended
	Dec. 31, 2018
Accumulated Units Disclosure [Abstract]
Accumulation Units	Accumulation Units Changes in the number of Accumulation Units outstanding were as follows (millions): Years ended December 31, 2018 2017 2016 Outstanding: Beginning of period 61.3 62.4 60.4 Credited for premiums 6.5 6.6 8.2 Annuity, other periodic payments, withdrawals and death benefits (7.1 ) (7.7 ) (6.2 ) End of period 60.7 61.3 62.4

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Commitments —As of December 31, 2018 and 2017 , the Account had the following immediately callable commitments to purchase additional interests in its limited partnership investments: December 31, 2018 2017 Taconic New York City GP Fund $ 26.0 $ 32.0 LCS SHIP Venture I, LLC 75.0 — $ 101.0 $ 32.0 Taconic New York City GP Fund—The general partner can call capital during the commitment period at any time. The commitment period ends on the fifth anniversary from closing (November 2020). The commitment period may be closed earlier at the joint election of TIAA and the general partner if 90% of the commitment has been satisfied. LCS SHIP Venture I, LLC—The general partner can call capital at any time during the commitment period, which ends one year from closing (June 2019). The Account has committed a total of $ 83.3 million and $47.6 million as of December 2018 and 2017, respectively, to various tenants for tenant improvements and leasing inducements. Contingencies —In the normal course of business, the Account may be named, from time to time, as a defendant or may be involved in various legal actions, including arbitrations, class actions and other litigation. The Account establishes an accrual for all litigation and regulatory matters when it believes it is probable that a loss has been incurred and the amount of the loss can be reasonably estimated. Once established, accruals are adjusted, as appropriate, in light of additional information. The amount of loss ultimately incurred in relation to those matters may be higher or lower than the amounts accrued for those matters. As of the date of this report, management of the Account does not believe that the results of any such claims or litigation, individually or in the aggregate, will have a material effect on the Account’s business, financial position or results of operations.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Purchases Property Name Purchase Date Ownership Percentage Sector Location Net Purchase Price (1) Glen Lake 01/09/2019 100.00% Apartments Atlanta, GA $ 54.8 1600 Broadway 01/10/2019 100.00% Office Denver, CO 109.1 The Theory 01/15/2019 97.00% Apartments Raleigh, NC 63.0 Colony Industrial Portfolio 02/20/2019 100.00% Industrial Various, U.S.A. 137.0 Storage Portfolio III (2) 02/22/2019 90.00% Storage Various, U.S.A. 17.9 (1) The net purchase price represents the purchase price and closing costs. (2) The Account entered into a 90% interest in a joint venture designed for future investment in storage properties. The Account's maximum potential investment is $100.0 million and on February 22, 2019, the first storage property in Glen Burnie, MD, was acquired for $17.9 million (the Account's Share). Sales Property Name Sales Date Ownership Percentage Sector Location Net Sales Price (1) Realized Gain/Loss on Sale (3) 1858 Meca Way (2) 03/01/2019 100.00% Industrial Norcross, GA $ 2.9 $ — (1) The net sales price represents the sales price, less selling expenses. (2) Property held within Colony Industrial Portfolio. (3) No realized gain or loss was realized from the sale. Loans Receivable Borrower Name Financing Date Interest Rate Sector Maturity Date Location Loan Amount (1) SCG Oakland Portfolio 03/01/2019 4.25% + LIBOR Office 03/01/2024 Oakland, CA $ 53.5 (1) Loan Amount represents the Account's mezzanine loan receivable position. Financings Property Name Financing Date Ownership Percentage Interest Rate Sector Maturity Date Location Financing Amount (1) The Theory 01/15/2019 97.00% 3.94% Apartments 01/15/2024 Raleigh, NC $ 31.3 Marketable Securities In the first two months of 2019, the Account sold approximately $400 million in real estate-related securities.

Organization and Significant _2

Organization and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation: The accompanying Consolidated Financial Statements include the Account and those subsidiaries wholly-owned by TIAA for the benefit of the Account. All significant intercompany accounts and transactions between the Account and such subsidiaries have been eliminated. The Accumulation Unit Value (“AUV”) used for financial reporting purposes may differ from the AUV used for processing transactions. The AUV used for financial reporting purposes includes security and participant transactions effective through the period end date to which this report relates. Total return is computed based on the AUV used for processing transactions.
Determination of Investments at Fair Value	Determination of Investments at Fair Value: The Account reports all investments at fair value in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 946, Financial Services—Investment Companies. Further in accordance with the adoption of the fair value option allowed under ASC 825, Financial Instruments , and at the election of Account management, mortgage loans payable are reported at fair value. The FASB has defined fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. The following is a description of the valuation methodologies used to determine the fair value of the Account’s investments and investment related mortgage loans payable. Valuation of Real Estate Properties —Investments in real estate properties are stated at fair value, as determined in accordance with policies and procedures reviewed by the Investment Committee of the Board and in accordance with the responsibilities of the Board as a whole. Accordingly, the Account does not record depreciation. Determination of fair value involves significant levels of judgment because the actual fair value of real estate can be determined only by negotiation between the parties in a sales transaction. The Account’s primary objective when valuing its real estate investments will be to produce a valuation that represents a reasonable estimate of the fair value of its investments. Implicit in the Account’s definition of fair value are the consummation of a sale as of a specified date and the passing of title from seller to buyer under conditions whereby: • Buyer and seller are typically motivated; • Both parties are well informed or well advised, and acting in what they consider their best interests; • A reasonable time is allowed for exposure in the open market; • Payment is made in terms of cash or in terms of financial arrangements comparable thereto; and • The price represents the normal consideration for the property sold unaffected by special or creative financing or sales concessions granted by anyone associated with the sale. Property and investment values are affected by, among other things, the availability of capital, occupancy rates, rental rates, and interest and inflation rates. As a result, determining real estate and investment values involves many assumptions. Key inputs and assumptions include rental income and expense amounts, related rental income and expense growth rates, capital expenditures, discount rates and capitalization rates. Valuation techniques include discounted cash flow analysis, prevailing market capitalization rates or multiples applied to earnings from the property, analysis of recent comparable sales transactions, actual sale negotiations and bona fide purchase offers received from third parties. Amounts ultimately realized from each investment may vary significantly from the fair value presented. Real estate properties owned by the Account are initially valued based on an independent third party appraisal, as reviewed by TIAA’s internal appraisal staff and as applicable by the Account’s independent fiduciary at the time of the closing of the purchase. Such initial valuation may result in a potential unrealized gain or loss reflecting the difference between an investment’s fair value (i.e., exit price) and its cost basis (which is inclusive of transaction costs). Subsequently, each property is appraised each quarter by an independent third party appraiser, reviewed by TIAA’s internal appraisal staff and as applicable the Account’s independent fiduciary. In general, the Account obtains appraisals of its real estate properties spread out throughout the quarter, which is intended to result in appraisal adjustments, and thus, adjustments to the valuations of its holdings (to the extent such adjustments are made) that happen regularly throughout each quarter and not on one specific day or month in each period. Further, management reserves the right to order an appraisal and/or conduct another valuation outside of the normal quarterly process when facts or circumstances at a specific property change. For example, under certain circumstances a valuation adjustment could be made when the account receives a bona fide bid for the sale of a property held within the Account or one of the Account’s joint ventures. Adjustments may be made for events or circumstances indicating an impairment of a tenant’s ability to pay amounts due to the Account under a lease (including due to a bankruptcy filing of that tenant). Alternatively, adjustments may be made to reflect the execution or renewal of a significant lease. Also, adjustments may be made to reflect factors (such as sales values for comparable properties or local employment rate) bearing uniquely on a particular region in which the Account holds properties. TIAA’s internal appraisal staff oversees the entire appraisal process, in conjunction with the Account’s independent fiduciary (the independent fiduciary is more fully described in the following paragraph). Any differences in the conclusions of TIAA’s internal appraisal staff and the independent appraiser will be reviewed by the independent fiduciary, which will make a final determination on the matter (which may include ordering a subsequent independent appraisal). The independent fiduciary, RERC, LLC, has been appointed by a special subcommittee of the Investment Committee of the Board to, among other things, oversee the appraisal process. The independent fiduciary must approve all independent appraisers used by the Account. All appraisals are performed in accordance with Uniform Standards of Professional Appraisal Practices, the real estate appraisal industry standards created by The Appraisal Foundation. Real estate appraisals are estimates of property values based on a professional’s opinion. Appraisals of properties held outside of the U.S. are performed in accordance with industry standards commonly applied in the applicable jurisdiction. These independent appraisers are always expected to be MAI-designated members of the Appraisal Institute (or its European equivalent, Royal Institute of Chartered Surveyors) and state certified appraisers from national or regional firms with relevant property type experience and market knowledge. Under the Account’s current procedures, each independent appraisal firm will be rotated off of a particular property at least every three years, although such appraisal firm may perform appraisals of other Account properties subsequent to such rotation. Also, the independent fiduciary can require additional appraisals if factors or events have occurred that could materially change a property’s value (including those identified above) and such change is not reflected in the quarterly valuation review, or otherwise to ensure that the Account is valued appropriately. The independent fiduciary must also approve any valuation change of real estate-related assets where a property’s value changed by more than 6% from the most recent independent annual appraisal, or if the value of the Account would change by more than 4% within any calendar quarter or more than 2% since the prior calendar month. When a real estate property is subject to a mortgage, the property is valued independently of the mortgage and the property and mortgage fair values are reported separately (see Valuation of Loans Payable ). The independent fiduciary reviews and approves all mortgage valuation adjustments before such adjustments are recorded by the Account. The Account continues to use the revised value for each real estate property and mortgage loan payable to calculate the Account’s daily net asset value until the next valuation review or appraisal. Valuation of Real Estate Joint Ventures —Real estate joint ventures are stated at the fair value of the Account’s ownership interests of the underlying entities. The Account’s ownership interests are valued based on the fair value of the underlying real estate, any related mortgage loans payable, and other factors, such as ownership percentage, ownership rights, buy/sell agreements, distribution provisions and capital call obligations. Upon the disposition of all real estate investments by an investee entity, the Account will continue to state its equity in the remaining net assets of the investee entity during the wind down period, if any, which occurs prior to the dissolution of the investee entity. Valuation of Real Estate Limited Partnerships —Limited partnership interests are stated at the fair value of the Account’s ownership in the partnership. Management uses net asset value information provided by limited partners as a practical expedient to estimate fair value. The Account receives estimates from limited partners on a quarterly basis, and audited information is provided annually. Upon receipt of the information, management reviews and concludes on whether the net asset values provided are an appropriate representation of the fair value of the Account's interests in the limited partnerships and makes valuation adjustments as necessary. Valuation of limited partnerships proceeds under the direction of the Investment Committee of the Board and in accordance with the responsibilities of the Board as a whole. Valuation of Marketable Securities —Equity securities listed or traded on any national market or exchange are valued at the last sale price as of the close of the principal securities market or exchange on which such securities are traded or, if there is no sale, at the mean of the last bid and asked prices on such market or exchange, exclusive of transaction costs. Valuation of Debt Securities —Debt securities with readily available market quotations, other than money market instruments, are generally valued at the most recent bid price or the equivalent quoted yield for such securities (or those of comparable maturity, quality and type). Debt securities for which market quotations are not readily available, are valued at fair value as determined by management and the Investment Committee of the Board and in accordance with the responsibilities of the Board as a whole. Short-term investments are valued in the same manner as debt securities, as described above. Money market instruments are valued at amortized cost, which approximates fair value. Valuation of Loans Receivable (i.e. the Account as a creditor) —Loans receivable are stated at fair value and are initially valued at the face amount of the loan funding. Subsequently, loans receivable are valued at least quarterly by TIAA’s internal valuation department based on market factors, such as market interest rates and spreads for comparable loans, the liquidity for loans of similar characteristics, the performance of the underlying collateral (such as the loan-to-value ratio and the cash flow of the underlying collateral) and the credit quality of the counterparty. The independent fiduciary reviews and approves all loan receivable valuation adjustments before such adjustments are recorded by the Account. The Account continues to use the revised value for each loan receivable to calculate the Account’s daily net asset value until the next valuation review. Valuation of Loans Payable (i.e. the Account as a debtor) —Mortgage or other loans payable are stated at fair value. The estimated fair value of mortgage loans payable is generally based on the amount at which the liability could be transferred in a current transaction, exclusive of transaction costs. Fair values are estimated based on market factors, such as market interest rates and spreads on comparable loans, the liquidity for mortgage loans of similar characteristics, the performance of the underlying collateral (such as the loan-to-value ratio and the cash flow of the underlying collateral), the maturity date of the loan, the return demands of the market, and the credit quality of the Account. Different assumptions or changes in future market conditions could significantly affect estimated fair values. At times, the Account may assume debt in connection with the purchase of real estate (including under the Account's Line of Credit or additional credit facilities).
Accumulation and Annuity Funds	Accumulation and Annuity Funds: The accumulation fund represents the net assets attributable to participants in the accumulation phase of their investment (“Accumulation Fund”). The annuity fund represents the net assets attributable to the participants currently receiving annuity payments (“Annuity Fund”). The net increase or decrease in net assets from investment operations is apportioned between the accounts based upon their relative daily net asset values. Once an Account participant begins receiving lifetime annuity income benefits, payment levels cannot be reduced as a result of the Account’s actual mortality experience. In addition, the contracts pursuant to which the Account is offered are required to stipulate the maximum expense charge for all Account level expenses that can be assessed, which is not to exceed 2.5% of average net assets per year. The Account pays a fee to TIAA to assume mortality and expense risks.
Accounting for Investments	Accounting for Investments: The investments held by the Account are accounted for as follows: Real Estate Properties —Rent from real estate properties consists of all amounts earned under tenant operating leases, including base rent, recoveries of real estate taxes and other expenses and charges for miscellaneous services provided to tenants. Rental income is recognized in accordance with the billing terms of the lease agreements. The Account bears the direct expenses of the real estate properties owned. These expenses include, but are not limited to, fees to local property management companies, property taxes, utilities, maintenance, repairs, insurance, and other operating and administrative costs. An estimate of the net operating income earned from each real estate property is accrued by the Account on a daily basis and such estimates are adjusted when actual operating results are determined. Real Estate Joint Ventures —The Account has limited ownership interests in various real estate joint ventures (collectively, the “joint ventures”). The Account records its contributions as increases to its investments in the joint ventures, and distributions from the joint ventures are treated as income within income from real estate joint ventures and limited partnerships in the Account’s Consolidated Statements of Operations. Distributions that are identified as returns of capital are recorded as a reduction to the cost basis of the investment, whereas distributions identified as capital gains or losses are recorded as realized gains or losses. Income distributions from the joint ventures are recorded based on the Account’s proportional interest of the income distributed by the joint ventures. Income earned but not yet distributed to the Account by the joint ventures is recorded as unrealized gains and losses. Limited Partnerships —The Account has limited ownership interests in various private real estate funds (primarily limited partnerships) and a private real estate investment trust (collectively, the “limited partnerships”). The Account records its contributions as increases to the investments, and distributions from the investments are treated as income within income from real estate joint ventures and limited partnerships in the Account’s Consolidated Statements of Operations. Distributions that are identified as returns of capital are recorded as a reduction to the cost basis of the investment, whereas distributions identified as capital gains or losses are recorded as realized gains or losses. Unrealized gains and losses are recorded based upon the changes in the net asset values of the limited partnerships as determined from the financial statements of the limited partnerships when received by the Account. Prior to the receipt of the financial statements from the limited partnerships, the Account estimates the value of its interest using information provided by the limited partners. Changes in value based on such estimates are recorded by the Account as unrealized gains and losses. Marketable Securities —Transactions in marketable securities are accounted for as of the date the securities are purchased or sold (trade date). Interest income is recorded as earned. Dividend income is recorded on the ex-dividend date within dividend income. Dividends that are identified as returns of capital are recorded as a reduction to the cost basis of the investment, whereas dividends identified as capital gains or losses are recorded as realized gains or losses. Realized gains and losses on securities transactions are accounted for on the specific identification method. Loans Receivable —The Account may originate, purchase or sell loans collateralized by real estate. The cost basis of originated loans is comprised of the principal balance and direct costs incurred that represent a component of loan’s reported fair value. The cost basis of purchased loans consists of the purchase price of the loan and additional direct costs incurred that represent a component of the loan’s reported fair value. Additional costs incurred by the Account to originate or purchase loans that do not represent a component of a loan’s fair value are recorded as expenses in the period incurred. Nonrefundable origination fees paid by borrowers are recognized as interest income once all activities required to execute the loan are completed. Prepayment fees received from the payoff of loans in advance of their maturity date are recognized as interest income on the date the payoff occurs. Interest income from loans in accrual status is recognized based on the current coupon rate of the loans. Interest income accruals are suspended when a loan becomes a non-performing loan, defined as a loan more than ninety days in arrears or at any point when management believes the full collection of principal is doubtful. Interest income on non-performing loans is recognized only as cash payments are received. Loans can be rehabilitated to normal accrual status once all past due interest has been collected and management believes the full collection of principal is likely. Realized and Unrealized Gains and Losses —Realized gains and losses are recorded at the time an investment is sold or a distribution is received in relation to an investment sale from a joint venture or limited partnership. Real estate and loan receivable transactions are accounted for as of the date on which the purchase or sale transactions close (settlement date). The Account recognizes a realized gain on the sale of an investment to the extent that the contract sales price exceeds the cost-to-date of the investment being sold. A realized loss occurs when the cost-to-date exceeds the sales price. Realized gains and losses from partial sales of non-financial assets are recognized in accordance with ASC 610-20 - Gains and Losses from the Derecognition of Nonfinancial Assets . Realized gains and losses from the sale of financial assets are recognized in accordance with ASC 860 - Transfers and Servicing . Unrealized gains and losses are recorded as the fair values of the Account’s investments are adjusted, and as discussed within the Real Estate Joint Ventures, Limited Partnerships and Loans Receivable sections above. Net Assets —The Account’s net assets as of the close of each valuation day are valued by taking the sum of: • the value of the Account’s cash; cash equivalents, and short-term and other debt instruments; • the value of the Account’s other securities and other non-real estate assets; • the value of the individual real properties (based on the most recent valuation of that property) and other real estate-related investments owned by the Account; • an estimate of the net operating income accrued by the Account from its properties, other real estate-related investments and non-real estate-related investments (including short-term marketable securities) since the end of the prior valuation day; and • actual net operating income earned from the Account’s properties, other real estate-related investments and non-real estate-related investments (but only to the extent any such item of income differs from the estimated income accrued for on such investments), and then reducing the sum by liabilities held within the Account, including the daily investment management fee, administration and distribution fees, mortality and expense fee, liquidity guarantee fee, and certain other expenses attributable to operating the Account. Daily estimates of net operating income are adjusted to reflect actual net operating income on a monthly basis, at which time such adjustments (if any) are reflected in the Account’s unit value. After the end of every quarter, the Account reconciles the amount of expenses deducted from the Account (which is established in order to approximate the costs that the Account will incur) with the expenses the Account actually incurred. If there is a difference, the Account adds it to or deducts it from the Account in equal daily installments over the remaining days of the following quarter. Material differences may be repaid in the current calendar quarter. The Account’s at-cost deductions are based on projections of Account assets and overall expenses, and the size of any adjusting payments will be directly affected by the difference between management’s projections and the Account’s actual assets or expenses.
Cash and Cash Equivalents	Cash and Cash Equivalents: Cash and cash equivalents are balances held by the Account in bank deposit accounts which, at times, exceed federally insured limits. The Account’s management monitors these balances to mitigate the exposure of risk due to concentration and has not experienced any losses from such concentration.
Other Assets and Other Liabilities	Other Assets and Other Liabilities: Other assets and other liabilities consist of operating assets and liabilities utilized and held at each individual real estate property investment. Other assets consist of, amongst other items, cash, tenant receivables and prepaid expenses; whereas other liabilities primarily consist of security deposits. Other assets also include cash collateral held for securities on loan.
Federal Income Taxes	Federal Income Taxes: Based on provisions of the Internal Revenue Code, Section 817, the Account is taxed as a segregated asset account of TIAA and as such, the Account incurs no material federal income tax attributable to the net investment activity of the Account. The Account’s federal income tax return is generally subject to examination for a period of three years after filed. State and local tax returns may be subject to examination for an additional period of time depending on the jurisdiction. Management has analyzed the Account’s tax positions taken for all open federal income tax years and has concluded that no provision for federal income tax is required in the Account’s Consolidated Financial Statements.
Restricted Cash	Restricted Cash: The Account held restricted cash in escrow accounts for security deposits, as required by certain states, as well as property taxes, insurance, and various other property related matters as required by certain creditors related to outstanding mortgage loans payable collateralized by certain real estate investments. These amounts are recorded within other assets on the Consolidated Statements of Assets and Liabilities.
Changes In Net Assets	Changes in Net Assets: Premiums include premiums paid by existing accumulation unit holders in the Account and transfers into the Account. Withdrawals and death benefits include withdrawals out of the Account which include transfers out of the Account and required minimum distributions.
Due to/from Investment Manager	Due to/from Investment Manager: Due to/from investment manager represents amounts that are to be paid or received by TIAA on behalf of the Account. Amounts generally are paid or received by the Account within one or two business days and no interest is contractually charged on these amounts.
Securities Lending	Securities Lending: The Account may lend securities to qualified borrowers to earn additional income. The Account receives cash collateral against the loaned securities and maintains cash collateral in an amount not less than 100% of the market value of loaned securities during the period of the loan; any additional collateral required due to changes in security values is delivered to the Account the next business day. Cash collateral received by the Account is invested exclusively in an interest-bearing deposit account. The value of the loaned securities and the liability to return the cash collateral received are reflected in the Consolidated Statements of Assets and Liabilities. When loaning securities, the Account retains the benefits of owning the securities, including the economic equivalent of dividends or interest generated by the securities. All income generated by the securities lending program is reflected within interest income on the Consolidated Statements of Operations. As of December 31, 2018 and 2017, securities lending transactions are for real-estate related equity securities, and the resulting loans are continuous, can be recalled at any time, and have no set maturity. Securities lending income recognized by the Account consists of interest earned on cash collateral and lending fees, net of any rebates to the borrower and compensation to the agent. Such income is reflected within interest income on the Consolidated Statements of Operations. In lending its securities, the Account bears the market risk with respect to the investment of collateral and the risk that the agent may default on its contractual obligations to the Account. The agent bears the risk that the borrower may default on its obligation to return the loaned securities as the agent is contractually obligated to indemnify the Account if at the time of a default by a borrower some or all of the loan securities have not been returned.
New Accounting Pronouncement	New Accounting Pronouncements In May 2014, the FASB issued Accounting Standard Update 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”). ASU 2014-09 supersedes all existing revenue recognition guidance and establishes a five-step model to measure and recognize revenue. ASU 2014-09 was effective for fiscal years beginning after December 15, 2017 and the Account adopted this guidance as of January 1, 2018 utilizing the modified retrospective adoption approach. Under this approach, ASU 2014-09 was applied to all contracts that were not completed as of the date of adoption. Based on the Accounts implementation procedures, the adoption of ASU 2014-09 had an immaterial impact to the Account. In February 2016, the FASB issued Accounting Standards Update 2016-02 Leases (Topic 842) (“ASU 2016-02”) which will supersede Topic 840, Leases. This ASU applies to all entities that enter into a lease. Lessees will be required to report assets and liabilities that arise from leases. Lessor accounting is expected to remain unchanged; however, certain refinements were made to conform with the recently issued revenue recognition guidance in ASU 2014-09, specifically related to the allocation and recognition of contract consideration earned from lease and non-lease revenue components. The ASU contains certain practical expedients, which the Account plans to elect. The Account is electing the transition package of practical expedients permitted within the new standard. This practical expedient permits the Account to carryforward the historical lease classification and not to reassess initial direct costs for any existing leases. Further, the Account will initially apply the new lease requirements at the effective date of January 1, 2019, and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. In addition, the Account plans to elect the practical expedient that allows lessors to avoid separating lease and non-lease components within a contract if certain criteria are met. The lessor’s practical expedient election would be limited to circumstances in which (i) the timing and pattern of revenue recognition are the same for the non-lease component and the related lease component and (ii) the combined single lease component would be classified as an operating lease. This practical expedient would allow the Account the ability to combine the lease and non-lease components if the underlying asset meets the two criteria above. This ASU is effective for public business entities for fiscal years beginning after December 15, 2018, including all interim periods within those fiscal years. Management has completed its initial scoping for the adoption of the ASU 2016-02 and does not expect the adoption of such guidance to materially impact the Account. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement: Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurements. ASU 2018-13 modifies the disclosures required for fair value measurements. This guidance is effective for fiscal years beginning after December 15, 2019. Management is currently evaluating the impact of this guidance but does not expect it to materially impact the Account's Notes to the Consolidated Financial Statements.

Concentration Risk (Tables)

Concentration Risk (Tables)	12 Months Ended
	Dec. 31, 2018
Risks and Uncertainties [Abstract]
Schedules of Diversification of Portfolio, by Region and Property Type	The following table represents the diversification of the Account’s portfolio by region and property type as of December 31, 2018 : Diversification by Fair Value (1) West East South Midwest Total Office 13.9 % 19.0 % 5.3 % — % 38.2 % Apartment 9.6 % 7.5 % 6.6 % 1.0 % 24.7 % Retail 7.7 % 3.1 % 7.9 % 0.8 % 19.5 % Industrial 8.3 % 1.3 % 4.2 % 0.5 % 14.3 % Other (2) 0.6 % 2.5 % 0.1 % 0.1 % 3.3 % Total 40.1 % 33.4 % 24.1 % 2.4 % 100.0 % (1) Wholly-owned properties are represented at fair value and gross of any debt, while joint venture properties are represented at the net equity value. (2) Represents interests in Storage Portfolio investments, a fee interest encumbered by a ground lease real estate investment and land. Properties in the “West” region are located in: AK, AZ, CA, CO, HI, ID, MT, NM, NV, OR, UT, WA, WY Properties in the “East” region are located in: CT, DC, DE, KY, MA, MD, ME, NC, NH, NJ, NY, PA, RI, SC, VA, VT, WV Properties in the “South” region are located in: AL, AR, FL, GA, LA, MS, OK, TN, TX Properties in the “Midwest” region are located in: IA, IL, IN, KS, MI, MN, MO, ND, NE, OH, SD, WI

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2018
Leases, Operating [Abstract]
Schedule of Aggregate Minimum Annual Rental Payments	Aggregate minimum annual rentals for wholly-owned real estate investments owned by the Account through the non-cancelable lease term, excluding short-term residential leases, are as follows (millions): Years Ending December 31, 2019 $ 535.2 2020 497.7 2021 431.5 2022 366.9 2023 307.8 Thereafter 2,701.8 Total $ 4,840.9

Assets and Liabilities Measur_2

Assets and Liabilities Measured at Fair Value on a Recurring Basis (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following tables show the major categories of assets and liabilities measured at fair value on a recurring basis as of December 31, 2018 and 2017 , using unadjusted quoted prices in active markets for identical assets (Level 1); significant other observable inputs (Level 2); significant unobservable inputs (Level 3); and Practical Expedient (millions): Description Level 1: Quoted Prices in Active Markets for Identical Assets Level 2: Significant Other Observable Inputs Level 3: Significant Unobservable Inputs Fair Value Using Practical Expedient Total at December 31, 2018 Real estate properties $ — $ — $ 15,531.1 $ — $ 15,531.1 Real estate joint ventures — — 6,356.6 — 6,356.6 Limited partnerships — — — 175.9 175.9 Marketable securities: Real estate-related 1,415.1 — — — 1,415.1 Government agency notes — 2,050.7 — — 2,050.7 United States Treasury securities — 2,038.0 — — 2,038.0 Loans receivable — — 913.0 — 913.0 Total Investments at $ 1,415.1 $ 4,088.7 $ 22,800.7 $ 175.9 $ 28,480.4 Mortgage loans payable $ — $ — $ (2,608.0 ) $ — $ (2,608.0 ) Description Level 1: Quoted Prices in Active Markets for Identical Assets Level 2: Significant Other Observable Inputs Level 3: Significant Unobservable Inputs Fair Value Using Practical Expedient Total at December 31, 2017 Real estate properties $ — $ — $ 15,742.7 $ — $ 15,742.7 Real estate joint ventures — — 5,860.6 — 5,860.6 Limited partnerships — — — 142.4 142.4 Marketable securities: Real estate-related 1,238.0 — — — 1,238.0 Government agency notes — 2,872.3 — — 2,872.3 United States Treasury securities — 1,015.2 — — 1,015.2 Loans receivable — — 298.8 — 298.8 Total Investments at $ 1,238.0 $ 3,887.5 $ 21,902.1 $ 142.4 $ 27,170.0 Mortgage loans payable $ — $ — $ (2,238.3 ) $ — $ (2,238.3 )
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation	The following tables show the reconciliation of the beginning and ending balances for assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) during the years ended December 31, 2018 and 2017 (millions): Real Estate Properties Real Estate Joint Ventures Loans Receivable Total Level 3 Investments Mortgage Loans Payable For the year ended December 31, 2018 Beginning balance January 1, 2018 $ 15,742.7 $ 5,860.6 $ 298.8 $ 21,902.1 $ (2,238.3 ) Total realized and unrealized gains included in changes in net assets 315.8 116.3 0.3 432.4 79.4 Purchases (1) 1,151.8 941.5 939.2 3,032.5 (817.9 ) Sales (1,679.2 ) — (257.3 ) (1,936.5 ) — Settlements (2) — (561.8 ) (68.0 ) (629.8 ) 368.8 Ending balance December 31, 2018 $ 15,531.1 $ 6,356.6 $ 913.0 $ 22,800.7 $ (2,608.0 ) Real Estate Properties Real Estate Joint Ventures Loans Receivable Total Level 3 Investments Mortgage Loans Payable For the year ended December 31, 2017 Beginning balance January 1, 2017 $ 15,452.8 $ 5,622.4 $ 295.7 $ 21,370.9 $ (2,332.1 ) Total realized and unrealized gains included in changes in net assets 177.5 123.5 1.2 302.2 15.9 Purchases (1) 682.9 419.0 1.9 1,103.8 (17.7 ) Sales (570.5 ) — — (570.5 ) — Settlements (2) — (304.3 ) — (304.3 ) 95.6 Ending balance December 31, 2017 $ 15,742.7 $ 5,860.6 $ 298.8 $ 21,902.1 $ (2,238.3 ) (1) Includes purchases, contributions for joint ventures, capital expenditures, lending for loans receivable and assumption of mortgage loans payable. (2) Includes operating income for real estate joint ventures net of distributions, principal payments and payoffs of loans receivable, and principal payments and extinguishment of mortgage loans payable.
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation	The following tables show the reconciliation of the beginning and ending balances for assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) during the years ended December 31, 2018 and 2017 (millions): Real Estate Properties Real Estate Joint Ventures Loans Receivable Total Level 3 Investments Mortgage Loans Payable For the year ended December 31, 2018 Beginning balance January 1, 2018 $ 15,742.7 $ 5,860.6 $ 298.8 $ 21,902.1 $ (2,238.3 ) Total realized and unrealized gains included in changes in net assets 315.8 116.3 0.3 432.4 79.4 Purchases (1) 1,151.8 941.5 939.2 3,032.5 (817.9 ) Sales (1,679.2 ) — (257.3 ) (1,936.5 ) — Settlements (2) — (561.8 ) (68.0 ) (629.8 ) 368.8 Ending balance December 31, 2018 $ 15,531.1 $ 6,356.6 $ 913.0 $ 22,800.7 $ (2,608.0 ) Real Estate Properties Real Estate Joint Ventures Loans Receivable Total Level 3 Investments Mortgage Loans Payable For the year ended December 31, 2017 Beginning balance January 1, 2017 $ 15,452.8 $ 5,622.4 $ 295.7 $ 21,370.9 $ (2,332.1 ) Total realized and unrealized gains included in changes in net assets 177.5 123.5 1.2 302.2 15.9 Purchases (1) 682.9 419.0 1.9 1,103.8 (17.7 ) Sales (570.5 ) — — (570.5 ) — Settlements (2) — (304.3 ) — (304.3 ) 95.6 Ending balance December 31, 2017 $ 15,742.7 $ 5,860.6 $ 298.8 $ 21,902.1 $ (2,238.3 ) (1) Includes purchases, contributions for joint ventures, capital expenditures, lending for loans receivable and assumption of mortgage loans payable. (2) Includes operating income for real estate joint ventures net of distributions, principal payments and payoffs of loans receivable, and principal payments and extinguishment of mortgage loans payable.
Schedule of Unobservable Inputs Related to Level 3 Fair Value Measurements	The following table shows quantitative information about unobservable inputs related to the Level 3 fair value measurements as of December 31, 2018 . Type Asset Class Valuation Technique(s) Unobservable Inputs Range (Weighted Average) Real Estate Properties and Joint Ventures Office Income Approach—Discounted Cash Flow Discount Rate 5.5%–8.6% (6.5%) Terminal Capitalization Rate 4.0%–7.5% (5.4%) Income Approach—Direct Capitalization Overall Capitalization Rate 4.0%–7.0% (4.8%) Industrial Income Approach—Discounted Cash Flow Discount Rate 5.3%–8.9% (6.8%) Terminal Capitalization Rate 4.4%–7.3% (5.5%) Income Approach—Direct Capitalization Overall Capitalization Rate 4.0%–7.0% (4.9%) Residential Income Approach—Discounted Cash Flow Discount Rate 5.5%–7.8% (6.5%) Terminal Capitalization Rate 3.8%–6.8% (5.0%) Income Approach—Direct Capitalization Overall Capitalization Rate 3.3%–6.0% (4.5%) Retail Income Approach—Discounted Cash Flow Discount Rate 5.0%–10.7% (6.4%) Terminal Capitalization Rate 4.3%–9.0% (5.3%) Income Approach—Direct Capitalization Overall Capitalization Rate 3.3%–8.5% (4.7%) Mortgage Loans Payable Office and Industrial Discounted Cash Flow Loan-to-Value Ratio 36.4%–67.8% (47.6%) Equivalency Rate 3.9%–6.2% (4.6%) Net Present Value Loan-to-Value Ratio 36.4%–67.8% (47.6%) Weighted Average Cost of Capital Risk Premium Multiple 1.2–1.4 (1.3) Residential Discounted Cash Flow Loan-to-Value Ratio 31.9%–63.6% (48.1%) Equivalency Rate 3.4%–4.6% (4.1%) Net Present Value Loan-to-Value Ratio 31.9%–63.6% (48.1%) Weighted Average Cost of Capital Risk Premium Multiple 1.1–1.4 (1.2) Retail Discounted Cash Flow Loan-to-Value Ratio 31.9%–55.3% (39.3%) Equivalency Rate 4.3%–5.3% (4.5%) Net Present Value Loan-to-Value Ratio 31.9%–55.3% (39.3%) Weighted Average Cost of Capital Risk Premium Multiple 1.1–1.3 (1.2) Loans Receivable Residential, Industrial, Office, Retail and Storage Discounted Cash Flow Loan-to-Value Ratio 70.8%-79.2% (75.6%) Equivalency Rate 6.0%-8.3% (6.9%) The following table shows quantitative information about unobservable inputs related to the Level 3 fair value measurements as of December 31, 2017. Type Asset Class Valuation Technique(s) Unobservable Inputs Range (Weighted Average) Real Estate Properties and Joint Ventures Office Income Approach—Discounted Cash Flow Discount Rate 5.5%–8.0% (6.5%) Terminal Capitalization Rate 4.5%–7.0% (5.5%) Income Approach—Direct Capitalization Overall Capitalization Rate 3.8%–7.0% (4.8%) Industrial Income Approach—Discounted Cash Flow Discount Rate 5.5%–8.9% (6.8%) Terminal Capitalization Rate 4.5%–8.3% (5.5%) Income Approach—Direct Capitalization Overall Capitalization Rate 4.0%–7.5% (5.0%) Residential Income Approach—Discounted Cash Flow Discount Rate 5.0%–8.0% (6.1%) Terminal Capitalization Rate 3.5%–6.5% (4.8%) Income Approach—Direct Capitalization Overall Capitalization Rate 3.3%–6.0% (4.3%) Retail Income Approach—Discounted Cash Flow Discount Rate 5.0%–10.5% (6.4%) Terminal Capitalization Rate 4.3%–8.8% (5.2%) Income Approach—Direct Capitalization Overall Capitalization Rate 3.8%–8.8% (4.7%) Mortgage Loans Payable Office and Industrial Discounted Cash Flow Loan-to-Value Ratio 37.7%–69.5% (45.6%) Equivalency Rate 3.7%–5.2% (3.9%) Net Present Value Loan-to-Value Ratio 37.7%–69.5% (45.6%) Weighted Average Cost of Capital Risk Premium Multiple 1.2–1.5 (1.3) Residential Discounted Cash Flow Loan-to-Value Ratio 28.1%–64.2% (38.6%) Equivalency Rate 3.3%–3.6% (3.4%) Net Present Value Loan-to-Value Ratio 28.1%–64.2% (38.6%) Weighted Average Cost of Capital Risk Premium Multiple 1.1–1.5 (1.3) Retail Discounted Cash Flow Loan-to-Value Ratio 17.9%–56.0% (32.7%) Equivalency Rate 3.1%–4.4% (3.8%) Net Present Value Loan-to-Value Ratio 17.9%–56.0% (32.7%) Weighted Average Cost of Capital Risk Premium Multiple 1.1–1.4 (1.2) Loans Receivable Office, Retail and Storage Discounted Cash Flow Loan-to-Value Ratio 59.4%-77.3% (75.1%) Equivalency Rate 4.2%-8.3% (6.2%)
Fair Value of Net Unrealized Gains Included in Changes in Net Assets Attributable to Investments and Mortgage Loans Payable Using Significant Unobservable Inputs	The amount of total net unrealized gains included in changes in net assets attributable to the change in net unrealized gains relating to Level 3 investments and mortgage loans payable using significant unobservable inputs still held as of the reporting date is as follows (millions): Real Estate Properties Real Estate Joint Ventures Loans Receivable Total Level 3 Investments Mortgage Loans Payable For the year ended December 31, 2018 $ 282.6 $ 80.8 $ 0.3 $ 363.7 $ 86.2 For the year ended December 31, 2017 $ 185.1 $ 125.2 $ 1.2 $ 311.5 $ 15.9

Investments in Joint Ventures (

Investments in Joint Ventures (Tables)	12 Months Ended
	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Financial Position of the Joint Venture	A condensed summary of the financial position and results of operations of the combined joint ventures is shown below (millions): December 31, 2018 2017 Assets Real estate properties, at fair value $ 16,134.1 $ 14,240.8 Other assets 460.3 337.1 Total assets $ 16,594.4 $ 14,577.9 Liabilities & Equity Mortgage notes payable and other obligations, at fair value $ 5,035.3 $ 3,995.7 Other liabilities 262.5 150.7 Total liabilities 5,297.8 4,146.4 Total equity 11,296.6 10,431.5 Total liabilities and equity $ 16,594.4 $ 14,577.9
Schedule of Results of Operations of the Joint Venture	Years ended December 31, 2018 2017 2016 Operating Revenue and Expenses Revenues $ 950.6 $ 869.2 $ 714.6 Expenses 487.1 426.9 365.0 Excess of revenues over expenses $ 463.5 $ 442.3 $ 349.6

Loans Receivable (Tables)

Loans Receivable (Tables)	12 Months Ended
	Dec. 31, 2018
Receivables [Abstract]
Schedule of Loans Receivable, Property Types	The following property types represent the underlying real estate collateral for the Account's mezzanine loans: December 31, 2018 2017 Fair Value % Fair Value % Office $ 512.1 56.2 % $ 227.0 76.0 % Industrial 176.4 19.3 % — — % Retail 101.6 11.1 % 34.2 11.4 % Storage 63.2 6.9 % 37.6 12.6 % Apartments 59.7 6.5 % — — % $ 913.0 100.0 % $ 298.8 100.0 %
Schedule of Fair Value and Risk Ratings	The following table presents the fair values of the Account's loan portfolio based on the risk ratings as of December 31, 2018, listed in order of the strength of the risk rating (from strongest to weakest): Number of Loans Fair Value % BBB 3 $ 175.0 19.2 % BB 5 561.5 61.5 % B 5 170.2 18.6 % NR 1 1 6.3 0.7 % 14 $ 913.0 100.0 % (1) " NR" designates loans not assigned an internal credit rating. As of December 31, 2018, this is representative of one loan collateralized by an interest in a joint venture invested in real estate. The loan is scheduled to mature on July 12, 2019. Management expects all principal and interest owed to the Account for this loan to be collected in full.

Mortgage Loans Payable (Tables)

Mortgage Loans Payable (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Schedule of Outstanding Mortgage Loans Payable Secured by Properties	At December 31, 2018 and 2017, the Account had outstanding mortgage loans payable secured by the following properties (millions): Property Interest Rate and Payment Frequency (2) Principal Amounts Outstanding as of December 31, Maturity 2018 2017 Mass Court (1) 2.88% paid monthly $ 90.2 $ 92.1 September 1, 2019 Red Canyon at Palomino Park (4) 5.34% paid monthly 27.1 27.1 August 1, 2020 Green River at Palomino Park (4) 5.34% paid monthly 33.2 33.2 August 1, 2020 Blue Ridge at Palomino Park (4) 5.34% paid monthly 33.4 33.4 August 1, 2020 Ashford Meadows Apartments 5.17% paid monthly 44.6 44.6 August 1, 2020 The Knoll (1) 3.98% paid monthly 16.9 17.5 December 5, 2020 The Corner 4.66% paid monthly — 105.0 June 1, 2021 Ascent at Windward 3.51% paid monthly 34.6 — January 1, 2022 The Palatine (1) 4.25% paid monthly 77.4 78.8 January 10, 2022 The Forum at Carlsbad (1) 4.25% paid monthly 87.3 88.9 March 1, 2022 Fusion 1560 3.42% paid monthly 37.4 — June 10, 2022 The Colorado (1) 3.69% paid monthly 89.9 91.7 November 1, 2022 The Legacy at Westwood (1) 3.69% paid monthly 45.8 46.7 November 1, 2022 Regents Court (1) 3.69% paid monthly 38.8 39.6 November 1, 2022 Fourth & Madison (1) 3.75% paid monthly 198.2 200.0 June 1, 2023 Fourth & Madison 4.17% paid monthly 90.0 — June 1, 2023 1001 Pennsylvania Avenue (1) 3.70% paid monthly 327.0 330.0 June 1, 2023 Biltmore at Midtown 3.94% paid monthly 36.4 — July 5, 2023 Cherry Knoll 3.78% paid monthly 35.3 — July 5, 2023 Lofts at SoDo 3.94% paid monthly 35.1 — July 5, 2023 1401 H Street, NW 3.65% paid monthly 115.0 115.0 November 5, 2024 Circa Green Lake 3.71% paid monthly 52.0 — March 5, 2025 Union - South Lake Union 3.66% paid monthly 57.0 — March 5, 2025 Holly Street Village 3.65% paid monthly 81.0 — May 1, 2025 Township Apartments 3.65% paid monthly 49.0 — May 1, 2025 32 South State Street 4.48% paid monthly 24.0 24.0 June 6, 2025 780 Third Avenue 3.55% paid monthly 150.0 150.0 August 1, 2025 Property Interest Rate and Payment Frequency (2) Principal Amounts Outstanding as of December 31, Maturity 2018 2017 780 Third Avenue 3.55% paid monthly $ 20.0 $ 20.0 August 1, 2025 701 Brickell Avenue 3.66% paid monthly 184.0 184.0 April 1, 2026 55 Second Street (5) 3.74% paid monthly 137.5 137.5 October 1, 2026 1900 K Street, NW 3.93% paid monthly 163.0 163.0 April 1, 2028 501 Boylston Street (6) 3.70% paid monthly — 216.5 April 1, 2028 99 High Street 3.90% paid monthly 277.0 — March 1, 2030 Total Principal Outstanding $ 2,688.1 $ 2,238.6 Fair Value Adjustment (3) (80.1 ) (0.3 ) Total Mortgage Loans Payable $ 2,608.0 $ 2,238.3 (1) The mortgage is adjusted monthly for principal payments. (2) Interest rates are fixed. Some mortgages held by the Account are structured to begin principal and interest payments after an initial interest only period. (3) The fair value adjustment consists of the difference (positive or negative) between the principal amount of the outstanding debt and the fair value of the outstanding debt. See Note 1—Organization and Significant Accounting Policies. (4) Represents mortgage loans on these individual properties which are held within the Palomino Park portfolio. (5) This mortgage is comprised of three individual loans, all with equal recourse, interest and maturity. The principal balances by loan are $79.0 million , $45.0 million , and $13.5 million . (6) On August 21, 2018, the Account sold a 49.9% interest in the property and transferred the remaining 50.1% to a joint venture investment. The debt was assumed by the buyer and new joint venture, respectively.
Schedule of Maturities of Long-term Debt	Principal payment schedule on mortgage loans payable as of December 31, 2018 was as follows (millions): Amount 2019 $ 107.2 2020 171.7 2021 20.0 2022 407.7 2023 686.4 Thereafter 1,295.1 Total maturities $ 2,688.1

Financial Highlights (Tables)

Financial Highlights (Tables)	12 Months Ended
	Dec. 31, 2018
Condensed Financial Information Disclosure [Abstract]
Schedule of Condensed Financial Information for an Accumulation Unit of the Account	Selected condensed financial information for an Accumulation Unit of the Account is presented below. Per Accumulation Unit data is calculated on average units outstanding. Years ended December 31, 2018 2017 2016 2015 2014 Per Accumulation Unit Data: Rental income $ 17.757 $ 17.132 $ 16.433 $ 15.538 $ 15.862 Real estate property level expenses and taxes 8.548 7.722 7.534 7.319 7.788 Real estate income, net 9.209 9.410 8.899 8.219 8.074 Other income 6.162 4.762 3.594 3.342 3.459 Total income 15.371 14.172 12.493 11.561 11.533 Expense charges (1) 3.161 3.318 3.290 3.092 2.880 Investment income, net 12.210 10.854 9.203 8.469 8.653 Net realized and unrealized gain on investments and mortgage loans payable 6.877 5.839 9.660 18.911 27.868 Net increase in Accumulation Unit Value 19.087 16.693 18.863 27.380 36.521 Accumulation Unit Value: Beginning of period 398.329 381.636 362.773 335.393 298.872 End of period $ 417.416 $ 398.329 $ 381.636 $ 362.773 $ 335.393 Total return 4.79 % 4.37 % 5.20 % 8.16 % 12.22 % Ratios to Average net Assets: Expenses (1) 0.76 % 0.83 % 0.86 % 0.86 % 0.89 % Investment income, net 2.95 % 2.72 % 2.41 % 2.37 % 2.68 % Portfolio turnover rate: Real estate properties (2) 11.8 % 2.7 % 1.3 % 5.7 % 6.5 % Marketable securities (3) 5.1 % 5.7 % 3.5 % 10.0 % 15.9 % Accumulation Units outstanding at end of period (millions): 60.7 61.3 62.4 60.4 57.9 Net assets end of period (millions) $ 25,842.6 $ 24,942.6 $ 24,304.7 $ 22,360.0 $ 19,829.0 (1) Expense charges per Accumulation Unit and the Ratio of Expenses to average net assets reflect the year to date Account level expenses and exclude real estate property level expenses which are included in real estate income, net. (2) Real estate investment portfolio turnover rate is calculated by dividing the lesser of purchases or sales of real estate property investments (including contributions to, or return of capital distributions received from, existing joint venture and limited partnership investments) by the average value of the portfolio of real estate investments held during the period. (3) Marketable securities portfolio turnover rate is calculated by dividing the lesser of purchases or sales of securities, excluding securities having maturity dates at acquisition of one year or less, by the average value of the portfolio securities held during the period.

Accumulation Units (Tables)

Accumulation Units (Tables)	12 Months Ended
	Dec. 31, 2018
Accumulated Units Disclosure [Abstract]
Schedule of Changes in the Number of Accumulation Units Outstanding	Changes in the number of Accumulation Units outstanding were as follows (millions): Years ended December 31, 2018 2017 2016 Outstanding: Beginning of period 61.3 62.4 60.4 Credited for premiums 6.5 6.6 8.2 Annuity, other periodic payments, withdrawals and death benefits (7.1 ) (7.7 ) (6.2 ) End of period 60.7 61.3 62.4

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of Callable Commitments	As of December 31, 2018 and 2017 , the Account had the following immediately callable commitments to purchase additional interests in its limited partnership investments: December 31, 2018 2017 Taconic New York City GP Fund $ 26.0 $ 32.0 LCS SHIP Venture I, LLC 75.0 — $ 101.0 $ 32.0

Subsequent Events (Tables)

Subsequent Events (Tables)	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Schedule of Subsequent Events	Purchases Property Name Purchase Date Ownership Percentage Sector Location Net Purchase Price (1) Glen Lake 01/09/2019 100.00% Apartments Atlanta, GA $ 54.8 1600 Broadway 01/10/2019 100.00% Office Denver, CO 109.1 The Theory 01/15/2019 97.00% Apartments Raleigh, NC 63.0 Colony Industrial Portfolio 02/20/2019 100.00% Industrial Various, U.S.A. 137.0 Storage Portfolio III (2) 02/22/2019 90.00% Storage Various, U.S.A. 17.9 (1) The net purchase price represents the purchase price and closing costs. (2) The Account entered into a 90% interest in a joint venture designed for future investment in storage properties. The Account's maximum potential investment is $100.0 million and on February 22, 2019, the first storage property in Glen Burnie, MD, was acquired for $17.9 million (the Account's Share). Sales Property Name Sales Date Ownership Percentage Sector Location Net Sales Price (1) Realized Gain/Loss on Sale (3) 1858 Meca Way (2) 03/01/2019 100.00% Industrial Norcross, GA $ 2.9 $ — (1) The net sales price represents the sales price, less selling expenses. (2) Property held within Colony Industrial Portfolio. (3) No realized gain or loss was realized from the sale. Loans Receivable Borrower Name Financing Date Interest Rate Sector Maturity Date Location Loan Amount (1) SCG Oakland Portfolio 03/01/2019 4.25% + LIBOR Office 03/01/2024 Oakland, CA $ 53.5 (1) Loan Amount represents the Account's mezzanine loan receivable position. Financings Property Name Financing Date Ownership Percentage Interest Rate Sector Maturity Date Location Financing Amount (1) The Theory 01/15/2019 97.00% 3.94% Apartments 01/15/2024 Raleigh, NC $ 31.3

Organization and Significant _3

Organization and Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2018
Principal Transaction Revenue [Line Items]
Independent appraisal firm, property rotation, period (at least)	3 years
Description of valuation change of real estate related assets	Also, the independent fiduciary can require additional appraisals if factors or events have occurred that could materially change a property’s value (including those identified above) and such change is not reflected in the quarterly valuation review, or otherwise to ensure that the Account is valued appropriately. The independent fiduciary must also approve any valuation change of real estate-related assets where a property’s value changed by more than 6% from the most recent independent annual appraisal, or if the value of the Account would change by more than 4% within any calendar quarter or more than 2% since the prior calendar month. When a real estate property is subject to a mortgage, the property is valued independently of the mortgage and the property and mortgage fair values are reported separately (see Valuation of Mortgage Loans Payable). The independent fiduciary reviews and approves all mortgage valuation adjustments before such adjustments are recorded by the Account. The Account continues to use the revised value for each real estate property and mortgage loan payable to calculate the Account’s daily net asset value until the next valuation review or appraisal.
Threshold percentage, property value change compared to most recent independent annual appraisal (more than)	6.00%
Threshold percentage, property value change within any calendar quarter (more than)	4.00%
Threshold percentage, property value change compared to prior calendar month (more than)	2.00%
Maximum percentage of average net assets for all account level expenses, percent (not to exceed)	2.50%
Minimum
Principal Transaction Revenue [Line Items]
Investment advisory fees, paid or received, period	1 day
Maximum
Principal Transaction Revenue [Line Items]
Investment advisory fees, paid or received, period	2 days

Related Party Transactions (Det

Related Party Transactions (Details)	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Distribution agreement, termination period	60 days
Percentage of trigger point on outstanding accumulation units, percent	45.00%

Concentration Risk (Details)

Concentration Risk (Details)	12 Months Ended
	Dec. 31, 2018
Risks and Uncertainties [Abstract]
Maximum percentage of annual contract rent of rental income (more than)	3.00%

Concentration Risk - Schedule o

Concentration Risk - Schedule of diversification of the Account's portfolio by region and property type (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Concentration Risk [Line Items]
Diversification by fair value	100.00%	100.00%
Office
Concentration Risk [Line Items]
Diversification by fair value	38.20%
Apartment
Concentration Risk [Line Items]
Diversification by fair value	24.70%
Retail
Concentration Risk [Line Items]
Diversification by fair value	19.50%
Industrial
Concentration Risk [Line Items]
Diversification by fair value	14.30%
Other
Concentration Risk [Line Items]
Diversification by fair value	3.30%
West
Concentration Risk [Line Items]
Diversification by fair value	40.10%
West | Office
Concentration Risk [Line Items]
Diversification by fair value	13.90%
West | Apartment
Concentration Risk [Line Items]
Diversification by fair value	9.60%
West | Retail
Concentration Risk [Line Items]
Diversification by fair value	7.70%
West | Industrial
Concentration Risk [Line Items]
Diversification by fair value	8.30%
West | Other
Concentration Risk [Line Items]
Diversification by fair value	0.60%
East
Concentration Risk [Line Items]
Diversification by fair value	33.40%
East | Office
Concentration Risk [Line Items]
Diversification by fair value	19.00%
East | Apartment
Concentration Risk [Line Items]
Diversification by fair value	7.50%
East | Retail
Concentration Risk [Line Items]
Diversification by fair value	3.10%
East | Industrial
Concentration Risk [Line Items]
Diversification by fair value	1.30%
East | Other
Concentration Risk [Line Items]
Diversification by fair value	2.50%
South
Concentration Risk [Line Items]
Diversification by fair value	24.10%
South | Office
Concentration Risk [Line Items]
Diversification by fair value	5.30%
South | Apartment
Concentration Risk [Line Items]
Diversification by fair value	6.60%
South | Retail
Concentration Risk [Line Items]
Diversification by fair value	7.90%
South | Industrial
Concentration Risk [Line Items]
Diversification by fair value	4.20%
South | Other
Concentration Risk [Line Items]
Diversification by fair value	0.10%
Midwest
Concentration Risk [Line Items]
Diversification by fair value	2.40%
Midwest | Office
Concentration Risk [Line Items]
Diversification by fair value	0.00%
Midwest | Apartment
Concentration Risk [Line Items]
Diversification by fair value	1.00%
Midwest | Retail
Concentration Risk [Line Items]
Diversification by fair value	0.80%
Midwest | Industrial
Concentration Risk [Line Items]
Diversification by fair value	0.50%
Midwest | Other
Concentration Risk [Line Items]
Diversification by fair value	0.10%

Leases - Schedule of future min

Leases - Schedule of future minimum rental payments for operating leases (Details) $ in Millions	Dec. 31, 2018USD ($)
Leases, Operating [Abstract]
2019	$ 535.2
2020	497.7
2021	431.5
2022	366.9
2023	307.8
Thereafter	2,701.8
Total	$ 4,840.9

Assets and Liabilities Measur_3

Assets and Liabilities Measured at Fair Value on a Recurring Basis - Schedule of fair value assets and liabilities measured on recurring basis (Details) - USD ($) $ in Millions		Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate properties		$ 15,531.1	$ 15,742.7
Marketable securities:
Real estate-related	[1]	1,415.1	1,238
Marketable securities excluding real estate		4,088.7	3,887.5
Total Investments		28,480.4	27,170
Mortgage loans payable		(2,608)	(2,238.3)
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate properties		15,531.1	15,742.7
Real estate joint ventures		6,356.6	5,860.6
Limited partnerships		175.9	142.4
Marketable securities:
Real estate-related		1,415.1	1,238
Loans receivable		913	298.8
Total Investments		28,480.4	27,170
Mortgage loans payable		(2,608)	(2,238.3)
Recurring | Government agency notes
Marketable securities:
Marketable securities excluding real estate		2,050.7	2,872.3
Recurring | United States Treasury securities
Marketable securities:
Marketable securities excluding real estate		2,038	1,015.2
Recurring | Level 1: Quoted Prices in Active Markets for Identical Assets
Marketable securities:
Real estate-related		1,415.1	1,238
Total Investments		1,415.1	1,238
Recurring | Level 2: Significant Other Observable Inputs
Marketable securities:
Total Investments		4,088.7	3,887.5
Recurring | Level 2: Significant Other Observable Inputs | Government agency notes
Marketable securities:
Marketable securities excluding real estate		2,050.7	2,872.3
Recurring | Level 2: Significant Other Observable Inputs | United States Treasury securities
Marketable securities:
Marketable securities excluding real estate		2,038	1,015.2
Recurring | Level 3: Significant Unobservable Inputs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate properties		15,531.1	15,742.7
Real estate joint ventures		6,356.6	5,860.6
Marketable securities:
Loans receivable		913	298.8
Total Investments		22,800.7	21,902.1
Mortgage loans payable		$ (2,608)	$ (2,238.3)
[1]	Includes securities loaned of $67.4 million at December 31, 2018 and $18.1 million at December 31, 2017.

Assets and Liabilities Measur_4

Assets and Liabilities Measured at Fair Value on a Recurring Basis - Schedule of fair value assets and liabilities measured on recurring basis using unobservable inputs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total realized and unrealized gains included in changes in net assets	$ 363.7	$ 311.5
Mortgage Loans Payable
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(2,238.3)	(2,332.1)
Total realized and unrealized gains included in changes in net assets	79.4	15.9
Purchases	(817.9)	(17.7)
Settlements	368.8	95.6
Ending balance	(2,608)	(2,238.3)
Real Estate Properties
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	15,742.7	15,452.8
Total realized and unrealized gains included in changes in net assets	315.8	177.5
Purchases	1,151.8	682.9
Sales	(1,679.2)	(570.5)
Ending balance	15,531.1	15,742.7
Real Estate Joint Ventures
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	5,860.6	5,622.4
Total realized and unrealized gains included in changes in net assets	116.3	123.5
Purchases	941.5	419
Settlements	(561.8)	(304.3)
Ending balance	6,356.6	5,860.6
Loans Receivable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	298.8	295.7
Total realized and unrealized gains included in changes in net assets	0.3	1.2
Purchases	939.2	1.9
Sales	(257.3)
Settlements	(68)
Ending balance	913	298.8
Total Level 3 Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	21,902.1	21,370.9
Total realized and unrealized gains included in changes in net assets	432.4	302.2
Purchases	3,032.5	1,103.8
Sales	(1,936.5)	(570.5)
Settlements	(629.8)	(304.3)
Ending balance	$ 22,800.7	$ 21,902.1

Assets and Liabilities Measur_5

Assets and Liabilities Measured at Fair Value on a Recurring Basis - Schedule of unobservable inputs related to Level 3 fair value measurements (Details) - Fair Value, Inputs, Level 3	Dec. 31, 2018	Dec. 31, 2017
Real Estate Properties and Joint Ventures | Discount Rate | Office | Income Approach—Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.055	0.055
Real Estate Properties and Joint Ventures | Discount Rate | Office | Income Approach—Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.086	0.080
Real Estate Properties and Joint Ventures | Discount Rate | Office | Income Approach—Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.065	0.065
Real Estate Properties and Joint Ventures | Discount Rate | Industrial | Income Approach—Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.053	0.055
Real Estate Properties and Joint Ventures | Discount Rate | Industrial | Income Approach—Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.089	0.089
Real Estate Properties and Joint Ventures | Discount Rate | Industrial | Income Approach—Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.068	0.068
Real Estate Properties and Joint Ventures | Discount Rate | Residential | Income Approach—Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.055	0.050
Real Estate Properties and Joint Ventures | Discount Rate | Residential | Income Approach—Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.078	0.080
Real Estate Properties and Joint Ventures | Discount Rate | Residential | Income Approach—Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.065	0.061
Real Estate Properties and Joint Ventures | Discount Rate | Retail | Income Approach—Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.050	0.050
Real Estate Properties and Joint Ventures | Discount Rate | Retail | Income Approach—Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.107	0.105
Real Estate Properties and Joint Ventures | Discount Rate | Retail | Income Approach—Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.064	0.064
Real Estate Properties and Joint Ventures | Capitalization Rate | Office | Income Approach—Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.040	0.045
Real Estate Properties and Joint Ventures | Capitalization Rate | Office | Income Approach—Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.075	0.070
Real Estate Properties and Joint Ventures | Capitalization Rate | Office | Income Approach—Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.054	0.055
Real Estate Properties and Joint Ventures | Capitalization Rate | Office | Income Approach—Direct Capitalization | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.040	0.038
Real Estate Properties and Joint Ventures | Capitalization Rate | Office | Income Approach—Direct Capitalization | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.070	0.070
Real Estate Properties and Joint Ventures | Capitalization Rate | Office | Income Approach—Direct Capitalization | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.048	0.048
Real Estate Properties and Joint Ventures | Capitalization Rate | Industrial | Income Approach—Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.044	0.045
Real Estate Properties and Joint Ventures | Capitalization Rate | Industrial | Income Approach—Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.073	0.083
Real Estate Properties and Joint Ventures | Capitalization Rate | Industrial | Income Approach—Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.055	0.055
Real Estate Properties and Joint Ventures | Capitalization Rate | Industrial | Income Approach—Direct Capitalization | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.040	0.040
Real Estate Properties and Joint Ventures | Capitalization Rate | Industrial | Income Approach—Direct Capitalization | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.070	0.075
Real Estate Properties and Joint Ventures | Capitalization Rate | Industrial | Income Approach—Direct Capitalization | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.049	0.050
Real Estate Properties and Joint Ventures | Capitalization Rate | Residential | Income Approach—Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.038	0.035
Real Estate Properties and Joint Ventures | Capitalization Rate | Residential | Income Approach—Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.068	0.065
Real Estate Properties and Joint Ventures | Capitalization Rate | Residential | Income Approach—Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.050	0.048
Real Estate Properties and Joint Ventures | Capitalization Rate | Residential | Income Approach—Direct Capitalization | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.033	0.033
Real Estate Properties and Joint Ventures | Capitalization Rate | Residential | Income Approach—Direct Capitalization | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.060	0.060
Real Estate Properties and Joint Ventures | Capitalization Rate | Residential | Income Approach—Direct Capitalization | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.045	0.043
Real Estate Properties and Joint Ventures | Capitalization Rate | Retail | Income Approach—Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.043	0.043
Real Estate Properties and Joint Ventures | Capitalization Rate | Retail | Income Approach—Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.090	0.088
Real Estate Properties and Joint Ventures | Capitalization Rate | Retail | Income Approach—Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.053	0.052
Real Estate Properties and Joint Ventures | Capitalization Rate | Retail | Income Approach—Direct Capitalization | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.033	0.038
Real Estate Properties and Joint Ventures | Capitalization Rate | Retail | Income Approach—Direct Capitalization | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.085	0.088
Real Estate Properties and Joint Ventures | Capitalization Rate | Retail | Income Approach—Direct Capitalization | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.047	0.047
Mortgage Loans Payable | Loan-to-Value Ratio | Residential | Income Approach—Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.319	0.281
Mortgage Loans Payable | Loan-to-Value Ratio | Residential | Income Approach—Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.636	0.642
Mortgage Loans Payable | Loan-to-Value Ratio | Residential | Income Approach—Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.481	0.386
Mortgage Loans Payable | Loan-to-Value Ratio | Residential | Net Present Value | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.319	0.281
Mortgage Loans Payable | Loan-to-Value Ratio | Residential | Net Present Value | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.636	0.642
Mortgage Loans Payable | Loan-to-Value Ratio | Residential | Net Present Value | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.481	0.386
Mortgage Loans Payable | Loan-to-Value Ratio | Retail | Income Approach—Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.319	0.179
Mortgage Loans Payable | Loan-to-Value Ratio | Retail | Income Approach—Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.553	0.560
Mortgage Loans Payable | Loan-to-Value Ratio | Retail | Income Approach—Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.393	0.327
Mortgage Loans Payable | Loan-to-Value Ratio | Retail | Net Present Value | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.319	0.179
Mortgage Loans Payable | Loan-to-Value Ratio | Retail | Net Present Value | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.553	0.560
Mortgage Loans Payable | Loan-to-Value Ratio | Retail | Net Present Value | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.393	0.327
Mortgage Loans Payable | Loan-to-Value Ratio | Office and Industrial | Income Approach—Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.364	0.377
Mortgage Loans Payable | Loan-to-Value Ratio | Office and Industrial | Income Approach—Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.678	0.695
Mortgage Loans Payable | Loan-to-Value Ratio | Office and Industrial | Income Approach—Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.476	0.456
Mortgage Loans Payable | Loan-to-Value Ratio | Office and Industrial | Net Present Value | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.364	0.377
Mortgage Loans Payable | Loan-to-Value Ratio | Office and Industrial | Net Present Value | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.678	0.695
Mortgage Loans Payable | Loan-to-Value Ratio | Office and Industrial | Net Present Value | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.476	0.456
Mortgage Loans Payable | Equivalency Rate | Residential | Income Approach—Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.034	0.033
Mortgage Loans Payable | Equivalency Rate | Residential | Income Approach—Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.046	0.036
Mortgage Loans Payable | Equivalency Rate | Residential | Income Approach—Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.041	0.034
Mortgage Loans Payable | Equivalency Rate | Retail | Income Approach—Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.043	0.031
Mortgage Loans Payable | Equivalency Rate | Retail | Income Approach—Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.053	0.044
Mortgage Loans Payable | Equivalency Rate | Retail | Income Approach—Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.045	0.038
Mortgage Loans Payable | Equivalency Rate | Office and Industrial | Income Approach—Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.039	0.037
Mortgage Loans Payable | Equivalency Rate | Office and Industrial | Income Approach—Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.062	0.052
Mortgage Loans Payable | Equivalency Rate | Office and Industrial | Income Approach—Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.046	0.039
Mortgage Loans Payable | Weighted Average Cost of Capital Risk Premium Multiple | Residential | Net Present Value | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	1.10	1.10
Mortgage Loans Payable | Weighted Average Cost of Capital Risk Premium Multiple | Residential | Net Present Value | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	1.40	1.50
Mortgage Loans Payable | Weighted Average Cost of Capital Risk Premium Multiple | Residential | Net Present Value | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	1.20	1.30
Mortgage Loans Payable | Weighted Average Cost of Capital Risk Premium Multiple | Retail | Net Present Value | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	1.10	1.10
Mortgage Loans Payable | Weighted Average Cost of Capital Risk Premium Multiple | Retail | Net Present Value | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	1.30	1.40
Mortgage Loans Payable | Weighted Average Cost of Capital Risk Premium Multiple | Retail | Net Present Value | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	1.20	1.20
Mortgage Loans Payable | Weighted Average Cost of Capital Risk Premium Multiple | Office and Industrial | Net Present Value | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	1.20	1.20
Mortgage Loans Payable | Weighted Average Cost of Capital Risk Premium Multiple | Office and Industrial | Net Present Value | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	1.40	1.50
Mortgage Loans Payable | Weighted Average Cost of Capital Risk Premium Multiple | Office and Industrial | Net Present Value | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	1.30	1.30
Loans Receivable | Loan-to-Value Ratio | Office, Retail and Storage | Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans Receivable	0.708	0.594
Loans Receivable | Loan-to-Value Ratio | Office, Retail and Storage | Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans Receivable	0.792	0.773
Loans Receivable | Loan-to-Value Ratio | Office, Retail and Storage | Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans Receivable	0.756	0.751
Loans Receivable | Equivalency Rate | Office, Retail and Storage | Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans Receivable	0.060	0.042
Loans Receivable | Equivalency Rate | Office, Retail and Storage | Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans Receivable	0.083	0.083
Loans Receivable | Equivalency Rate | Office, Retail and Storage | Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans Receivable	0.069	0.062

Assets and Liabilities Measur_6

Assets and Liabilities Measured at Fair Value on a Recurring Basis - Schedule of net unrealized gains included in changes in net assets attributable to investments and mortgage loans payable (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total net realized and unrealized gains included in changes in net assets	$ 363.7	$ 311.5
Mortgage Loans Payable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total realized and unrealized gains, still held, included in changes in net assets	86.2	15.9
Real Estate Properties
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total net realized and unrealized gains included in changes in net assets	282.6	185.1
Real Estate Joint Ventures
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total net realized and unrealized gains included in changes in net assets	80.8	125.2
Loans Receivable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total net realized and unrealized gains included in changes in net assets	$ 0.3	$ 1.2

Investments in Joint Ventures_2

Investments in Joint Ventures (Details)	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Minimum percentage of noncontrolling ownership interest in joint ventures, percent	33.30%
Maximum percentage of noncontrolling ownership interest in joint ventures, percent	97.00%

Investments in Joint Ventures -

Investments in Joint Ventures - Schedule of financial position of the joint ventures (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Assets
Real estate properties, at fair value	$ 16,134.1	$ 14,240.8
Other assets	460.3	337.1
Total assets	16,594.4	14,577.9
Liabilities & Equity
Mortgage notes payable and other obligations, at fair value	5,035.3	3,995.7
Other liabilities	262.5	150.7
Total liabilities	5,297.8	4,146.4
Total equity	11,296.6	10,431.5
Total liabilities and equity	$ 16,594.4	$ 14,577.9

Investments in Joint Ventures_3

Investments in Joint Ventures - Schedule of results of operations of the joint ventures (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Revenue and Expenses
Revenues	$ 950.6	$ 869.2	$ 714.6
Expenses	487.1	426.9	365
Excess of revenues over expenses	$ 463.5	$ 442.3	$ 349.6

Investments in Limited Partne_2

Investments in Limited Partnerships (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Limited Partners' Capital Account [Line Items]
Limited partnerships ownership interest fair value	$ 175.9	$ 142.4
Minimum
Limited Partners' Capital Account [Line Items]
Cost method investment, ownership percent	1.70%
Maximum
Limited Partners' Capital Account [Line Items]
Equity method investment, ownership percentage	90.00%

Loans Receivable - Scheduled of

Loans Receivable - Scheduled of loans receivable by property type (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value	$ 913	$ 298.8
Percentage	100.00%	100.00%
Office
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value	$ 512.1	$ 227
Office | Credit Concentration Risk | Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	56.20%	76.00%
Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value	$ 176.4	$ 0
Industrial | Credit Concentration Risk | Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	19.30%	0.00%
Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value	$ 101.6	$ 34.2
Retail | Credit Concentration Risk | Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	11.10%	11.40%
Storage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value	$ 63.2	$ 37.6
Storage | Credit Concentration Risk | Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	6.90%	12.60%
Apartments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value	$ 59.7	$ 0
Apartments | Credit Concentration Risk | Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	6.50%	0.00%

Loans Receivable - Schedule of

Loans Receivable - Schedule of fair values and risk ratings (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)loan	Dec. 31, 2017USD ($)
Financing Receivable, Recorded Investment [Line Items]
Number of Loans	14
Fair Value | $	$ 913	$ 298.8
Percentage	100.00%	100.00%
Number of loans collateralized by interest in a joint venture	1
BBB
Financing Receivable, Recorded Investment [Line Items]
Number of Loans	3
Fair Value | $	$ 175
BBB | Loans Receivable | Credit Concentration Risk
Financing Receivable, Recorded Investment [Line Items]
Percentage	19.20%
BB
Financing Receivable, Recorded Investment [Line Items]
Number of Loans	5
Fair Value | $	$ 561.5
BB | Loans Receivable | Credit Concentration Risk
Financing Receivable, Recorded Investment [Line Items]
Percentage	61.50%
B
Financing Receivable, Recorded Investment [Line Items]
Number of Loans	5
Fair Value | $	$ 170.2
B | Loans Receivable | Credit Concentration Risk
Financing Receivable, Recorded Investment [Line Items]
Percentage	18.60%
NR
Financing Receivable, Recorded Investment [Line Items]
Number of Loans	1
Fair Value | $	$ 6.3
NR | Loans Receivable | Credit Concentration Risk
Financing Receivable, Recorded Investment [Line Items]
Percentage	0.70%

Loans Receivable (Details)

Loans Receivable (Details)	Dec. 31, 2018loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans	14
Nonperforming Status
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans	0

Mortgage Loans Payable - Schedu

Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Principal Amount Outstanding	$ 2,688.1	$ 2,238.6
Fair Value Adjustment	(80.1)	(0.3)
Total mortgage loans payable	$ 2,608	2,238.3
Mass Court
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	2.88% paid monthly
Annual interest rate	2.88%
Principal Amount Outstanding	$ 90.2	92.1
Maturity	Sep. 1, 2019
Red Canyon at Palomino Park
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	5.34% paid monthly
Annual interest rate	5.34%
Principal Amount Outstanding	$ 27.1	27.1
Maturity	Aug. 1, 2020
Green River at Palomino Park
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	5.34% paid monthly
Annual interest rate	5.34%
Principal Amount Outstanding	$ 33.2	33.2
Maturity	Aug. 1, 2020
Blue Ridge at Palomino Park
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	5.34% paid monthly
Annual interest rate	5.34%
Principal Amount Outstanding	$ 33.4	33.4
Maturity	Aug. 1, 2020
Ashford Meadows Apartments
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	5.17% paid monthly
Annual interest rate	5.17%
Principal Amount Outstanding	$ 44.6	44.6
Maturity	Aug. 1, 2020
The Knoll
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.98% paid monthly
Annual interest rate	3.98%
Principal Amount Outstanding	$ 16.9	17.5
Maturity	Dec. 5, 2020
The Corner
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	4.66% paid monthly
Annual interest rate	4.66%
Principal Amount Outstanding	$ 0	105
Maturity	Jun. 1, 2021
Ascent at Windward
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.51% paid monthly
Annual interest rate	3.51%
Principal Amount Outstanding	$ 34.6	0
Maturity	Jan. 1, 2022
The Palatine
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	4.25% paid monthly
Annual interest rate	4.25%
Principal Amount Outstanding	$ 77.4	78.8
Maturity	Jan. 10, 2022
The Forum at Carlsbad
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	4.25% paid monthly
Annual interest rate	4.25%
Principal Amount Outstanding	$ 87.3	88.9
Maturity	Mar. 1, 2022
Fusion 1560
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.42% paid monthly
Annual interest rate	3.42%
Principal Amount Outstanding	$ 37.4	0
Maturity	Jun. 10, 2022
The Colorado
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.69% paid monthly
Annual interest rate	3.69%
Principal Amount Outstanding	$ 89.9	91.7
Maturity	Nov. 1, 2022
The Legacy at Westwood
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.69% paid monthly
Annual interest rate	3.69%
Principal Amount Outstanding	$ 45.8	46.7
Maturity	Nov. 1, 2022
Regents Court
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.69% paid monthly
Annual interest rate	3.69%
Principal Amount Outstanding	$ 38.8	39.6
Maturity	Nov. 1, 2022
Fourth & Madison | Loan A
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.75% paid monthly
Annual interest rate	3.75%
Principal Amount Outstanding	$ 198.2	200
Maturity	Jun. 1, 2023
Fourth & Madison | Loan B
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	4.17% paid monthly
Annual interest rate	4.17%
Principal Amount Outstanding	$ 90	0
Maturity	Jun. 1, 2023
1001 Pennsylvania Avenue
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.70% paid monthly
Annual interest rate	3.70%
Principal Amount Outstanding	$ 327	330
Maturity	Jun. 1, 2023
Biltmore at Midtown
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.94% paid monthly
Annual interest rate	3.94%
Principal Amount Outstanding	$ 36.4	0
Maturity	Jul. 5, 2023
Cherry Knoll
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.78% paid monthly
Annual interest rate	3.78%
Principal Amount Outstanding	$ 35.3	0
Maturity	Jul. 5, 2023
Lofts at SoDo
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.94% paid monthly
Annual interest rate	3.94%
Principal Amount Outstanding	$ 35.1	0
Maturity	Jul. 5, 2023
1401 H Street, NW
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.65% paid monthly
Annual interest rate	3.65%
Principal Amount Outstanding	$ 115	115
Maturity	Nov. 5, 2024
Circa Green Lake
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.71% paid monthly
Annual interest rate	3.71%
Principal Amount Outstanding	$ 52	0
Maturity	Mar. 5, 2025
Union - South Lake Union
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.66% paid monthly
Annual interest rate	3.66%
Principal Amount Outstanding	$ 57	0
Maturity	Mar. 5, 2025
Holly Street Village
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.65% paid monthly
Annual interest rate	3.65%
Principal Amount Outstanding	$ 81	0
Maturity	May 1, 2025
Township Apartments
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.65% paid monthly
Annual interest rate	3.65%
Principal Amount Outstanding	$ 49	0
Maturity	May 1, 2025
32 South State Street
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	4.48% paid monthly
Annual interest rate	4.48%
Principal Amount Outstanding	$ 24	24
Maturity	Jun. 6, 2025
780 Third Avenue | Loan A
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.55% paid monthly
Annual interest rate	3.55%
Principal Amount Outstanding	$ 150	150
Maturity	Aug. 1, 2025
780 Third Avenue | Loan B
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.55% paid monthly
Annual interest rate	3.55%
Principal Amount Outstanding	$ 20	20
Maturity	Aug. 1, 2025
701 Brickell Avenue
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.66% paid monthly
Annual interest rate	3.66%
Principal Amount Outstanding	$ 184	184
Maturity	Apr. 1, 2026
55 Second Street
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.74% paid monthly
Annual interest rate	3.74%
Principal Amount Outstanding	$ 137.5	137.5
Maturity	Oct. 1, 2026
1900 K Street, NW
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.93% paid monthly
Annual interest rate	3.93%
Principal Amount Outstanding	$ 163	163
Maturity	Apr. 1, 2028
501 Boylston Street
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.70% paid monthly
Annual interest rate	3.70%
Principal Amount Outstanding	$ 0	216.5
Maturity	Apr. 1, 2028
99 High Street
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	3.90% paid monthly
Annual interest rate	3.90%
Principal Amount Outstanding	$ 277	$ 0
Maturity	Mar. 1, 2030

Mortgage Loans Payable - Sche_2

Mortgage Loans Payable - Schedule of outstanding mortgage loans payable, additional information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)loan	Aug. 21, 2018	Dec. 31, 2017USD ($)
Mortgage Loans Payable [Line Items]
Principal amount outstanding	$ 2,688.1		$ 2,238.6
55 Second Street
Mortgage Loans Payable [Line Items]
Mortgage loans on real estate, number of loans | loan	3
Principal amount outstanding	$ 137.5		137.5
55 Second Street | Loan One
Mortgage Loans Payable [Line Items]
Principal amount outstanding	79
55 Second Street | Loan Two
Mortgage Loans Payable [Line Items]
Principal amount outstanding	45
55 Second Street | Loan Three
Mortgage Loans Payable [Line Items]
Principal amount outstanding	13.5
501 Boylston Street
Mortgage Loans Payable [Line Items]
Principal amount outstanding	$ 0		$ 216.5
Percentage of interest in the property sold		49.90%
Percentage of interest in the property transferred to joint venture investment		50.10%

Mortgage Loans Payable - Sche_3

Mortgage Loans Payable - Schedule of maturities of long-term debt (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
2019	$ 107.2
2020	171.7
2021	20
2022	407.7
2023	686.4
Thereafter	1,295.1
Total maturities	$ 2,688.1	$ 2,238.6

Line of Credit - Narrative (Det

Line of Credit - Narrative (Details) - Unsecured Revolving Credit Facility - Line of Credit	Sep. 20, 2018USD ($)loanterminstitution	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 500,000,000
Number of financial institutions | institution	4
Maximum borrowing capacity, per lender	$ 125,000,000
Number of extension periods | term	2
Extension period	12 months
Additional borrowing capacity	$ 250,000,000
Unused commitment fee, percentage	0.20%
Line of credit		$ 0
Eurodollar Loan
Debt Instrument [Line Items]
Minimum funding requirement	$ 5,000,000
Line of credit, term (or less)	12 months
Maximum active loan limit | loan	5
Eurodollar Loan | Minimum | Adjusted LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	0.85%
Eurodollar Loan | Maximum | Adjusted LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.05%
Alternate Base Rate Loan
Debt Instrument [Line Items]
Minimum funding requirement	$ 5,000,000
Alternate Base Rate Loan | Adjusted LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
Alternate Base Rate Loan | Federal Reserve Bank of New York
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%

Financial Highlights - Schedule

Financial Highlights - Schedule of condensed financial information for an accumulation unit of the account (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Per Accumulation Unit Data:
Rental income (in dollars per share)	$ 17.757	$ 17.132	$ 16.433	$ 15.538	$ 15.862
Real estate property level expenses and taxes (in dollars per share)	8.548	7.722	7.534	7.319	7.788
Real estate income, net (in dollars per share)	9.209	9.410	8.899	8.219	8.074
Other income (in dollars per share)	6.162	4.762	3.594	3.342	3.459
Total income (in dollars per share)	15.371	14.172	12.493	11.561	11.533
Expense charges (in dollars per share)	3.161	3.318	3.290	3.092	2.880
Investment income, net (in dollars per share)	12.210	10.854	9.203	8.469	8.653
Net realized and unrealized gain on investments and mortgage loans payable (in dollars per share)	6.877	5.839	9.660	18.911	27.868
Net increase in Accumulation Unit Value (in dollars per share)	19.087	16.693	18.863	27.380	36.521
Accumulation Unit Value:
Beginning of period (in dollars per share)	398.329	381.636	362.773	335.393	298.872
End of period (in dollars per share)	$ 417.416	$ 398.329	$ 381.636	$ 362.773	$ 335.393
Total return	4.79%	4.37%	5.20%	8.16%	12.22%
Ratios to Average net Assets:
Expenses	0.76%	0.83%	0.86%	0.86%	0.89%
Investment income, net	2.95%	2.72%	2.41%	2.37%	2.68%
Portfolio turnover rate:
Real estate properties	11.80%	2.70%	1.30%	5.70%	6.50%
Marketable securities	5.10%	5.70%	3.50%	10.00%	15.90%
Accumulation Units outstanding at end of period (millions) (in shares)	60.7	61.3	62.4	60.4	57.9
Net assets end of period (millions)	$ 25,842.6	$ 24,942.6	$ 24,304.7	$ 22,360	$ 19,829

Accumulation Units - Schedule o

Accumulation Units - Schedule of changes in the number of accumulation units outstanding (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Outstanding:
Beginning of period (in shares)	61.3	62.4	60.4
Credited for premiums (in shares)	6.5	6.6	8.2
Annuity, other periodic payments, withdrawals and death benefits (in shares)	(7.1)	(7.7)	(6.2)
End of period (in shares)	60.7	61.3	62.4

Commitments and Contingencies -

Commitments and Contingencies - Schedule of Limited Partners' Callable Commitments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Limited Partners' Capital Account [Line Items]
Callable commitments amount	$ 101	$ 32
Taconic New York City GP Fund
Limited Partners' Capital Account [Line Items]
Callable commitments amount	26	32
LCS SHIP Venture I, LLC
Limited Partners' Capital Account [Line Items]
Callable commitments amount	$ 75	$ 0

Commitments and Contingencies_2

Commitments and Contingencies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)anniversary	Dec. 31, 2017USD ($)
Commitments and Contingencies Disclosure [Abstract]
Commitment period anniversary from closing | anniversary	5
Right to close commitment period early, percentage of commitment satisfied	90.00%
Committed tenant improvements and leasing inducements amount | $	$ 83.3	$ 47.6

Subsequent Events - Schedule of

Subsequent Events - Schedule of Purchases After Period End (Details) - Subsequent Event - USD ($)	Feb. 22, 2019	Feb. 20, 2019	Jan. 15, 2019	Jan. 10, 2019	Jan. 09, 2019
Glen Lake
Subsequent Event [Line Items]
Ownership Percentage					100.00%
Net Purchase Price					$ 54,800,000
1600 Broadway
Subsequent Event [Line Items]
Ownership Percentage				100.00%
Net Purchase Price				$ 109,100,000
The Theory
Subsequent Event [Line Items]
Ownership Percentage			97.00%
Net Purchase Price			$ 63,000,000
Colony Industrial Portfolio
Subsequent Event [Line Items]
Ownership Percentage		100.00%
Net Purchase Price		$ 137,000,000
Storage Portfolio III
Subsequent Event [Line Items]
Ownership Percentage	90.00%
Net Purchase Price	$ 17,900,000
Maximum potential investment	$ 100,000,000

Subsequent Events - Schedule _2

Subsequent Events - Schedule of Sales After Period End (Details) - Subsequent Event - 1858 Meca Way $ in Millions	Mar. 01, 2019USD ($)
Subsequent Event [Line Items]
Ownership Percentage	100.00%
Net Sales Price	$ 2.9
Realized Gain/Loss on Sale	$ 0

Subsequent Events - Schedule _3

Subsequent Events - Schedule of Loan Receivables After Period End (Details) - SCG Oakland Portfolio - Subsequent Event $ in Millions	Mar. 01, 2019USD ($)
Subsequent Event [Line Items]
Loan Amount	$ 53.5
LIBOR
Subsequent Event [Line Items]
Interest Rate	4.25%

Subsequent Events - Schedule _4

Subsequent Events - Schedule of Financings After Period End (Details) - The Theory - Subsequent Event $ in Millions	Jan. 15, 2019USD ($)
Subsequent Event [Line Items]
Ownership Percentage	97.00%
The Theory-Raleigh, NC | The Theory | Mortgages
Subsequent Event [Line Items]
Ownership Percentage	97.00%
Interest Rate	3.94%
Financing Amount	$ 31.3

Subsequent Events - Marketable

Subsequent Events - Marketable Securities (Details) $ in Millions	2 Months Ended
	Feb. 28, 2019USD ($)
Subsequent Event
Subsequent Event [Line Items]
Sale, real estate-securities	$ 400