Tiaa Real Estate Account S-1 16 Mar 18 2017 FY IPO registration Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Jun. 30, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	TIAA REAL ESTATE ACCOUNT
Document Type	S1
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	946,155
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	No
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY

CONSOLIDATED STATEMENTS OF ASSE

CONSOLIDATED STATEMENTS OF ASSETS AND LIABILITIES - USD ($) shares in Millions, $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Investments, at fair value:
Real estate properties (cost: $12,972.5 and $12,818.1)		$ 15,742.7	$ 15,452.8
Real estate joint ventures and limited partnerships (cost: $4,675.3 and $4,530.4)		6,003	5,759.9
Marketable securities:
Real estate related (cost: $991.0 and $883.9)	[1]	1,238	1,081.5
Other (cost: $3,888.1 and $4,054.0)		3,887.5	4,053.8
Loans receivable (cost: $296.7 and $294.8)		298.8	295.7
Total investments (cost: $22,823.6 and $22,581.2)		27,170	26,643.7
Cash and cash equivalents		11.7	3
Due from investment manager		1	5.9
Other	[2]	270.9	332.6
TOTAL ASSETS		27,453.6	26,985.2
LIABILITIES
Mortgage loans payable, at fair value (principal outstanding: $2,238.6 and $2,316.5)		2,238.3	2,332.1
Accrued real estate property expenses		199.1	202.2
Payable for collateral for securities loaned		18.5	93
Other		55.1	53.2
TOTAL LIABILITIES		2,511	2,680.5
COMMITMENTS AND CONTINGENCIES
NET ASSETS
Accumulation Fund		24,430.8	23,813.5
Annuity Fund		511.8	491.2
TOTAL NET ASSETS		$ 24,942.6	$ 24,304.7
NUMBER OF ACCUMULATION UNITS OUTSTANDING (in shares)		61.3	62.4
NET ASSET VALUE, PER ACCUMULATION UNIT (in dollars per share)		$ 398.329	$ 381.636
[1]	Includes securities loaned of $18.1 million at December 31, 2017 and $91.2 million at December 31, 2016.
[2]	Includes cash collateral for securities loaned of $18.5 million at December 31, 2017 and $93.0 million at December 31, 2016.

CONSOLIDATED STATEMENTS OF ASS3

CONSOLIDATED STATEMENTS OF ASSETS AND LIABILITIES (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Securities loaned	$ 18.1	$ 91.2
Collateral for securities loaned	18.5	93
Real estate properties at cost	12,972.5	12,818.1
Real estate joint ventures and limited partnerships at cost	4,675.3	4,530.4
Real estate related marketable securities at cost	991	883.9
Other marketable securities at cost	3,888.1	4,054
Loan Receivable at cost	296.7	294.8
Cost of total investments	22,823.6	22,581.2
Principal outstanding on mortgage loans payable	$ 2,238.6	$ 2,316.5

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Real estate income, net
Rental income	$ 1,059.6	$ 1,009	$ 919.1
Real estate property level expenses and taxes:
Operating expenses	221.2	218.1	207.4
Real estate taxes	166.7	158.7	144.4
Interest expense	89.7	85.8	81.1
Total real estate property level expenses and taxes	477.6	462.6	432.9
Real estate income, net	582	546.4	486.2
Income from real estate joint ventures and limited partnerships	214.1	161.8	140.1
Interest	54.1	26.4	10.1
Dividends	26.3	32.5	47.5
TOTAL INVESTMENT INCOME	876.5	767.1	683.9
Expenses
Investment management charges	72	72.6	69.3
Administrative charges	59.3	62.1	56.9
Distribution charges	25.7	27.7	23.9
Mortality and expense risk charges	1.2	1.2	1.1
Liquidity guarantee charges	47	38.4	31.7
TOTAL EXPENSES	205.2	202	182.9
INVESTMENT INCOME, NET	671.3	565.1	501
Net realized gain (loss) on investments
Real estate properties	42	(6.2)	215.4
Real estate joint ventures and limited partnerships	(21.9)	0.6	167.3
Marketable securities	17.6	25.6	235.8
Net realized gain on investments	37.7	20	618.5
Net change in unrealized appreciation (depreciation) on
Real estate properties	135.5	317.5	487.2
Real estate joint ventures and limited partnerships	146.8	236.9	288.6
Marketable securities	50	30	(255.1)
Loans receivable	1.2	0.3	0.6
Mortgage loans payable	15.9	15.1	5.6
Net change in unrealized appreciation on investments and mortgage loans payable	349.4	599.8	526.9
NET REALIZED AND UNREALIZED GAIN ON INVESTMENTS AND MORTGAGE LOANS PAYABLE	387.1	619.8	1,145.4
NET INCREASE IN NET ASSETS RESULTING FROM OPERATIONS	$ 1,058.4	$ 1,184.9	$ 1,646.4

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN NET ASSETS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
FROM OPERATIONS
Investment income, net	$ 671.3	$ 565.1	$ 501
Net realized gain on investments	37.7	20	618.5
Net change in unrealized appreciation on investments and mortgage loans payable	349.4	599.8	526.9
NET INCREASE IN NET ASSETS RESULTING FROM OPERATIONS	1,058.4	1,184.9	1,646.4
FROM PARTICIPANT TRANSACTIONS
Premiums	2,561.7	3,064.2	2,852.3
Annuity payments	(43.4)	(41)	(36.7)
Withdrawals and death benefits	(2,938.8)	(2,263.4)	(1,931)
NET INCREASE (DECREASE) IN NET ASSETS RESULTING FROM PARTICIPANT TRANSACTIONS	(420.5)	759.8	884.6
NET INCREASE IN NET ASSETS	637.9	1,944.7	2,531
NET ASSETS
Beginning of period	24,304.7	22,360	19,829
End of period	$ 24,942.6	$ 24,304.7	$ 22,360

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES
Net increase in net assets resulting from operations	$ 1,058.4	$ 1,184.9	$ 1,646.4
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	(37.7)	(20)	(618.5)
Net change in unrealized appreciation on investments and mortgage loans payable	(349.4)	(599.8)	(526.9)
Purchase of real estate properties	(538.2)	(623.9)	(1,229.6)
Capital improvements on real estate properties	(130.1)	(157.2)	(167.9)
Proceeds from sale of real estate properties	525.5	251.1	442.9
Purchases of long term investments	(592)	(1,379.4)	(1,102.4)
Proceeds from long term investments	385.3	68.3	1,499.8
Increase in loans receivable	(1.9)	(194.8)	(100)
(Increase) decrease in other investments	165.9	153.6	(376.5)
Change in due to (from) investment manager	4.9	(0.2)	1.5
(Increase) decrease in other assets	61.7	(102.4)	(33.3)
Increase (decrease) in other liabilities	(72.6)	122.3	29.1
NET CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES	479.8	(1,297.5)	(535.4)
CASH FLOWS FROM FINANCING ACTIVITIES
Mortgage loan proceeds received	0	563.5	0
Payments of mortgage loans	(50.6)	(34.7)	(373.8)
Premiums	2,561.7	3,064.2	2,852.3
Annuity payments	(43.4)	(41)	(36.7)
Withdrawals and death benefits	(2,938.8)	(2,263.4)	(1,931)
NET CASH (USED IN) PROVIDED BY FINANCING ACTIVITIES	(471.1)	1,288.6	510.8
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	8.7	(8.9)	(24.6)
CASH AND CASH EQUIVALENTS
Beginning of period	3	11.9	36.5
End of period	11.7	3	11.9
SUPPLEMENTAL DISCLOSURES
Cash paid for interest	89.9	84.2	82.7
Debt assumed as part of a real estate acquisition	17.7	24	0
Loan assignment as part of a real estate disposition	45	0	200
Conversion of note receivable	$ 0	$ 0	$ 100.6

Organization and Significant Ac

Organization and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
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 capital appreciation from real estate and real estate-related investments owned by the Account. The Account holds real estate properties directly and through subsidiaries wholly-owned by TIAA for the 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). 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 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. 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 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. 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 which 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 in good faith and will from time to time seek input from the issuer or the sponsor of the investments. Since market quotations are not readily available, the limited partnership interests are valued at fair value as determined in good faith by management 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. 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 in good faith by 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. Equity and fixed income securities traded on a foreign exchange or in foreign markets are valued using their closing values under the valuation methods generally accepted in the country where traded, as of the valuation date. This value is converted to U.S. dollars at the exchange rate in effect on the valuation day. Under certain circumstances (for example, if there are significant movements in the U.S. markets and there is an expectation the securities traded on foreign markets will adjust based on such movements when the foreign markets open the next day), the Account may adjust the value of equity or fixed income securities that trade on a foreign exchange or market after the foreign exchange or market has closed. 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. Loan origination costs are expensed as incurred. Valuation of Mortgage Loans Payable (i.e. the Account as a debtor) —Mortgage loans payable are stated at fair value. The estimated fair values of mortgage loans payable are based on the amount at which the liability could be transferred to a third party exclusive of transaction costs. Mortgage loans payable are valued internally by TIAA’s internal valuation department, as reviewed by the Account’s independent fiduciary, at least quarterly based on market factors, such as market interest rates and spreads for comparable loans, the performance of the underlying collateral (such as the loan-to-value ratio and the cash flow of the underlying collateral), the liquidity for mortgage loans of similar characteristics, the maturity date of the loan and the return demands of the market. 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. Foreign Currency Transactions and Translation: Portfolio investments and other assets and liabilities denominated in foreign currencies are translated into U.S. dollars at the exchange rates prevailing at the end of the period. Purchases and sales of securities, income receipts and expense payments made in foreign currencies are translated into U.S. dollars at the exchange rates prevailing on the respective dates of the transactions. The effect of any changes in foreign currency exchange rates on portfolio investments and mortgage loans payable are included in net realized and unrealized gains and losses on real estate properties and mortgage loans payable. Net realized gains and losses on foreign currency transactions include disposition of foreign currencies, and currency gains and losses between the accrual and receipt dates of portfolio investment income and between the trade and settlement dates of portfolio investment transactions. 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 in good faith and will from time to time seek input from the issuer or the sponsor of the investments. 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 —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 with changes in fair value flowing through unrealized gain (loss). Interest income from loans receivable is recognized using the effective interest method over the expected life of the loan. All loans receivable held to date were originated directly by the Account. 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 transactions are accounted for as of the date on which the purchase or sale transactions for the real estate properties close (settlement date). The Account recognizes a realized gain on the sale of a real estate property to the extent that the contract sales price exceeds the cost-to-date of the property being sold. A realized loss occurs when the cost-to-date exceeds the sales price. 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 and Limited Partnerships 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, and 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. Income from Securities Lending: The Account may lend securities to qualified borrowers to generate additional income. When loaning securities, the Account retains the benefits of owning the securities, including the economic equivalent of dividends or interest generated by the securities. Cash collateral received for securities on loan is maintained exclusively in an interest-bearing deposit account. All income generated by the securities lending program is reflected within interest income on the Account's Consolidated Statements of Operations. 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. The Tax Cuts and Jobs Act (the “Act”) was signed into law on December 22, 2017. The Act changes existing United States tax law and includes numerous provisions that will affect businesses. The Act reduces the U.S. corporate tax rate from 35% to 21%, includes several base broadening provisions, as well as, reform to the US international tax system. The Act does not result in any material impact to the Account. Restricted Cash: The Account held $42.3 million and $45.8 million as of December 31, 2017 and 2016 , respectively, in escrow accounts for 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 Account's Consolidated Statements of Assets and Liabilities. See Note 8—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. 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 will be effective for fiscal years beginning after December 15, 2017, the Account will adopt ASU 2014-09 as of January 1, 2018 utilizing the modified retrospective adoption approach. The Account has completed its implementation analysis of ASU 2014-09 and determined it will be immaterially impacted by the adoption. In January 2016, the FASB issued ASU 2016-1 Financial Instruments (Topic 825): Recognition and Measurement of Financial Assets and Financial Liabilities (“ASU 2016-1”). This ASU amends, among other items, certain aspects of the recognition, measurement, presentation, and disclosure of financial instruments. These amendments are effective for public business entities for fiscal years and interim periods within those fiscal years beginning after December 15, 2017, and the Account plans to adopt the guidance as of January 1, 2018. Management has completed its initial scoping for the adoption of the ASU 2016-01 and does not expect the guidance to materially impact the Account. In February 2016, the FASB issued ASU 2016-2 Leases (Topic 842) (“ASU 2016-2”) 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 except in certain circumstances. The ASU also contains certain practical expedients, which the Account plans to elect, including the practical expedient not to separate lease and non-lease components whereby both components are accounted for and recognized as lease components. In January 2018, the FASB issued a proposal for comment that would allow lessors to elect a similar practical expedient by class of underlying assets to not separate non-lease components from the lease component. 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. If the exposed practical expedient is issued in its existing form, the Account expects to elect the practical expedient which 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 2016-2 and does not expect the adoption of such guidance to materially impact the Account. In August 2016, the FASB issued Accounting Standards Update 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”). ASU 2016-15 clarifies how to present cash receipts and cash payments for certain activity in the Statement of Cash Flows. These amendments are effective for public business entities within those fiscal years beginning after December 15, 2017, and interim periods within those fiscal years and should be applied using a retrospective transition method to each period presented. Management has completed its initial scoping for the adoption of the ASU 2016-15 and does not expect the adoption of such guidance to materially impact the Account. The Account plans to adopt the guidance as of January 1, 2018. In November 2016, the FASB issued Accounting Standards Update 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash ("ASU 2016-18"). The statement of cash flows should present beginning-of-period and end-of-period total amounts that include cash and restricted cash. Transfers between cash and restricted cash will no longer be presented as operating activities within the statement of cash flows. ASU 2016-18 is effectiv

Management Agreements, Arrangem

Management Agreements, Arrangements and Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Management Agreements And Arrangements [Abstract]
Management Agreements, Arrangements and Related Party Transactions	Management Agreements, Arrangements and Related Party Transactions Investment advisory services for the Account are provided by TIAA employees, under the direction of the Board and its Investment Committee, 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. TIAA and Services provide investment management, administrative and distribution services at cost. TIAA and Services receive payments from the Account on a daily basis according to formulas established each year and adjusted periodically with the objective of keeping the payments as close as possible to the Account’s expenses actually incurred. Any differences between actual expenses and the amounts paid by the Account are adjusted quarterly. TIAA also provides a liquidity guarantee to the Account, for a fee, to ensure 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. TIAA ensures sufficient funds are available for such transfer and withdrawal requests by purchasing accumulation units of the Account. In accordance with this liquidity guarantee obligation, TIAA guarantees that all participants in the Account may redeem their accumulation units at their accumulation unit value next determined after their transfer or cash withdrawal request is received in good order. Liquidity units owned by TIAA are valued in the same manner as accumulation units owned by the Account’s participants. Management believes that TIAA has the ability to meet its obligations under the liquidity guarantee. In accordance with a prohibited transaction exemption from the U.S. Department of Labor (PTE 96-76), the Account’s independent fiduciary, RERC, has certain responsibilities with respect to the Account that it has undertaken or is currently undertaking with respect to TIAA’s purchase of liquidity units, including among other things, reviewing the purchase and redemption of liquidity units by TIAA to ensure the Account uses the correct unit values. In addition, as set forth in PTE 96-76, the independent fiduciary’s responsibilities include: • establishing the percentage of total accumulation units that TIAA’s ownership should not exceed (the “trigger point”) and creating a method for changing the trigger point; • approving any adjustment of TIAA’s ownership interest in the Account and, in its discretion, requiring an adjustment if TIAA’s ownership of liquidity units reaches the trigger point; and • once the trigger point has been reached, participating in any program to reduce TIAA’s ownership in the Account by utilizing cash flow or liquid investments in the Account, or by utilizing the proceeds from asset sales. The independent fiduciary’s role in participating in any such asset sales program would include (i) participating in the selection of properties for sale, (ii) providing sales guidelines and (iii) approving those sales if, in the independent fiduciary’s opinion, such sales are desirable to reduce TIAA’s ownership of liquidity units. To the extent TIAA owns accumulation units issued pursuant to the liquidity guarantee, the independent fiduciary monitors and oversees, among other things, TIAA’s ownership interest in the Account and may require TIAA to eventually redeem some of its units, particularly when the Account has un-invested cash or liquid investments available. TIAA also receives a fee for assuming certain mortality and expense risks. 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. TIAA and Services provide certain services to the Account on an at cost basis. See Note 9—Financial Highlights for details of the expense charge and expense ratio.

Credit Risk Concentrations

Credit Risk Concentrations	12 Months Ended
	Dec. 31, 2017
Risks and Uncertainties [Abstract]
Credit Risk Concentrations	Credit Risk Concentrations Concentrations of credit risk may arise when a number of properties or tenants 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. The Account has no significant concentrations of tenants as no single tenant has annual contract rent that makes up more than 2% of the rental income of the Account. 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, 2017 : Diversification by Fair Value (1) West East South Midwest Total Office 16.1 % 20.2 % 5.6 % — % 41.9 % Apartment 8.4 % 8.0 % 3.6 % 0.9 % 20.9 % Retail 8.1 % 3.0 % 7.6 % 0.7 % 19.4 % Industrial 7.5 % 2.0 % 4.1 % 0.8 % 14.4 % Other (2) 0.6 % 2.6 % 0.1 % 0.1 % 3.4 % Total 40.7 % 35.8 % 21.0 % 2.5 % 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, 2017
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 (in millions): Years Ending December 31, 2018 $ 592.3 2019 556.9 2020 503.6 2021 426.7 2022 354.1 Thereafter 2,764.6 Total $ 5,198.2 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, 2017
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—Valuations using unadjusted quoted prices for assets traded in active markets, such as stocks listed on the New York Stock Exchange. Active markets are defined as having the following characteristics for the measured asset or liability: (i) many transactions, (ii) current prices, (iii) price quotes not varying substantially among market makers, (iv) narrow bid/ask spreads and (v) most information regarding the issuer is publicly available. Level 1 assets held by the Account are generally marketable equity securities. Level 2—Valuations for assets and liabilities traded in less active, dealer or broker markets. Fair values are primarily obtained from third party pricing services for identical or comparable assets or liabilities. Level 2 inputs for fair value measurements are inputs, other than quoted prices included within Level 1, that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include: a. Quoted prices for similar assets or liabilities in active markets; b. Quoted prices for identical or similar assets or liabilities in markets that are not active (that is, markets in which there are few transactions for the asset (or liability), the prices are not current, price quotations vary substantially either over time or among market makers (for example, some brokered markets), or in which little information is released publicly); c. Inputs other than quoted prices that are observable within the market for the asset (or liability) (for example, interest rates and yield curves, implied volatilities, prepayment speeds, loss severities, credit risks, and default rates that are observable at commonly quoted intervals); and d. Inputs that are derived principally from or corroborated by observable market data by correlation or other means (for example, market-corroborated inputs). Examples of securities which may be held by the Account and included in Level 2 include certificates of deposit, commercial paper, government agency notes, variable notes, United States Treasury securities, and debt securities. Level 3—Valuations for assets and liabilities that are derived from other valuation methodologies, including pricing models, discounted cash flow models and similar techniques, and are not based on market exchange, dealer, or broker-traded transactions. Level 3 valuations incorporate certain assumptions and projections that are not observable in the market, and require significant professional judgment in determining the fair value assigned to such assets or liabilities. Examples of Level 3 assets and liabilities which may be held by the Account from time to time include investments in real estate, investments in joint ventures, and loans receivable and payable. 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. The Account’s limited partnership investments are valued using the net asset value per share as a practical expedient, which excludes the investments from the valuation hierarchy. 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 a good faith estimate 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, 2017 and 2016 , 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 (in 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, 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 ) 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, 2016 Real estate properties $ — $ — $ 15,452.8 $ — $ 15,452.8 Real estate joint ventures — — 5,622.4 — 5,622.4 Limited partnerships — — — 137.5 137.5 Marketable securities: Real estate-related 1,081.5 — — — 1,081.5 Government agency notes — 2,308.9 — — 2,308.9 United States Treasury securities — 1,744.9 — — 1,744.9 Loans receivable — — 295.7 — 295.7 Total Investments at $ 1,081.5 $ 4,053.8 $ 21,370.9 $ 137.5 $ 26,643.7 Mortgage loans payable $ — $ — $ (2,332.1 ) $ — $ (2,332.1 ) 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, 2017 and 2016 (in millions): 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 ) Real Estate Properties Real Estate Joint Ventures Loans Receivable Total Level 3 Investments Mortgage Loans Payable For the year ended December 31, 2016 Beginning balance January 1, 2016 $ 14,606.2 $ 4,068.4 $ 100.6 $ 18,775.2 $ (1,794.4 ) Total realized and unrealized gains included in changes in net assets 311.3 242.8 0.3 554.4 15.1 Purchases (1) 786.4 1,313.6 194.8 2,294.8 (587.5 ) Sales (251.1 ) — — (251.1 ) — Settlements (2) — (2.4 ) — (2.4 ) 34.7 Ending balance December 31, 2016 $ 15,452.8 $ 5,622.4 $ 295.7 $ 21,370.9 $ (2,332.1 ) (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, 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, 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%) The following table shows quantitative information about unobservable inputs related to the Level 3 fair value measurements as of December 31, 2016 . Type Asset Valuation Unobservable Inputs Range (Weighted Real Estate Properties and Joint Ventures Office Income Approach—Discounted Cash Flow Discount Rate 5.5%–8.3% (6.5%) Terminal Capitalization Rate 4.3%–7.3% (5.5%) Income Approach—Direct Capitalization Overall Capitalization Rate 3.8%–7.0% (4.7%) Industrial Income Approach—Discounted Cash Flow Discount Rate 5.7%–8.7% (6.7%) Terminal Capitalization Rate 4.8%–8.0% (5.6%) Income Approach—Direct Capitalization Overall Capitalization Rate 4.0%–7.5% (5.0%) Residential Income Approach—Discounted Cash Flow Discount Rate 5.3%–7.3% (6.2%) Terminal Capitalization Rate 3.8%–6.0% (4.8%) Income Approach—Direct Capitalization Overall Capitalization Rate 3.3%–5.5% (4.2%) Retail Income Approach—Discounted Cash Flow Discount Rate 5.0%–10.4% (6.4%) Terminal Capitalization Rate 4.3%–8.5% (5.2%) Income Approach—Direct Capitalization Overall Capitalization Rate 3.9%–8.3% (4.7%) Mortgage Loans Payable Office and Industrial Discounted Cash Flow Loan-to-Value Ratio 35.7%–71.0% (43.4%) Equivalency Rate 3.7%–4.7% (3.9%) Net Present Value Loan-to-Value Ratio 35.7%–71.0% (43.4%) Weighted Average Cost of Capital Risk Premium Multiple 1.2–1.6 (1.3) Residential Discounted Cash Flow Loan-to-Value Ratio 29.5%–61.2% (41.4%) Equivalency Rate 2.9%–3.6% (3.3%) Net Present Value Loan-to-Value Ratio 29.5%–61.2% (41.4%) Weighted Average Cost of Capital Risk Premium Multiple 1.2–1.5 (1.3) Retail Discounted Cash Flow Loan-to-Value Ratio 18.3%–51.6% (31.3%) Equivalency Rate 2.9%–4.0% (3.5%) Net Present Value Loan-to-Value Ratio 18.3%–51.6% (31.3%) Weighted Average Cost of Capital Risk Premium Multiple 1.1–1.3 (1.2) Loans Receivable Office, Retail and Storage Discounted Cash Flow Loan-to-Value Ratio 55.6%-79.2% (75.8%) Equivalency Rate 4.2%-8.3% (6.3%) 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, 2017 and 2016 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 (in millions): Real Estate Properties Real Estate Joint Ventures Loans Receivable Total Level 3 Investments Mortgage Loans Payable For the year ended December 31, 2017 $ 185.1 $ 125.2 $ 1.2 $ 311.5 $ 15.9 For the year ended December 31, 2016 $ 314.2 $ 242.4 $ 0.3 $ 556.9 $ 15.1

Investments in Joint Ventures

Investments in Joint Ventures	12 Months Ended
	Dec. 31, 2017
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, 2017 , the Account held investments in joint ventures with ownership interest percentages that ranged from 33.3% to 97.5% . Certain joint ventures are subject to adjusted distribution percentages when earnings in the investment reach a pre-determined threshold. The fair value of the Account’s equity interest in these joint ventures was $5.9 billion and $5.6 billion at December 31, 2017 and 2016, respectively. The Account’s proportionate share of the mortgage loans payable held within the joint venture investments at fair value was $2.4 billion and $2.1 billion at December 31, 2017 and 2016 , respectively. The Account’s share in the outstanding principal of the mortgage loans payable held within the joint venture investments was $2.4 billion and $2.1 billion at December 31, 2017 and 2016 , respectively. A condensed summary of the financial position and results of operations of the combined joint ventures is shown below (in millions): December 31, 2017 2016 Assets Real estate properties, at fair value $ 14,240.8 $ 13,539.0 Other assets 337.1 316.1 Total assets $ 14,577.9 $ 13,855.1 Liabilities & Equity Mortgage notes payable and other obligations, at fair value $ 3,995.7 $ 3,452.9 Other liabilities 150.7 213.9 Total liabilities 4,146.4 3,666.8 Total equity 10,431.5 10,188.3 Total liabilities and equity $ 14,577.9 $ 13,855.1 Years ended December 31, 2017 2016 2015 Operating Revenue and Expenses Revenues $ 869.2 $ 714.6 $ 609.5 Expenses 426.9 365.0 318.6 Excess of revenues over expenses $ 442.3 $ 349.6 $ 290.9

Investments in Limited Partners

Investments in Limited Partnerships	12 Months Ended
	Dec. 31, 2017
Investments In Limited Partnerships [Abstract]
Investments in Limited Partnerships	Investments in Limited Partnerships The Account invests in limited partnerships, limited liability companies and private real estate equity investment trusts that own real estate properties and real estate related securities including mezzanine debt. The Account receives distributions from these investments based on the Account’s ownership interest percentage. At December 31, 2017 , the Account held ownership interests in three limited partnerships and one limited liability company ranging from 5.3% to 60.0% . As of December 31, 2017 and 2016 , the fair value of the Account’s ownership interest was $142.4 million and $137.5 million , respectively. As of December 31, 2017 , one of the limited partnership investments was in dissolution. Colony Realty Partners LP began liquidation in May 2014, with final dissolution anticipated during 2018. Transwestern Mezzanine Realty Partners III, LLC (“Transwestern”) may engage in liquidation activities in 2018 based on the terms of its partnership agreement. The Account may elect to sell or transfer its ownership units by giving notice and acquiring consent from the management committee of Transwestern, which requires approval by a majority of the members. Redemption of the Account’s interest in Transwestern prior to liquidation is prohibited, unless a supermajority of the members approves the redemption request. 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.

Mortgage Loans Payable

Mortgage Loans Payable	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Mortgage Loans Payable	Mortgage Loans Payable At December 31, 2017 and 2016, the Account had outstanding mortgage loans payable secured by the following properties (in millions): Property Interest Rate and Payment Frequency (2) Principal Amounts Outstanding as of December 31, Maturity 2017 2016 The Legend at Kierland (4)(5) 4.97% paid monthly $ — $ 21.8 August 1, 2017 The Tradition at Kierland (4)(5) 4.97% paid monthly — 25.8 August 1, 2017 Mass Court (1)(4) 2.88% paid monthly 92.1 92.6 September 1, 2019 Red Canyon at Palomino Park (4)(6) 5.34% paid monthly 27.1 27.1 August 1, 2020 Green River at Palomino Park (4)(6) 5.34% paid monthly 33.2 33.2 August 1, 2020 Blue Ridge at Palomino Park (4)(6) 5.34% paid monthly 33.4 33.4 August 1, 2020 Ashford Meadows Apartments (4) 5.17% paid monthly 44.6 44.6 August 1, 2020 The Knoll (1)(4) 3.98% paid monthly 17.5 — December 5, 2020 The Corner (4) 4.66% paid monthly 105.0 105.0 June 1, 2021 The Palatine (1)(4) 4.25% paid monthly 78.8 80.0 January 10, 2022 The Forum at Carlsbad (1)(4) 4.25% paid monthly 88.9 90.0 March 1, 2022 The Colorado (4) 3.69% paid monthly 91.7 91.7 November 1, 2022 The Legacy at Westwood (1)(4) 3.69% paid monthly 46.7 46.7 November 1, 2022 Regents Court (1)(4) 3.69% paid monthly 39.6 39.6 November 1, 2022 The Caruth (4)(8) 3.69% paid monthly — 45.0 November 1, 2022 Fourth & Madison (4) 3.75% paid monthly 200.0 200.0 June 1, 2023 1001 Pennsylvania Avenue 3.70% paid monthly 330.0 330.0 June 1, 2023 1401 H Street NW (4) 3.65% paid monthly 115.0 115.0 November 5, 2024 32 South State Street (4) 4.48% paid monthly 24.0 24.0 June 6, 2025 780 Third Avenue (4) 3.55% paid monthly 150.0 150.0 August 1, 2025 780 Third Avenue (4) 3.55% paid monthly 20.0 20.0 August 1, 2025 701 Brickell Avenue (4) 3.66% paid monthly 184.0 184.0 April 1, 2026 55 Second Street (4)(7) 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 (4) 3.70% paid monthly 216.5 216.5 April 1, 2028 Total Principal Outstanding 2,238.6 2,316.5 Fair Value Adjustment (3) (0.3 ) 15.6 Total mortgage loans payable $ 2,238.3 $ 2,332.1 (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) These properties are each owned by separate wholly-owned subsidiaries of TIAA for benefit of the Account. (5) Mortgage loans on the individual properties in the Kierland Apartment Portfolio were paid off on May 1, 2017. (6) Represents mortgage loans on these individual properties which are held within the Palomino Park portfolio. (7) 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 . (8) This mortgage loan was assumed by the Purchaser of the property, which was sold on November 13, 2017. Principal payment schedule on mortgage loans payable as of December 31, 2017 was as follows (in millions): Amount 2018 $ 13.7 2019 107.2 2020 171.7 2021 125.0 2022 335.7 Thereafter 1,485.3 Total maturities $ 2,238.6

Financial Highlights

Financial Highlights	12 Months Ended
	Dec. 31, 2017
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, 2017 2016 2015 2014 2013 Per Accumulation Unit Data: Rental income $ 17.132 $ 16.433 $ 15.538 $ 15.862 $ 15.313 Real estate property level expenses and taxes 7.722 7.534 7.319 7.788 8.112 Real estate income, net 9.410 8.899 8.219 8.074 7.201 Other income 4.762 3.594 3.342 3.459 2.759 Total income 14.172 12.493 11.561 11.533 9.960 Expense charges (1) 3.318 3.290 3.092 2.880 2.672 Investment income, net 10.854 9.203 8.469 8.653 7.288 Net realized and unrealized gain on investments and mortgage loans payable 5.839 9.660 18.911 27.868 19.015 Net increase in Accumulation Unit Value 16.693 18.863 27.380 36.521 26.303 Accumulation Unit Value: Beginning of period 381.636 362.773 335.393 298.872 272.569 End of period $ 398.329 $ 381.636 $ 362.773 $ 335.393 $ 298.872 Total return 4.37 % 5.20 % 8.16 % 12.22 % 9.65 % Ratios to Average net Assets: Expenses (1) 0.83 % 0.86 % 0.86 % 0.89 % 0.92 % Investment income, net 2.72 % 2.41 % 2.37 % 2.68 % 2.50 % Portfolio turnover rate: Real estate properties (2) 2.7 % 1.3 % 5.7 % 6.5 % 2.1 % Marketable securities (3) 5.7 % 3.5 % 10.0 % 15.9 % 8.4 % Accumulation Units outstanding at end of period (in millions): 61.3 62.4 60.4 57.9 55.3 Net assets end of period (in millions) $ 24,942.6 $ 24,304.7 $ 22,360.0 $ 19,829.0 $ 16,907.9 (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, 2017
Accumulated Units Disclosure [Abstract]
Accumulation Units	Accumulation Units Changes in the number of Accumulation Units outstanding were as follows (in millions): Years ended December 31, 2017 2016 2015 Outstanding: Beginning of period 62.4 60.4 57.9 Credited for premiums 6.6 8.2 8.1 Annuity, other periodic payments, withdrawals and death benefits (7.7 ) (6.2 ) (5.6 ) End of period 61.3 62.4 60.4

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Commitments —The Account had $32.0 million and $39.0 million of outstanding immediately callable commitments to purchase additional interests in its limited partnership investments as of December 31, 2017 and 2016 , respectively. The commitment at December 31, 2017 is related to the Taconic New York City GP Fund, LP, in which the Account has entered into an agreement to provide funding. As of December 31, 2017 , $13.0 million of the original $45.0 million commitment has been funded. Once the remaining commitment is funded, the Account anticipates holding a 60% - 90% interest in the fund. The Account has committed a total of $47.6 million and $38.8 million as of December 31, 2017 and 2016 , 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 annual 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.

Securities Lending

Securities Lending	12 Months Ended
	Dec. 31, 2017
Brokers and Dealers [Abstract]
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 Account's Consolidated Statements of Assets and Liabilities. As of December 31, 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 Account's 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.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Purchases 30700 Russell Ranch—Westlake Village, CA On January 4, 2018, the Account purchased an office property located in Westlake Village, California for $32.8 million . Carrington Park—Plano, TX On February 22, 2018, the Account purchased an apartment property located in Plano, Texas for $64.2 million . Churchill on the Park—Dallas, TX On March 1, 2018, the Account purchased an apartment property located in Dallas, Texas for $71.2 million . Sales Urban Centre—Tampa, FL On March 8, 2018, the Account sold an office property located in Tampa, Florida for a net sales price of $141.1 million , realizing a loss of $12.1 million from the sale, the majority of which has been previously recognized as unrealized losses in the Account’s Consolidated Statements of Operations. The Account’s cost basis in the property at the date of the sale was $153.2 million . Loans Receivable Aspen Lake Office Portfolio —Austin, TX On March 2, 2018, the Account entered into a $20.0 million mezzanine loan receivable position secured by Borrower's ownership interest in Aspen Lake Office Portfolio. The loan has an interest rate of 8.25% and is interest only through maturity. The loan matures on March 10, 2028. Financings Storage Portfolio I—Various, U.S.A. On February 2, 2018, Storage Portfolio I, LLC joint venture investment, in which the Account holds a 66.02% interest, refinanced a mortgage loan that is secured with a portfolio of storage properties located throughout the United States.The mortgage loan now has an outstanding principal balance of $151.2 million . The debt has an interest rate of 4.5325% , maturing March 1, 2028 and is interest only. Circa Green Lake—Seattle, WA On February 21, 2018, the Account entered into a new mortgage loan with a principal amount of $52.0 million , secured by an apartment property investment located in Seattle, Washington. The debt has an interest rate of 3.710% , maturing March 5, 2025 and is interest only. Union - South Lake Union—Seattle, WA On February 21, 2018, the Account entered into a new mortgage loan with a principal amount of $57.0 million , secured by an apartment property investment located in Seattle, Washington. The debt has an interest rate of 3.660% , maturing March 5, 2025 and is interest only. 99 High Street—Boston, MA On February 22, 2018, the Account entered into a new mortgage loan with a principal amount of $277.0 million , secured by an office property investment located in Boston, Massachusetts. The debt has an interest rate of 3.900% , maturing March 1, 2030 and is interest only. Marketable Securities On February 22, 2018, the Account purchased $100.0 million of real estate-related securities. Other Storage Portfolio I—Various, U.S.A. On February 2, 2018, the Account restructured its Storage Portfolio I, LLC joint venture, which holds a portfolio of storage properties across the United States, reducing the Account's interest in the joint venture to 66.02% .

Organization and Significant 20

Organization and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
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 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. 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 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. 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 which 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 in good faith and will from time to time seek input from the issuer or the sponsor of the investments. Since market quotations are not readily available, the limited partnership interests are valued at fair value as determined in good faith by management 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. 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 in good faith by 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. Equity and fixed income securities traded on a foreign exchange or in foreign markets are valued using their closing values under the valuation methods generally accepted in the country where traded, as of the valuation date. This value is converted to U.S. dollars at the exchange rate in effect on the valuation day. Under certain circumstances (for example, if there are significant movements in the U.S. markets and there is an expectation the securities traded on foreign markets will adjust based on such movements when the foreign markets open the next day), the Account may adjust the value of equity or fixed income securities that trade on a foreign exchange or market after the foreign exchange or market has closed. 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. Loan origination costs are expensed as incurred. Valuation of Mortgage Loans Payable (i.e. the Account as a debtor) —Mortgage loans payable are stated at fair value. The estimated fair values of mortgage loans payable are based on the amount at which the liability could be transferred to a third party exclusive of transaction costs. Mortgage loans payable are valued internally by TIAA’s internal valuation department, as reviewed by the Account’s independent fiduciary, at least quarterly based on market factors, such as market interest rates and spreads for comparable loans, the performance of the underlying collateral (such as the loan-to-value ratio and the cash flow of the underlying collateral), the liquidity for mortgage loans of similar characteristics, the maturity date of the loan and the return demands of the market.
Foreign Currency Transactions and Translation	Foreign Currency Transactions and Translation: Portfolio investments and other assets and liabilities denominated in foreign currencies are translated into U.S. dollars at the exchange rates prevailing at the end of the period. Purchases and sales of securities, income receipts and expense payments made in foreign currencies are translated into U.S. dollars at the exchange rates prevailing on the respective dates of the transactions. The effect of any changes in foreign currency exchange rates on portfolio investments and mortgage loans payable are included in net realized and unrealized gains and losses on real estate properties and mortgage loans payable. Net realized gains and losses on foreign currency transactions include disposition of foreign currencies, and currency gains and losses between the accrual and receipt dates of portfolio investment income and between the trade and settlement dates of portfolio investment transactions.
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 in good faith and will from time to time seek input from the issuer or the sponsor of the investments. 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 —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 with changes in fair value flowing through unrealized gain (loss). Interest income from loans receivable is recognized using the effective interest method over the expected life of the loan. All loans receivable held to date were originated directly by the Account. 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 transactions are accounted for as of the date on which the purchase or sale transactions for the real estate properties close (settlement date). The Account recognizes a realized gain on the sale of a real estate property to the extent that the contract sales price exceeds the cost-to-date of the property being sold. A realized loss occurs when the cost-to-date exceeds the sales price. 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 and Limited Partnerships 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, and 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.
Income from Securities Lending	Income from Securities Lending: The Account may lend securities to qualified borrowers to generate additional income. When loaning securities, the Account retains the benefits of owning the securities, including the economic equivalent of dividends or interest generated by the securities. Cash collateral received for securities on loan is maintained exclusively in an interest-bearing deposit account. All income generated by the securities lending program is reflected within interest income on the Account's Consolidated Statements of Operations.
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 $42.3 million and $45.8 million as of December 31, 2017 and 2016 , respectively, in escrow accounts for 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 Account's 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.
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 will be effective for fiscal years beginning after December 15, 2017, the Account will adopt ASU 2014-09 as of January 1, 2018 utilizing the modified retrospective adoption approach. The Account has completed its implementation analysis of ASU 2014-09 and determined it will be immaterially impacted by the adoption. In January 2016, the FASB issued ASU 2016-1 Financial Instruments (Topic 825): Recognition and Measurement of Financial Assets and Financial Liabilities (“ASU 2016-1”). This ASU amends, among other items, certain aspects of the recognition, measurement, presentation, and disclosure of financial instruments. These amendments are effective for public business entities for fiscal years and interim periods within those fiscal years beginning after December 15, 2017, and the Account plans to adopt the guidance as of January 1, 2018. Management has completed its initial scoping for the adoption of the ASU 2016-01 and does not expect the guidance to materially impact the Account. In February 2016, the FASB issued ASU 2016-2 Leases (Topic 842) (“ASU 2016-2”) 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 except in certain circumstances. The ASU also contains certain practical expedients, which the Account plans to elect, including the practical expedient not to separate lease and non-lease components whereby both components are accounted for and recognized as lease components. In January 2018, the FASB issued a proposal for comment that would allow lessors to elect a similar practical expedient by class of underlying assets to not separate non-lease components from the lease component. 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. If the exposed practical expedient is issued in its existing form, the Account expects to elect the practical expedient which 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 2016-2 and does not expect the adoption of such guidance to materially impact the Account. In August 2016, the FASB issued Accounting Standards Update 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”). ASU 2016-15 clarifies how to present cash receipts and cash payments for certain activity in the Statement of Cash Flows. These amendments are effective for public business entities within those fiscal years beginning after December 15, 2017, and interim periods within those fiscal years and should be applied using a retrospective transition method to each period presented. Management has completed its initial scoping for the adoption of the ASU 2016-15 and does not expect the adoption of such guidance to materially impact the Account. The Account plans to adopt the guidance as of January 1, 2018. In November 2016, the FASB issued Accounting Standards Update 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash ("ASU 2016-18"). The statement of cash flows should present beginning-of-period and end-of-period total amounts that include cash and restricted cash. Transfers between cash and restricted cash will no longer be presented as operating activities within the statement of cash flows. ASU 2016-18 is effective for annual financial statements issued for fiscal years beginning after December 15, 2017 and should be applied using a retrospective transition method to each period presented. Management expects that the impact of ASU 2016-18 will require modification to the presentation of restricted cash on the Account's Consolidated Statements of Cash Flows. The Account plans to adopt the guidance as of January 1, 2018. In January 2017, the FASB issued Accounting Standard Update 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business ("ASU 2017-01"). ASU 2017-01 provides guidance for evaluating whether a set of transferred assets and activities is a business, which may result in certain real estate acquisitions being accounted for as asset acquisitions rather than business combinations. ASU 2017-01 will be effective for fiscal years beginning after December 15, 2017, however, this guidance will not impact the Account. In March 2017, the FASB issued ASU 2017-05, Other Income-Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets. The amendments in ASU 2017-05 clarify the scope and application of ASC 610-20 on the sale or transfer of nonfinancial assets and in substance nonfinancial assets to noncustomers, including partial sales. ASU 2017-05 is effective for public business entities for annual periods beginning after December 15, 2017, including interim periods within those annual periods. The amendments may be either retrospectively applied to each period presented within the financial statements or by a cumulative-effect adjustment to retained earnings or net assets as of the beginning of the fiscal year of adoption. The Account will elect the modified retrospective approach upon adoption. Management has completed its initial scoping for the adoption of the ASU 2017-05 and does not expect the guidance to materially impact the Account. The Account plans to adopt the guidance as of January 1, 2018.

Credit Risk Concentrations (Tab

Credit Risk Concentrations (Tables)	12 Months Ended
	Dec. 31, 2017
Risks and Uncertainties [Abstract]
Schedules of Concentration of Risk, by Risk Factor	The following table represents the diversification of the Account’s portfolio by region and property type as of December 31, 2017 : Diversification by Fair Value (1) West East South Midwest Total Office 16.1 % 20.2 % 5.6 % — % 41.9 % Apartment 8.4 % 8.0 % 3.6 % 0.9 % 20.9 % Retail 8.1 % 3.0 % 7.6 % 0.7 % 19.4 % Industrial 7.5 % 2.0 % 4.1 % 0.8 % 14.4 % Other (2) 0.6 % 2.6 % 0.1 % 0.1 % 3.4 % Total 40.7 % 35.8 % 21.0 % 2.5 % 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, 2017
Leases, Operating [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	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 (in millions): Years Ending December 31, 2018 $ 592.3 2019 556.9 2020 503.6 2021 426.7 2022 354.1 Thereafter 2,764.6 Total $ 5,198.2

Assets and Liabilities Measur23

Assets and Liabilities Measured at Fair Value on a Recurring Basis (Tables)	12 Months Ended
	Dec. 31, 2017
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, 2017 and 2016 , 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 (in 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, 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 ) 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, 2016 Real estate properties $ — $ — $ 15,452.8 $ — $ 15,452.8 Real estate joint ventures — — 5,622.4 — 5,622.4 Limited partnerships — — — 137.5 137.5 Marketable securities: Real estate-related 1,081.5 — — — 1,081.5 Government agency notes — 2,308.9 — — 2,308.9 United States Treasury securities — 1,744.9 — — 1,744.9 Loans receivable — — 295.7 — 295.7 Total Investments at $ 1,081.5 $ 4,053.8 $ 21,370.9 $ 137.5 $ 26,643.7 Mortgage loans payable $ — $ — $ (2,332.1 ) $ — $ (2,332.1 )
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, 2017 and 2016 (in millions): 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 ) Real Estate Properties Real Estate Joint Ventures Loans Receivable Total Level 3 Investments Mortgage Loans Payable For the year ended December 31, 2016 Beginning balance January 1, 2016 $ 14,606.2 $ 4,068.4 $ 100.6 $ 18,775.2 $ (1,794.4 ) Total realized and unrealized gains included in changes in net assets 311.3 242.8 0.3 554.4 15.1 Purchases (1) 786.4 1,313.6 194.8 2,294.8 (587.5 ) Sales (251.1 ) — — (251.1 ) — Settlements (2) — (2.4 ) — (2.4 ) 34.7 Ending balance December 31, 2016 $ 15,452.8 $ 5,622.4 $ 295.7 $ 21,370.9 $ (2,332.1 ) (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, 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, 2017 and 2016 (in millions): 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 ) Real Estate Properties Real Estate Joint Ventures Loans Receivable Total Level 3 Investments Mortgage Loans Payable For the year ended December 31, 2016 Beginning balance January 1, 2016 $ 14,606.2 $ 4,068.4 $ 100.6 $ 18,775.2 $ (1,794.4 ) Total realized and unrealized gains included in changes in net assets 311.3 242.8 0.3 554.4 15.1 Purchases (1) 786.4 1,313.6 194.8 2,294.8 (587.5 ) Sales (251.1 ) — — (251.1 ) — Settlements (2) — (2.4 ) — (2.4 ) 34.7 Ending balance December 31, 2016 $ 15,452.8 $ 5,622.4 $ 295.7 $ 21,370.9 $ (2,332.1 ) (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, 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, 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%) The following table shows quantitative information about unobservable inputs related to the Level 3 fair value measurements as of December 31, 2016 . Type Asset Valuation Unobservable Inputs Range (Weighted Real Estate Properties and Joint Ventures Office Income Approach—Discounted Cash Flow Discount Rate 5.5%–8.3% (6.5%) Terminal Capitalization Rate 4.3%–7.3% (5.5%) Income Approach—Direct Capitalization Overall Capitalization Rate 3.8%–7.0% (4.7%) Industrial Income Approach—Discounted Cash Flow Discount Rate 5.7%–8.7% (6.7%) Terminal Capitalization Rate 4.8%–8.0% (5.6%) Income Approach—Direct Capitalization Overall Capitalization Rate 4.0%–7.5% (5.0%) Residential Income Approach—Discounted Cash Flow Discount Rate 5.3%–7.3% (6.2%) Terminal Capitalization Rate 3.8%–6.0% (4.8%) Income Approach—Direct Capitalization Overall Capitalization Rate 3.3%–5.5% (4.2%) Retail Income Approach—Discounted Cash Flow Discount Rate 5.0%–10.4% (6.4%) Terminal Capitalization Rate 4.3%–8.5% (5.2%) Income Approach—Direct Capitalization Overall Capitalization Rate 3.9%–8.3% (4.7%) Mortgage Loans Payable Office and Industrial Discounted Cash Flow Loan-to-Value Ratio 35.7%–71.0% (43.4%) Equivalency Rate 3.7%–4.7% (3.9%) Net Present Value Loan-to-Value Ratio 35.7%–71.0% (43.4%) Weighted Average Cost of Capital Risk Premium Multiple 1.2–1.6 (1.3) Residential Discounted Cash Flow Loan-to-Value Ratio 29.5%–61.2% (41.4%) Equivalency Rate 2.9%–3.6% (3.3%) Net Present Value Loan-to-Value Ratio 29.5%–61.2% (41.4%) Weighted Average Cost of Capital Risk Premium Multiple 1.2–1.5 (1.3) Retail Discounted Cash Flow Loan-to-Value Ratio 18.3%–51.6% (31.3%) Equivalency Rate 2.9%–4.0% (3.5%) Net Present Value Loan-to-Value Ratio 18.3%–51.6% (31.3%) Weighted Average Cost of Capital Risk Premium Multiple 1.1–1.3 (1.2) Loans Receivable Office, Retail and Storage Discounted Cash Flow Loan-to-Value Ratio 55.6%-79.2% (75.8%) Equivalency Rate 4.2%-8.3% (6.3%)
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 (in millions): Real Estate Properties Real Estate Joint Ventures Loans Receivable Total Level 3 Investments Mortgage Loans Payable For the year ended December 31, 2017 $ 185.1 $ 125.2 $ 1.2 $ 311.5 $ 15.9 For the year ended December 31, 2016 $ 314.2 $ 242.4 $ 0.3 $ 556.9 $ 15.1

Investments in Joint Ventures (

Investments in Joint Ventures (Tables)	12 Months Ended
	Dec. 31, 2017
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 (in millions): December 31, 2017 2016 Assets Real estate properties, at fair value $ 14,240.8 $ 13,539.0 Other assets 337.1 316.1 Total assets $ 14,577.9 $ 13,855.1 Liabilities & Equity Mortgage notes payable and other obligations, at fair value $ 3,995.7 $ 3,452.9 Other liabilities 150.7 213.9 Total liabilities 4,146.4 3,666.8 Total equity 10,431.5 10,188.3 Total liabilities and equity $ 14,577.9 $ 13,855.1
Schedule of Results of Operations of the Joint Venture	Years ended December 31, 2017 2016 2015 Operating Revenue and Expenses Revenues $ 869.2 $ 714.6 $ 609.5 Expenses 426.9 365.0 318.6 Excess of revenues over expenses $ 442.3 $ 349.6 $ 290.9

Mortgage Loans Payable (Tables)

Mortgage Loans Payable (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Outstanding Mortgage Loans Payable Secured by Properties	At December 31, 2017 and 2016, the Account had outstanding mortgage loans payable secured by the following properties (in millions): Property Interest Rate and Payment Frequency (2) Principal Amounts Outstanding as of December 31, Maturity 2017 2016 The Legend at Kierland (4)(5) 4.97% paid monthly $ — $ 21.8 August 1, 2017 The Tradition at Kierland (4)(5) 4.97% paid monthly — 25.8 August 1, 2017 Mass Court (1)(4) 2.88% paid monthly 92.1 92.6 September 1, 2019 Red Canyon at Palomino Park (4)(6) 5.34% paid monthly 27.1 27.1 August 1, 2020 Green River at Palomino Park (4)(6) 5.34% paid monthly 33.2 33.2 August 1, 2020 Blue Ridge at Palomino Park (4)(6) 5.34% paid monthly 33.4 33.4 August 1, 2020 Ashford Meadows Apartments (4) 5.17% paid monthly 44.6 44.6 August 1, 2020 The Knoll (1)(4) 3.98% paid monthly 17.5 — December 5, 2020 The Corner (4) 4.66% paid monthly 105.0 105.0 June 1, 2021 The Palatine (1)(4) 4.25% paid monthly 78.8 80.0 January 10, 2022 The Forum at Carlsbad (1)(4) 4.25% paid monthly 88.9 90.0 March 1, 2022 The Colorado (4) 3.69% paid monthly 91.7 91.7 November 1, 2022 The Legacy at Westwood (1)(4) 3.69% paid monthly 46.7 46.7 November 1, 2022 Regents Court (1)(4) 3.69% paid monthly 39.6 39.6 November 1, 2022 The Caruth (4)(8) 3.69% paid monthly — 45.0 November 1, 2022 Fourth & Madison (4) 3.75% paid monthly 200.0 200.0 June 1, 2023 1001 Pennsylvania Avenue 3.70% paid monthly 330.0 330.0 June 1, 2023 1401 H Street NW (4) 3.65% paid monthly 115.0 115.0 November 5, 2024 32 South State Street (4) 4.48% paid monthly 24.0 24.0 June 6, 2025 780 Third Avenue (4) 3.55% paid monthly 150.0 150.0 August 1, 2025 780 Third Avenue (4) 3.55% paid monthly 20.0 20.0 August 1, 2025 701 Brickell Avenue (4) 3.66% paid monthly 184.0 184.0 April 1, 2026 55 Second Street (4)(7) 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 (4) 3.70% paid monthly 216.5 216.5 April 1, 2028 Total Principal Outstanding 2,238.6 2,316.5 Fair Value Adjustment (3) (0.3 ) 15.6 Total mortgage loans payable $ 2,238.3 $ 2,332.1 (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) These properties are each owned by separate wholly-owned subsidiaries of TIAA for benefit of the Account. (5) Mortgage loans on the individual properties in the Kierland Apartment Portfolio were paid off on May 1, 2017. (6) Represents mortgage loans on these individual properties which are held within the Palomino Park portfolio. (7) 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 . (8) This mortgage loan was assumed by the Purchaser of the property, which was sold on November 13, 2017.
Schedule of Maturities of Long-term Debt	Principal payment schedule on mortgage loans payable as of December 31, 2017 was as follows (in millions): Amount 2018 $ 13.7 2019 107.2 2020 171.7 2021 125.0 2022 335.7 Thereafter 1,485.3 Total maturities $ 2,238.6

Financial Highlights (Tables)

Financial Highlights (Tables)	12 Months Ended
	Dec. 31, 2017
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, 2017 2016 2015 2014 2013 Per Accumulation Unit Data: Rental income $ 17.132 $ 16.433 $ 15.538 $ 15.862 $ 15.313 Real estate property level expenses and taxes 7.722 7.534 7.319 7.788 8.112 Real estate income, net 9.410 8.899 8.219 8.074 7.201 Other income 4.762 3.594 3.342 3.459 2.759 Total income 14.172 12.493 11.561 11.533 9.960 Expense charges (1) 3.318 3.290 3.092 2.880 2.672 Investment income, net 10.854 9.203 8.469 8.653 7.288 Net realized and unrealized gain on investments and mortgage loans payable 5.839 9.660 18.911 27.868 19.015 Net increase in Accumulation Unit Value 16.693 18.863 27.380 36.521 26.303 Accumulation Unit Value: Beginning of period 381.636 362.773 335.393 298.872 272.569 End of period $ 398.329 $ 381.636 $ 362.773 $ 335.393 $ 298.872 Total return 4.37 % 5.20 % 8.16 % 12.22 % 9.65 % Ratios to Average net Assets: Expenses (1) 0.83 % 0.86 % 0.86 % 0.89 % 0.92 % Investment income, net 2.72 % 2.41 % 2.37 % 2.68 % 2.50 % Portfolio turnover rate: Real estate properties (2) 2.7 % 1.3 % 5.7 % 6.5 % 2.1 % Marketable securities (3) 5.7 % 3.5 % 10.0 % 15.9 % 8.4 % Accumulation Units outstanding at end of period (in millions): 61.3 62.4 60.4 57.9 55.3 Net assets end of period (in millions) $ 24,942.6 $ 24,304.7 $ 22,360.0 $ 19,829.0 $ 16,907.9 (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, 2017
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 (in millions): Years ended December 31, 2017 2016 2015 Outstanding: Beginning of period 62.4 60.4 57.9 Credited for premiums 6.6 8.2 8.1 Annuity, other periodic payments, withdrawals and death benefits (7.7 ) (6.2 ) (5.6 ) End of period 61.3 62.4 60.4

Organization and Significant 28

Organization and Significant Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
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%
Restricted cash and cash equivalents	$ 42.3	$ 45.8
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

Management Agreements, Arrang29

Management Agreements, Arrangements and Related Party Transactions (Details)	12 Months Ended
	Dec. 31, 2017
Management Agreements And Arrangements [Abstract]
Distribution agreement, termination period (in days)	60 days
Percentage of trigger point on outstanding accumulation units, percent	45.00%

Credit Risk Concentrations (Det

Credit Risk Concentrations (Details)	12 Months Ended
	Dec. 31, 2017
Risks and Uncertainties [Abstract]
Maximum percentage of annual contract rent of rental income (more than)	2.00%

Credit Risk Concentrations - Sc

Credit Risk Concentrations - Schedule of diversification of the Account's portfolio by region and property type (Details)	12 Months Ended
	Dec. 31, 2017
Concentration Risk [Line Items]
Diversification by fair value	100.00%
Office
Concentration Risk [Line Items]
Diversification by fair value	41.90%
Apartment
Concentration Risk [Line Items]
Diversification by fair value	20.90%
Retail
Concentration Risk [Line Items]
Diversification by fair value	19.40%
Industrial
Concentration Risk [Line Items]
Diversification by fair value	14.40%
Other
Concentration Risk [Line Items]
Diversification by fair value	3.40%
West
Concentration Risk [Line Items]
Diversification by fair value	40.70%
West | Office
Concentration Risk [Line Items]
Diversification by fair value	16.10%
West | Apartment
Concentration Risk [Line Items]
Diversification by fair value	8.40%
West | Retail
Concentration Risk [Line Items]
Diversification by fair value	8.10%
West | Industrial
Concentration Risk [Line Items]
Diversification by fair value	7.50%
West | Other
Concentration Risk [Line Items]
Diversification by fair value	0.60%
East
Concentration Risk [Line Items]
Diversification by fair value	35.80%
East | Office
Concentration Risk [Line Items]
Diversification by fair value	20.20%
East | Apartment
Concentration Risk [Line Items]
Diversification by fair value	8.00%
East | Retail
Concentration Risk [Line Items]
Diversification by fair value	3.00%
East | Industrial
Concentration Risk [Line Items]
Diversification by fair value	2.00%
East | Other
Concentration Risk [Line Items]
Diversification by fair value	2.60%
South
Concentration Risk [Line Items]
Diversification by fair value	21.00%
South | Office
Concentration Risk [Line Items]
Diversification by fair value	5.60%
South | Apartment
Concentration Risk [Line Items]
Diversification by fair value	3.60%
South | Retail
Concentration Risk [Line Items]
Diversification by fair value	7.60%
South | Industrial
Concentration Risk [Line Items]
Diversification by fair value	4.10%
South | Other
Concentration Risk [Line Items]
Diversification by fair value	0.10%
Midwest
Concentration Risk [Line Items]
Diversification by fair value	2.50%
Midwest | Office
Concentration Risk [Line Items]
Diversification by fair value	0.00%
Midwest | Apartment
Concentration Risk [Line Items]
Diversification by fair value	0.90%
Midwest | Retail
Concentration Risk [Line Items]
Diversification by fair value	0.70%
Midwest | Industrial
Concentration Risk [Line Items]
Diversification by fair value	0.80%
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, 2017USD ($)
Leases, Operating [Abstract]
2,018	$ 592.3
2,019	556.9
2,020	503.6
2,021	426.7
2,022	354.1
Thereafter	2,764.6
Total	$ 5,198.2

Assets and Liabilities Measur33

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, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate properties		$ 15,742.7	$ 15,452.8
Marketable securities:
Real estate-related	[1]	1,238	1,081.5
Marketable securities excluding real estate		3,887.5	4,053.8
Total Investments		27,170	26,643.7
Mortgage loans payable		(2,238.3)	(2,332.1)
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate properties		15,742.7	15,452.8
Real estate joint ventures		5,860.6	5,622.4
Limited partnerships		142.4	137.5
Marketable securities:
Real estate-related		1,238	1,081.5
Loans receivable		298.8	295.7
Total Investments		27,170	26,643.7
Mortgage loans payable		(2,238.3)	(2,332.1)
Recurring | Government agency notes
Marketable securities:
Marketable securities excluding real estate		2,872.3	2,308.9
Recurring | United States Treasury securities
Marketable securities:
Marketable securities excluding real estate		1,015.2	1,744.9
Recurring | Level 1: Quoted Prices in Active Markets for Identical Assets
Marketable securities:
Real estate-related		1,238	1,081.5
Total Investments		1,238	1,081.5
Recurring | Level 2: Significant Other Observable Inputs
Marketable securities:
Total Investments		3,887.5	4,053.8
Recurring | Level 2: Significant Other Observable Inputs | Government agency notes
Marketable securities:
Marketable securities excluding real estate		2,872.3	2,308.9
Recurring | Level 2: Significant Other Observable Inputs | United States Treasury securities
Marketable securities:
Marketable securities excluding real estate		1,015.2	1,744.9
Recurring | Level 3: Significant Unobservable Inputs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate properties		15,742.7	15,452.8
Real estate joint ventures		5,860.6	5,622.4
Marketable securities:
Loans receivable		298.8	295.7
Total Investments		21,902.1	21,370.9
Mortgage loans payable		$ (2,238.3)	$ (2,332.1)
[1]	Includes securities loaned of $18.1 million at December 31, 2017 and $91.2 million at December 31, 2016.

Assets and Liabilities Measur34

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, 2017	Dec. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total realized and unrealized gains included in changes in net assets	$ 311.5	$ 556.9
Mortgage Loans Payable
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(2,332.1)	(1,794.4)
Total realized and unrealized gains included in changes in net assets	15.9	15.1
Purchases	(17.7)	(587.5)
Settlements	95.6	34.7
Ending balance	(2,238.3)	(2,332.1)
Real Estate Properties
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	15,452.8	14,606.2
Total realized and unrealized gains included in changes in net assets	177.5	311.3
Purchases	682.9	786.4
Sales	(570.5)	(251.1)
Ending balance	15,742.7	15,452.8
Real Estate Joint Ventures
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	5,622.4	4,068.4
Total realized and unrealized gains included in changes in net assets	123.5	242.8
Purchases	419	1,313.6
Settlements	(304.3)	(2.4)
Ending balance	5,860.6	5,622.4
Loans Receivable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	295.7	100.6
Total realized and unrealized gains included in changes in net assets	1.2	0.3
Purchases	1.9	194.8
Ending balance	298.8	295.7
Total Level 3 Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	21,370.9	18,775.2
Total realized and unrealized gains included in changes in net assets	302.2	554.4
Purchases	1,103.8	2,294.8
Sales	(570.5)	(251.1)
Settlements	(304.3)	(2.4)
Ending balance	$ 21,902.1	$ 21,370.9

Assets and Liabilities Measur35

Assets and Liabilities Measured at Fair Value on a Recurring Basis - Schedule of unobservable inputs related to Level 3 fair value measurements (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Real Estate Properties and Joint Ventures | Office | Income Approach | Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discount Rate	5.50%	5.50%
Terminal Capitalization Rate	4.50%	4.30%
Real Estate Properties and Joint Ventures | Office | Income Approach | Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discount Rate	8.00%	8.30%
Terminal Capitalization Rate	7.00%	7.30%
Real Estate Properties and Joint Ventures | Office | Income Approach | Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discount Rate	6.50%	6.50%
Terminal Capitalization Rate	5.50%	5.50%
Real Estate Properties and Joint Ventures | Office | Income Approach | Direct Capitalization, Overall Capitalization Rate | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Overall Capitalization Rate	3.80%	3.80%
Real Estate Properties and Joint Ventures | Office | Income Approach | Direct Capitalization, Overall Capitalization Rate | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Overall Capitalization Rate	7.00%	7.00%
Real Estate Properties and Joint Ventures | Office | Income Approach | Direct Capitalization, Overall Capitalization Rate | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Overall Capitalization Rate	4.80%	4.70%
Real Estate Properties and Joint Ventures | Industrial | Income Approach | Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discount Rate	5.50%	5.70%
Terminal Capitalization Rate	4.50%	4.80%
Real Estate Properties and Joint Ventures | Industrial | Income Approach | Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discount Rate	8.90%	8.70%
Terminal Capitalization Rate	8.30%	8.00%
Real Estate Properties and Joint Ventures | Industrial | Income Approach | Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discount Rate	6.80%	6.70%
Terminal Capitalization Rate	5.50%	5.60%
Real Estate Properties and Joint Ventures | Industrial | Income Approach | Direct Capitalization, Overall Capitalization Rate | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Overall Capitalization Rate	4.00%	4.00%
Real Estate Properties and Joint Ventures | Industrial | Income Approach | Direct Capitalization, Overall Capitalization Rate | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Overall Capitalization Rate	7.50%	7.50%
Real Estate Properties and Joint Ventures | Industrial | Income Approach | Direct Capitalization, Overall Capitalization Rate | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Overall Capitalization Rate	5.00%	5.00%
Real Estate Properties and Joint Ventures | Residential | Income Approach | Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discount Rate	5.00%	5.30%
Terminal Capitalization Rate	3.50%	3.80%
Real Estate Properties and Joint Ventures | Residential | Income Approach | Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discount Rate	8.00%	7.30%
Terminal Capitalization Rate	6.50%	6.00%
Real Estate Properties and Joint Ventures | Residential | Income Approach | Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discount Rate	6.10%	6.20%
Terminal Capitalization Rate	4.80%	4.80%
Real Estate Properties and Joint Ventures | Residential | Income Approach | Direct Capitalization, Overall Capitalization Rate | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Overall Capitalization Rate	3.30%	3.30%
Real Estate Properties and Joint Ventures | Residential | Income Approach | Direct Capitalization, Overall Capitalization Rate | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Overall Capitalization Rate	6.00%	5.50%
Real Estate Properties and Joint Ventures | Residential | Income Approach | Direct Capitalization, Overall Capitalization Rate | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Overall Capitalization Rate	4.30%	4.20%
Real Estate Properties and Joint Ventures | Retail | Income Approach | Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discount Rate	5.00%	5.00%
Terminal Capitalization Rate	4.30%	4.30%
Real Estate Properties and Joint Ventures | Retail | Income Approach | Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discount Rate	10.50%	10.40%
Terminal Capitalization Rate	8.80%	8.50%
Real Estate Properties and Joint Ventures | Retail | Income Approach | Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discount Rate	6.40%	6.40%
Terminal Capitalization Rate	5.20%	5.20%
Real Estate Properties and Joint Ventures | Retail | Income Approach | Direct Capitalization, Overall Capitalization Rate | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Overall Capitalization Rate	3.80%	3.90%
Real Estate Properties and Joint Ventures | Retail | Income Approach | Direct Capitalization, Overall Capitalization Rate | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Overall Capitalization Rate	8.80%	8.30%
Real Estate Properties and Joint Ventures | Retail | Income Approach | Direct Capitalization, Overall Capitalization Rate | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Overall Capitalization Rate	4.70%	4.70%
Mortgage Loans Payable | Office and Industrial | Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	37.70%	35.70%
Equivalency Rate	3.70%	3.70%
Mortgage Loans Payable | Office and Industrial | Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	69.50%	71.00%
Equivalency Rate	5.20%	4.70%
Mortgage Loans Payable | Office and Industrial | Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	45.60%	43.40%
Equivalency Rate	3.90%	3.90%
Mortgage Loans Payable | Office and Industrial | Net Present Value | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	37.70%	35.70%
Weighted Average Cost of Capital Risk Premium Multiple	120.00%	120.00%
Mortgage Loans Payable | Office and Industrial | Net Present Value | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	69.50%	71.00%
Weighted Average Cost of Capital Risk Premium Multiple	150.00%	160.00%
Mortgage Loans Payable | Office and Industrial | Net Present Value | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	45.60%	43.40%
Weighted Average Cost of Capital Risk Premium Multiple	130.00%	130.00%
Mortgage Loans Payable | Residential | Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	28.10%	29.50%
Equivalency Rate	3.30%	2.90%
Mortgage Loans Payable | Residential | Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	64.20%	61.20%
Equivalency Rate	3.60%	3.60%
Mortgage Loans Payable | Residential | Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	38.60%	41.40%
Equivalency Rate	3.40%	3.30%
Mortgage Loans Payable | Residential | Net Present Value | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	28.10%	29.50%
Weighted Average Cost of Capital Risk Premium Multiple	110.00%	120.00%
Mortgage Loans Payable | Residential | Net Present Value | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	64.20%	61.20%
Weighted Average Cost of Capital Risk Premium Multiple	150.00%	150.00%
Mortgage Loans Payable | Residential | Net Present Value | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	38.60%	41.40%
Weighted Average Cost of Capital Risk Premium Multiple	130.00%	130.00%
Mortgage Loans Payable | Retail | Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	17.90%	18.30%
Equivalency Rate	3.10%	2.90%
Mortgage Loans Payable | Retail | Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	56.00%	51.60%
Equivalency Rate	4.40%	4.00%
Mortgage Loans Payable | Retail | Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	32.70%	31.30%
Equivalency Rate	3.80%	3.50%
Mortgage Loans Payable | Retail | Net Present Value | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	17.90%	18.30%
Weighted Average Cost of Capital Risk Premium Multiple	110.00%	110.00%
Mortgage Loans Payable | Retail | Net Present Value | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	56.00%	51.60%
Weighted Average Cost of Capital Risk Premium Multiple	140.00%	130.00%
Mortgage Loans Payable | Retail | Net Present Value | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	32.70%	31.30%
Weighted Average Cost of Capital Risk Premium Multiple	120.00%	120.00%
Loans Receivable | Office, Retail and Storage | Discounted Cash Flow | Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	59.40%	55.60%
Equivalency Rate	4.20%	4.20%
Loans Receivable | Office, Retail and Storage | Discounted Cash Flow | Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	77.30%	79.20%
Equivalency Rate	8.30%	8.30%
Loans Receivable | Office, Retail and Storage | Discounted Cash Flow | Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loan-to-Value Ratio	75.10%	75.80%
Equivalency Rate	6.20%	6.30%

Assets and Liabilities Measur36

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, 2017	Dec. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total net realized and unrealized gains included in changes in net assets	$ 311.5	$ 556.9
Mortgage Loans Payable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total realized and unrealized gains included in changes in net assets	15.9	15.1
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	185.1	314.2
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	125.2	242.4
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	$ 1.2	$ 0.3

Investments in Joint Ventures37

Investments in Joint Ventures (Details) - USD ($) $ in Billions	Dec. 31, 2017	Dec. 31, 2016
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	97.50%
Equity investments fair value joint ventures	$ 5.9	$ 5.6
Accounts proportionate share of mortgage loans payable within joint venture investments at fair value	2.4	2.1
Accounts share in outstanding principal of mortgage loans payable within joint ventures	$ 2.4	$ 2.1

Investments in Joint Ventures -

Investments in Joint Ventures - Schedule of financial position of the joint ventures (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Assets
Real estate properties, at fair value	$ 14,240.8	$ 13,539
Other assets	337.1	316.1
Total assets	14,577.9	13,855.1
Liabilities & Equity
Mortgage notes payable and other obligations, at fair value	3,995.7	3,452.9
Other liabilities	150.7	213.9
Total liabilities	4,146.4	3,666.8
Total equity	10,431.5	10,188.3
Total liabilities and equity	$ 14,577.9	$ 13,855.1

Investments in Joint Ventures39

Investments in Joint Ventures - Schedule of results of operations of the joint ventures (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Revenue and Expenses
Revenues	$ 869.2	$ 714.6	$ 609.5
Expenses	426.9	365	318.6
Excess of revenues over expenses	$ 442.3	$ 349.6	$ 290.9

Investments in Limited Partne40

Investments in Limited Partnerships (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)limited_partnershiplimited_liability_company	Dec. 31, 2016USD ($)
Schedule of Cost-method Investments [Line Items]
Number of investments held in limited partnership	3
Number of investments held in limited companies | limited_liability_company	1
Limited partnerships ownership interest fair value | $	$ 142.4	$ 137.5
Number of investments held in limited partnership in dissolution	1
Minimum
Schedule of Cost-method Investments [Line Items]
Cost method investment, ownership percent	5.30%
Maximum
Schedule of Cost-method Investments [Line Items]
Equity method investment, ownership percentage	60.00%

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, 2017	Dec. 31, 2016
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Principal Amount Outstanding	$ 2,238.6	$ 2,316.5
Fair Value Adjustment	(0.3)	15.6
Total mortgage loans payable	$ 2,238.3	2,332.1
The Legend at Kierland
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	4.97% paid monthly
Annual interest rate	4.97%
Principal Amount Outstanding	$ 0	21.8
Maturity	Aug. 1, 2017
The Tradition at Kierland
Mortgage Loans Payable - Schedule of outstanding mortgage loans payable secured by properties [Line Items]
Interest Rate and Payment Frequency	4.97% paid monthly
Annual interest rate	4.97%
Principal Amount Outstanding	$ 0	25.8
Maturity	Aug. 1, 2017
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	$ 92.1	92.6
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	$ 17.5	0
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	$ 105	105
Maturity	Jun. 1, 2021
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	$ 78.8	80
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	$ 88.9	90
Maturity	Mar. 1, 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	$ 91.7	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	$ 46.7	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	$ 39.6	39.6
Maturity	Nov. 1, 2022
The Caruth
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	$ 0	45
Maturity	Nov. 1, 2022
Fourth & Madison
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	$ 200	200
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	$ 330	330
Maturity	Jun. 1, 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
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	$ 216.5	$ 216.5
Maturity	Apr. 1, 2028

Mortgage Loans Payable - Sche42

Mortgage Loans Payable - Schedule of outstanding mortgage loans payable, additional information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)loan	Dec. 31, 2016USD ($)
Mortgage Loans Payable [Line Items]
Principal amount outstanding	$ 2,238.6	$ 2,316.5
Loan One
Mortgage Loans Payable [Line Items]
Principal amount outstanding	79
Loan Two
Mortgage Loans Payable [Line Items]
Principal amount outstanding	45
Loan Three
Mortgage Loans Payable [Line Items]
Principal amount outstanding	$ 13.5
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

Mortgage Loans Payable - Sche43

Mortgage Loans Payable - Schedule of maturities of long-term debt (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
2,018	$ 13.7
2,019	107.2
2,020	171.7
2,021	125
2,022	335.7
Thereafter	1,485.3
Total maturities	$ 2,238.6	$ 2,316.5

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, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Per Accumulation Unit Data:
Rental income (in dollars per share)	$ 17.132	$ 16.433	$ 15.538	$ 15.862	$ 15.313
Real estate property level expenses and taxes (in dollars per share)	7.722	7.534	7.319	7.788	8.112
Real estate income, net (in dollars per share)	9.410	8.899	8.219	8.074	7.201
Other income (in dollars per share)	4.762	3.594	3.342	3.459	2.759
Total income (in dollars per share)	14.172	12.493	11.561	11.533	9.960
Expense charges (in dollars per share)	3.318	3.290	3.092	2.880	2.672
Investment income, net (in dollars per share)	10.854	9.203	8.469	8.653	7.288
Net realized and unrealized gain on investments and mortgage loans payable (in dollars per share)	5.839	9.660	18.911	27.868	19.015
Net increase in Accumulation Unit Value (in dollars per share)	16.693	18.863	27.380	36.521	26.303
Accumulation Unit Value:
Beginning of period (in dollars per share)	381.636	362.773	335.393	298.872	272.569
End of period (in dollars per share)	$ 398.329	$ 381.636	$ 362.773	$ 335.393	$ 298.872
Total return	4.37%	5.20%	8.16%	12.22%	9.65%
Ratios to Average net Assets:
Expenses	0.83%	0.86%	0.86%	0.89%	0.92%
Investment income, net	2.72%	2.41%	2.37%	2.68%	2.50%
Portfolio turnover rate:
Real estate properties	2.70%	1.30%	5.70%	6.50%	2.10%
Marketable securities	5.70%	3.50%	10.00%	15.90%	8.40%
Accumulation Units outstanding at end of period (in millions) (in shares)	61.3	62.4	60.4	57.9	55.3
Net assets end of period (in millions)	$ 24,942.6	$ 24,304.7	$ 22,360	$ 19,829	$ 16,907.9

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, 2017	Dec. 31, 2016	Dec. 31, 2015
Outstanding:
Beginning of period (in shares)	62.4	60.4	57.9
Credited for premiums (in shares)	6.6	8.2	8.1
Annuity, other periodic payments, withdrawals and death benefits (in shares)	(7.7)	(6.2)	(5.6)
End of period (in shares)	61.3	62.4	60.4

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies [Line Items]
Callable commitments, amount	$ 32	$ 39
Callable commitments funded	13
Increase in callable commitments	$ 47.6	$ 38.8
Minimum
Commitments and Contingencies [Line Items]
Minority interest, ownership percentage by noncontrolling owners upon funding	60.00%
Maximum
Commitments and Contingencies [Line Items]
Minority interest, ownership percentage by noncontrolling owners upon funding	90.00%
Callable Commitment, Additional Limited Partnership Investments
Commitments and Contingencies [Line Items]
Callable commitment, original amount	$ 45

Securities Lending (Details)

Securities Lending (Details)	12 Months Ended
	Dec. 31, 2017
Brokers and Dealers [Abstract]
Minimum cash collateral maintained, percentage (not less than)	100.00%

Subsequent Events (Details)

Subsequent Events (Details) - Subsequent Event - USD ($) $ in Millions	Mar. 08, 2018	Mar. 02, 2018	Mar. 01, 2018	Feb. 22, 2018	Jan. 04, 2018	Feb. 21, 2018	Feb. 02, 2018
Subsequent Event [Line Items]
Payments to acquire real estate			$ 71.2	$ 64.2	$ 32.8
Sale of office property	$ 141.1
Realized loss on sale of office property	12.1
Cost basis of office property sold	$ 153.2
Stated interest rate on receivable		8.25%
Collateralized Mortgage Backed Securities
Subsequent Event [Line Items]
Payments to acquire marketable securities				100
Mortgage | Storage Portfolio I—Various, U.S.A. | Storage Portfolio I, LLC
Subsequent Event [Line Items]
Debt outstanding							$ 151.2
Annual interest rate							4.5325%
Mortgage | Circa Green Lake—Seattle, WA | Circa Green Lake
Subsequent Event [Line Items]
Debt outstanding						$ 52
Annual interest rate						3.71%
Mortgage | Union - South Lake Union—Seattle, WA | Union
Subsequent Event [Line Items]
Debt outstanding						$ 57
Annual interest rate						3.66%
Mortgage | 99 High Street—Boston, MA | 99 High Street
Subsequent Event [Line Items]
Debt outstanding				$ 277
Annual interest rate				3.90%
Storage Portfolio I, LLC
Subsequent Event [Line Items]
Equity method investment, ownership percentage							66.02%
Aspen Lake Office Portfolio
Subsequent Event [Line Items]
Loan receivable		$ 20