Principal Financial (PFG) 10-Q 31 Oct 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 24, 2018
Document and Entity Information
Entity Registrant Name	PRINCIPAL FINANCIAL GROUP INC
Entity Central Index Key	1,126,328
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		283,048,481
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3

Consolidated Statements of Fina

Consolidated Statements of Financial Position - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Assets
Fixed maturities, available-for-sale (2018 and 2017 include $241.6 million and $268.0 million related to consolidated variable interest entities)	$ 60,447.2	$ 59,388.4
Fixed maturities, trading	642.1	566
Equity securities (2018 and 2017 include $795.5 million and $811.4 million related to consolidated variable interest entities)	1,885.8	1,866.6
Mortgage loans	14,919.7	14,150.5
Real estate (2018 and 2017 include $347.4 million and $370.3 million related to consolidated variable interest entities)	1,699.7	1,736.7
Policy loans	804.4	808.3
Other investments (2018 and 2017 include $208.6 million and $139.8 million related to consolidated variable interest entities and $24.1 million and $61.0 million measured at fair value under the fair value option)	3,608.3	3,586.2
Total investments	84,007.2	82,102.7
Cash and cash equivalents	2,926.7	2,470.8
Accrued investment income	660.7	610.6
Premiums due and other receivables	1,514.4	1,469.8
Deferred acquisition costs	3,671.9	3,540.7
Property and equipment	770.6	759.5
Goodwill	1,128.7	1,068.8
Other intangibles	1,353.9	1,314.7
Separate account assets (2018 and 2017 include $39,636.3 million and $41,540.8 million related to consolidated variable interest entities)	161,302.9	159,272.7
Other assets	1,421.3	1,330.9
Total assets	258,758.3	253,941.2
Liabilities
Contractholder funds (2018 and 2017 include $392.3 million and $380.6 million related to consolidated variable interest entities)	39,813.2	38,082.5
Future policy benefits and claims	34,818.3	33,019.3
Other policyholder funds	849.4	922.3
Short-term debt	36.1	39.5
Long-term debt (2018 and 2017 include $49.1 million and $2.8 million related to consolidated variable interest entities)	3,245.5	3,178.4
Income taxes currently payable	29.3	16.7
Deferred income taxes	911.4	1,092.5
Separate account liabilities (2018 and 2017 include $39,636.3 million and $41,540.8 million related to consolidated variable interest entities)	161,302.9	159,272.7
Other liabilities (2018 and 2017 include $245.9 million and $270.2 million related to consolidated variable interest entities)	5,835	5,294.1
Total liabilities	246,841.1	240,918
Redeemable noncontrolling interest (2018 and 2017 include $75.4 million and $52.4 million related to consolidated variable interest entities)	148.5	101.3
Stockholders' equity
Common stock, par value $.01 per share - 2,500.0 million shares authorized, 476.4 million and 474.1 million shares issued, and 283.6 million and 289.0 million shares outstanding in 2018 and 2017	4.8	4.7
Additional paid-in capital	10,026.2	9,925.2
Retained earnings (accumulated deficit)	10,207.9	9,482.9
Accumulated other comprehensive income (loss)	(1,347.6)	165.5
Treasury stock, at cost (192.8 million and 185.1 million shares in 2018 and 2017)	(7,190.5)	(6,729)
Total stockholders' equity attributable to Principal Financial Group, Inc.	11,700.8	12,849.3
Noncontrolling interest	67.9	72.6
Total stockholders' equity	11,768.7	12,921.9
Total liabilities and stockholders' equity	$ 258,758.3	$ 253,941.2

Consolidated Statements of Fi_2

Consolidated Statements of Financial Position (Parenthetical) - USD ($) shares in Millions, $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Fixed maturities, available-for-sale	$ 60,447.2	$ 59,388.4
Equity securities	1,885.8	1,866.6
Real estate	1,699.7	1,736.7
Other investments	3,608.3	3,586.2
Other investments measured at fair value under fair value option	24.1	61
Separate account assets	161,302.9	159,272.7
Contractholder funds	39,813.2	38,082.5
Long-term debt	3,245.5	3,178.4
Separate account liabilities	161,302.9	159,272.7
Other liabilities	5,835	5,294.1
Redeemable noncontrolling interest	$ 148.5	$ 101.3
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	2,500	2,500
Common stock, issued (in shares)	476.4	474.1
Common stock, outstanding (in shares)	283.6	289
Treasury stock (in shares)	192.8	185.1
Aggregate consolidated variable interest entities
Fixed maturities, available-for-sale	$ 241.6	$ 268
Equity securities	795.5	811.4
Real estate	347.4	370.3
Other investments	208.6	139.8
Separate account assets	39,636.3	41,540.8
Contractholder funds	392.3	380.6
Long-term debt	49.1	2.8
Separate account liabilities	39,636.3	41,540.8
Other liabilities	245.9	270.2
Redeemable noncontrolling interest	$ 75.4	$ 52.4

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues
Premiums and other considerations	$ 2,172.4	$ 2,126.1	$ 4,433.4	$ 4,826.8
Fees and other revenues	1,261.8	987.1	3,285.7	2,882.8
Net investment income (loss)	919.4	838	2,710.7	2,581.8
Net realized capital gains (losses), excluding impairment losses on available-for-sale securities	(1.9)	693.2	59.3	623.7
Net other-than-temporary impairment (losses) recoveries on available-for-sale securities	(1.4)	2.6	(8.3)	(27.1)
Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified to (from) other comprehensive income	(2.2)	(19.2)	(14.2)	(32.5)
Net impairment (losses) recoveries on available-for-sale securities	(3.6)		(22.5)
Net impairment (losses) recoveries on available-for-sale securities		(16.6)		(59.6)
Net realized capital gains (losses)	(5.5)	676.6	36.8	564.1
Total revenues	4,348.1	4,627.8	10,466.6	10,855.5
Expenses
Benefits, claims and settlement expenses	2,642.1	2,504.6	5,752.4	6,020.7
Dividends to policyholders	31.9	32.6	92.6	92.7
Operating expenses	1,105	932.8	3,080.1	2,804.7
Total expenses	3,779	3,470	8,925.1	8,918.1
Income (loss) before income taxes	569.1	1,157.8	1,541.5	1,937.4
Income taxes (benefits)	109.1	344.6	219.5	455.8
Net income (loss)	460	813.2	1,322	1,481.6
Net income (loss) attributable to noncontrolling interest	3.7	3	12	13
Net income (loss) attributable to Principal Financial Group, Inc.	$ 456.3	$ 810.2	$ 1,310	$ 1,468.6
Earnings per common share
Basic earnings per common share (in dollars per share)	$ 1.60	$ 2.80	$ 4.57	$ 5.08
Diluted earnings per common share (in dollars per share)	1.59	2.76	4.52	5.02
Dividends declared per common share (in dollars per share)	$ 0.53	$ 0.47	$ 1.56	$ 1.38

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Consolidated Statements of Comprehensive Income
Net income (loss)	$ 460	$ 813.2	$ 1,322	$ 1,481.6
Other comprehensive income (loss), net:
Net unrealized gains (losses) on available-for-sale securities	(199.2)	70.1	(1,470.8)	569.1
Noncredit component of impairment losses on fixed maturities, available-for-sale	2	13.3	12.1	21
Net unrealized gains (losses) on derivative instruments	2.7	(11.1)	8.6	(29.3)
Foreign currency translation adjustment	(22.9)	88.6	(193.2)	151.3
Net unrecognized postretirement benefit obligation	8.7	4.2	26.2	12.8
Other comprehensive income (loss)	(208.7)	165.1	(1,617.1)	724.9
Comprehensive income (loss)	251.3	978.3	(295.1)	2,206.5
Comprehensive income (loss) attributable to noncontrolling interest	3.1	5	8.6	15.7
Comprehensive income (loss) attributable to Principal Financial Group, Inc.	$ 248.2	$ 973.3	$ (303.7)	$ 2,190.8

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions		Common stock	Additional paid-in capital	Retained earnings (accumulated deficit)	Accumulated other comprehensive income (loss)	Treasury stock	Noncontrolling interest	Total
Balances at Dec. 31, 2016		$ 4.7	$ 9,686	$ 7,720.4	$ (675.2)	$ (6,508.6)	$ 66.5	$ 10,293.8
Increase (decrease) in stockholders' equity
Common stock issued			143.1					143.1
Stock-based compensation			68.1	(5.9)			0.2	62.4
Treasury stock acquired, common						(218.1)		(218.1)
Dividends to common stockholders				(398.5)				(398.5)
Distributions to noncontrolling interest							(6.1)	(6.1)
Contributions from noncontrolling interest							4.2	4.2
Purchase of subsidiary shares from noncontrolling interest	[1]		(7.6)				(1.3)	(8.9)
Adjustments to redemption amount of redeemable noncontrolling interest			(2.8)					(2.8)
Net income (loss)	[1]			1,468.6			6.1	1,474.7
Other comprehensive income (loss)	[1]				722.2		1.3	723.5
Balances at Sep. 30, 2017		4.7	9,886.8	8,784.6	47	(6,726.7)	70.9	12,067.3
Balances at Dec. 31, 2017		4.7	9,925.2	9,482.9	165.5	(6,729)	72.6	12,921.9
Increase (decrease) in stockholders' equity
Common stock issued		0.1	52.3					52.4
Stock-based compensation			65.7	(5.6)			(0.4)	59.7
Treasury stock acquired, common						(461.5)		(461.5)
Dividends to common stockholders				(446.5)				(446.5)
Distributions to noncontrolling interest							(10.5)	(10.5)
Contributions from noncontrolling interest							2.2	2.2
Purchase of subsidiary shares from noncontrolling interest	[1]		(20)		(1.6)		(1.6)	(23.2)
Adjustments to redemption amount of redeemable noncontrolling interest			3				(0.3)	2.7
Effects of implementation of accounting change | ASU 2016-16 - Intra-entity asset transfer taxes				8.7				8.7
Effects of implementation of accounting change | ASU 2016-01 - Equity investments				1	(1)
Effects of implementation of accounting change | ASU 2014-09 - Revenue recognition				(65)	25.6		(0.3)	(39.7)
Effects of implementation of accounting change | ASU 2018-02 - Reclassification of certain tax effects				(77.6)	77.6
Net income (loss)	[1]			1,310			7.9	1,317.9
Other comprehensive income (loss)	[1]				(1,613.7)		(1.7)	(1,615.4)
Balances at Sep. 30, 2018		$ 4.8	$ 10,026.2	$ 10,207.9	$ (1,347.6)	$ (7,190.5)	$ 67.9	$ 11,768.7
[1]	Excludes amounts attributable to redeemable noncontrolling interest. See Note 10, Stockholders’ Equity, for further details.

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating activities
Net income (loss)	$ 1,322	$ 1,481.6
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Net realized capital (gains) losses	(36.8)	(564.1)
Depreciation and amortization expense	151.9	144.8
Amortization of deferred acquisition costs and contract costs	160.1	173.8
Additions to deferred acquisition costs and contract costs	(331.1)	(307.2)
Stock-based compensation	60.3	62.2
(Income) loss from equity method investments, net of dividends received	(54.6)	(73.1)
Changes in:
Accrued investment income	(49.8)	(54)
Net cash flows for trading securities and equity securities with operating intent	(137.9)	55.3
Premiums due and other receivables	(33.7)	(158.2)
Contractholder and policyholder liabilities and dividends	2,458.9	2,693.5
Current and deferred income taxes (benefits)	182.3	456
Real estate acquired through operating activities	(79.5)	(55.2)
Real estate sold through operating activities	133.6	1.3
Other assets and liabilities	13.1	(242.1)
Other	(44.9)	14.1
Net adjustments	2,391.9	2,147.1
Net cash provided by (used in) operating activities	3,713.9	3,628.7
Investing activities
Fixed maturities available-for-sale and equity securities with intent to hold: Purchases	(10,992.3)	(10,425.7)
Fixed maturities available-for-sale and equity securities with intent to hold: Sales	2,900.4	1,011.2
Fixed maturities available-for-sale and equity securities with intent to hold: Maturities	4,703.5	6,577.2
Mortgage loans acquired or originated	(2,347.4)	(2,036.5)
Mortgage loans sold or repaid	1,567.6	1,297.4
Real estate acquired	(53.7)	(113.6)
Real estate sold	63.5	457.1
Net (purchases) sales of property and equipment	(73.4)	(133.3)
Purchase of interests in subsidiaries, net of cash acquired	(184.7)
Net change in other investments	7.8	48.5
Net cash provided by (used in) investing activities	(4,408.7)	(3,317.7)
Financing activities
Issuance of common stock	52.4	143.1
Acquisition of treasury stock	(461.5)	(218.1)
Proceeds from financing element derivatives		0.1
Payments for financing element derivatives	(53.7)	(59.5)
Purchase of subsidiary shares from noncontrolling interest	(30.3)	(13.3)
Dividends to common stockholders	(446.5)	(398.5)
Issuance of long-term debt	66.8
Principal repayments of long-term debt	(1)	(56.2)
Net proceeds from (repayments of) short-term borrowings	(0.8)	4.9
Investment contract deposits	6,228.5	8,244.4
Investment contract withdrawals	(4,361.6)	(7,963.1)
Net increase (decrease) in banking operation deposits	159.5	79.8
Other	(1.1)	0.8
Net cash provided by (used in) financing activities	1,150.7	(235.6)
Net increase (decrease) in cash and cash equivalents	455.9	75.4
Cash and cash equivalents at beginning of period	2,470.8	2,719.6
Cash and cash equivalents at end of period	$ 2,926.7	2,795
Asset and liability changes resulting from exchange agreement to exit real estate joint ventures:
Real estate properties received		743.2
Long-term debt assumed on real estate properties received		269
Increase in other investments due to discontinuing equity method accounting		$ 222.4

Nature of Operations and Signif

Nature of Operations and Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Nature of Operations and Significant Accounting Policies
Nature of Operations and Significant Accounting Policies	1. Nature of Operations and Significant Accounting Policies Basis of Presentation The accompanying unaudited consolidated financial statements of Principal Financial Group, Inc. (“PFG”) have been prepared in conformity with accounting principles generally accepted in the U.S. (“U.S. GAAP”) for interim financial statements and with the instructions to Form 10-Q and Article 10 of Regulation S-X. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the three and nine months ended September 30, 2018, are not necessarily indicative of the results that may be expected for the year ended December 31, 2018. These interim unaudited consolidated financial statements should be read in conjunction with our annual audited financial statements as of December 31, 2017, included in our Form 10-K for the year ended December 31, 2017, filed with the United States Securities and Exchange Commission (“SEC”). The accompanying consolidated statement of financial position as of December 31, 2017, has been derived from the audited consolidated statement of financial position but does not include all of the information and footnotes required by U.S. GAAP for complete financial statements. Certain reclassifications have been made to the prior period consolidated statements of cash flows to conform to the current period presentation. Consolidation We have relationships with various special purpose entities and other legal entities that must be evaluated to determine if the entities meet the criteria of a variable interest entity (“VIE”) or a voting interest entity (“VOE”). This assessment is performed by reviewing contractual, ownership and other rights, including involvement of related parties, and requires use of judgment. First, we determine if we hold a variable interest in an entity by assessing if we have the right to receive expected losses and expected residual returns of the entity. If we hold a variable interest, then the entity is assessed to determine if it is a VIE. An entity is a VIE if the equity at risk is not sufficient to support its activities, if the equity holders lack a controlling financial interest or if the entity is structured with non-substantive voting rights. In addition to the previous criteria, if the entity is a limited partnership or similar entity, it is a VIE if the limited partners do not have the power to direct the entity’s most significant activities through substantive kick-out rights or participating rights. A VIE is evaluated to determine the primary beneficiary. The primary beneficiary of a VIE is the enterprise with (1) the power to direct the activities of a VIE that most significantly impact the entity’s economic performance and (2) the obligation to absorb losses of the entity or the right to receive benefits from the entity that could potentially be significant to the VIE. When we are the primary beneficiary, we are required to consolidate the entity in our financial statements. We reassess our involvement with VIEs on a quarterly basis. For further information about VIEs, refer to Note 2, Variable Interest Entities. If an entity is not a VIE, it is considered a VOE. VOEs are generally consolidated if we own a greater than 50% voting interest. If we determine our involvement in an entity no longer meets the requirements for consolidation under either the VIE or VOE models, the entity is deconsolidated. Entities in which we have management influence over the operating and financing decisions but are not required to consolidate, other than investments accounted for at fair value under the fair value option, are reported using the equity method. Recent Accounting Pronouncements Description Date of Effect on our consolidated Standards not yet adopted: Targeted improvements to the accounting for long-duration insurance contracts This authoritative guidance updates certain requirements in the accounting for long-duration insurance and annuity contracts. The assumptions used to calculate the liability for future policy benefits on traditional and limited-payment contracts will be reviewed and updated periodically. Cash flow assumptions will be reviewed and updated at least annually with the change recognized in net income. Discount rate assumptions will be updated quarterly with the change recognized in other comprehensive income. Market risk benefits, which are certain market-based options or guarantees associated with deposit or account balance contracts, will be measured at fair value. The periodic change in fair value related to instrument-specific credit risk will be recognized in other comprehensive income while the remaining change in fair value will be recognized in net income. Deferred acquisition costs for all insurance and annuity contracts will be amortized on a constant basis over the expected term of the related contracts. Additional disclosures, including rollforwards of significant insurance and account balances and disclosures about significant inputs, judgments, assumptions and methods used in measurement, are required. The guidance for the liability for future policy benefits for traditional and limited-payment contracts and deferred acquisition costs will be applied on a modified retrospective basis; that is, to contracts in force as of the beginning of the earliest period presented based on their existing carrying amounts. An entity may elect to apply the changes retrospectively. The guidance for market risk benefits will be applied retrospectively. Early adoption is permitted. January 1, 2021 We are currently evaluating the impact this guidance will have on our consolidated financial statements. We expect this guidance to significantly change how we account for many of our insurance and annuity products. Goodwill impairment testing This authoritative guidance simplifies how an entity is required to test goodwill for impairment by eliminating Step 2 (which measures a goodwill impairment loss by comparing the implied fair value of a reporting unit’s goodwill to the carrying amount of that goodwill) from the goodwill impairment test. A goodwill impairment loss will be the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. Entities will continue to have the option to perform a qualitative assessment to determine if a quantitative impairment test is necessary. Early adoption is permitted. January 1, 2020 We are currently evaluating the impact this guidance will have on our consolidated financial statements. Description Date of Effect on our consolidated Credit losses This authoritative guidance requires entities to use a current expected credit loss (“CECL”) model to measure impairment for most financial assets that are not recorded at fair value through net income. Under the CECL model, an entity will estimate lifetime expected credit losses considering available relevant information about historical events, current conditions and reasonable and supportable forecasts. The CECL model does not apply to available-for-sale debt securities. This guidance also expands the required credit loss disclosures and will be applied using a modified retrospective approach by recording a cumulative effect adjustment to retained earnings as of the beginning of the fiscal year of adoption. Early adoption is permitted. January 1, 2020 We are currently evaluating the impact this guidance will have on our consolidated financial statements. We believe estimated credit losses under the CECL model will generally result in earlier loss recognition for loans and other receivables. Implementation costs in a cloud computing arrangement that is a service contract This authoritative guidance aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. This guidance can be applied either retrospectively or prospectively and early adoption is permitted. January 1, 2020 We are currently evaluating the impact this guidance will have on our consolidated financial statements. Targeted improvements to accounting for hedging activities This authoritative guidance updates certain recognition and measurement requirements for hedge accounting. The objective of the guidance is to more closely align the economics of a company’s risk management activities in its financial results and reduce the complexity of applying hedge accounting. The updates include the expansion of hedging strategies that are eligible for hedge accounting, elimination of the separate measurement and reporting of hedge ineffectiveness, presentation of the changes in the fair value of the hedging instrument in the same consolidated statement of operations line as the earnings effect of the hedged item and simplification of hedge effectiveness assessments. This guidance also includes new disclosures and will be applied using a modified retrospective approach by recording a cumulative effect adjustment to retained earnings as of the beginning of the fiscal year of adoption. Early adoption is permitted. January 1, 2019 We have nearly completed our evaluation of this guidance and do not expect it to have a material impact on our consolidated financial statements. Premium amortization on purchased callable debt securities This authoritative guidance applies to entities that hold certain non-contingently callable debt securities, where the amortized cost basis is at a premium to the price repayable by the issuer at the earliest call date. Under the guidance the premium will be amortized to the first call date. This guidance requires adoption through a cumulative effect adjustment to retained earnings as of the beginning of the fiscal year of adoption. Early adoption is permitted. January 1, 2019 We have nearly completed our evaluation of this guidance and do not expect it to have a material impact on our consolidated financial statements. Description Date of Effect on our consolidated Nonemployee share-based payment accounting This authoritative guidance simplifies the accounting for share-based payments to nonemployees by generally aligning it with the accounting for share-based payments to employees. Under the guidance, the measurement of equity-classified nonemployee awards will be fixed at the grant date, where today the measurement is fixed at performance completion date. The guidance will be applied to equity-classified nonemployee awards for which a measurement date has not been established as of the date of adoption. Early adoption is permitted. January 1, 2019 We have nearly completed our evaluation of this guidance and do not expect it to have a material impact on our consolidated financial statements. Leases This authoritative guidance requires lessee recognition of lease assets and lease liabilities on the balance sheet. The concept of an operating lease, where the lease assets and liabilities are off balance sheet, is eliminated under the new guidance. For lessors, the guidance modifies lease classification criteria and accounting for certain types of leases. Other key aspects of the guidance relate to the removal of the current real estate-specific guidance and new presentation and disclosure requirements. Lessees and lessors are required to recognize and measure leases at the beginning of the earliest period presented using a modified retrospective approach, which includes certain optional practical expedients that may be elected. An alternative transition method allows entities to initially apply the new standard at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. January 1, 2019 Our evaluation process includes, but is not limited to, identifying leases that are within the scope of the guidance, reviewing and documenting our accounting for these contracts, implementing system and process changes and determining disclosure impacts. The guidance requires us to establish a lease asset and liability for our operating leases. As we continue to progress with our implementation process, we believe the impact will not be significant to our consolidated financial statements. Standards adopted: Reclassification of certain tax effects from accumulated other comprehensive income This authoritative guidance permits a reclassification from accumulated other comprehensive income (“AOCI”) to retained earnings for the stranded tax effects resulting from U.S. tax legislation enacted on December 22, 2017, which is referred to as the ‘‘Tax Cuts and Jobs Act’’ (‘‘U.S. tax reform’’). The amount of that reclassification includes the change in corporate income tax rate, as well as an election to include other income tax effects related to the application of U.S. tax reform. The guidance also requires disclosures about stranded tax effects. January 1, 2018 We elected to early adopt the guidance. The guidance was applied at the beginning of the period of adoption and comparative periods were not restated. We reclassified the stranded tax effects in AOCI resulting from U.S. tax reform, which includes the change in corporate income tax rate and an election to reclassify the tax effects of the one-time deemed repatriation tax. A reclassification of $77.6 million was recorded as an increase to AOCI and a decrease to retained earnings. Description Date of Effect on our consolidated Revenue recognition This authoritative guidance replaces all general and most industry specific revenue recognition guidance currently prescribed by U.S. GAAP. The core principle is that an entity recognizes revenue to reflect the transfer of a promised good or service to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for that good or service. This guidance also provides clarification on when an entity is a principal or an agent in a transaction. In addition, the guidance updates the accounting for certain costs associated with obtaining and fulfilling a customer contract. The guidance may be applied using one of the following two methods: (1) retrospectively to each prior reporting period presented, or (2) retrospectively with the cumulative effect of initially applying the standard recognized at the date of initial application. January 1, 2018 We adopted the guidance using the modified retrospective approach. The guidance did not have a material impact on our consolidated financial statements. Further details are included under the caption “Adoption of Revenue Recognition Guidance” and in Note 13, Revenues from Contracts with Customers. Income tax - intra-entity transfers of assets This authoritative guidance requires entities to recognize current and deferred income tax resulting from an intra-entity asset transfer when the transfer occurs. Prior to issuance of this guidance, U.S. GAAP did not allow recognition of income tax consequences until the asset had been sold to a third party. This guidance requires adoption through a cumulative effect adjustment to the balance sheet as of the beginning of the fiscal year of adoption with early adoption permitted. January 1, 2018 We adopted the guidance using the modified retrospective approach. A cumulative effect adjustment of $8.7 million was recorded as an increase to retained earnings. In addition, other assets and deferred income taxes decreased $21.1 million and $29.8 million, respectively, due to the adoption of this guidance. Financial instruments - recognition and measurement This authoritative guidance addresses certain aspects of recognition, measurement, presentation and disclosure of financial instruments. The guidance eliminated the classification of equity securities into different categories (trading or available-for-sale) and requires equity investments to be measured at fair value with changes in the fair value recognized through net income. The guidance also updated certain financial instrument disclosures and eliminated the requirement to disclose the methods and significant assumptions used to estimate the fair value of financial instruments that are measured at amortized cost on the balance sheet. January 1, 2018 We adopted this guidance using the modified retrospective approach. A cumulative effect adjustment of $1.0 million was recorded as a decrease to AOCI and a corresponding increase to retained earnings. The guidance did not have a material impact on our consolidated financial statements. As of December 31, 2017, we had $96.0 million of equity securities classified as available-for-sale and $1,770.6 million classified as trading. The consolidated statements of financial position have been updated to eliminate these classifications and present only equity securities. See Note 3, Investments, for further details. Description Date of Effect on our consolidated Nonfinancial asset derecognition and partial sales of nonfinancial assets This authoritative guidance clarifies the scope of the recently established guidance on nonfinancial asset derecognition and the accounting for partial sales of nonfinancial assets. The guidance conforms the derecognition guidance on nonfinancial assets with the model for transactions in the new revenue recognition standard. January 1, 2018 The guidance was adopted and did not have a material impact on our consolidated financial statements. Presentation of net periodic pension cost and net periodic postretirement benefit cost This authoritative guidance requires that an employer disaggregate the service cost component from the other components of net benefit cost. The guidance also provides explicit guidance on the presentation of the service cost component and the other components of net benefit cost in the consolidated statement of operations and allows only the service cost component of net benefit cost to be eligible for capitalization. January 1, 2018 The guidance was adopted and did not have a material impact on our consolidated financial statements. Definition of a business This authoritative guidance clarifies the definition of a business to assist with evaluating when transactions involving an integrated set of assets and activities (a “set”) should be accounted for as acquisitions or disposals of assets or businesses. The guidance requires that when substantially all of the fair value of the gross assets acquired or disposed of is concentrated in a single identifiable asset or a group of similar identifiable assets, the set is not a business. The guidance also requires a set to include, at a minimum, an input and a substantive process that together significantly contribute to the ability to create output to be considered a business. Lastly, the guidance removes the evaluation of whether a market participant could replace missing elements and narrows the definition of outputs by more closely aligning it with how outputs are described in the revenue recognition guidance. The guidance will be applied prospectively. Early application is permitted in certain circumstances. January 1, 2018 The guidance was adopted and did not have a material impact on our consolidated financial statements. Employee share-based payment accounting This authoritative guidance changes certain aspects of accounting for and reporting share-based payments to employees including changes related to the income tax effects of share-based payments, tax withholding requirements and accounting for forfeitures. Various transition methods will apply depending on the situation being addressed. January 1, 2017 The guidance was adopted prospectively as indicated by the guidance for each area of change and did not have a material impact on our consolidated financial statements. When we adopt new accounting standards, we have a process in place to perform a thorough review of the pronouncement, identify the financial statement and system impacts and create an implementation plan among our impacted business units to ensure we are compliant with the pronouncement on the date of adoption. This includes having effective processes and controls in place to support the reported amounts. Each of the standards listed above is in varying stages in our implementation process based on its issuance and adoption dates. We are on track to implement guidance by the respective effective dates. Adoption of Revenue Recognition Guidance On January 1, 2018, we adopted the guidance using the modified retrospective approach. A cumulative effect adjustment of $39.7 million was recorded as a decrease to total stockholders’ equity. The impact of the guidance to our consolidated financial statements primarily relates to a change to the amortization pattern, or a write-off, of existing capitalized costs transferred from deferred acquisition costs (“DAC”) to a contract cost asset, where authoritative guidance was superseded. This was offset in part by deferring certain sales compensation related to obtaining customer contracts that was not previously capitalized. Results of reporting periods beginning January 1, 2018, are presented under the new guidance, while prior period amounts are not adjusted and continue to be reported in accordance with our legacy accounting. The guidance did not have a material impact on our consolidated statements of operations and did not impact earnings per common share. The impacts to the consolidated statements of financial position were as follows: Consolidated Statements of Financial Position September 30, 2018 Impact of adopting revenue recognition As reported As adjusted (1) accounting guidance (in millions) Assets Deferred acquisition costs (2) $ $ $ Other assets (3) Liabilities Deferred income taxes Stockholders’ equity Total stockholders’ equity (1) Excludes the impact of adopting revenue recognition accounting guidance. (2) Certain costs to obtain a contract previously recorded as DAC are now recorded as a contract cost asset or are no longer deferrable under revenue recognition guidance. (3) Includes the contract cost asset. Separate Accounts The separate accounts are legally segregated and are not subject to the claims that arise out of any of our other business. The client, rather than us, directs the investments and bears the investment risk of these funds. The separate account assets represent the fair value of funds that are separately administered by us for contracts with equity, real estate and fixed income investments and are presented as a summary total within the consolidated statements of financial position. An equivalent amount is reported as separate account liabilities, which represent the obligation to return the monies to the client. We receive fees for mortality, withdrawal and expense risks, as well as administrative, maintenance and investment advisory services that are included in the consolidated statements of operations. Net deposits, net investment income and realized and unrealized capital gains and losses of the separate accounts are not reflected in the consolidated statements of operations. Separate account assets and separate account liabilities include certain international retirement accumulation products where the segregated funds and associated obligation to the client are consolidated within our financial statements. We have determined that summary totals are the most meaningful presentation for these funds. As of September 30, 2018 and December 31, 2017, the separate accounts included a separate account valued at $131.7 million and $170.5 million, respectively, which primarily included shares of our stock that were allocated and issued to eligible participants of qualified employee benefit plans administered by us as part of the policy credits issued under our 2001 demutualization. These shares are included in both basic and diluted earnings per share calculations. In the consolidated statements of financial position, the separate account shares are recorded at fair value and are reported as separate account assets with a corresponding separate account liability to eligible participants of the qualified plan. Changes in fair value of the separate account shares are reflected in both the separate account assets and separate account liabilities and do not impact our results of operations.

Variable Interest Entities

Variable Interest Entities	9 Months Ended
	Sep. 30, 2018
Variable Interest Entities
Variable Interest Entities	2. Variable Interest Entities We have relationships with various types of entities which may be VIEs. Certain VIEs are consolidated in our financial results. See Note 1, Nature of Operations and Significant Accounting Policies, under the caption “Consolidation” for further details of our consolidation accounting policies. We did not provide financial or other support to investees designated as VIEs for the periods ended September 30, 2018 and December 31, 2017. Consolidated Variable Interest Entities Grantor Trusts We contributed undated subordinated floating rate notes to two grantor trusts. The trusts separated their cash flows by issuing an interest-only certificate and a residual certificate related to each note contributed. Each interest-only certificate entitles the holder to interest on the stated note for a specified term, while the residual certificate entitles the holder to interest payments subsequent to the term of the interest-only certificate and to all principal payments. We retained the interest-only certificates and the residual certificates were subsequently sold to third parties. We determined these grantor trusts are VIEs due to insufficient equity to sustain them. We determined we are the primary beneficiary as a result of our contribution of securities into the trusts and our significant continuing interest in the trusts. Commercial Mortgage-Backed Securities We sold commercial mortgage loans to a real estate mortgage investment conduit trust. The trust issued various commercial mortgage-backed securities (“CMBS”) certificates using the cash flows of the underlying commercial mortgage loans it purchased. This is considered a VIE due to insufficient equity to sustain itself. We determined we are the primary beneficiary as we retained the special servicing role for the assets within the trust as well as the ownership of the bond class that controls the unilateral kick-out rights of the special servicer. Mandatory Retirement Savings Funds We hold an equity interest in Chilean mandatory privatized social security funds in which we provide asset management services. We determined the mandatory privatized social security funds, which also include contributions for voluntary pension savings, voluntary non-pension savings and compensation savings accounts, are VIEs. This is because the equity holders as a group lack the power, due to voting rights or similar rights, to direct the activities of the entity that most significantly impact the entity’s economic performance and also because equity investors are protected from below-average market investment returns relative to the industry’s return, due to a regulatory guarantee that we provide. Further we concluded we are the primary beneficiary through our power to make decisions and our significant variable interest in the funds. The purpose of the funds, which reside in legally segregated entities, is to provide long-term retirement savings. The obligation to the customer is directly related to the assets held in the funds and, as such, we present the assets as separate account assets and the obligation as separate account liabilities within our consolidated statements of financial position. Principal International Hong Kong offers retirement pension schemes in which we provide trustee, administration and asset management services to employers and employees under the Hong Kong Mandatory Provident Fund (“MPF”) and Occupational Retirement Schemes Ordinance (“ORSO”) pension schemes. Each pension scheme has various guaranteed and non-guaranteed constituent funds, or investment options, in which customers can invest their money. The guaranteed funds provide either a guaranteed rate of return to the customer or a minimum guarantee on withdrawals under certain qualifying events. We determined the guaranteed funds are VIEs due to the fact the equity holders, as a group, lack the obligation to absorb expected losses due to the guarantee we provide. We concluded we are the primary beneficiary because we have the power to make decisions and to receive benefits and the obligation to absorb losses that could be potentially significant to the VIE. Therefore, we consolidate the underlying assets and liabilities of the funds and present as separate accounts or within the general account, depending on the terms of the guarantee. Real Estate We invest in several real estate limited partnerships and limited liability companies. The entities invest in real estate properties. Certain of these entities are VIEs based on the combination of our significant economic interest and related voting rights. We determined we are the primary beneficiary as a result of our power to control the entities through our significant ownership. Due to the nature of these real estate investments, the investment balance will fluctuate as we purchase and sell interests in the entities and as capital expenditures are made to improve the underlying real estate. Sponsored Investment Funds We sponsor and invest in certain investment funds for which we provide asset management services. Although our asset management fee is commensurate with the services provided and consistent with fees for similar services negotiated at arms-length, we have a variable interest for funds where our other interests are more than insignificant. The funds are VIEs as the equity holders lack power through voting rights to direct the activities of the entity that most significantly impact its economic performance. We determined we are the primary beneficiary of the VIEs where our interest in the entity is more than insignificant and we are the asset manager. We also invest in certain series of another investment fund. These series are VIEs as the equity holders of each series lack the power to direct the most significant activities of the VIE. We determined we are the primary beneficiary of these series as our interest is more than insignificant and collectively we have the power to direct the most significant activities of the fund. Assets and Liabilities of Consolidated Variable Interest Entities The carrying amounts of our consolidated VIE assets, which can only be used to settle obligations of consolidated VIEs, and liabilities of consolidated VIEs for which creditors do not have recourse were as follows: September 30, 2018 December 31, 2017 Total Total Total Total assets liabilities assets liabilities (in millions) Grantor trusts (1) $ $ $ $ CMBS — — Mandatory retirement savings funds (2) Real estate (3) Sponsored investment funds (4) Total $ $ $ $ (1) The assets of grantor trusts are primarily fixed maturities, available-for-sale. The liabilities are primarily other liabilities that reflect an embedded derivative of the forecasted transaction to deliver the underlying securities. (2) The assets of the mandatory retirement savings funds include separate account assets and equity securities. The liabilities include separate account liabilities and contractholder funds. (3) The assets of the real estate VIEs primarily include real estate, other investments and cash. Liabilities primarily include long-term debt and other liabilities. (4) The assets of sponsored investment funds are primarily fixed maturities and equity securities, which are reported with other investments, and cash. The consolidated statements of financial position included a $75.4 million and $52.4 million redeemable noncontrolling interest for sponsored investment funds as of September 30, 2018 and December 31, 2017, respectively. Unconsolidated Variable Interest Entities We hold a variable interest in a number of VIEs where we are not the primary beneficiary. Our investments in these VIEs are reported in fixed maturities, available-for-sale; fixed maturities, trading; equity securities (equity securities, trading as of December 31, 2017) and other investments in the consolidated statements of financial position and are described below. Unconsolidated VIEs include certain CMBS, residential mortgage-backed pass-through securities (“RMBS”) and other asset-backed securities (“ABS”). All of these entities were deemed VIEs because the equity within these entities is insufficient to sustain them. We determined we are not the primary beneficiary in the entities within these categories of investments. This determination was based primarily on the fact we do not own the class of security that controls the unilateral right to replace the special servicer or equivalent function. We invest in cash collateralized debt obligations, collateralized bond obligations, collateralized loan obligations and other collateralized structures, which are VIEs due to insufficient equity to sustain the entities. We have determined we are not the primary beneficiary of these entities primarily because we do not control the economic performance of the entities and were not involved with the design of the entities or because we do not have a potentially significant variable interest in the entities for which we are the asset manager. We have invested in various VIE trusts and similar entities as a debt holder. Most of these entities are classified as VIEs due to insufficient equity to sustain them. In addition, we have an entity classified as a VIE based on the combination of our significant economic interest and lack of voting rights. We have determined we are not the primary beneficiary primarily because we do not control the economic performance of the entities and were not involved with the design of the entities. We have invested in partnerships and other funds, which are classified as VIEs. The entities are VIEs as equity holders lack the power to control the most significant activities of the entities because the equity holders do not have either the ability by a simple majority to exercise substantive kick-out rights or substantive participating rights. We have determined we are not the primary beneficiary because we do not have the power to direct the most significant activities of the entities. As previously discussed, we sponsor, invest in and have other interests in certain investment funds that are VIEs. We determined we are not the primary beneficiary of the VIEs for which we are the asset manager but do not have a potentially significant variable interest in the funds. We hold an equity interest in Mexican mandatory privatized social security funds in which we provide asset management services. Our equity interest in the funds is considered a variable interest. We concluded the funds are VIEs because the equity holders as a group lack decision-making ability through their voting rights. We are not the primary beneficiary of the VIEs because although we, as the asset manager, have the power to direct the activities of the VIEs, we do not have a potentially significant variable interest in the funds. The carrying value and maximum loss exposure for our unconsolidated VIEs were as follows: Maximum exposure to Asset carrying value loss (1) (in millions) September 30, 2018 Fixed maturities, available-for-sale: Corporate $ $ Residential mortgage-backed pass-through securities Commercial mortgage-backed securities Collateralized debt obligations Other debt obligations Fixed maturities, trading: Residential mortgage-backed pass-through securities Commercial mortgage-backed securities Collateralized debt obligations Other debt obligations Equity securities Other investments: Other limited partnership and fund interests (2) December 31, 2017 Fixed maturities, available-for-sale: Corporate $ $ Residential mortgage-backed pass-through securities Commercial mortgage-backed securities Collateralized debt obligations Other debt obligations Fixed maturities, trading: Residential mortgage-backed pass-through securities Commercial mortgage-backed securities Equity securities Other investments: Other limited partnership and fund interests (1) Our risk of loss is limited to our initial investment measured at amortized cost for fixed maturities, available-for-sale. Our risk of loss is limited to our investment measured at fair value for our fixed maturities, trading and equity securities. Our risk of loss is limited to our carrying value plus any unfunded commitments and/or guarantees and similar provisions for our other investments. Unfunded commitments are not liabilities on our consolidated statements of financial position because we are only required to fund additional equity when called upon to do so by the general partner or investment manager. (2) As of September 30, 2018, the maximum exposure to loss for other limited partnership and fund interests includes $144.5 million of debt within certain of our managed international real estate funds that is fully secured by assets whose value exceeds the amount of the debt, but also includes recourse to the investment manager. Money Market Funds We are the investment manager for certain money market mutual funds. These types of funds are exempt from assessment under any consolidation model due to a scope exception for money market funds registered under Rule 2a-7 of the Investment Company Act of 1940 or similar funds. As of both September 30, 2018 and December 31, 2017, money market mutual funds we manage held $4.4 billion in total assets. We have no contractual obligation to contribute to these funds; however, we provide support through the waiver of fees and through expense reimbursements. The amount of fees waived and expenses reimbursed was insignificant.

Investments

Investments	9 Months Ended
	Sep. 30, 2018
Investments
Investments	3. Investments Fixed Maturities and Equity Securities Fixed maturities include bonds, ABS, redeemable preferred stock and certain non-redeemable preferred securities. Equity securities include mutual funds, common stock, non-redeemable preferred stock and required regulatory investments. We classify fixed maturities as either available-for-sale or trading at the time of the purchase and, accordingly, carry them at fair value. Equity securities are also carried at fair value. See Note 11, Fair Value Measurements, for methodologies related to the determination of fair value. Unrealized gains and losses related to fixed maturities, available-for-sale, excluding those in fair value hedging relationships, are reflected in stockholders’ equity, net of adjustments associated with DAC and related actuarial balances, derivatives in cash flow hedge relationships and applicable income taxes. Mark-to-market adjustments on equity securities, unrealized gains and losses related to hedged portions of fixed maturities, available-for-sale in fair value hedging relationships and mark-to-market adjustments on certain fixed maturities, trading are reflected in net realized capital gains (losses). Mark-to-market adjustments related to certain securities carried at fair value with an investment objective to realize economic value through mark-to-market changes are reflected in net investment income. The cost of fixed maturities is adjusted for amortization of premiums and accrual of discounts, both computed using the interest method. The cost of fixed maturities, available-for-sale is adjusted for declines in value that are other than temporary. Impairments in value deemed to be other than temporary are primarily reported in net income as a component of net realized capital gains (losses), with noncredit impairment losses for certain fixed maturities, available-for-sale reported in other comprehensive income (“OCI”). For loan-backed and structured securities, we recognize income using a constant effective yield based on currently anticipated cash flows. The recognition and measurement of equity investments was changed under authoritative guidance effective January 1, 2018. The guidance eliminated the classification of equity securities into different categories (trading or available-for-sale) and requires equity investments to be measured at fair value with changes in the fair value recognized through net income. See Note 1, Nature of Operations and Significant Accounting Policies, under the caption “Recent Accounting Pronouncements” for details of the adoption. The amortized cost, gross unrealized gains and losses, other-than-temporary impairments in AOCI and fair value of available-for-sale securities were as follows: Other-than- Gross Gross temporary Amortized unrealized unrealized impairments in cost gains losses Fair value AOCI (1) (in millions) September 30, 2018 Fixed maturities, available-for-sale: U.S. government and agencies $ $ $ $ $ — Non-U.S. governments — States and political subdivisions — Corporate Residential mortgage-backed pass-through securities — Commercial mortgage-backed securities Collateralized debt obligations Other debt obligations Total fixed maturities, available-for-sale $ $ $ $ $ December 31, 2017 Fixed maturities, available-for-sale: U.S. government and agencies $ $ $ $ $ — Non-U.S. governments — States and political subdivisions — Corporate Residential mortgage-backed pass-through securities — Commercial mortgage-backed securities Collateralized debt obligations Other debt obligations Total fixed maturities, available-for-sale $ $ $ $ $ Total equity securities, available-for-sale $ $ $ $ (1) Excludes $86.2 million and $103.0 million as of September 30, 2018 and December 31, 2017 , respectively, of net unrealized gains on impaired fixed maturities, available-for-sale related to changes in fair value subsequent to the impairment date, which are included in gross unrealized gains and gross unrealized losses. The amortized cost and fair value of fixed maturities, available-for-sale as of September 30, 2018, by expected maturity, were as follows: Amortized cost Fair value (in millions) Due in one year or less $ $ Due after one year through five years Due after five years through ten years Due after ten years Subtotal Mortgage-backed and other asset-backed securities Total $ $ Actual maturities may differ because borrowers may have the right to call or prepay obligations. Our portfolio is diversified by industry, issuer and asset class. Credit concentrations are managed to established limits. Net Realized Capital Gains and Losses Net realized capital gains and losses on sales of investments are determined on the basis of specific identification. In general, in addition to realized capital gains and losses on investment sales and periodic settlements on derivatives not designated as hedges, we report gains and losses related to the following in net realized capital gains (losses): other-than-temporary impairments of securities and subsequent realized recoveries, mark-to-market adjustments on equity securities, mark-to-market adjustments on certain fixed maturities, trading, mark-to-market adjustments on sponsored investment funds, fair value hedge and cash flow hedge ineffectiveness, mark-to-market adjustments on derivatives not designated as hedges, changes in the mortgage loan valuation allowance provision, impairments of real estate held for investment and impairments on equity method investments. Investment gains and losses on sales of certain real estate held for sale due to investment strategy and mark-to-market adjustments on certain securities carried at fair value with an investment objective to realize economic value through mark-to-market changes are reported as net investment income and are excluded from net realized capital gains (losses). The major components of net realized capital gains (losses) on investments were as follows: For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Fixed maturities, available-for-sale: Gross gains $ $ $ $ Gross losses Net impairment losses Hedging, net Fixed maturities, trading (1) Equity securities, trading (2) — — Equity securities (3) — — Mortgage loans Derivatives Other (4) Net realized capital gains (losses) $ $ $ $ (1) Unrealized gains (losses) on fixed maturities, trading still held at the reporting date were $(3.4) million and $(3.0) million for the three months ended September 30, 2018 and 2017, respectively, and $(16.7) million and $(0.4) million for the nine months ended September 30, 2018 and 2017, respectively. (2) Unrealized gains (losses) on equity securities, trading still held at the reporting date were $9.1 million and $36.6 million for the three and nine months ended September 30, 2017, respectively. This excludes $4.9 million and $32.2 million of unrealized gains (losses) on equity securities, trading still held at the reporting date for the three and nine months ended September 30, 2017, respectively, that were reported in net investment income. (3) Unrealized gains (losses) on equity securities still held at the reporting date were $8.8 million and $(5.2) million for the three and nine months ended September 30, 2018, respectively. This excludes $9.6 million and $12.8 million of unrealized gains (losses) on equity securities still held at the reporting date for the three and nine months ended September 30, 2018, respectively, that were reported in net investment income. (4) See Real Estate Transactions, for further details relating to other gains in 2017. Proceeds from sales of investments (excluding call and maturity proceeds) in fixed maturities, available-for-sale were $613.3 million and $163.2 million for the three months ended September 30, 2018 and 2017, and $2,351.0 million and $968.6 million for the nine months ended September 30, 2018 and 2017, respectively. Other-Than-Temporary Impairments We have a process in place to identify fixed maturity securities that could potentially have an impairment that is other than temporary. Prior to 2018, we also used this process to assess equity securities for impairment. This process involves monitoring market events that could impact issuers’ credit ratings, business climate, management changes, litigation and government actions and other similar factors. This process also involves monitoring late payments, pricing levels, downgrades by rating agencies, key financial ratios, financial statements, revenue forecasts and cash flow projections as indicators of credit issues. Each reporting period, all securities are reviewed to determine whether an other-than-temporary decline in value exists and whether losses should be recognized. We consider relevant facts and circumstances in evaluating whether a credit or interest rate related impairment of a security is other than temporary. Relevant facts and circumstances considered include: (1) the extent and length of time the fair value has been below cost; (2) the reasons for the decline in value; (3) the financial position and access to capital of the issuer, including the current and future impact of any specific events; (4) for structured securities, the adequacy of the expected cash flows; (5) for fixed maturities, our intent to sell a security or whether it is more likely than not we will be required to sell the security before the recovery of its amortized cost which, in some cases, may extend to maturity and (6) for equity securities, our ability and intent to hold the security for a period of time that allows for the recovery in value. To the extent we determine a security is deemed to be other than temporarily impaired, an impairment loss is recognized. The way in which impairment losses on fixed maturities are recognized in the financial statements is dependent on the facts and circumstances related to the specific security. If we intend to sell a security or it is more likely than not that we would be required to sell a security before the recovery of its amortized cost, we recognize an other-than-temporary impairment in net income for the difference between amortized cost and fair value. If we do not expect to recover the amortized cost basis, we do not plan to sell the security and if it is not more likely than not that we would be required to sell a security before the recovery of its amortized cost, the recognition of the other-than-temporary impairment is bifurcated. We recognize the credit loss portion in net income and the noncredit loss portion in OCI (“bifurcated OTTI”). Prior to 2018, impairment losses on equity securities were recognized in net income and were measured as the difference between amortized cost and fair value. Total other-than-temporary impairment losses, net of recoveries from the sale of previously impaired securities, were as follows: For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Fixed maturities, available-for-sale $ $ $ $ Total other-than-temporary impairment losses, net of recoveries from the sale of previously impaired securities Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified from OCI (1) Net impairment losses on available-for-sale securities $ $ $ $ (1) Represents the net impact of (a) gains resulting from reclassification of noncredit impairment losses for fixed maturities with bifurcated OTTI from net realized capital gains (losses) to OCI and (b) losses resulting from reclassification of previously recognized noncredit impairment losses from OCI to net realized capital gains (losses) for fixed maturities with bifurcated OTTI that had additional credit losses or fixed maturities that previously had bifurcated OTTI that have now been sold or are intended to be sold. We estimate the amount of the credit loss component of a fixed maturity security impairment as the difference between amortized cost and the present value of the expected cash flows of the security. The present value is determined using the best estimate cash flows discounted at the effective interest rate implicit to the security at the date of purchase or the current yield to accrete an asset-backed or floating rate security. The methodology and assumptions for establishing the best estimate cash flows vary depending on the type of security. The ABS cash flow estimates are based on security specific facts and circumstances that may include collateral characteristics, expectations of delinquency and default rates, loss severity and prepayment speeds and structural support, including subordination and guarantees. The corporate security cash flow estimates are derived from scenario-based outcomes of expected corporate restructurings or liquidations using bond specific facts and circumstances including timing, security interests and loss severity. The following table provides a rollforward of accumulated credit losses for fixed maturities with bifurcated credit losses. The purpose of the table is to provide detail of (1) additions to the bifurcated credit loss amounts recognized in net realized capital gains (losses) during the period and (2) decrements for previously recognized bifurcated credit losses where the loss is no longer bifurcated and/or there has been a positive change in expected cash flows or accretion of the bifurcated credit loss amount. For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Beginning balance $ $ $ $ Credit losses for which an other-than-temporary impairment was not previously recognized — Credit losses for which an other-than-temporary impairment was previously recognized Reduction for credit losses previously recognized on fixed maturities now sold, paid down or intended to be sold Net reduction for positive changes in cash flows expected to be collected and amortization (1) Foreign currency translation adjustment — — — Ending balance $ $ $ $ (1) Amounts are recognized in net investment income. Gross Unrealized Losses for Available-for-Sale Securities For available-for-sale securities with unrealized losses, including other-than-temporary impairment losses reported in OCI, the gross unrealized losses and fair value, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position were as follows: September 30, 2018 Less than Greater than or twelve months equal to twelve months Total Gross Gross Gross Fair unrealized Fair unrealized Fair unrealized value losses value losses value losses (in millions) Fixed maturities, available-for-sale: U.S. government and agencies $ $ $ $ $ $ Non-U.S. governments States and political subdivisions Corporate Residential mortgage-backed pass-through securities Commercial mortgage-backed securities Collateralized debt obligations Other debt obligations Total fixed maturities, available-for-sale $ $ $ $ $ $ Of the total amounts, Principal Life Insurance Company’s (“Principal Life’s”) consolidated portfolio represented $35,846.3 million in available-for-sale fixed maturities with gross unrealized losses of $1,106.5 million. Of the available-for-sale fixed maturities within Principal Life’s consolidated portfolio in a gross unrealized loss position, 97% were investment grade (rated AAA through BBB-) with an average price of 97 (carrying value/amortized cost) as of September 30, 2018. Gross unrealized losses in our fixed maturities portfolio increased during the nine months ended September 30, 2018, primarily due to an increase in interest rates. For those securities that had been in a continuous unrealized loss position for less than twelve months, Principal Life’s consolidated portfolio held 3,276 securities with a carrying value of $28,160.0 million and unrealized losses of $684.2 million reflecting an average price of 98 as of September 30, 2018. Of this portfolio, 97% was investment grade (rated AAA through BBB-) as of September 30, 2018, with associated unrealized losses of $660.2 million. The unrealized losses on these securities can primarily be attributed to changes in market interest rates and changes in credit spreads since the securities were acquired. For those securities that had been in a continuous unrealized loss position greater than or equal to twelve months, Principal Life’s consolidated portfolio held 1,215 securities with a carrying value of $7,686.3 million and unrealized losses of $422.3 million. The average credit rating of this portfolio was AA with an average price of 95 as of September 30, 2018. Of the $422.3 million in unrealized losses, the corporate sector accounts for $148.5 million in unrealized losses with an average price of 94 and an average credit rating of A-. The remaining unrealized losses also include $79.2 million within the commercial mortgage-backed securities sector with an average price of 95 and an average credit rating of AA+. The unrealized losses on these securities can primarily be attributed to changes in market interest rates and changes in credit spreads since the securities were acquired. Because we expected to recover our amortized cost, it was not our intent to sell the fixed maturity available-for-sale securities with unrealized losses and it was not more likely than not that we would be required to sell these securities before recovery of the amortized cost, which may be at maturity, we did not consider these investments to be other-than-temporarily impaired as of September 30, 2018. December 31, 2017 Less than Greater than or twelve months equal to twelve months Total Gross Gross Gross Fair unrealized Fair unrealized Fair unrealized value losses value losses value losses (in millions) Fixed maturities, available-for-sale: U.S. government and agencies $ $ $ $ $ $ Non-U.S. governments States and political subdivisions Corporate Residential mortgage-backed pass-through securities Commercial mortgage-backed securities Collateralized debt obligations Other debt obligations Total fixed maturities, available-for-sale $ $ $ $ $ $ Total equity securities, available-for-sale $ — $ — $ $ $ $ Of the total amounts, Principal Life Insurance Company’s (“Principal Life’s”) consolidated portfolio represented $14,059.5 million in available-for-sale fixed maturities with gross unrealized losses of $239.7 million. Of the available-for-sale fixed maturities within Principal Life’s consolidated portfolio in a gross unrealized loss position, 97% were investment grade (rated AAA through BBB-) with an average price of 98 (carrying value/amortized cost) as of December 31, 2017. Gross unrealized losses in our fixed maturities portfolio decreased during the year ended December 31, 2017, primarily due to tightening of credit spreads. For those securities that had been in a continuous unrealized loss position for less than twelve months, Principal Life’s consolidated portfolio held 1,209 securities with a carrying value of $9,360.9 million and unrealized losses of $75.4 million reflecting an average price of 99 as of December 31, 2017. Of this portfolio, 98% was investment grade (rated AAA through BBB-) as of December 31, 2017, with associated unrealized losses of $71.5 million. The unrealized losses on these securities can primarily be attributed to changes in market interest rates and changes in credit spreads since the securities were acquired. For those securities that had been in a continuous unrealized loss position greater than or equal to twelve months, Principal Life’s consolidated portfolio held 775 securities with a carrying value of $4,698.6 million and unrealized losses of $164.3 million. The average credit rating of this portfolio was AA- with an average price of 97 as of December 31, 2017. Of the $164.3 million in unrealized losses, the corporate sector accounts for $52.2 million in unrealized losses with an average price of 97 and an average credit rating of BBB+. The remaining unrealized losses also include $38.1 million within the commercial mortgage-backed securities sector with an average price of 96 and an average credit rating of AA+. The unrealized losses on these securities can primarily be attributed to changes in market interest rates and changes in credit spreads since the securities were acquired. Because we expected to recover our amortized cost, it was not our intent to sell the fixed maturity available-for-sale securities with unrealized losses and it was not more likely than not that we would be required to sell these securities before recovery of the amortized cost, which may be at maturity, we did not consider these investments to be other-than-temporarily impaired as of December 31, 2017. Net Unrealized Gains and Losses on Available-for-Sale Securities and Derivative Instruments The net unrealized gains and losses on investments in available-for-sale securities, the noncredit component of impairment losses on fixed maturities available-for-sale and the net unrealized gains and losses on derivative instruments in cash flow hedge relationships are reported as separate components of stockholders’ equity. The cumulative amount of net unrealized gains and losses on available-for-sale securities and derivative instruments in cash flow hedge relationships net of adjustments related to DAC and related actuarial balances and applicable income taxes was as follows: September 30, 2018 December 31, 2017 (in millions) Net unrealized gains on fixed maturities, available-for-sale (1) $ $ Noncredit component of impairment losses on fixed maturities, available-for-sale Net unrealized gains on equity securities, available-for-sale — Adjustments for assumed changes in amortization patterns Adjustments for assumed changes in policyholder liabilities Net unrealized gains on derivative instruments Net unrealized gains on equity method subsidiaries and noncontrolling interest adjustments Provision for deferred income taxes Net unrealized gains on available-for-sale securities and derivative instruments $ $ (1) Excludes net unrealized gains (losses) on fixed maturities, available-for-sale included in fair value hedging relationships. Mortgage Loans Mortgage loans consist of commercial and residential mortgage loans. We evaluate risks inherent in our commercial mortgage loans in two classes: (1) brick and mortar property loans, including mezzanine loans, where we analyze the property’s rent payments as support for the loan, and (2) credit tenant loans (“CTL”), where we rely on the credit analysis of the tenant for the repayment of the loan. We evaluate risks inherent in our residential mortgage loan portfolio in two classes: (1) home equity mortgages and (2) first lien mortgages. The carrying amount of our mortgage loan portfolio was as follows: September 30, 2018 December 31, 2017 (in millions) Commercial mortgage loans $ $ Residential mortgage loans Total amortized cost Valuation allowance Total carrying value $ $ We periodically purchase mortgage loans as well as sell mortgage loans we have originated. Mortgage loans purchased and sold were as follows: For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Commercial mortgage loans: Purchased $ $ $ $ Sold — — — Residential mortgage loans: Purchased Sold Our commercial mortgage loan portfolio consists primarily of non-recourse, fixed rate mortgages on stabilized properties. Our commercial mortgage loan portfolio is diversified by geographic region and specific collateral property type as follows: September 30, 2018 December 31, 2017 Amortized Percent Amortized Percent cost of total cost of total ($ in millions) Geographic distribution New England $ % $ % Middle Atlantic East North Central West North Central South Atlantic East South Central West South Central Mountain Pacific International Total $ % $ % Property type distribution Office $ % $ % Retail Industrial Apartments Hotel Mixed use/other Total $ % $ % Our residential mortgage loan portfolio is composed of home equity mortgages with an amortized cost of $17.1 million and $23.0 million and first lien mortgages with an amortized cost of $1,336.4 million and $1,262.9 million as of September 30, 2018 and December 31, 2017, respectively. Our residential home equity mortgages are concentrated in the United States and are generally second lien mortgages comprised of closed-end loans and lines of credit. Our first lien loans are concentrated in Chile and the United States. Mortgage Loan Credit Monitoring Commercial Credit Risk Profile Based on Internal Rating We actively monitor and manage our commercial mortgage loan portfolio. All commercial mortgage loans are analyzed regularly and substantially all are internally rated, based on a proprietary risk rating cash flow model, in order to monitor the financial quality of these assets. The model stresses expected cash flows at various levels and at different points in time depending on the durability of the income stream, which includes our assessment of factors such as location (macro and micro markets), tenant quality and lease expirations. Our internal rating analysis presents expected losses in terms of an S&P Global (“S&P”) bond equivalent rating. As the credit risk for commercial mortgage loans increases, we adjust our internal ratings downward with loans in the category “B+ and below” having the highest risk for credit loss. Internal ratings on commercial mortgage loans are updated at least annually and potentially more often for certain loans with material changes in collateral value or occupancy and for loans on an internal “watch list”. Commercial mortgage loans that require more frequent and detailed attention are identified and placed on an internal “watch list”. Among the criteria that would indicate a potential problem are significant negative changes in ratios of loan to value or contract rents to debt service, major tenant vacancies or bankruptcies, borrower sponsorship problems, late payments, delinquent taxes and loan relief/restructuring requests. The amortized cost of our commercial mortgage loan portfolio by credit risk, as determined by our internal rating system expressed in terms of an S&P bond equivalent rating, was as follows: September 30, 2018 Brick and mortar CTL Total (in millions) A- and above $ $ $ BBB+ thru BBB- BB+ thru BB- — B+ and below Total $ $ $ December 31, 2017 Brick and mortar CTL Total (in millions) A- and above $ $ $ BBB+ thru BBB- BB+ thru BB- — B+ and below Total $ $ $ Residential Credit Risk Profile Based on Performance Status Our residential mortgage loan portfolio is monitored based on performance of the loans. Monitoring on a residential mortgage loan increases when the loan is delinquent or earlier if there is an indication of potential impairment. We define non-performing residential mortgage loans as loans 90 days or greater delinquent or on non-accrual status. The amortized cost of our performing and non-performing residential mortgage loans was as follows: September 30, 2018 Home equity First liens Total (in millions) Performing $ $ $ Non-performing Total $ $ $ December 31, 2017 Home equity First liens Total (in millions) Performing $ $ $ Non-performing Total $ $ $ Non-Accrual Mortgage Loans Commercial and residential mortgage loans are placed on non-accrual status if we have concern regarding the collectability of future payments or if a loan has matured without being paid off or extended. Factors considered may include conversations with the borrower, loss of major tenant, bankruptcy of borrower or major tenant, decreased property cash flow for commercial mortgage loans or number of days past due and other circumstances for residential mortgage loans. Based on an assessment as to the collectability of the principal, a determination is made to apply any payments received either against the principal, against the valuation allowance or according to the contractual terms of the loan. When a loan is placed on non-accrual status, the accrued unpaid interest receivable is reversed against interest income. Accrual of interest resumes after factors resulting in doubts about collectability have improved. Residential first lien mortgages in the Chilean market are carried on accrual for a longer period of delinquency than domestic loans, as assessment of collectability is based on the nature of the loans and collection practices in that market. The amortized cost of mortgage loans on non-accrual status was as follows: September 30, 2018 December 31, 2017 (in millions) Residential: Home equity $ $ First liens Total $ $ The aging of our mortgage loans, based on amortized cost, was as follows: September 30, 2018 Recorded investment 90 days or 90 days or 30-59 days 60-89 days more past Total past more and past due past due due due Current Total loans accruing (in millions) Commercial-brick and mortar $ — $ — $ — $ — $ $ $ — Commercial-CTL — — — — — Residential-home equity — Residential-first liens Total $ $ $ $ $ $ $ December 31, 2017 Recorded investment 90 days or 90 days or 30-59 days 60-89 days more past Total past more and past due past due due due Current Total loans accruing (in millions) Commercial-brick and mortar $ — $ — $ — $ — $ $ $ — Commercial-CTL — — — — — Residential-home equity — Residential-first liens Total $ $ $ $ $ $ $ Mortgage Loan Valuation Allowance We establish a valuation allowance to provide for the risk of credit losses inherent in our portfolio. The valuation allowance includes loan specific reserves for loans that are deemed to be impaired as well as reserves for pools of loans with similar risk characteristics where a property risk or market specific risk has not been identified but for which we anticipate a loss may occur. Mortgage loans on real estate are considered impaired when, based on current information and events, it is probable we will be unable to collect all amounts due according to contractual terms of the loan agreement. When we determine a loan is impaired, a valuation allowance is established equal to the difference between the carrying amount of the mortgage loan and the estimated value reduced by the cost to sell. Estimated value is based on either the present value of the expected future cash flows discounted at the loan’s effective interest rate, the loan’s observable market price or fair value of the collateral. Subsequent changes in the estimated value are reflected in the valuation allowance. Amounts on loans deemed to be uncollectible are charged off and removed from the valuation allowance. The change in the valuation allowance provision is included in net realized capital gains (losses) on our consolidated statements of operations. The valuation allowance is maintained at a level believed adequate by management to absorb estimated probable credit losses. Management’s periodic evaluation and assessment of the valuation allowance adequacy is based on known and inherent risks in the portfolio, adverse situations that may affect a borrower’s ability to repay, the estimated value of the underlying collateral, composition of the loan portfolio, portfolio delinquency information, underwriting standards, peer group information, current economic conditions, loss experience and other relevant factors. The evaluation of our impaired loan component is subjective, as it requires the estimation of timing and amount of future cash flows expected to be received on impaired loans. We review our commercial mortgage loan portfolio and analyze the need for a valuation allowance for any loan that is delinquent for 60 days or more, in process of foreclosure, restructured, on the internal “watch list” or that currently has a valuation allowance. In addition to establishing allowance levels for specifically identified impaired commercial mortgage loans, management determines an allowance for all other loans in the portfolio for which historical experience and current economic conditions indicate certain losses exist. These loans are segregated by risk rating level with an estimated loss ratio applied against each risk rating level. The loss ratio is generally based upon historical loss experience for each risk rating level as adjusted for certain current environmental factors management believes to be relevant. For our residential mortgage loan portfolio, we separate the loans into several homogeneous pools, each of which consist of loans of a similar nature including but not limited to loans similar in collateral, term and structure and loan purpose or type. We evaluate loan pools based on aggregated risk ratings, estimated specific loss potential in the different classes of credits, and h

Derivative Financial Instrument

Derivative Financial Instruments	9 Months Ended
	Sep. 30, 2018
Derivative Financial Instruments
Derivative Financial Instruments	4. Derivative Financial Instruments Derivatives are generally used to hedge or reduce exposure to market risks associated with assets held or expected to be purchased or sold and liabilities incurred or expected to be incurred. Derivatives are used to change the characteristics of our asset/liability mix consistent with our risk management activities. Derivatives are also used in asset replication strategies. Types of Derivative Instruments Interest Rate Contracts Interest rate risk is the risk we will incur economic losses due to adverse changes in interest rates. Sources of interest rate risk include the difference between the maturity and interest rate changes of assets with the liabilities they support, timing differences between the pricing of liabilities and the purchase or procurement of assets and changing cash flow profiles from original projections due to prepayment options embedded within asset and liability contracts. We use various derivatives to manage our exposure to fluctuations in interest rates. Interest rate swaps are contracts in which we agree with other parties to exchange, at specified intervals, the difference between fixed rate and/or floating rate interest amounts based upon designated market rates or rate indices and an agreed upon notional principal amount. Generally, no cash is exchanged at the outset of the contract and no principal payments are made by any party. Cash is paid or received based on the terms of the swap. We use interest rate swaps primarily to more closely match the interest rate characteristics of assets and liabilities and to mitigate the risks arising from timing mismatches between assets and liabilities (including duration mismatches). We also use interest rate swaps to hedge against changes in the value of assets we anticipate acquiring and other anticipated transactions and commitments. Interest rate swaps are used to hedge against changes in the value of the guaranteed minimum withdrawal benefit (“GMWB”) liability. The GMWB rider on our variable annuity products provides for guaranteed minimum withdrawal benefits regardless of the actual performance of various equity and/or fixed income funds available with the product. Interest rate options, including interest rate caps and interest rate floors, which can be combined to form interest rate collars, are contracts that entitle the purchaser to pay or receive the amounts, if any, by which a specified market rate exceeds a cap strike interest rate, or falls below a floor strike interest rate, respectively, at specified dates. We use interest rate options to manage prepayment risks in our assets and minimum guaranteed interest rates and lapse risks in our liabilities. A swaption is an option to enter into an interest rate swap at a future date. We have purchased swaptions to offset or modify existing exposures. Swaptions provide us the benefit of the agreed-upon strike rate if the market rates for liabilities are higher, with the flexibility to enter into the current market rate swap if the market rates for liabilities are lower. Swaptions not only hedge against the downside risk, but also allow us to take advantage of any upside benefits. In exchange-traded futures transactions, we agree to purchase or sell a specified number of contracts, the values of which are determined by the values of designated classes of securities, and to post variation margin on a daily basis in an amount equal to the difference in the daily market values of those contracts. We enter into exchange-traded futures with regulated futures commissions merchants who are members of a trading exchange. We have used exchange-traded futures to reduce market risks from changes in interest rates and to alter mismatches between the assets in a portfolio and the liabilities supported by those assets. Foreign Exchange Contracts Foreign currency risk is the risk we will incur economic losses due to adverse fluctuations in foreign currency exchange rates. This risk arises from foreign currency ‑ denominated funding agreements issued to nonqualified institutional investors in the international market, foreign currency ‑ denominated fixed maturity and equity securities, and our international operations, including expected cash flows and potential acquisition and divestiture activity. We use various derivatives to manage our exposure to fluctuations in foreign currency exchange rates. Currency swaps are contracts in which we agree with other parties to exchange, at specified intervals, a series of principal and interest payments in one currency for that of another currency. Generally, the principal amount of each currency is exchanged at the beginning and termination of the currency swap by each party. The interest payments are primarily fixed-to-fixed rate; however, they may also be fixed-to-floating rate or floating-to-fixed rate. These transactions are entered into pursuant to master agreements that provide for a single net payment to be made by one counterparty for payments made in the same currency at each due date. We use currency swaps to reduce market risks from changes in currency exchange rates with respect to investments or liabilities denominated in foreign currencies that we either hold or intend to acquire or sell. Currency forwards are contracts in which we agree with other parties to deliver or receive a specified amount of an identified currency at a specified future date. Typically, the price is agreed upon at the time of the contract and payment for such a contract is made at the specified future date. We use currency forwards to reduce market risks from changes in currency exchange rates with respect to investments or liabilities denominated in foreign currencies that we either hold or intend to acquire or sell. We sometimes use currency forwards to hedge the currency risk associated with a business combination or to hedge certain net equity investments in or expected cash flows from our foreign operations. Currency options are contracts that give the holder the right, but not the obligation to buy or sell a specified amount of the identified currency within a limited period of time at a contracted price. The contracts are net settled in cash, based on the differential in the current foreign exchange rate and the strike price. Purchased and sold options can be combined to form a foreign currency collar where we receive a payment if the foreign exchange rate is below the purchased option strike price and make a payment if the foreign exchange rate is above the sold option strike price. We use currency options to hedge expected cash flows from our foreign operations. Equity Contracts Equity risk is the risk that we will incur economic losses due to adverse fluctuations in common stock prices. We use various derivatives to manage our exposure to equity risk, which arises from products in which the interest we credit is tied to an external equity index as well as products subject to minimum contractual guarantees. We purchase equity call spreads (“option collars”) to hedge the equity participation rates promised to contractholders in conjunction with our fixed deferred annuity and universal life products that credit interest based on changes in an external equity index. We use exchange-traded futures and equity put options to hedge against changes in the value of the GMWB liability related to the GMWB rider on our variable annuity product. The premium associated with certain options is paid quarterly over the life of the option contract. Credit Contracts Credit risk relates to the uncertainty associated with the continued ability of a given obligor to make timely payments of principal and interest. We use credit default swaps to enhance the return on our investment portfolio by providing comparable exposure to fixed income securities that might not be available in the primary market. They are also used to hedge credit exposures in our investment portfolio. Credit derivatives are used to sell or buy credit protection on an identified name or names on an unfunded or synthetic basis in return for receiving or paying a quarterly premium. The premium generally corresponds to a referenced name’s credit spread at the time the agreement is executed. In cases where we sell protection, we also buy a quality cash bond to match against the credit default swap, thereby entering into a synthetic transaction replicating a cash security. When selling protection, if there is an event of default by the referenced name, as defined by the agreement, we are obligated to pay the counterparty the referenced amount of the contract and receive in return the referenced security in a principal amount equal to the notional value of the credit default swap. Total return swaps are contracts in which we agree with other parties to exchange, at specified intervals, an amount determined by the difference between the previous price and the current price of a reference asset based upon an agreed upon notional principal amount plus an additional amount determined by the financing spread. We have used futures traded on an exchange (“exchange-traded”) and total return swaps referencing equity indices to hedge our portfolio from potential credit losses related to systemic events. Other Contracts Embedded Derivatives. We purchase or issue certain financial instruments or products that contain a derivative instrument that is embedded in the financial instrument or product. When it is determined that the embedded derivative possesses economic characteristics that are not clearly or closely related to the economic characteristics of the host contract and a separate instrument with the same terms would qualify as a derivative instrument, the embedded derivative is bifurcated from the host instrument for measurement purposes. The embedded derivative, which is reported with the host instrument in the consolidated statements of financial position, is carried at fair value. We had investment contracts in which the return was tied to a leveraged inflation index. We economically hedged the risk associated with these investment contracts. We offer group annuity contracts that have guaranteed separate accounts as an investment option. We also offer funds with embedded fixed-rate guarantees as investment options in our defined contribution plans in Hong Kong. We have structured investment relationships with trusts we have determined to be VIEs, which are consolidated in our financial statements. The notes issued by these trusts include obligations to deliver an underlying security to residual interest holders and the obligations contain an embedded derivative of the forecasted transaction to deliver the underlying security. We have fixed deferred annuities and universal life products that credit interest based on changes in an external equity index. We also have certain variable annuity products with a GMWB rider, which allows the customer to make withdrawals of a specified annual amount, either for a fixed number of years or for the lifetime of the customer, even if the account value is fully exhausted. Declines in the equity markets may increase our exposure to benefits under contracts with the GMWB. We economically hedge the exposure in these contracts, as previously explained. Exposure Our risk of loss is typically limited to the fair value of our derivative instruments and not to the notional or contractual amounts of these derivatives. We are also exposed to credit losses in the event of nonperformance of the counterparties. Our current credit exposure is limited to the value of derivatives that have become favorable to us. This credit risk is minimized by purchasing such agreements from financial institutions with high credit ratings and by establishing and monitoring exposure limits. We also utilize various credit enhancements, including collateral and credit triggers to reduce the credit exposure to our derivative instruments. Derivatives may be exchange-traded or they may be privately negotiated contracts, which are usually referred to as over-the-counter (“OTC”) derivatives. Certain of our OTC derivatives are cleared and settled through central clearing counterparties (“OTC cleared”), while others are bilateral contracts between two counterparties (“bilateral OTC”). Our derivative transactions are generally documented under International Swaps and Derivatives Association, Inc. (“ISDA”) Master Agreements. Management believes that such agreements provide for legally enforceable set-off and close-out netting of exposures to specific counterparties. Under such agreements, in connection with an early termination of a transaction, we are permitted to set off our receivable from a counterparty against our payables to the same counterparty arising out of all included transactions. For reporting purposes, we do not offset fair value amounts of bilateral OTC derivatives for the right to reclaim cash collateral or the obligation to return cash collateral against fair value amounts recognized for derivative instruments executed with the same counterparties under master netting agreements. OTC cleared derivatives have variation margin that is legally characterized as settlement of the derivative exposure, which reduces their fair value in the consolidated statements of financial position. We posted $203.6 million and $195.0 million in cash and securities under collateral arrangements as of September 30, 2018 and December 31, 2017, respectively, to satisfy collateral and initial margin requirements associated with our derivative credit support agreements and FCM agreements. Certain of our derivative instruments contain provisions that require us to maintain an investment grade rating from each of the major credit rating agencies on our debt. If the ratings on our debt were to fall below investment grade, it would be in violation of these provisions and the counterparties to the derivative instruments could request immediate payment or demand immediate and ongoing full overnight collateralization on derivative instruments in net liability positions. The aggregate fair value, inclusive of accrued interest, of all derivative instruments with credit-risk-related contingent features that were in a liability position without regard to netting under derivative credit support annex agreements as of September 30, 2018 and December 31, 2017, was $233.2 million and $280.4 million, respectively. Cleared derivatives have contingent features that require us to post excess margin as required by the FCM. The terms surrounding excess margin vary by FCM agreement. With respect to derivatives containing collateral triggers, we posted collateral and initial margin of $203.6 million and $195.0 million as of September 30, 2018 and December 31, 2017, respectively, in the normal course of business, which reflects netting under derivative agreements. If the credit-risk-related contingent features underlying these agreements were triggered on September 30, 2018, we would be required to post an additional $20.6 million of collateral to our counterparties. As of September 30, 2018 and December 31, 2017, we had received $61.6 million and $124.7 million, respectively, of cash collateral associated with our derivative credit support annex agreements and FCM agreements, for which we recorded a corresponding liability reflecting our obligation to return the collateral. Notional amounts are used to express the extent of our involvement in derivative transactions and represent a standard measurement of the volume of our derivative activity. Notional amounts represent those amounts used to calculate contractual flows to be exchanged and are not paid or received, except for contracts such as currency swaps. Credit exposure represents the gross amount owed to us under derivative contracts as of the valuation date. The notional amounts and credit exposure of our derivative financial instruments by type were as follows: September 30, 2018 December 31, 2017 (in millions) Notional amounts of derivative instruments Interest rate contracts: Interest rate swaps $ $ Interest rate options Interest rate futures Swaptions — Foreign exchange contracts: Currency forwards Currency swaps Currency options Equity contracts: Equity options Equity futures Credit contracts: Credit default swaps Other contracts: Embedded derivatives Total notional amounts at end of period $ $ Credit exposure of derivative instruments Interest rate contracts: Interest rate swaps $ $ Interest rate options Foreign exchange contracts: Currency swaps Currency forwards Currency options Equity contracts: Equity options Credit contracts: Credit default swaps Total gross credit exposure Less: collateral received Net credit exposure $ $ The fair value of our derivative instruments classified as assets and liabilities was as follows: Derivative assets (1) Derivative liabilities (2) September 30, 2018 December 31, 2017 September 30, 2018 December 31, 2017 (in millions) Derivatives designated as hedging instruments Interest rate contracts $ — $ — $ $ Foreign exchange contracts Total derivatives designated as hedging instruments $ $ $ $ Derivatives not designated as hedging instruments Interest rate contracts $ $ $ $ Foreign exchange contracts Equity contracts Credit contracts Other contracts — — Total derivatives not designated as hedging instruments Total derivative instruments $ $ $ $ (1) The fair value of derivative assets is reported with other investments on the consolidated statements of financial position. (2) The fair value of derivative liabilities is reported with other liabilities on the consolidated statements of financial position, with the exception of certain embedded derivative liabilities. Embedded derivatives with a net (asset) liability fair value of $(81.9) million and $160.3 million as of September 30, 2018 and December 31, 2017, respectively, are reported with contractholder funds on the consolidated statements of financial position. Credit Derivatives Sold When we sell credit protection, we are exposed to the underlying credit risk similar to purchasing a fixed maturity security instrument. Our credit derivative contracts sold reference a single name or reference security (referred to as “single name credit default swaps”). These instruments are either referenced in an OTC credit derivative transaction or embedded within an investment structure that has been fully consolidated into our financial statements. These credit derivative transactions are subject to events of default defined within the terms of the contract, which normally consist of bankruptcy, failure to pay, or modified restructuring of the reference entity and/or issue. If a default event occurs for a reference name or security, we are obligated to pay the counterparty an amount equal to the notional amount of the credit derivative transaction. As a result, our maximum future payment is equal to the notional amount of the credit derivative. In certain cases, we also may have purchased credit protection with identical underlyings to certain of our sold protection transactions. As of September 30, 2018 and December 31, 2017, we did not purchase credit protection relating to our sold protection transactions. In certain circumstances, our potential loss could also be reduced by any amount recovered in the default proceedings of the underlying credit name. The following tables show our credit default swap protection sold by types of contract, types of referenced/underlying asset class and external agency rating for the underlying reference security. The maximum future payments are undiscounted and have not been reduced by the effect of any offsetting transactions, collateral or recourse features described above. September 30, 2018 Weighted Maximum average Notional Fair future expected life amount value payments (in years) (in millions) Single name credit default swaps Corporate debt AAA $ $ $ A BBB B Government/municipalities AA Sovereign A BBB Total credit default swap protection sold $ $ $ December 31, 2017 Weighted Maximum average Notional Fair future expected life amount value payments (in years) (in millions) Single name credit default swaps Corporate debt AAA $ $ $ AA A BBB B Government/municipalities AA Sovereign A BBB Total credit default swap protection sold $ $ $ Fair Value Hedges We use fixed-to-floating rate interest rate swaps to more closely align the interest rate characteristics of certain assets and have used them to align the interest rate characteristics of certain liabilities. In general, these swaps are used in asset and liability management to modify duration, which is a measure of sensitivity to interest rate changes. The net interest effect of interest rate swap transactions for derivatives in fair value hedges is recorded as an adjustment to income or expense of the underlying hedged item in our consolidated statements of operations. Hedge effectiveness testing for fair value relationships is performed utilizing a regression analysis approach for both prospective and retrospective evaluations. This regression analysis will consider multiple data points for the assessment that the hedge continues to be highly effective in achieving offsetting changes in fair value. In certain periods, the comparison of the change in value of the derivative and the change in the value of the hedged item may not be offsetting at a specific period in time due to small movements in value. However, any amounts recorded as fair value hedges have shown to be highly effective in achieving offsetting changes in fair value both for present and future periods. The following table shows the effect of derivatives in fair value hedging relationships and the related hedged items on the consolidated statements of operations. All gains or losses on derivatives were included in the assessment of hedge effectiveness. Amount of loss Amount of gain recognized in net income on recognized in net income on related hedged item for the derivatives for the three months three months ended Derivatives in fair value hedging ended September 30, (1) Hedged items in fair value September 30, (1) relationships 2018 2017 hedging relationships 2018 2017 (in millions) (in millions) Interest rate contracts $ $ Fixed maturities, available-for-sale $ $ Interest rate contracts — Investment contracts — Total $ $ Total $ $ Amount of gain (loss) Amount of gain (loss) recognized in net income recognized in net income on on related hedged item derivatives for the nine months for the nine months Derivatives in fair value hedging ended September 30, (1) Hedged items in fair value ended September 30, (1) relationships 2018 2017 hedging relationships 2018 2017 (in millions) (in millions) Interest rate contracts $ $ Fixed maturities, available-for-sale $ $ Interest rate contracts — Investment contracts — Total $ $ Total $ $ (1) The gain (loss) on both derivatives and hedged items in fair value relationships is reported in net realized capital gains (losses) on the consolidated statements of operations. The net amount represents the ineffective portion of our fair value hedges. The following table shows the periodic settlements on interest rate contracts and foreign exchange contracts in fair value hedging relationships. Amount of gain (loss) for the three Amount of gain (loss) for the months ended September 30, nine months ended September 30, Hedged item 2018 2017 2018 2017 (in millions) Fixed maturities, available-for-sale (1) $ $ $ $ Investment contracts (2) — — (1) Reported in net investment income on the consolidated statements of operations. (2) Reported in benefits, claims and settlement expenses on the consolidated statements of operations. Cash Flow Hedges We utilize floating-to-fixed rate interest rate swaps to eliminate the variability in cash flows of recognized financial assets and liabilities and forecasted transactions. We enter into currency exchange swap agreements to convert both principal and interest payments of certain foreign denominated assets and liabilities into U.S. dollar denominated fixed-rate instruments to eliminate the exposure to future currency volatility on those items. The net interest effect of interest rate swap and currency swap transactions for derivatives in cash flow hedges is recorded as an adjustment to income or expense of the underlying hedged item in our consolidated statements of operations. The maximum length of time we are hedging our exposure to the variability in future cash flows for forecasted transactions, excluding those related to the payments of variable interest on existing financial assets and liabilities, is 1.8 years. As of September 30, 2018, we had $0.0 million of net gains reported in AOCI on the consolidated statements of financial position related to active hedges of forecasted transactions. If a hedged forecasted transaction is no longer probable of occurring, cash flow hedge accounting is discontinued. If it is probable that the hedged forecasted transaction will not occur, the deferred gain or loss is immediately reclassified from AOCI into net income. We reclassified $0.2 million and $0.0 million from AOCI into net realized capital gains (losses) as a result of the determination that hedged cash flows were probable of not occurring during the nine months ended September 30, 2018 and 2017, respectively. The following table shows the effect of derivatives in cash flow hedging relationships on the consolidated statements of operations and consolidated statements of financial position. All gains or losses on derivatives were included in the assessment of hedge effectiveness. Amount of gain (loss) Amount of gain (loss) recognized in AOCI on reclassified from AOCI on derivatives (effective portion) Location of gain (loss) derivatives (effective portion) Derivatives in cash for the three months ended reclassified from AOCI for the three months ended flow hedging September 30, into net income September 30, relationships Related hedged item 2018 2017 (effective portion) 2018 2017 (in millions) (in millions) Interest rate contracts Fixed maturities, available-for-sale $ $ Net investment income $ $ Interest rate contracts Debt — — Operating expense Foreign exchange contracts Fixed maturities, available-for-sale Net realized capital gains (losses) Total $ $ Total $ $ Amount of gain (loss) Amount of gain (loss) recognized in AOCI on reclassified from AOCI on derivatives (effective portion) Location of gain (loss) derivatives (effective portion) Derivatives in cash for the nine months ended reclassified from AOCI for the nine months ended flow hedging September 30, into net income September 30, relationships Related hedged item 2018 2017 (effective portion) 2018 2017 (in millions) (in millions) Interest rate contracts Fixed maturities, available-for-sale $ $ Net investment income $ $ Net realized capital losses — Interest rate contracts Debt — — Operating expense Foreign exchange contracts Fixed maturities, available-for-sale Net realized capital gains Foreign exchange contracts Investment contracts Benefits, claims and settlement expenses — — Total $ $ Total $ $ The following table shows the periodic settlements on interest rate contracts and foreign exchange contracts in cash flow hedging relationships. Amount of gain (loss) for the Amount of gain (loss) for the three months ended September 30, nine months ended September 30, Hedged item 2018 2017 2018 2017 (in millions) Fixed maturities, available-for-sale (1) $ $ $ $ Investment contracts (2) — (1) Reported in net investment income on the consolidated statements of operations. (2) Reported in benefits, claims and settlement expenses on the consolidated statements of operations. The ineffective portion of our cash flow hedges is reported in net realized capital gains (losses) on the consolidated statements of operations. The net gain (loss) resulting from the ineffective portion of derivatives in cash flow hedging relationships was $0.0 million and $0.0 million for the three months ended September 30, 2018 and 2017, respectively. The net gain (loss) resulting from the ineffective portion of derivatives in cash flow hedging relationships was $0.0 million and $0.0 million for the nine months ended September 30, 2018 and 2017, respectively. We expect to reclassify net gains of $16.7 million from AOCI into net income in the next 12 months, which includes net deferred gains on discontinued hedges and net losses on periodic settlements of active hedges. Actual amounts may vary from this amount as a result of market conditions. Derivatives Not Designated as Hedging Instruments Our use of futures, certain swaptions and swaps, option collars, options and forwards are effective from an economic standpoint, but they have not been designated as hedges for financial reporting purposes. As such, periodic changes in the market value of these instruments, which includes mark-to-market gains and losses as well as periodic and final settlements, primarily flow directly into net realized capital gains (losses) on the consolidated statements of operations. The following table shows the effect of derivatives not designated as hedging instruments, including fair value changes of embedded derivatives that have been bifurcated from the host contract, on the consolidated statements of operations. Amount of gain (loss) recognized in Amount of gain (loss) recognized in net income on derivatives for the net income on derivatives for the three months ended September 30, nine months ended September 30, Derivatives not designated as hedging instruments 2018 2017 2018 2017 (in millions) Interest rate contracts $ $ $ $ Foreign exchange contracts Equity contracts Credit contracts — Other contracts Total $ $ $ $

Insurance Liabilities

Insurance Liabilities	9 Months Ended
	Sep. 30, 2018
Insurance Liabilities
Insurance Liabilities	5. Insurance Liabilities Liability for Unpaid Claims The liability for unpaid claims is reported in future policy benefits and claims within our consolidated statements of financial position. Activity associated with unpaid claims was as follows: For the nine months ended September 30, 2018 2017 (in millions) Balance at beginning of period $ $ Less reinsurance recoverable Net balance at beginning of period Incurred: Current year Prior years Total incurred Payments: Current year Prior years Total payments Net balance at end of period Plus reinsurance recoverable Balance at end of period $ $ Amounts not included in the rollforward above: Claim adjustment expense liabilities $ $ Incurred liability adjustments relating to prior years, which affected current operations during 2018 and 2017, resulted in part from developed claims for prior years being different than were anticipated when the liabilities for unpaid claims were originally estimated. These trends have been considered in establishing the current year liability for unpaid claims.

Long-Term Debt

Long-Term Debt	9 Months Ended
	Sep. 30, 2018
Long-Term Debt
Long-Term Debt	6. Long-Term Debt Contingent Funding Agreements for Senior Debt Issuance On March 8, 2018, we entered into two contingent funding agreements: (1) a 10-year contingent funding agreement with a Delaware trust (“2028 Trust”) formed by us in connection with the sale by the trust of $400.0 million pre-capitalized trust securities redeemable February 15, 2028 (“2028 P-Caps”) in a Rule 144A private placement and (2) a 30-year contingent funding agreement with a Delaware trust (“2048 Trust”) formed by us in connection with the sale by the trust of $350.0 million pre-capitalized trust securities redeemable February 15, 2048 (“2048 P-Caps”) in a Rule 144A private placement. The trusts invested the proceeds from the sale of the 2028 P-Caps and 2048 P-Caps in a portfolio of principal and interest strips of U.S. Treasury securities. The contingent funding agreements provide us a put option that gives us the right to sell at any time: (1) to the 2028 Trust up to $400.0 million of its 4.111% Senior Notes due 2028 (“4.111% Senior Notes”) and (2) to the 2048 Trust up to $350.0 million of its 4.682% Senior Notes due 2048 (“4.682% Senior Notes”) and receive in exchange a corresponding amount of the principal and interest strips of U.S. Treasury securities held by the trusts. The 4.111% Senior Notes and 4.682% Senior Notes will not be issued unless and until a put option is exercised. We agreed to pay a semi-annual put premium of 1.275% and 1.580% per annum on the unexercised portion of the put option to the 2028 Trust and 2048 Trust, respectively, and to reimburse the trusts for expenses. The put option premiums are recorded in operating expenses in the consolidated statements of operations. The 4.111% Senior Notes and 4.682% Senior Notes will be fully, irrevocably and unconditionally guaranteed by Principal Financial Services, Inc. (“PFS”). In addition, our obligations under the put option agreement and the expense reimbursement agreement with the trusts are also guaranteed by PFS. The contingent funding agreements with the trusts provide us with a source of liquid assets, which could be used to meet future financial obligations or to provide additional capital. The put options described above will be exercised automatically in full if we fail to make certain payments to the trusts, including any failure to pay the put option premium or expense reimbursements when due, if such failure is not cured within 30 days, and upon certain bankruptcy events involving us or PFS. We are also required to exercise the put option in full: (i) if we reasonably believe that our consolidated shareholders’ equity, calculated in accordance with U.S. GAAP but excluding AOCI and noncontrolling interest, has fallen below $4.0 billion, subject to adjustment in certain cases; (ii) upon the occurrence of an event of default under the 4.111% Senior Notes and 4.682% Senior Notes; and (iii) if certain events occur relating to each trust’s status as an “investment company” under the Investment Company Act of 1940. In addition, we are required to purchase from the trusts any principal and interest strips of U.S. Treasury securities that are due and not paid. We have an unlimited right to unwind a prior voluntary exercise of the put options by repurchasing all of the 4.111% Senior Notes and 4.682% Senior Notes held by the trusts in exchange for a corresponding amount of principal and interest strips of U.S. Treasury securities. If the put options have been fully exercised, the 4.111% Senior Notes and 4.682% Senior Notes issued may be redeemed by us prior to their maturity at par or, if greater, at a make-whole redemption price, in each case plus accrued and unpaid interest to the date of redemption. The 2028 P-Caps are to be redeemed by the 2028 Trust on February 15, 2028, or upon any early redemption of the 4.111% Senior Notes. The 2048 P-Caps are to be redeemed by the 2048 Trust on February 15, 2048, or upon any early redemption of the 4.682% Senior Notes.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Taxes
Income Taxes	7. Income Taxes Effective Income Tax Rate Our provision for income taxes may not have the customary relationship of taxes to income. A reconciliation between the U.S. corporate income tax rate and the effective income tax rate was as follows: For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 U.S. corporate income tax rate % % % % Impact of the Tax Cuts and Jobs Act — — Dividends received deduction Tax credits Impact of equity method presentation — Local country permanent tax adjustments State income taxes Other — Effective income tax rate % % % % The U.S. tax reform enacted on December 22, 2017, made broad and complex changes to the U.S. Internal Revenue Code applicable to us. The U.S. statutory tax rate was reduced from 35% to 21% effective January 1, 2018. Other provisions of the U.S. tax reform effective January 1, 2018, include, but are not limited to: 1) provisions reducing the dividends received deduction; 2) essentially eliminating U.S. federal income taxes on dividends from foreign subsidiaries; 3) retaining an element of current inclusion of certain earnings of controlled foreign corporations; 4) eliminating the corporate alternative minimum tax (“AMT”); and 5) changing how existing AMT credits will be realized. The effects of tax legislation on deferred taxes are recognized in the period of enactment. The primary impact on our fourth quarter 2017 financial results was associated with the effect of reducing the U.S. statutory tax rate from 35% to 21% on our deferred tax balances as of December 31, 2017, and a one-time deemed repatriation tax on certain unremitted earnings of foreign subsidiaries. The effects of the U.S. tax reform were reflected in the December 2017 financial statements as determined or as reasonably estimated provisional amounts based on available information subject to interpretation in accordance with the SEC’s Staff Accounting Bulletin No. 118 (“SAB 118”). SAB 118 provides guidance on accounting for the effects of the U.S. tax reform where our determinations are incomplete but we are able to determine a reasonable estimate. A final determination is required to be made within a measurement period not to extend beyond one year from the enactment date of the U.S. tax reform. The provisional amounts were primarily associated with estimation of the one-time deemed repatriation tax considering complexity, as well as limited and changing technical tax guidance. Further, the provisional amounts also apply in regard to other potential technical interpretations of accounting and taxing authorities related to elements of the U.S. tax reform subject to change. Proposed regulations were issued on August 1, 2018, regarding the 2017 provision for the one-time deemed repatriation tax. The regulations clarified the calculation of the repatriation tax, resulting in a $5.4 million increase to our provisional estimate of income tax expense during both the three and nine months ended September 30, 2018. Unrecognized Tax Benefits Our changes in unrecognized tax benefits were as follows: For the nine months ended For the year ended September 30, 2018 December 31, 2017 (in millions) Balance at beginning of period $ $ Additions based on tax positions related to the current year Additions for tax positions of prior years Reductions for tax positions related to the current year Reductions for tax positions of prior years — Settlements Balance at end of period (1) $ $ (1) Of this amount, $4.8 million, if recognized, would reduce the 2018 effective income tax rate. We recognize interest and penalties related to uncertain tax positions in operating expenses within the consolidated statements of operations. As of September 30, 2018 and December 31, 2017, we had recognized $1.2 million and $125.5 million of accumulated pre-tax interest and penalties related to unrecognized tax benefits, respectively. During the nine months ended September 30, 2018, settlement agreements applicable to tax years 1995 to 2003 were executed with the Department of Justice, as previously approved by the Joint Committee of Taxation in August 2017. We do not expect the final determination of these unrecognized tax benefits to have a material impact on our net income.

Employee and Agent Benefits

Employee and Agent Benefits	9 Months Ended
	Sep. 30, 2018
Employee and Agent Benefits
Employee and Agent Benefits	8. Employee and Agent Benefits Components of Net Periodic Benefit Cost Other postretirement Pension benefits benefits For the three months ended For the three months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Service cost $ $ $ — $ — Interest cost Expected return on plan assets Amortization of prior service benefit Recognized net actuarial (gain) loss Net periodic benefit cost (income) $ $ $ $ Other postretirement Pension benefits benefits For the nine months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Service cost $ $ $ — $ Interest cost Expected return on plan assets Amortization of prior service benefit Recognized net actuarial (gain) loss Net periodic benefit cost (income) $ $ $ $ The components of net periodic benefit cost including the service cost component are included in operating expenses on the consolidated statements of operations. Contributions Our funding policy for our qualified pension plan is to fund the plan annually in an amount at least equal to the minimum annual contribution required under the Employee Retirement Income Security Act (“ERISA”) and, generally, not greater than the maximum amount that can be deducted for federal income tax purposes. It is too early to determine, but we do not anticipate that we will be required to fund a minimum required contribution under ERISA. Regardless, it is possible that we may fund the qualified and nonqualified pension plans in 2018 for a combined total of up to $200.0 million. During the three and nine months ended September 30, 2018, we contributed $92.4 million and $182.2 million to these plans, respectively.

Contingencies, Guarantees and I

Contingencies, Guarantees and Indemnifications	9 Months Ended
	Sep. 30, 2018
Contingencies, Guarantees and Indemnifications
Contingencies, Guarantees and Indemnifications	9. Contingencies, Guarantees and Indemnifications Litigation and Regulatory Contingencies We are regularly involved in litigation, both as a defendant and as a plaintiff, but primarily as a defendant. Litigation naming us as a defendant ordinarily arises out of our business operations as a provider of asset management and accumulation products and services, individual life insurance, specialty benefits insurance and our investment activities. Some of the lawsuits may be class actions, or purport to be, and some may include claims for unspecified or substantial punitive and treble damages. We may discuss such litigation in one of three ways. We accrue a charge to income and disclose legal matters for which the chance of loss is probable and for which the amount of loss can be reasonably estimated. We may disclose contingencies for which the chance of loss is reasonably possible and provide an estimate of the possible loss or range of loss or a statement that such an estimate cannot be made. Finally, we may voluntarily disclose loss contingencies for which the chance of loss is remote in order to provide information concerning matters that potentially expose us to possible losses. In addition, regulatory bodies such as state insurance departments, the SEC, the Financial Industry Regulatory Authority (“FINRA”), the Department of Labor (“DOL”) and other regulatory agencies in the U.S. and in international locations in which we do business, regularly make inquiries and conduct examinations or investigations concerning our compliance with, among other things, insurance laws, securities laws, ERISA and laws governing the activities of broker-dealers. We receive requests from regulators and other governmental authorities relating to industry issues and may receive additional requests, including subpoenas and interrogatories, in the future. As of September 30, 2018, we had no litigation or regulatory contingencies for which we believe disclosure is appropriate. Guarantees and Indemnifications In the normal course of business, we have provided guarantees to third parties primarily related to former subsidiaries and joint ventures. The terms of these agreements range in duration and often are not explicitly defined. The maximum exposure under these agreements as of September 30, 2018, was approximately $131.0 million. At inception, the fair value of such guarantees was insignificant. In addition, we believe the likelihood is remote that material payments will be required. Therefore, any liability accrued within our consolidated statements of financial position is insignificant. Should we be required to perform under these guarantees, we generally could recover a portion of the loss from third parties through recourse provisions included in agreements with such parties, the sale of assets held as collateral that can be liquidated in the event performance is required under the guarantees or other recourse generally available to us; therefore, such guarantees would not result in a material adverse effect on our business or financial position. While the likelihood is remote, such outcomes could materially affect net income in a particular quarter or annual period. Furthermore, in connection with our P-Caps contingent funding agreements, we are required to purchase any principal and interest strips of U.S. Treasury securities that are due and not paid from the associated unconsolidated trusts. The maximum exposure under these agreements as of September 30, 2018, was $750.0 million. See Note 6, Long-Term Debt, for further details. We manage mandatory privatized social security funds in Chile. By regulation, we have a required minimum guarantee on the funds’ relative return. Because the guarantee has no limitation with respect to duration or amount, the maximum exposure of the guarantee in the future is indeterminable. We are also subject to various other indemnification obligations issued in conjunction with divestitures, acquisitions and financing transactions whose terms range in duration and often are not explicitly defined. Certain portions of these indemnifications may be capped, while other portions are not subject to such limitations; therefore, the overall maximum amount of the obligation under the indemnifications cannot be reasonably estimated. At inception, the fair value of such indemnifications was insignificant. In addition, we believe the likelihood is remote that material payments will be required. Therefore, any liability accrued within our consolidated statements of financial position is insignificant. While we are unable to estimate with certainty the ultimate legal and financial liability with respect to these indemnifications, we believe that performance under these indemnifications would not result in a material adverse effect on our business or financial position. While the likelihood is remote, performance under these indemnifications could materially affect net income in a particular quarter or annual period.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2018
Stockholders' Equity
Stockholders' Equity	10. Stockholders’ Equity Reconciliation of Outstanding Common Shares For the nine months ended September 30, 2018 2017 (in millions) Beginning balance Shares issued Treasury stock acquired Ending balance In February 2016, our Board of Directors authorized a share repurchase program of up to $400.0 million of our outstanding common stock, which was completed in February 2018. In May 2017, our Board of Directors authorized a share repurchase program of up to $250.0 million of our outstanding common stock, which was completed in April 2018. In May 2018, our Board of Directors authorized a share repurchase program of up to $300.0 million of our outstanding common stock. Shares repurchased under these programs are accounted for as treasury stock, carried at cost and reflected as a reduction to stockholders’ equity. Other Comprehensive Income (Loss) For the three months ended For the nine months ended September 30, 2018 September 30, 2018 Pre-Tax Tax After-Tax Pre-Tax Tax After-Tax (in millions) Net unrealized losses on available-for-sale securities during the period $ $ $ $ $ $ Reclassification adjustment for (gains) losses included in net income (1) Adjustments for assumed changes in amortization patterns Adjustments for assumed changes in policyholder liabilities Net unrealized losses on available- for-sale securities Noncredit component of impairment losses on fixed maturities, available-for-sale during the period Adjustments for assumed changes in amortization patterns Adjustments for assumed changes in policyholder liabilities — — — Noncredit component of impairment losses on fixed maturities, available-for-sale (2) Net unrealized gains on derivative instruments during the period Reclassification adjustment for gains included in net income (3) Adjustments for assumed changes in amortization patterns — Adjustments for assumed changes in policyholder liabilities Net unrealized gains on derivative instruments Foreign currency translation adjustment Amortization of amounts included in net periodic benefit cost (4) Net unrecognized postretirement benefit obligation Other comprehensive loss $ $ $ $ $ $ For the three months ended For the nine months ended September 30, 2017 September 30, 2017 Pre-Tax Tax After-Tax Pre-Tax Tax After-Tax (in millions) Net unrealized gains on available-for-sale securities during the period $ $ $ $ $ $ Reclassification adjustment for losses included in net income (1) Adjustments for assumed changes in amortization patterns Adjustments for assumed changes in policyholder liabilities Net unrealized gains on available- for-sale securities Noncredit component of impairment losses on fixed maturities, available-for-sale during the period Adjustments for assumed changes in amortization patterns Adjustments for assumed changes in policyholder liabilities — Noncredit component of impairment losses on fixed maturities, available-for-sale (2) Net unrealized losses on derivative instruments during the period Reclassification adjustment for gains included in net income (3) Adjustments for assumed changes in amortization patterns Adjustments for assumed changes in policyholder liabilities Net unrealized losses on derivative instruments Foreign currency translation adjustment Amortization of amounts included in net periodic benefit cost (4) Net unrecognized postretirement benefit obligation Other comprehensive income $ $ $ $ $ $ (1) Pre-tax reclassification adjustments relating to available-for-sale securities are reported in net realized capital gains (losses) on the consolidated statements of operations. (2) Represents the net impact of (1) unrealized gains resulting from reclassification of previously recognized noncredit impairment losses from OCI to net realized capital gains (losses) for fixed maturities with bifurcated OTTI that had additional credit losses or fixed maturities that previously had bifurcated OTTI that have now been sold or are intended to be sold and (2) unrealized losses resulting from reclassification of noncredit impairment losses for fixed maturities with bifurcated OTTI from net realized capital gains (losses) to OCI. (3) See Note 4, Derivative Financial Instruments – Cash Flow Hedges, for further details. (4) Amount is comprised of amortization of prior service cost (benefit) and recognized net actuarial (gain) loss, which is reported in operating expenses on the consolidated statements of operations. See Note 8, Employee and Agent Benefits – Components of Net Periodic Benefit Cost, for further details. Accumulated Other Comprehensive Income (Loss) Noncredit Net unrealized component of Net unrealized Foreign Unrecognized Accumulated gains on impairment losses gains currency postretirement other available-for-sale on fixed maturities on derivative translation benefit comprehensive securities available-for-sale instruments adjustment obligation income (loss) (in millions) Balances as of January 1, 2017 $ $ $ $ $ $ Other comprehensive income during the period, net of adjustments — — Amounts reclassified from AOCI — Other comprehensive income Balances as of September 30, 2017 $ $ $ $ $ $ Balances as of January 1, 2018 $ $ $ $ $ $ Other comprehensive loss during the period, net of adjustments — — Amounts reclassified from AOCI — Other comprehensive loss Purchase of subsidiary shares from noncontrolling interest — — — — Effects of implementation of accounting change related to equity investments, net — — — — Effects of implementation of accounting change related to revenue recognition, net — — — — Effects of implementation of accounting change related to the reclassification of certain tax effects, net Balances as of September 30, 2018 $ $ $ $ $ $ Noncontrolling Interest Interests held by unaffiliated parties in consolidated entities are reflected in noncontrolling interest, which represents the noncontrolling partners’ share of the underlying net assets of our consolidated subsidiaries. Noncontrolling interest that is not redeemable is reported in the equity section of the consolidated statements of financial position. The noncontrolling interest holders in certain of our consolidated entities maintain an equity interest that is redeemable at the option of the holder, which may be exercised on varying dates. Since redemption of the noncontrolling interest is outside of our control, this interest is excluded from stockholders’ equity and reported separately as redeemable noncontrolling interest on the consolidated statements of financial position. Our redeemable noncontrolling interest primarily relates to consolidated sponsored investment funds for which interests are redeemed at fair value from the net assets of the funds. For our redeemable noncontrolling interest related to other consolidated subsidiaries, redemptions are required to be purchased at fair value or a value based on a formula that management intended to reasonably approximate fair value based on a fixed multiple of earnings over a measurement period. The carrying value of the redeemable noncontrolling interest is compared to the redemption value at each reporting period. Any adjustments to the carrying amount of the redeemable noncontrolling interest for changes in redemption value prior to exercise of the redemption option are determined after the attribution of net income or loss of the subsidiary and are recognized in the redemption value as they occur. Adjustments to the carrying value of redeemable noncontrolling interest result in adjustments to additional paid-in capital and/or retained earnings. Adjustments are recorded in retained earnings to the extent the redemption value of the redeemable noncontrolling interest exceeds its fair value and will impact the numerator in our earnings per share calculations. All other adjustments to the redeemable noncontrolling interest are recorded in additional paid-in capital. Following is a reconciliation of the changes in the redeemable noncontrolling interest (in millions): Balance as of January 1, 2017 $ Net income attributable to redeemable noncontrolling interest Redeemable noncontrolling interest of deconsolidated entities (1) Contributions from redeemable noncontrolling interest Distributions to redeemable noncontrolling interest Purchase of subsidiary shares from redeemable noncontrolling interest Change in redemption value of redeemable noncontrolling interest Other comprehensive income attributable to redeemable noncontrolling interest Balance as of September 30, 2017 $ Balance as of January 1, 2018 $ Net income attributable to redeemable noncontrolling interest Redeemable noncontrolling interest of deconsolidated entities (1) Contributions from redeemable noncontrolling interest Distributions to redeemable noncontrolling interest Purchase of subsidiary shares from redeemable noncontrolling interest Change in redemption value of redeemable noncontrolling interest Stock-based compensation attributable to redeemable noncontrolling interest Other comprehensive loss attributable to redeemable noncontrolling interest Balance as of September 30, 2018 $ (1) We deconsolidated certain sponsored investment funds as they no longer met the requirements for consolidation.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2018
Fair Value Measurements
Fair Value Measurements	11. Fair Value Measurements We use fair value measurements to record fair value of certain assets and liabilities and to estimate fair value of financial instruments not recorded at fair value but required to be disclosed at fair value. Certain financial instruments, particularly policyholder liabilities other than investment contracts, are excluded from these fair value disclosure requirements. Valuation Hierarchy Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (an exit price). The fair value hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three levels. The level in the fair value hierarchy within which the fair value measurement in its entirety falls is determined based on the lowest level input that is significant to the fair value measurement in its entirety considering factors specific to the asset or liability. · Level 1 – Fair values are based on unadjusted quoted prices in active markets for identical assets or liabilities. Our Level 1 assets and liabilities primarily include exchange traded equity securities, mutual funds and U.S. Treasury bonds. · Level 2 – Fair values are based on inputs other than quoted prices within Level 1 that are observable for the asset or liability, either directly or indirectly. Our Level 2 assets and liabilities primarily include fixed maturities (including public and private bonds), equity securities, cash equivalents, derivatives and other investments. · Level 3 – Fair values are based on at least one significant unobservable input for the asset or liability. Our Level 3 assets and liabilities primarily include fixed maturities, real estate and commercial mortgage loan investments of our separate accounts, complex derivatives and embedded derivatives. Determination of Fair Value The following discussion describes the valuation methodologies and inputs used for assets and liabilities measured at fair value on a recurring basis or disclosed at fair value. The techniques utilized in estimating the fair value of financial instruments are reliant on the assumptions used. Care should be exercised in deriving conclusions about our business, its value or financial position based on the fair value information of financial instruments presented below. Fair value estimates are made based on available market information and judgments about the financial instrument at a specific point in time. Such estimates do not consider the tax impact of the realization of unrealized gains or losses. In addition, the disclosed fair value may not be realized in the immediate settlement of the financial instrument. We validate prices through an investment analyst review process, which includes validation through direct interaction with external sources, review of recent trade activity or use of internal models. In circumstances where broker quotes are used to value an instrument, we generally receive one non-binding quote. Broker quotes are validated through an investment analyst review process, which includes validation through direct interaction with external sources and use of internal models or other relevant information. We did not make any significant changes to our valuation processes during 2018. Fixed Maturities Fixed maturities include bonds, ABS, redeemable preferred stock and certain non-redeemable preferred securities. When available, the fair value of fixed maturities is based on quoted prices of identical assets in active markets. These are reflected in Level 1 and primarily include U.S. Treasury bonds and actively traded redeemable corporate preferred securities. When quoted prices of identical assets in active markets are not available, our first priority is to obtain prices from third party pricing vendors. We have regular interaction with these vendors to ensure we understand their pricing methodologies and to confirm they are utilizing observable market information. Their methodologies vary by asset class and include inputs such as estimated cash flows, benchmark yields, reported trades, broker quotes, credit quality, industry events and economic events. Fixed maturities with validated prices from pricing services, which includes the majority of our public fixed maturities in all asset classes, are generally reflected in Level 2. Also included in Level 2 are corporate bonds when quoted market prices are not available, for which an internal model using substantially all observable inputs or a matrix pricing valuation approach is used. In the matrix approach, securities are grouped into pricing categories that vary by sector, rating and average life. Each pricing category is assigned a risk spread based on studies of observable public market data from the investment professionals assigned to specific security classes. The expected cash flows of the security are then discounted back at the current Treasury curve plus the appropriate risk spread. Although the matrix valuation approach provides a fair valuation of each pricing category, the valuation of an individual security within each pricing category may also be impacted by company specific factors. If we are unable to price a fixed maturity security using prices from third party pricing vendors or other sources specific to the asset class, we may obtain a broker quote or utilize an internal pricing model specific to the asset utilizing relevant market information, to the extent available and where at least one significant unobservable input is utilized. These are reflected in Level 3 in the fair value hierarchy and can include fixed maturities across all asset classes. As of September 30, 2018, less than 1% of our total fixed maturities were Level 3 securities valued using internal pricing models. The primary inputs, by asset class, for valuations of the majority of our Level 2 investments from third party pricing vendors or our internal pricing valuation approach are described below. U.S. Government and Agencies/Non-U.S. Governments . Inputs include r ecently executed market transactions, interest rate yield curves, maturity dates, market price quotations and credit spreads relating to similar instruments. States and Political Subdivisions . Inputs include Municipal Securities Rulemaking Board reported trades, U.S. T reasury and other benchmark curves, material event notices, new issue data and obligor credit ratings. Corporate . Inputs include recently executed transactions, market price quotations, benchmark yields, issuer spreads and observations of equity and credit default swap curves related to the issuer . For private placement corporate securities valued through the matrix valuation approach inputs include the current Treasury curve and risk spreads based on sector, rating and average life of the issuance. RMBS, CMBS, Collateralized Debt Obligations and Other Debt Obligations . Inputs include cash flows, priority of the tranche in the capital structure, expected time to maturity for the specific tranche, reinvestment period remaining and performance of the underlying collateral including prepayments, defaults, deferrals, loss severity of defaulted collateral and, for RMBS, prepayment speed assumptions. Other inputs include market indices and recently executed market transactions. Equity Securities Equity securities include mutual funds, common stock, non-redeemable preferred stock and required regulatory investments. Fair values of equity securities are determined using quoted prices in active markets for identical assets when available, which are reflected in Level 1. When quoted prices are not available, we may utilize internal valuation methodologies appropriate for the specific asset that use observable inputs such as underlying share prices or the net asset value (“NAV”), which are reflected in Level 2. Fair values might also be determined using broker quotes or through the use of internal models or analysis that incorporate significant assumptions deemed appropriate given the circumstances and consistent with what other market participants would use when pricing such securities, which are reflected in Level 3. Derivatives The fair values of exchange-traded derivatives are determined through quoted market prices, which are reflected in Level 1. Exchange-traded derivatives include futures that are settled daily, which reduces their fair value in the consolidated statements of financial position. The fair values of OTC cleared derivatives are determined through market prices published by the clearinghouses, which are reflected in Level 2. The clearinghouses may utilize the overnight indexed swap (“OIS”) curve in their valuation. Variation margin associated with OTC cleared derivatives is settled daily, which reduces their fair value in the consolidated statements of financial position. The fair values of bilateral OTC derivative instruments are determined using either pricing valuation models that utilize market observable inputs or broker quotes. The majority of our bilateral OTC derivatives are valued with models that use market observable inputs, which are reflected in Level 2. Significant inputs include contractual terms, interest rates, currency exchange rates, credit spread curves, equity prices and volatilities. These valuation models consider projected discounted cash flows, relevant swap curves and appropriate implied volatilities. Certain bilateral OTC derivatives utilize unobservable market data, primarily independent broker quotes that are nonbinding quotes based on models that do not reflect the result of market transactions, which are reflected in Level 3. Our non-cleared derivative contracts are generally documented under ISDA Master Agreements, which provide for legally enforceable set-off and close-out netting of exposures to specific counterparties. Collateral arrangements are bilateral and based on current ratings of each entity. We utilize the LIBOR interest rate curve to value our positions, which includes a credit spread. This credit spread incorporates an appropriate level of nonperformance risk into our valuations given the current ratings of our counterparties, as well as the collateral agreements in place. Counterparty credit risk is routinely monitored to ensure our adjustment for non-performance risk is appropriate. Our centrally cleared derivative contracts are conducted with regulated centralized clearinghouses, which provide for daily exchange of cash collateral or variation margin equal to the difference in the daily market values of those contracts that eliminates the non-performance risk on these trades. Interest Rate Contracts. For non-cleared contracts we use discounted cash flow valuation techniques to determine the fair value of interest rate swaps using observable swap curves as the inputs. These are reflected in Level 2. For centrally cleared contracts we use published prices from clearinghouses. These are reflected in Level 2. In addition, we have interest rate options and have had a limited number of complex inflation-linked interest rate swaps and swaptions that are valued using broker quotes. These are reflected in Level 3. Foreign Exchange Contracts. We use discounted cash flow valuation techniques that utilize observable swap curves and exchange rates as the inputs to determine the fair value of foreign currency swaps. These are reflected in Level 2. Currency forwards and currency options are valued using observable market inputs, including forward currency exchange rates. These are reflected in Level 2. In addition, we have a limited number of non-standard currency swaps and currency options that are valued using broker quotes. These are reflected within Level 3. Equity Contracts. We use an option pricing model using observable implied volatilities, dividend yields, index prices and swap curves as the inputs to determine the fair value of equity options. These are reflected in Level 2. Credit Contracts. We use either the ISDA Credit Default Swap Standard discounted cash flow model that utilizes observable default probabilities and recovery rates as inputs or broker prices to determine the fair value of credit default swaps. These are reflected in Level 3. Other Investments Other investments reported at fair value include invested assets of consolidated sponsored investment funds, unconsolidated sponsored investment funds, other investment funds reported at fair value, commercial mortgage loans of consolidated VIEs for which the fair value option was elected and equity method real estate investments for which the fair value option was elected. In addition, in 2017 we had other investment funds for which the fair value option was elected. Invested assets of consolidated sponsored investment funds include equity securities, fixed maturities and other investments, for which fair values are determined as previously described, and are reflected in Level 1 and Level 2. The fair value of unconsolidated sponsored investment funds and other investment funds is determined using the NAV of the fund. The NAV of the fund represents the price at which we would be able to initiate a transaction. Investments for which the NAV represents a quoted price in an active market for identical assets are reflected in Level 1. Investments that do not have a quoted price in an active market are reflected in Level 2. Commercial mortgage loans of consolidated VIEs are valued using the more observable fair value of the liabilities of the consolidated collateralized financing entities (“CCFEs”) under the measurement alternative guidance and are reflected in Level 2. The liabilities are affiliated so are not reflected in our consolidated results. Equity method real estate investments for which the fair value option was elected are reflected in Level 3. The equity method real estate investments consist of underlying real estate and debt. The real estate fair value is estimated using a discounted cash flow valuation model that utilizes public real estate market data inputs such as transaction prices, market rents, vacancy levels, leasing absorption, market cap rates and discount rates. The debt fair value is estimated using a discounted cash flow analysis based on our incremental borrowing rate for similar borrowing arrangements. Cash Equivalents Certain cash equivalents are reported at fair value on a recurring basis and include money market instruments and other short-term investments with maturities of three months or less. Fair values of these cash equivalents may be determined using public quotations, when available, which are reflected in Level 1. When public quotations are not available, because of the highly liquid nature of these assets, carrying amounts may be used to approximate fair values, which are reflected in Level 2. Separate Account Assets Separate account assets include equity securities, debt securities, cash equivalents and derivative instruments, for which fair values are determined as previously described, and are reflected in Level 1, Level 2 and Level 3. Separate account assets also include commercial mortgage loans, for which the fair value is estimated by discounting the expected total cash flows using market rates that are applicable to the yield, credit quality and maturity of the loans. The market clearing spreads vary based on mortgage type, weighted average life, rating and liquidity. These are reflected in Level 3. Finally, separate account assets include real estate, for which the fair value is estimated using discounted cash flow valuation models that utilize various public real estate market data inputs. In addition, each property is appraised annually by an independent appraiser. The real estate included in separate account assets is recorded net of related mortgage encumbrances for which the fair value is estimated using discounted cash flow analysis based on our incremental borrowing rate for similar borrowing arrangements. The real estate within the separate accounts is reflected in Level 3. Investment Contracts Certain annuity contracts and other investment contracts include embedded derivatives that have been bifurcated from the host contract and are measured at fair value on a recurring basis, which are reflected in Level 3. The key assumptions for calculating the fair value of the embedded derivative liabilities are market assumptions (such as equity market returns, interest rate levels, market volatility and correlations) and policyholder behavior assumptions (such as lapse, mortality, utilization and withdrawal patterns). Risk margins are included in the policyholder behavior assumptions. The assumptions are based on a combination of historical data and actuarial judgment. The embedded derivative liabilities are valued using stochastic models that incorporate a spread reflecting our own creditworthiness. The assumption for our own non-performance risk for investment contracts and any embedded derivatives bifurcated from certain annuity and investment contracts is based on the current market credit spreads for debt-like instruments we have issued and are available in the market. Other Liabilities Certain obligations reported in other liabilities include embedded derivatives to deliver underlying securities of structured investments to third parties. The fair value of the embedded derivatives is calculated based on the value of the underlying securities that are valued based on prices obtained from third party pricing vendors as utilized and described in our discussion of how fair value is determined for fixed maturities, which are reflected in Level 2. As of December 31, 2016, obligations of consolidated VIEs for which the fair value option was elected were included in other liabilities. The synthetic entity that had these obligations matured in the first quarter of 2017. The VIEs’ unaffiliated obligations were valued utilizing internal pricing models, which were reflected in Level 3. Assets and Liabilities Measured at Fair Value on a Recurring Basis Assets and liabilities measured at fair value on a recurring basis were as follows: September 30, 2018 Assets/ Amount (liabilities) measured at Fair value hierarchy level measured at net asset fair value value (5) Level 1 Level 2 Level 3 (in millions) Assets Fixed maturities, available-for-sale: U.S. government and agencies $ $ — $ $ $ — Non-U.S. governments — States and political subdivisions — — — Corporate — Residential mortgage-backed securities — — — Commercial mortgage-backed securities — — Collateralized debt obligations — — Other debt obligations — — Total fixed maturities, available-for-sale — Fixed maturities, trading — — — Equity securities — — Derivative assets (1) — — Other investments (2) Cash equivalents (3) — — Sub-total excluding separate account assets Separate account assets Total assets $ $ $ $ $ Liabilities Investment contracts (4) $ $ — $ — $ — $ Derivative liabilities (1) — — Other liabilities (4) — — — Total liabilities $ $ — $ — $ $ Net assets $ $ $ $ $ December 31, 2017 Assets/ Amount (liabilities) measured at Fair value hierarchy level measured at net asset fair value value (5) Level 1 Level 2 Level 3 (in millions) Assets Fixed maturities, available-for-sale: U.S. government and agencies $ $ — $ $ $ — Non-U.S. governments — States and political subdivisions — — — Corporate — Residential mortgage-backed securities — — — Commercial mortgage-backed securities — — Collateralized debt obligations — — Other debt obligations — — Total fixed maturities, available-for-sale — Fixed maturities, trading — — — Equity securities, available-for-sale — Equity securities, trading — — Derivative assets (1) — — Other investments (2) Cash equivalents (3) — — Sub-total excluding separate account assets Separate account assets Total assets $ $ $ $ $ Liabilities Investment contracts (4) $ $ — $ — $ — $ Derivative liabilities (1) — — Other liabilities (4) — — — Total liabilities $ $ — $ — $ $ Net assets $ $ $ $ $ (1) Within the consolidated statements of financial position, derivative assets are reported with other investments and derivative liabilities are reported with other liabilities. Refer to Note 4, Derivative Financial Instruments, for further information on fair value by class of derivative instruments. (2) Primarily includes sponsored investment funds, other investment funds, equity method real estate investments reported at fair value and commercial mortgage loans of consolidated VIEs. (3) Includes money market instruments and short-term investments with a maturity date of three months or less when purchased. (4) Includes bifurcated embedded derivatives that are reported at net asset (liability) fair value within the same line item in the consolidated statements of financial position in which the host contract is reported. (5) Certain investments are measured at fair value using the NAV per share (or its equivalent) practical expedient and have not been classified in the fair value hierarchy. Other investments using the NAV practical expedient consist of certain fund interests that are restricted until maturity with unfunded commitments totaling $35.0 million and $46.1 million as of September 30, 2018 and December 31, 2017, respectively. Separate account assets using the NAV practical expedient consist of hedge funds with varying investment strategies that also have a variety of redemption terms and conditions. We do not have unfunded commitments associated with these hedge funds. Changes in Level 3 Fair Value Measurements The reconciliation for all assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) was as follows: For the three months ended September 30, 2018 Total realized/unrealized Changes in Beginning gains (losses) Net Ending unrealized asset/ purchases, asset/ gains (losses) (liability) sales, (liability) included in balance Included in issuances balance net income as of Included in other and Transfers Transfers as of relating to June 30, net income comprehensive settlements into out of September 30, positions still 2018 (1) income (3) (4) Level 3 Level 3 2018 held (1) (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ $ — $ — $ $ — $ $ $ — Corporate — Commercial mortgage-backed securities — — — — — Collateralized debt obligations Other debt obligations — — — Total fixed maturities, available-for-sale Fixed maturities, trading — — — — — — Derivative assets — — — Other investments — — — — Separate account assets (2) Liabilities Investment contracts — — Derivative liabilities — — — For the three months ended September 30, 2017 Total realized/unrealized Changes in Beginning gains (losses) Net Ending unrealized asset/ purchases, asset/ gains (losses) (liability) sales, (liability) included in balance Included in Included in issuances balance net income as of net other and Transfers Transfers as of relating to June 30, income comprehensive settlements into out of September 30, positions still 2017 (1) income (3) (4) Level 3 Level 3 2017 held (1) (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ $ $ $ $ — $ — $ $ Corporate — — Commercial mortgage-backed securities Collateralized debt obligations — — Other debt obligations — — — — — Total fixed maturities, available-for-sale Equity securities, available-for-sale — — — — — — Derivative assets — — — Other investments — — — Separate account assets (2) — Liabilities Investment contracts — — — Derivative liabilities — — — For the nine months ended September 30, 2018 Total realized/unrealized Changes in Beginning gains (losses) Net Ending unrealized asset/ purchases, asset/ gains (losses) (liability) sales, (liability) included in balance Included Included in issuances balance net income as of in net other and Transfers Transfers as of relating to December 31, income comprehensive settlements into out of September 30, positions still 2017 (1) income (3) (4) Level 3 Level 3 2018 held (1) (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ $ — $ $ $ — $ $ $ — Corporate Commercial mortgage-backed securities — Collateralized debt obligations Other debt obligations — — — Total fixed maturities, available-for-sale Fixed maturities, trading — — — — — — Equity securities — — — — — Derivative assets — — — Other investments — — — Separate account assets (2) Liabilities Investment contracts — — — Derivative liabilities — — — For the nine months ended September 30, 2017 Total realized/unrealized Changes in Beginning gains (losses) Net Ending unrealized asset/ purchases, asset/ gains (losses) (liability) sales, (liability) included in balance Included Included in issuances balance net income as of in net other and Transfers Transfers as of relating to December 31, income comprehensive settlements into out of September 30, positions still 2016 (1) income (3) (4) Level 3 Level 3 2017 held (1) (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ $ $ $ $ — $ — $ $ Corporate Commercial mortgage-backed securities Collateralized debt obligations — — Other debt obligations — — — Total fixed maturities, available-for-sale Fixed maturities, trading — — — — Equity securities, available-for-sale — — — — — — Equity securities, trading — — — — — — Derivative assets — — — Other investments — — — Separate account assets (2) Liabilities Investment contracts — — Derivative liabilities — — — Other liabilities — — — — — (1) Both realized gains (losses) and mark-to-market unrealized gains (losses) are generally reported in net realized capital gains (losses) within the consolidated statements of operations. Realized and unrealized gains (losses) on certain securities with an investment objective to realize economic value through mark-to-market changes are reported in net investment income within the consolidated statements of operations. (2) Gains and losses for separate account assets do not impact net income as the change in value of separate account assets is offset by a change in value of separate account liabilities. Foreign currency translation adjustments related to the Principal International segment separate account assets are recorded in AOCI and are offset by foreign currency translation adjustments of the corresponding separate account liabilities. (3) Includes foreign currency translation adjustments related to our Principal International segment. (4) Gross purchases, sales, issuances and settlements were: For the three months ended September 30, 2018 Net purchases, sales, issuances Purchases Sales Issuances Settlements and settlements (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ — $ — $ — $ $ Corporate — Collateralized debt obligations — — Other debt obligations — — Total fixed maturities, available-for-sale — Derivative assets — — — Other investments — — — Separate account assets (5) Liabilities Investment contracts — — Derivative liabilities — — For the three months ended September 30, 2017 Net purchases, sales, issuances Purchases Sales Issuances Settlements and settlements (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ $ $ — $ $ Corporate — Commercial mortgage-backed securities — — — Collateralized debt obligations — — Other debt obligations — — — Total fixed maturities, available-for-sale — Derivative assets — — Other investments — — — Separate account assets (5) Liabilities Investment contracts — — Derivative liabilities — — — For the nine months ended September 30, 2018 Net purchases, sales, issuances Purchases Sales Issuances Settlements and settlements (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ — $ — $ — $ $ Corporate — Commercial mortgage-backed securities — — — Collateralized debt obligations — — Other debt obligations — — Total fixed maturities, available-for-sale — Fixed maturities, trading — — — Equity securities — — — Derivative assets — — Other investments — — — Separate account assets (5) Liabilities Investment contracts — — Derivative liabilities — — For the nine months ended September 30, 2017 Net purchases, sales, issuances Purchases Sales Issuances Settlements and settlements (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ $ $ — $ $ Corporate — Commercial mortgage-backed securities — — — Collateralized debt obligations — — Other debt obligations — — — Total fixed maturities, available-for-sale — Fixed maturities, trading — — — Equity securities, trading — — — Derivative assets — — — Other investments — — Separate account assets (5) Liabilities Investment contracts — — Derivative liabilities — — Other liabilities — — — (5) Issuances and settlements include amounts related to mortgage encumbrances associated with real estate in our separate accounts. Transfers Transfers of assets and liabilities measured at fair value on a recurring basis between fair value hierarchy levels were as follows: For the three months ended September 30, 2018 Transfers out Transfers out Transfers out Transfers out Transfers out Transfers out of Level 1 into of Level 1 into of Level 2 into of Level 2 into of Level 3 into of Level 3 into Level 2 Level 3 Level 1 Level 3 Level 1 Level 2 (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ — $ — $ — $ — $ — $ Corporate — — — — — Collateralized debt obligations — — — — Other debt obligations — — — — — Total fixed maturities, available-for-sale — — — — Fixed maturities, trading — — — — — Separate account assets — — — For the three months ended September 30, 2017 Transfers out Transfers out Transfers out Transfers out Transfers out Transfers out of Level 1 into of Level 1 into of Level 2 into of Level 2 into of Level 3 into of Level 3 into Level 2 Level 3 Level 1 Level 3 Level 1 Level 2 (in millions) Assets Fixed maturities, available-for-sale: Commercial mortgage-backed securities $ — $ — $ — $ $ — $ Collateralized debt obligations — — — — Total fixed maturities, available-for-sale — — — — Separate account assets — — For the nine months ended September 30, 2018 Transfers out Transfers out Transfers out Transfers out Transfers out Transfers out of Level 1 into of Level 1 into of Level 2 into of Level 2 into of Level 3 into of Level 3 into Level 2 Level 3 Level 1 Level 3 Level 1 Level 2 (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ — $ — $ — $ — $ — $ Corporate — — — — Commercial mortgage-backed securities — — — — Collateralized debt obligations — — — — Other debt obligations — — — — — Total fixed maturities, available-for-sale — — — — Fixed maturities, trading — — — — — Separate account assets — For the nine months ended September 30, 2017 Transfers out Transfers out Transfers out Transfers out Transfers out Transfers out of Level 1 into of Level 1 into of Level 2 into of Level 2 into of Level 3 into of Level 3 into Level 2 Level 3 Level 1 Level 3 Level 1 Level 2 (in millions) Assets Fixed maturities, available-for-sale: Corporate $ — $ — $ — $ $ — $ Commercial mortgage-backed securities — — — — Collateralized debt obligations — — — — Other debt obligations — — — — Total fixed maturities, available-for-sale — — — — Fixed maturities, trading — — — — — Equity securities, trading — — — — — Separate account assets — — Transfers between fair value hierarchy levels are recognized at the beginning of the reporting period. Separate account assets transferred from Level 1 to Level 2 during the nine months ended September 30, 2018, primarily included cash equivalents as a result of additional analysis to clarify the source of the price. Assets transferred into Level 3 during the three and nine months ended September 30, 2018 and 2017, primarily included those assets for which we are now unable to obtain pricing from a recognized third party pricing vendor as well as assets that were previously priced using a matrix valuation approach that may no longer be relevant when applied to asset-specific situations. Assets transferred out of Level 3 during the three and nine months ended September 30, 2018 and 2017, primarily included those for which we are now able to obtain pricing from a recognized third party pricing vendor or from internal models using substantially all market observable information. Quantitative Information about Level 3 Fair Value Measurements The following table provides quantitative information about the significant unobservable inputs used for recurring fair value measurements categorized within Level 3, excluding assets and liabilities for which significant quantitative unobservable input

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2018
Segment Information
Segment Information	12. Segment Information We provide financial products and services through the following segments: Retirement and Income Solutions, Principal Global Investors, Principal International and U.S. Insurance Solutions. In addition, we have a Corporate segment. The segments are managed and reported separately because they provide different products and services, have different strategies or have different markets and distribution channels. The Retirement and Income Solutions segment provides retirement and related financial products and services primarily to businesses, their employees and other individuals. The segment is organized into Retirement and Income Solutions – Fee, which includes full service accumulation, trust services and individual variable annuities; and Retirement and Income Solutions – Spread, which includes individual fixed annuities, investment only, full service payout and banking services. The Principal Global Investors segment provides asset management services to our asset accumulation business, our insurance operations, the Corporate segment and third party clients. This segment also includes our mutual fund business. The Principal International segment has operations in Latin America (Brazil, Chile and Mexico) and Asia (China, Hong Kong Special Administrative Region, India and Southeast Asia). We focus on locations with large middle classes, favorable demographics and growing long-term savings, ideally with voluntary or mandatory pension markets. We entered these locations through acquisitions, start-up operations and joint ventures. The U.S. Insurance Solutions segment focuses on solutions for individuals and small-to-medium sized businesses and their employees. The segment is organized into Specialty Benefits insurance, which provides group dental and vision insurance, individual and group disability insurance, critical illness, accident, group life insurance and non-medical fee-for-service claims administration; and Individual Life insurance, which provides universal life, variable universal life, indexed universal life and traditional life insurance. Our Corporate segment manages the assets representing capital that has not been allocated to any other segment. Financial results of the Corporate segment primarily reflect our financing activities (including financing costs), income on capital not allocated to other segments, inter-segment eliminations, income tax risks and certain income, expenses and other adjustments not allocated to the segments based on the nature of such items. Results of Principal Securities, Inc. (“PSI”), our retail broker-dealer and registered investment advisor (“RIA”); RobustWealth, Inc. (“RobustWealth”), our financial technology company; and our exited group medical and long-term care insurance businesses are reported in this segment. Management uses segment pre-tax operating earnings in evaluating performance, which is consistent with the financial results provided to and discussed with securities analysts. We determine segment pre-tax operating earnings by adjusting U.S. GAAP income before income taxes for pre-tax net realized capital gains (losses), as adjusted, pre-tax other adjustments that management believes are not indicative of overall operating trends and certain adjustments related to equity method investments and noncontrolling interest. Pre-tax net realized capital gains (losses), as adjusted, are net of related changes in the amortization pattern of DAC and related actuarial balances, recognition of deferred front-end fee revenues for sales charges on retirement and life insurance products and services, amortization of hedge accounting book value adjustments for certain discontinued hedges, net realized capital gains and losses distributed, certain adjustments related to equity method investments, certain adjustments related to sponsored investment funds and certain market value adjustments to fee revenues. Pre-tax net realized capital gains (losses), as adjusted, exclude periodic settlements and accruals on derivative instruments not designated as hedging instruments and exclude certain market value adjustments of embedded derivatives and realized capital gains (losses) associated with our exited group medical insurance business. Segment operating revenues exclude net realized capital gains (losses) (except periodic settlements and accruals on derivatives not designated as hedging instruments), including their impact on recognition of front-end fee revenues, certain market value adjustments to fee revenues, certain adjustments related to equity method investments, certain adjustments related to sponsored investment funds and amortization of hedge accounting book value adjustments for certain discontinued hedges; certain adjustments related to equity method investments, pre-tax other adjustments management believes are not indicative of overall operating trends and revenue from our exited group medical insurance business. While these items may be significant components in understanding and assessing the consolidated financial performance, management believes the presentation of pre-tax operating earnings enhances the understanding of our results of operations by highlighting pre-tax earnings attributable to the normal, ongoing operations of the business. The accounting policies of the segments are consistent with the accounting policies for the consolidated financial statements, with the exception of: (1) pension and other postretirement employee benefits (“OPEB”) cost allocations and (2) income tax allocations. For purposes of determining pre-tax operating earnings, the segments are allocated the service component of pension and other postretirement benefit costs. The Corporate segment reflects the non-service components of pension and other postretirement benefit costs as assumptions are established and funding decisions are managed from a company-wide perspective. The Corporate segment functions to absorb the risk inherent in interpreting and applying tax law. For purposes of determining non-GAAP operating earnings, the segments are allocated tax adjustments consistent with the positions we took on tax returns. The Corporate segment results reflect any differences between the tax returns and the estimated resolution of any disputes. The following tables summarize select financial information by segment, including operating revenues for our products and services, and reconcile segment totals to those reported in the consolidated financial statements: September 30, 2018 December 31, 2017 (in millions) Assets: Retirement and Income Solutions $ $ Principal Global Investors Principal International U.S. Insurance Solutions Corporate Total consolidated assets $ $ For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Operating revenues by segment: Retirement and Income Solutions: Retirement and Income Solutions – Fee $ $ $ $ Retirement and Income Solutions – Spread Total Retirement and Income Solutions (1) Principal Global Investors (2) Principal International U.S. Insurance Solutions: Specialty Benefits insurance Individual Life insurance Eliminations — — Total U.S. Insurance Solutions Corporate Total segment operating revenues Net realized capital gains (losses), net of related revenue adjustments Adjustments related to equity method investments Total revenues per consolidated statements of operations $ $ $ $ Pre-tax operating earnings (losses) by segment: Retirement and Income Solutions $ $ $ $ Principal Global Investors Principal International U.S. Insurance Solutions Corporate Total segment pre-tax operating earnings Pre-tax net realized capital gains (losses), as adjusted (3) Adjustments related to equity method investments and noncontrolling interest Income before income taxes per consolidated statements of operations $ $ $ $ (1) Reflects inter-segment revenues of $103.9 million and $103.7 million for the three months ended September 30, 2018 and 2017, respectively, $304.5 million and $296.6 million for the nine months ended September 30, 2018 and 2017, respectively. (2) Reflects inter-segment revenues of $69.2 million and $68.2 million for the three months ended September 30, 2018 and 2017, respectively, $199.2 million and $188.7 million for the nine months ended September 30, 2018 and 2017, respectively. (3) Pre-tax net realized capital gains (losses), as adjusted, is derived as follows: For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Net realized capital gains (losses): Net realized capital gains (losses) $ $ $ $ Derivative and hedging-related adjustments Adjustments related to equity method investments Market value adjustments to fee revenues — Adjustments related to sponsored investment funds Recognition of front-end fee revenue Net realized capital gains (losses), net of related revenue adjustments Amortization of deferred acquisition costs and other actuarial balances Capital gains distributed Market value adjustments of embedded derivatives Pre-tax net realized capital gains (losses), as adjusted (a) $ $ $ $ (a) As adjusted before noncontrolling interest capital gains (losses).

Revenues from Contracts with Cu

Revenues from Contracts with Customers	9 Months Ended
	Sep. 30, 2018
Revenues from Contracts with Customers
Revenues from Contracts with Customers	13. Revenues from Contracts with Customers The following tables summarize disaggregation of revenues from contracts with customers, including select financial information by segment, and reconcile totals to those reported in the consolidated financial statements. Revenues from contracts with customers are included in fees and other revenues on the consolidated statements of operations. For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Revenue from contracts with customers by segment: Retirement and Income Solutions: Retirement and Income Solutions – Fee $ $ $ $ Retirement and Income Solutions – Spread Total Retirement and Income Solutions Principal Global Investors Principal International U.S. Insurance Solutions: Specialty Benefits insurance Individual Life insurance Eliminations — — Total U.S. Insurance Solutions Corporate Total segment revenue from contracts with customers Adjustments for fees and other revenues not within the scope of revenue recognition guidance (1) Pre-tax other adjustments (2) — Total fees and other revenues per consolidated statements of operations $ $ $ $ (1) Fees and other revenues not within the scope of the revenue recognition guidance primarily represent revenue on contracts accounted for under the financial instruments or insurance contracts standards. (2) Pre-tax other adjustments relate to the recognition of deferred front-end fee revenues for sales charges on retirement and life insurance products and certain market value adjustments to fee revenues. Retirement and Income Solutions - Fee Retirement and Income Solutions - Fee offers service and trust agreements for defined contribution plans, including 401(k) plans, 403(b) plans, and employee stock ownership plans. The investment components of these service agreements are in the form of mutual fund offerings. In addition, plan sponsor trust services are also available through an affiliated trust company. Fees and other revenues are earned for administrative activities performed for the defined contribution plans including recordkeeping and reporting as well as trust, asset management and investment services. The majority of these activities are performed daily over time. Fee-for-service transactions are also provided upon client request. These services are considered distinct or grouped into a bundle until a distinct performance obligation is identified. Some performance obligations are considered a series of distinct services, which are substantially the same and have the same pattern of transfer to the customer. Fees and other revenues can be based on a fixed contractual rate for these services or can be variable based upon contractual rates applied to the market value of the client’s investment portfolio each day. If the consideration for this series of performance obligations is based on daily market value, it is considered variable each day as the services are performed over time. The consideration becomes unconstrained and thus recognized as revenue for each day’s series of distinct services once the market value of the clients’ investment portfolios is determined at market close or carried over at the end of the day for days when the market is closed. Additionally, fixed fees and other revenues are recognized point-in-time as fee-for-service transactions upon completion. The types of revenues from contracts with customers were as follows: For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Administrative service fee revenue $ $ $ $ Other fee revenue Total revenues from contracts with customers Fees and other revenues not within the scope of revenue recognition guidance Total fees and other revenues Premiums and other considerations Net investment income Total operating revenues $ $ $ $ Retirement and Income Solutions - Spread Retirement and Income Solutions – Spread offers individual retirement accounts (“IRAs”) through Principal Bank, which are primarily funded by retirement savings rolled over from qualified retirement plans. The IRAs are held in savings accounts, money market accounts and certificates of deposit. Revenues are earned through fees as the performance of establishing and maintaining IRA accounts is completed. Fee-for-service transactions are also provided upon client request. The establishment fees and annual maintenance fees are accrued into earnings over a period of time using the average account life. Upfront and recurring bank fees are related to performance obligations that have the same pattern of transfer to the customer and are recognized in income over time with control transferred to the customers utilizing the output method. These fees are based on a fixed contractual rate. Fixed fees and other revenues are also recognized point-in-time as fee-for-service transactions upon completion. The types of revenues from contracts with customers were as follows: For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Deposit account fee revenue $ $ $ $ Total revenues from contracts with customers Fees and other revenues not within the scope of revenue recognition guidance Total fees and other revenues Premiums and other considerations Net investment income Total operating revenues $ $ $ $ Principal Global Investors Fees and other revenues earned for asset management, investment advisory and distribution services provided to institutional and retail clients are based largely upon contractual rates applied to the specified amounts of the clients’ portfolios. Each service is a distinct performance obligation, or a series of distinct services that are a single performance obligation in that the services are substantially the same and have the same pattern of transfer to the customer. Fees and other revenues received for performance obligations such as asset management and other services are typically recognized over time utilizing the output method as the service is performed. Performance fees and transaction fees on certain accounts are recognized in income when the probability of significant reversal will not occur upon resolution of the uncertainty, which could be based on a variety of factors such as market performance or other internal metrics. Asset management fees are accrued each month based on the fee terms within the applicable agreement and are generally billed quarterly when values used for the calculation are available. Management fees and performance fees are variable consideration as they are subject to fluctuation based on assets under management (“AUM”) and other constraints. These fees are not recognized until unconstrained at the end of each reporting period. The types of revenues from contracts with customers were as follows: For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Management fee revenue $ $ $ $ Other fee revenue (1) Total revenues from contracts with customers Fees and other revenues not within the scope of revenue recognition guidance Total fees and other revenues Net investment income Total operating revenues $ $ $ $ (1) During the third quarter of 2018, we recognized a $253.1 million accelerated performance fee resulting from the realignment of a real estate investment team. Principal International Fees and other revenues are earned for asset management and distribution services provided to retail and institutional clients in addition to trustee and/or administrative services performed for retirement savings plans. Each service is considered a distinct performance obligation; however, if the services are not distinct on their own, we combine them into a distinct bundle or we have a series of distinct services that are substantially the same and have the same pattern of transfer to the customer. Fees and other revenues are typically based upon contractual rates applied to the market value of the clients’ investment portfolios and are considered variable consideration. The transaction price generally includes the amount determined at the end of the reporting period, whereby fees are deducted from the clients’ investment portfolios and are recognized as revenue when no longer constrained and satisfied as the services are performed over time utilizing the output method. In addition, payments to customers can take the form of an incentive given by us to entice the customer to purchase its goods or services. Incentives offered to customers are recognized as part of the transaction price as a reduction of revenue either over the period the customer remains in order to receive the incentive or monthly throughout the life of the contract. Incentive-based fees are recognized in income when the probability of significant reversal will not occur upon the resolution of the uncertainty, which is based on market performance. Fees for managing customers’ mandatory retirement savings accounts in Chile are collected with each monthly deposit made by our customers. If a customer stops contributing before retirement age, we collect no fees but services are still provided. We recognize revenue from these contracts as services are performed over the life of the contract and review annually. The types of revenues from contracts with customers were as follows: For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Management fee revenue $ $ $ $ Other fee revenue Total revenues from contracts with customers Fees and other revenues not within the scope of revenue recognition guidance Total fees and other revenues Premiums and other considerations Net investment income Total operating revenues $ $ $ $ Revenues from contracts with customers by region: Latin America $ $ $ $ Asia Principal International corporate / regional offices Eliminations Total revenues from contracts with customers $ $ $ $ U.S. Insurance Solutions Fees and other revenues are earned for administrative services performed including recordkeeping and reporting services for fee-for-service products, nonqualified benefit plans, separate accounts and dental networks. Services within contracts are not distinct on their own; however, we combine the services into a distinct bundle and account for the bundle as a single performance obligation, which is satisfied over time utilizing the output method as services are rendered. The transaction price corresponds with the performance completed to date, for which the value is recognized as revenue during the period. Variability of consideration is resolved at the end of each period and payments are due when billed. Commission income is earned through sponsored brokerage services. Performance obligations are satisfied at a point in time, upon delivery of a placed case, and the transaction price calculated per the compensation schedule is recognized as revenue. The types of revenues from contracts with customers were as follows: For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Specialty Benefits Insurance: Administrative service fees $ $ $ $ Total revenues from contracts with customers Fees and other revenues not within the scope of revenue recognition guidance Total fees and other revenues Premiums and other considerations Net investment income Total operating revenues $ $ $ $ For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Individual Life Insurance: Administrative service fees $ $ $ $ Commission income Total revenues from contracts with customers Fees and other revenues not within the scope of revenue recognition guidance Total fees and other revenues Premiums and other considerations Net investment income Total operating revenues $ $ $ $ Corporate Fees and other revenues are earned on the performance of selling and servicing of securities and related products offered through PSI, an introducing broker-dealer registered with the FINRA. PSI enters into selling and distribution agreements with the obligation to sell or distribute the securities products, such as mutual funds, annuities and products sold through RIAs, to individual clients in return for a front-end sales charges, 12b-1 service fees, annuity fees and asset-based fees. Front-end sales charges, 12b-1 fees and annuity fees are related to a single sale and are earned at the time of sale. PSI also enters into agreements with individual customers to provide securities trade execution and custody through a brokerage services platform in return for ticket charge and other service fee revenue. These services are bundled as one single distinct service referred to as brokerage services. This revenue is related to distinct transactions and is earned at a point in time. PSI also enters into agreements with individual customers to provide trade execution, clearing services, custody services and investment research services through our proprietary offered fee-based products. These services are bundled as one single distinct service referred to as advisory services. In addition, for outside RIA business PSI performs sales and distribution services only. The revenues are earned over time as the service is performed utilizing the output method. A majority of our revenue is based upon contractual rates applied to the market value of the clients’ portfolios and considered variable consideration. The Corporate segment also includes inter-segment eliminations of fees and other revenues. The types of revenues from contracts with customers were as follows: For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Commission income $ $ $ $ Other fee revenue Eliminations Total revenues from contracts with customers Fees and other revenues not within the scope of revenue recognition guidance Total fees and other revenues Net investment income Total operating revenues $ $ $ $ Contract Costs Sales compensation and other incremental costs of obtaining a contract are capitalized and amortized over the period of contract benefit if the costs are expected to be recovered. The contract cost asset, which is included in other assets on the consolidated statements of financial position, was $141.4 million as of September 30, 2018. We apply the practical expedient for certain costs where we recognize the incremental costs of obtaining these contracts as an expense when incurred if the amortization period of the assets is one year or less. These costs, along with costs that are not deferrable, are included in operating expenses on the consolidated statements of operations. Deferred contract costs consist primarily of commissions and variable compensation. We amortize capitalized contract costs on a straight-line basis over the expected contract life, reflecting lapses as they are incurred. Deferred contract costs on contracts are subject to impairment testing on an annual basis, or when a triggering event occurs that could warrant an impairment. To the extent future revenues less future maintenance expenses are not adequate to cover the asset balance, an impairment is recognized. For the three and nine months ended September 30, 2018, $6.1 million and $17.7 million, respectively, of amortization expense was recorded in operating expenses on the consolidated statements of operations and no impairment loss was recognized in relation to the costs capitalized.

Stock-Based Compensation Plans

Stock-Based Compensation Plans	9 Months Ended
	Sep. 30, 2018
Stock-Based Compensation Plans
Stock-Based Compensation Plans	14. Stock-Based Compensation Plans As of September 30, 2018, we had the 2014 Stock Incentive Plan, the Employee Stock Purchase Plan, the 2014 Directors Stock Plan, the Amended and Restated 2010 Stock Incentive Plan, the 2005 Directors Stock Plan, the Stock Incentive Plan and the Directors Stock Plan (“Stock-Based Compensation Plans”). As of May 20, 2014, no new grants will be made under the Amended and Restated 2010 Stock Incentive Plan or the 2005 Directors Stock Plan. No grants have been made under the Stock Incentive Plan or the Directors Stock Plan since at least 2005. Under the terms of the 2014 Stock Incentive Plan, grants may be nonqualified stock options, incentive stock options qualifying under Section 422 of the Internal Revenue Code, restricted stock, restricted stock units, stock appreciation rights, performance shares, performance units or other stock-based awards. The 2014 Directors Stock Plan provides for the grant of nonqualified stock options, restricted stock, restricted stock units or other stock-based awards to our nonemployee directors. To date, we have not granted any incentive stock options, restricted stock or performance units under any plans. As of September 30, 2018, the maximum number of new shares of common stock available for grant under the 2014 Stock Incentive Plan and the 2014 Directors Stock Plan was 7.3 million. For awards with graded vesting, we use an accelerated expense attribution method. The compensation cost that was charged against net income for stock-based awards granted under the Stock-Based Compensation Plans was as follows: For the nine months ended September 30, 2018 2017 (in millions) Compensation cost $ $ Related income tax benefit Capitalized as part of an asset Nonqualified Stock Options Nonqualified stock options were granted to certain employees under the 2014 Stock Incentive Plan. Total options granted were 0.8 million for the nine months ended September 30, 2018. The fair value of stock options is estimated using the Black-Scholes option pricing model. The following is a summary of the assumptions used in this model for the stock options granted during the period: For the nine months ended September 30, 2018 Expected volatility 26.0 % Expected term (in years) 7.0 Risk-free interest rate 2.8 % Expected dividend yield 3.19 % Weighted average estimated fair value per common share $ As of September 30, 2018, we had $4.5 million of total unrecognized compensation cost related to nonvested stock options. The cost is expected to be recognized over a weighted-average service period of approximately 1.2 years. Performance Share Awards Performance share awards were granted to certain employees under the 2014 Stock Incentive Plan. Total performance share awards granted were 0.2 million for the nine months ended September 30, 2018. The performance share awards granted represent initial target awards and do not reflect potential increases or decreases resulting from the final performance results to be determined at the end of the performance period. The actual number of common shares to be awarded at the end of each performance period will range between 0% and 150% of the initial target awards. The fair value of performance share awards is determined based on the closing stock price of our common shares on the grant date. The weighted-average grant date fair value of these performance share awards granted was $63.98 per common share. As of September 30, 2018, we had $5.0 million of total unrecognized compensation cost related to nonvested performance share awards granted. The cost is expected to be recognized over a weighted-average service period of approximately 1.1 years. Restricted Stock Units Restricted stock units were issued to certain employees pursuant to the 2014 Stock Incentive Plan and non-employee directors pursuant to the 2014 Directors Stock Plan. Total restricted stock units granted were 0.8 million for the nine months ended September 30, 2018. The fair value of restricted stock units is determined based on the closing stock price of our common shares on the grant date. The weighted-average grant date fair value of these restricted stock units granted was $63.70 per common share. As of September 30, 2018, we had $55.0 million of total unrecognized compensation cost related to nonvested restricted stock unit awards granted. The cost is expected to be recognized over a weighted-average period of approximately 1.8 years. Employee Stock Purchase Plan Under the Employee Stock Purchase Plan, employees purchased 0.5 million shares for the nine months ended September 30, 2018. The weighted average fair value of the discount on the stock purchased was $10.02 per share. As of September 30, 2018, a total of 2.4 million of new shares were available to be made issuable by us for this plan.

Earnings Per Common Share

Earnings Per Common Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Common Share
Earnings Per Common Share	15. Earnings Per Common Share The computations of the basic and diluted per share amounts were as follows: For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions, except per share data) Net income $ $ $ $ Subtract: Net income attributable to noncontrolling interest Total $ $ $ $ Weighted-average shares outstanding: Basic Dilutive effects: Stock options Restricted stock units Performance share awards Diluted Net income per common share: Basic $ $ $ $ Diluted $ $ $ $ The calculation of diluted earnings per share for the three and nine months ended September 30, 2018 and 2017, excludes the incremental effect related to certain outstanding stock-based compensation grants due to their anti-dilutive effect.

Condensed Consolidating Financi

Condensed Consolidating Financial Information	9 Months Ended
	Sep. 30, 2018
Condensed Consolidating Financial Information
Condensed Consolidating Financial Information	16. Condensed Consolidating Financial Information Principal Life has established special purpose entities to issue secured medium-term notes. Under the program, the payment obligations of principal and interest on the notes are secured by funding agreements issued by Principal Life. Principal Life’s payment obligations on the funding agreements are fully and unconditionally guaranteed by PFG. All of the outstanding stock of Principal Life is indirectly owned by PFG and PFG is the only guarantor of the payment obligations of the funding agreements. The following tables set forth condensed consolidating financial information of (i) PFG, (ii) Principal Life, (iii) PFS and all other direct and indirect subsidiaries of PFG on a combined basis and (iv) the eliminations necessary to arrive at the information for PFG on a consolidated basis as of September 30, 2018 and December 31, 2017, and for the nine months ended September 30, 2018 and 2017. In presenting the condensed consolidating financial statements, the equity method of accounting has been applied to (i) PFG’s interest in all direct subsidiaries of PFG, (ii) Principal Life’s interest in all direct subsidiaries of Principal Life and (iii) PFS’s interest in Principal Life even though all such subsidiaries meet the requirements to be consolidated under U.S. GAAP. Earnings of subsidiaries are, therefore, reflected in the parent’s investment and earnings. All intercompany balances and transactions, including elimination of the parent’s investment in subsidiaries, between PFG, Principal Life and PFS and all other subsidiaries have been eliminated, as shown in the column “Eliminations.” These condensed consolidating financial statements should be read in conjunction with the consolidated financial statements. The financial information may not necessarily be indicative of results of operations, cash flows or financial position had the subsidiaries operated as independent entities. PFG sponsors nonqualified benefit plans for select employees and agents and is responsible for the obligations of these plans. Nonqualified plan assets are held in Rabbi trusts for the benefit of all nonqualified plan participants. The Rabbi trusts are separate legal entities and are not a part of PFG on a stand-alone basis. The plan assets are available to satisfy the claims of general creditors only in the event of bankruptcy and are, therefore, consolidated in our statements of financial position. Condensed Consolidating Statements of Financial Position September 30, 2018 Principal Principal Life Principal Financial Eliminations Principal (in millions) Assets Fixed maturities, available-for-sale $ $ $ $ $ Fixed maturities, trading — Equity securities — — Mortgage loans — Real estate — — Policy loans — — Investment in unconsolidated entities Other investments Cash and cash equivalents Accrued investment income Premiums due and other receivables — Deferred acquisition costs — — Property and equipment — — Goodwill — — Other intangibles — — Separate account assets — — Other assets Total assets $ $ $ $ $ Liabilities Contractholder funds $ — $ $ $ $ Future policy benefits and claims — Other policyholder funds — Short-term debt — — — Long-term debt — Income taxes currently payable — — Deferred income taxes — Separate account liabilities — — Other liabilities Total liabilities Redeemable noncontrolling interest — — — Stockholders’ equity Common stock — Additional paid-in capital Retained earnings Accumulated other comprehensive income (loss) Treasury stock, at cost — — — Total stockholders’ equity attributable to PFG Noncontrolling interest — — — Total stockholders’ equity Total liabilities and stockholders’ equity $ $ $ $ $ (1) PFG sponsors nonqualified benefit plans. Nonqualified benefit plan assets and liabilities held in Rabbi trusts were $687.1 million and $558.4 million, respectively. Condensed Consolidating Statements of Financial Position December 31, 2017 Principal Principal Life Principal Financial Eliminations Principal (in millions) Assets Fixed maturities, available-for-sale $ — $ $ $ $ Fixed maturities, trading — Equity securities — — Mortgage loans — Real estate — — Policy loans — — Investment in unconsolidated entities Other investments Cash and cash equivalents Accrued investment income Premiums due and other receivables — Deferred acquisition costs — — Property and equipment — — Goodwill — — Other intangibles — — Separate account assets — — Other assets Total assets $ $ $ $ $ Liabilities Contractholder funds $ — $ $ $ $ Future policy benefits and claims — Other policyholder funds — Short-term debt — — — Long-term debt — Income taxes currently payable — — Deferred income taxes — Separate account liabilities — — Other liabilities Total liabilities Redeemable noncontrolling interest — — — Stockholders’ equity Common stock — Additional paid-in capital Retained earnings Accumulated other comprehensive income Treasury stock, at cost — — — Total stockholders’ equity attributable to PFG Noncontrolling interest — — Total stockholders’ equity Total liabilities and stockholders’ equity $ $ $ $ $ (1) PFG sponsors nonqualified benefit plans. Nonqualified benefit plan assets and liabilities held in Rabbi trusts were $643.3 million and $524.7 million, respectively. Condensed Consolidating Statements of Operations For the nine months ended September 30, 2018 Principal Principal Life Principal Financial Eliminations Principal (in millions) Revenues Premiums and other considerations $ — $ $ $ — $ Fees and other revenues — Net investment income Net realized capital gains (losses), excluding impairment losses on available-for-sale securities — Net other-than-temporary impairment losses on available-for-sale securities — — Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified from other comprehensive income — — Net impairment losses on available-for-sale securities — — Net realized capital gains (losses) — Total revenues Expenses Benefits, claims and settlement expenses — Dividends to policyholders — — — Operating expenses Total expenses Income (loss) before income taxes Income taxes (benefits) Equity in the net income (loss) of subsidiaries — Net income Net income attributable to noncontrolling interest — — — Net income attributable to PFG $ $ $ $ $ Net income $ $ $ $ $ Other comprehensive loss Comprehensive loss $ $ $ $ $ Condensed Consolidating Statements of Operations For the nine months ended September 30, 2017 Principal Principal Life Principal Financial Eliminations Principal (in millions) Revenues Premiums and other considerations $ — $ $ $ — $ Fees and other revenues Net investment income Net realized capital gains (losses), excluding impairment losses on available-for-sale securities — Net other-than-temporary impairment (losses) recoveries on available-for-sale securities — — Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified from other comprehensive income — — Net impairment losses on available-for-sale securities — — Net realized capital gains (losses) — Total revenues Expenses Benefits, claims and settlement expenses — Dividends to policyholders — — — Operating expenses Total expenses Income (loss) before income taxes Income taxes (benefits) Equity in the net income (loss) of subsidiaries (1) — Net income Net income attributable to noncontrolling interest — — — Net income attributable to PFG $ $ $ $ $ Net income $ $ $ $ $ Other comprehensive income Comprehensive income $ $ $ $ $ (1) Principal Life Insurance Company Only includes income from discontinued operations of $35.5 million related to its sale of Principal Global Investors, LLC to PFS in connection with a corporate reorganization. Condensed Consolidating Statements of Cash Flows For the nine months ended September 30, 2018 Principal Principal Life Principal Financial Eliminations Principal (in millions) Operating activities Net cash provided by (used in) operating activities $ $ $ $ $ Investing activities Fixed maturities available-for-sale and equity securities with operating intent: Purchases Sales — — Maturities — Mortgage loans acquired or originated — Mortgage loans sold or repaid — Real estate acquired — — — Real estate sold — — — Net purchases of property and equipment — — Purchase of interests in subsidiaries, net of cash acquired — — — Dividends and returns of capital received from unconsolidated entities — Net change in other investments Net cash provided by (used in) investing activities Financing activities Issuance of common stock — — — Acquisition of treasury stock — — — Payments for financing element derivatives — — — Purchase of subsidiary shares from noncontrolling interest — — — Dividends to common stockholders — — — Issuance of long-term debt — — Principal repayments of long-term debt — — Net repayments of short-term borrowings — — — Dividends and capital paid to parent — — Investment contract deposits — — Investment contract withdrawals — — Net increase in banking operation deposits — — — Other — — — Net cash provided by (used in) financing activities Net increase (decrease) in cash and cash equivalents Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period $ $ $ $ $ Condensed Consolidating Statements of Cash Flows For the nine months ended September 30, 2017 Principal Principal Life Principal Financial Eliminations Principal (in millions) Operating activities Net cash provided by (used in) operating activities $ $ $ $ $ Investing activities Fixed maturities available-for-sale and equity securities with intent to hold: Purchases — — Sales — Maturities — — Mortgage loans acquired or originated — Mortgage loans sold or repaid — Real estate acquired — — — Real estate sold — — — Net purchases of property and equipment — — Dividends and returns of capital received from unconsolidated entities — Net change in other investments Net cash provided by (used in) investing activities Financing activities Issuance of common stock — — — Acquisition of treasury stock — — — Proceeds from financing element derivatives — — — Payments for financing element derivatives — — — Purchase of subsidiary shares from noncontrolling interest — — Sale of subsidiary shares to noncontrolling interest — — — Dividends to common stockholders — — — Issuance of long-term debt — — — Principal repayments of long-term debt — — Net proceeds from short-term borrowings — — — Dividends and capital paid to parent — — Investment contract deposits — — Investment contract withdrawals — — Net increase in banking operation deposits — — — Other — — — Net cash provided by (used in) financing activities Net increase (decrease) in cash and cash equivalents Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period $ $ $ $ $ Under our current shelf registration that was filed with the SEC and became effective May 3, 2017, we have the ability to issue, in unlimited amounts, unsecured senior debt securities or subordinated debt securities, junior subordinated debt, preferred stock, common stock, warrants, depositary shares, purchase contracts and purchase units of PFG. Our wholly owned subsidiary, PFS, may guarantee, fully and unconditionally or otherwise, our obligations with respect to any non-convertible securities, other than common stock, described in the shelf registration. The following tables set forth condensed consolidating financial information of (i) PFG, (ii) PFS, (iii) Principal Life and all other direct and indirect subsidiaries of PFG on a combined basis and (iv) the eliminations necessary to arrive at the information for PFG on a consolidated basis as of September 30, 2018 and December 31, 2017, and for the nine months ended September 30, 2018 and 2017. In presenting the condensed consolidating financial statements, the equity method of accounting has been applied to (i) PFG’s interest in all direct subsidiaries of PFG and (ii) PFS’s interest in Principal Life and all other subsidiaries, where applicable, even though all such subsidiaries meet the requirements to be consolidated under U.S. GAAP. Earnings of subsidiaries are, therefore, reflected in the parent’s investment and earnings. All intercompany balances and transactions, including elimination of the parent’s investment in subsidiaries, between PFG, PFS and Principal Life and all other subsidiaries have been eliminated, as shown in the column “Eliminations.” These condensed consolidating financial statements should be read in conjunction with the consolidated financial statements. The financial information may not necessarily be indicative of results of operations, cash flows or financial position had the subsidiaries operated as independent entities. PFG sponsors nonqualified benefit plans for select employees and agents and is responsible for the obligations of these plans. Nonqualified plan assets are held in Rabbi trusts for the benefit of all nonqualified plan participants. The Rabbi trusts are separate legal entities and are not a part of PFG on a stand-alone basis. The plan assets are available to satisfy the claims of general creditors only in the event of bankruptcy and are, therefore, consolidated in our statements of financial position. Condensed Consolidating Statements of Financial Position September 30, 2018 Principal Life Principal Principal Insurance Company Principal Financial Financial and Other Financial Group, Inc. Services, Inc. Subsidiaries Group, Inc. Parent Only Only Combined (1) Eliminations Consolidated (in millions) Assets Fixed maturities, available-for-sale $ $ — $ $ — $ Fixed maturities, trading — — Equity securities — — Mortgage loans — — — Real estate — — — Policy loans — — — Investment in unconsolidated entities Other investments — Cash and cash equivalents Accrued investment income — — Premiums due and other receivables — Deferred acquisition costs — — — Property and equipment — — — Goodwill — — — Other intangibles — — — Separate account assets — — — Other assets Total assets $ $ $ $ $ Liabilities Contractholder funds $ — $ — $ $ — $ Future policy benefits and claims — — — Other policyholder funds — — — Short-term debt — — — Long-term debt Income taxes currently payable — Deferred income taxes — Separate account liabilities — — — Other liabilities Total liabilities Redeemable noncontrolling interest — — — Stockholders’ equity Common stock — Additional paid-in capital Retained earnings Accumulated other comprehensive loss Treasury stock, at cost — Total stockholders’ equity attributable to PFG Noncontrolling interest — — — Total stockholders’ equity Total liabilities and stockholders’ equity $ $ $ $ $ (1) PFG sponsors nonqualified benefit plans. Nonqualified benefit plan assets and liabilities held in Rabbi trusts were $687.1 million and $558.4 million, respectively. Condensed Consolidating Statements of Financial Position December 31, 2017 Principal Life Principal Principal Insurance Company Principal Financial Financial and Other Financial Group, Inc. Services, Inc. Subsidiaries Group, Inc. Parent Only Only Combined (1) Eliminations Consolidated (in millions) Assets Fixed maturities, available-for-sale $ — $ — $ $ — $ Fixed maturities, trading — — Equity securities — — Mortgage loans — — — Real estate — — — Policy loans — — — Investment in unconsolidated entities Other investments — Cash and cash equivalents Accrued investment income — Premiums due and other receivables — Deferred acquisition costs — — — Property and equipment — — — Goodwill — — — Other intangibles — — — Separate account assets — — — Other assets Total assets $ $ $ $ $ Liabilities Contractholder funds $ — $ — $ $ — $ Future policy benefits and claims — — — Other policyholder funds — — — Short-term debt — — — Long-term debt Income taxes currently payable — Deferred income taxes — Separate account liabilities — — — Other liabilities Total liabilities Redeemable noncontrolling interest — — — Stockholders’ equity Common stock — Additional paid-in capital Retained earnings Accumulated other comprehensive income Treasury stock, at cost — Total stockholders’ equity attributable to PFG Noncontrolling interest — — — Total stockholders’ equity Total liabilities and stockholders’ equity $ $ $ $ $ (1) PFG sponsors nonqualified benefit plans. Nonqualified benefit plan assets and liabilities held in Rabbi trusts were $643.3 million and $524.7 million, respectively. Condensed Consolidating Statements of Operations For the nine months ended September 30, 2018 Principal Life Principal Principal Insurance Principal Financial Financial Company and Financial Group, Inc. Services, Inc. Other Subsidiaries Group, Inc. Parent Only Only Combined Eliminations Consolidated (in millions) Revenues Premiums and other considerations $ — $ — $ $ — $ Fees and other revenues — Net investment income (loss) Net realized capital gains (losses), excluding impairment losses on available-for-sale securities — Net other-than-temporary impairment losses on available-for-sale securities — — — Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified from other comprehensive income — — — Net impairment losses on available-for-sale securities — — — Net realized capital gains (losses) — Total revenues Expenses Benefits, claims and settlement expenses — — — Dividends to policyholders — — — Operating expenses Total expenses Income (loss) before income taxes Income taxes (benefits) — Equity in the net income of subsidiaries — — Net income Net income attributable to noncontrolling interest — — — Net income attributable to PFG $ $ $ $ $ Net income $ $ $ $ $ Other comprehensive loss Comprehensive loss $ $ $ $ $ Condensed Consolidating Statements of Operations For the nine months ended September 30, 2017 Principal Life Principal Principal Insurance Principal Financial Financial Company and Financial Group, Inc. Services, Inc. Other Subsidiaries Group, Inc. Parent Only Only Combined Eliminations Consolidated (in millions) Revenues Premiums and other considerations $ — $ — $ $ — $ Fees and other revenues Net investment income (loss) Net realized capital gains, excluding impairment losses on available-for-sale securities — — Net other-than-temporary impairment losses on available-for-sale securities — — — Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified from other comprehensive income — — — Net impairment losses on available-for-sale securities — — — Net realized capital gains — — Total revenues Expenses Benefits, claims and settlement expenses — — — Dividends to policyholders — — — Operating expenses Total expenses Income (loss) before income taxes Income taxes (benefits) Equity in the net income of subsidiaries — — Net income Net income attributable to noncontrolling interest — — — Net income attributable to PFG $ $ $ $ $ Net income $ $ $ $ $ Other comprehensive income Comprehensive income $ $ $ $ $ Condensed Consolidating Statements of Cash Flows For the nine months ended September 30, 2018 Principal Life Principal Principal Insurance Principal Financial Financial Company and Financial Group, Inc. Services, Inc. Other Subsidiaries Group, Inc. Parent Only Only Combined Eliminations Consolidated (in millions) Operating activities Net cash provided by (used in) operating activities $ $ $ $ $ Investing activities Fixed maturities available-for-sale and equity securities with intent to hold: Purchases — — Sales — — — Maturities — — Mortgage loans acquired or originated — — — Mortgage loans sold or repaid — — — Real estate acquired — — — Real estate sold — — — Net purchases of property and equipment — — — Purchase of interests in subsidiaries, net of cash acquired — — — Dividends and returns of capital received from unconsolidated entities — — Net change in other investments Net cash provided by (used in) investing activities Financing activities Issuance of common stock — — — Acquisition of treasury stock — — — Payments for financing element derivatives — — — Purchase of subsidiary shares from noncontrolling interest — — — Dividends to common stockholders — — — Issuance of long-term debt — Principal repayments of long-term debt — Net repayments of short-term borrowings — — — Dividends and capital paid to parent — — Investment contract deposits — — — Investment contract withdrawals — — — Net increase in banking operation deposits — — — Other — — — Net cash provided by (used in) financing activities Net increase (decrease) in cash and cash equivalents Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period $ $ $ $ $ Condensed Consolidating Statements of Cash Flows For the nine months ended September 30, 2017 Principal Life Principal Principal Insurance Principal Financial Financial Company and Financial Group, Inc. Services, Inc. Other Subsidiaries Group, Inc. Parent Only Only Combined Eliminations Consolidated (in millions) Operating activities Net cash provided by (used in) operating activities $ $ $ $ $ Investing activities Fixed maturities available-for-sale and equity securities with intent to hold: Purchases — — — Sales — — — Maturities — — — Mortgage loans acquired or originated — — — Mortgage loans sold or repaid — — — Real estate acquired — — — Real estate sold — — — Net purchases of property and equipment — — — Dividends and returns of capital received from (contributed to) unconsolidated entities — — Net change in other investments Net cash provided by (used in) investing activities Financing activities Issuance of common stock — — — Acquisition of treasury stock — — — Proceeds from financing element derivatives — — — Payments for financing element derivatives — — — Purchase of subsidiary shares from noncontrolling interest — — — Dividends to common stockholders — — — Issuance of long-term debt — — — Principal repayments of long-term debt — Net proceeds from (repayments of) short-term borrowings — — Dividends and capital received from (paid to) parent — — Investment contract deposits — — — Investment contract withdrawals — — — Net increase in banking operation deposits — — — Other — — — Net cash provided by (used in) financing activities Net increase (decrease) in cash and cash equivalents Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period $ $ $ $ $

Nature of Operations and Sign_2

Nature of Operations and Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Nature of Operations and Significant Accounting Policies
Separate Accounts - Policy	Separate Accounts The separate accounts are legally segregated and are not subject to the claims that arise out of any of our other business. The client, rather than us, directs the investments and bears the investment risk of these funds. The separate account assets represent the fair value of funds that are separately administered by us for contracts with equity, real estate and fixed income investments and are presented as a summary total within the consolidated statements of financial position. An equivalent amount is reported as separate account liabilities, which represent the obligation to return the monies to the client. We receive fees for mortality, withdrawal and expense risks, as well as administrative, maintenance and investment advisory services that are included in the consolidated statements of operations. Net deposits, net investment income and realized and unrealized capital gains and losses of the separate accounts are not reflected in the consolidated statements of operations. Separate account assets and separate account liabilities include certain international retirement accumulation products where the segregated funds and associated obligation to the client are consolidated within our financial statements. We have determined that summary totals are the most meaningful presentation for these funds. As of September 30, 2018 and December 31, 2017, the separate accounts included a separate account valued at $131.7 million and $170.5 million, respectively, which primarily included shares of our stock that were allocated and issued to eligible participants of qualified employee benefit plans administered by us as part of the policy credits issued under our 2001 demutualization. These shares are included in both basic and diluted earnings per share calculations. In the consolidated statements of financial position, the separate account shares are recorded at fair value and are reported as separate account assets with a corresponding separate account liability to eligible participants of the qualified plan. Changes in fair value of the separate account shares are reflected in both the separate account assets and separate account liabilities and do not impact our results of operations.

Nature of Operations and Sign_3

Nature of Operations and Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2018
ASU 2014-09 - Revenue recognition
Adoption of Revenue Recognition Guidance
Impacts to Consolidated Statements of Financial Position from Adoption of Guidance (Table)	September 30, 2018 Impact of adopting revenue recognition As reported As adjusted (1) accounting guidance (in millions) Assets Deferred acquisition costs (2) $ $ $ Other assets (3) Liabilities Deferred income taxes Stockholders’ equity Total stockholders’ equity (1) Excludes the impact of adopting revenue recognition accounting guidance. (2) Certain costs to obtain a contract previously recorded as DAC are now recorded as a contract cost asset or are no longer deferrable under revenue recognition guidance. (3) Includes the contract cost asset.

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	9 Months Ended
	Sep. 30, 2018
Variable Interest Entities
Carrying Amounts of Assets and Liabilities of Consolidated Variable Interest Entities (Table)	September 30, 2018 December 31, 2017 Total Total Total Total assets liabilities assets liabilities (in millions) Grantor trusts (1) $ $ $ $ CMBS — — Mandatory retirement savings funds (2) Real estate (3) Sponsored investment funds (4) Total $ $ $ $ (1) The assets of grantor trusts are primarily fixed maturities, available-for-sale. The liabilities are primarily other liabilities that reflect an embedded derivative of the forecasted transaction to deliver the underlying securities. (2) The assets of the mandatory retirement savings funds include separate account assets and equity securities. The liabilities include separate account liabilities and contractholder funds. (3) The assets of the real estate VIEs primarily include real estate, other investments and cash. Liabilities primarily include long-term debt and other liabilities. (4) The assets of sponsored investment funds are primarily fixed maturities and equity securities, which are reported with other investments, and cash. The consolidated statements of financial position included a $75.4 million and $52.4 million redeemable noncontrolling interest for sponsored investment funds as of September 30, 2018 and December 31, 2017, respectively.
Asset Carrying Value and Maximum Loss Exposure of Unconsolidated Variable Interest Entities (Table)	Maximum exposure to Asset carrying value loss (1) (in millions) September 30, 2018 Fixed maturities, available-for-sale: Corporate $ $ Residential mortgage-backed pass-through securities Commercial mortgage-backed securities Collateralized debt obligations Other debt obligations Fixed maturities, trading: Residential mortgage-backed pass-through securities Commercial mortgage-backed securities Collateralized debt obligations Other debt obligations Equity securities Other investments: Other limited partnership and fund interests (2) December 31, 2017 Fixed maturities, available-for-sale: Corporate $ $ Residential mortgage-backed pass-through securities Commercial mortgage-backed securities Collateralized debt obligations Other debt obligations Fixed maturities, trading: Residential mortgage-backed pass-through securities Commercial mortgage-backed securities Equity securities Other investments: Other limited partnership and fund interests (1) Our risk of loss is limited to our initial investment measured at amortized cost for fixed maturities, available-for-sale. Our risk of loss is limited to our investment measured at fair value for our fixed maturities, trading and equity securities. Our risk of loss is limited to our carrying value plus any unfunded commitments and/or guarantees and similar provisions for our other investments. Unfunded commitments are not liabilities on our consolidated statements of financial position because we are only required to fund additional equity when called upon to do so by the general partner or investment manager. (2) As of September 30, 2018, the maximum exposure to loss for other limited partnership and fund interests includes $144.5 million of debt within certain of our managed international real estate funds that is fully secured by assets whose value exceeds the amount of the debt, but also includes recourse to the investment manager.

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2018
Investments
Fixed Maturities and Equity Securities Available-for-Sale (Table)	Other-than- Gross Gross temporary Amortized unrealized unrealized impairments in cost gains losses Fair value AOCI (1) (in millions) September 30, 2018 Fixed maturities, available-for-sale: U.S. government and agencies $ $ $ $ $ — Non-U.S. governments — States and political subdivisions — Corporate Residential mortgage-backed pass-through securities — Commercial mortgage-backed securities Collateralized debt obligations Other debt obligations Total fixed maturities, available-for-sale $ $ $ $ $ December 31, 2017 Fixed maturities, available-for-sale: U.S. government and agencies $ $ $ $ $ — Non-U.S. governments — States and political subdivisions — Corporate Residential mortgage-backed pass-through securities — Commercial mortgage-backed securities Collateralized debt obligations Other debt obligations Total fixed maturities, available-for-sale $ $ $ $ $ Total equity securities, available-for-sale $ $ $ $ (1) Excludes $86.2 million and $103.0 million as of September 30, 2018 and December 31, 2017 , respectively, of net unrealized gains on impaired fixed maturities, available-for-sale related to changes in fair value subsequent to the impairment date, which are included in gross unrealized gains and gross unrealized losses.
Fixed Maturities Available-for-Sale by Contractual Maturity (Table)	The amortized cost and fair value of fixed maturities, available-for-sale as of September 30, 2018, by expected maturity, were as follows: Amortized cost Fair value (in millions) Due in one year or less $ $ Due after one year through five years Due after five years through ten years Due after ten years Subtotal Mortgage-backed and other asset-backed securities Total $ $
Net Realized Capital Gains and Losses (Table)	For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Fixed maturities, available-for-sale: Gross gains $ $ $ $ Gross losses Net impairment losses Hedging, net Fixed maturities, trading (1) Equity securities, trading (2) — — Equity securities (3) — — Mortgage loans Derivatives Other (4) Net realized capital gains (losses) $ $ $ $ (1) Unrealized gains (losses) on fixed maturities, trading still held at the reporting date were $(3.4) million and $(3.0) million for the three months ended September 30, 2018 and 2017, respectively, and $(16.7) million and $(0.4) million for the nine months ended September 30, 2018 and 2017, respectively. (2) Unrealized gains (losses) on equity securities, trading still held at the reporting date were $9.1 million and $36.6 million for the three and nine months ended September 30, 2017, respectively. This excludes $4.9 million and $32.2 million of unrealized gains (losses) on equity securities, trading still held at the reporting date for the three and nine months ended September 30, 2017, respectively, that were reported in net investment income. (3) Unrealized gains (losses) on equity securities still held at the reporting date were $8.8 million and $(5.2) million for the three and nine months ended September 30, 2018, respectively. This excludes $9.6 million and $12.8 million of unrealized gains (losses) on equity securities still held at the reporting date for the three and nine months ended September 30, 2018, respectively, that were reported in net investment income. (4) See Real Estate Transactions, for further details relating to other gains in 2017.
Other-Than-Temporary Impairment Losses, Net of Recoveries (Table)	For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Fixed maturities, available-for-sale $ $ $ $ Total other-than-temporary impairment losses, net of recoveries from the sale of previously impaired securities Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified from OCI (1) Net impairment losses on available-for-sale securities $ $ $ $ (1) Represents the net impact of (a) gains resulting from reclassification of noncredit impairment losses for fixed maturities with bifurcated OTTI from net realized capital gains (losses) to OCI and (b) losses resulting from reclassification of previously recognized noncredit impairment losses from OCI to net realized capital gains (losses) for fixed maturities with bifurcated OTTI that had additional credit losses or fixed maturities that previously had bifurcated OTTI that have now been sold or are intended to be sold.
Other-Than-Temporary Impairment, Credit Losses Recognized in Earnings (Table)	For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Beginning balance $ $ $ $ Credit losses for which an other-than-temporary impairment was not previously recognized — Credit losses for which an other-than-temporary impairment was previously recognized Reduction for credit losses previously recognized on fixed maturities now sold, paid down or intended to be sold Net reduction for positive changes in cash flows expected to be collected and amortization (1) Foreign currency translation adjustment — — — Ending balance $ $ $ $ (1) Amounts are recognized in net investment income.
Gross Unrealized Losses for Fixed Maturities and Equity Securities (Table)	September 30, 2018 Less than Greater than or twelve months equal to twelve months Total Gross Gross Gross Fair unrealized Fair unrealized Fair unrealized value losses value losses value losses (in millions) Fixed maturities, available-for-sale: U.S. government and agencies $ $ $ $ $ $ Non-U.S. governments States and political subdivisions Corporate Residential mortgage-backed pass-through securities Commercial mortgage-backed securities Collateralized debt obligations Other debt obligations Total fixed maturities, available-for-sale $ $ $ $ $ $ December 31, 2017 Less than Greater than or twelve months equal to twelve months Total Gross Gross Gross Fair unrealized Fair unrealized Fair unrealized value losses value losses value losses (in millions) Fixed maturities, available-for-sale: U.S. government and agencies $ $ $ $ $ $ Non-U.S. governments States and political subdivisions Corporate Residential mortgage-backed pass-through securities Commercial mortgage-backed securities Collateralized debt obligations Other debt obligations Total fixed maturities, available-for-sale $ $ $ $ $ $ Total equity securities, available-for-sale $ — $ — $ $ $ $
Net Unrealized Gains and Losses on Available-for-Sale Securities and Derivative Instruments (Table)	September 30, 2018 December 31, 2017 (in millions) Net unrealized gains on fixed maturities, available-for-sale (1) $ $ Noncredit component of impairment losses on fixed maturities, available-for-sale Net unrealized gains on equity securities, available-for-sale — Adjustments for assumed changes in amortization patterns Adjustments for assumed changes in policyholder liabilities Net unrealized gains on derivative instruments Net unrealized gains on equity method subsidiaries and noncontrolling interest adjustments Provision for deferred income taxes Net unrealized gains on available-for-sale securities and derivative instruments $ $ (1) Excludes net unrealized gains (losses) on fixed maturities, available-for-sale included in fair value hedging relationships.
Mortgage Loans (Table)	September 30, 2018 December 31, 2017 (in millions) Commercial mortgage loans $ $ Residential mortgage loans Total amortized cost Valuation allowance Total carrying value $ $
Mortgage Loans Purchased and Sold (Table)	For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Commercial mortgage loans: Purchased $ $ $ $ Sold — — — Residential mortgage loans: Purchased Sold
Commercial Mortgage Loans by Geographic Distribution and Property Type Distribution (Table)	September 30, 2018 December 31, 2017 Amortized Percent Amortized Percent cost of total cost of total ($ in millions) Geographic distribution New England $ % $ % Middle Atlantic East North Central West North Central South Atlantic East South Central West South Central Mountain Pacific International Total $ % $ % Property type distribution Office $ % $ % Retail Industrial Apartments Hotel Mixed use/other Total $ % $ %
Commercial Mortgage Loan Portfolio by Credit Risk (Table)	September 30, 2018 Brick and mortar CTL Total (in millions) A- and above $ $ $ BBB+ thru BBB- BB+ thru BB- — B+ and below Total $ $ $ December 31, 2017 Brick and mortar CTL Total (in millions) A- and above $ $ $ BBB+ thru BBB- BB+ thru BB- — B+ and below Total $ $ $
Performing and Non-Performing Residential Mortgage Loans (Table)	September 30, 2018 Home equity First liens Total (in millions) Performing $ $ $ Non-performing Total $ $ $ December 31, 2017 Home equity First liens Total (in millions) Performing $ $ $ Non-performing Total $ $ $
Non-Accrual Mortgage Loans (Table)	September 30, 2018 December 31, 2017 (in millions) Residential: Home equity $ $ First liens Total $ $
Mortgage Loans Aging (Table)	September 30, 2018 Recorded investment 90 days or 90 days or 30-59 days 60-89 days more past Total past more and past due past due due due Current Total loans accruing (in millions) Commercial-brick and mortar $ — $ — $ — $ — $ $ $ — Commercial-CTL — — — — — Residential-home equity — Residential-first liens Total $ $ $ $ $ $ $ December 31, 2017 Recorded investment 90 days or 90 days or 30-59 days 60-89 days more past Total past more and past due past due due due Current Total loans accruing (in millions) Commercial-brick and mortar $ — $ — $ — $ — $ $ $ — Commercial-CTL — — — — — Residential-home equity — Residential-first liens Total $ $ $ $ $ $ $
Mortgage Loan Valuation Allowance (Table)	For the three months ended September 30, 2018 Commercial Residential Total (in millions) Beginning balance $ $ $ Provision Charge-offs — Recoveries — Ending balance $ $ $ For the nine months ended September 30, 2018 Commercial Residential Total (in millions) Beginning balance $ $ $ Provision Charge-offs — Recoveries — Ending balance $ $ $ Allowance ending balance by basis of impairment method: Individually evaluated for impairment $ — $ $ Collectively evaluated for impairment Allowance ending balance $ $ $ Loan balance by basis of impairment method: Individually evaluated for impairment $ — $ $ Collectively evaluated for impairment Loan ending balance $ $ $ For the three months ended September 30, 2017 Commercial Residential Total (in millions) Beginning balance $ $ $ Provision Charge-offs — Recoveries — Ending balance $ $ $ For the nine months ended September 30, 2017 Commercial Residential Total (in millions) Beginning balance $ $ $ Provision Charge-offs — Recoveries — Ending balance $ $ $ Allowance ending balance by basis of impairment method: Individually evaluated for impairment $ — $ $ Collectively evaluated for impairment Allowance ending balance $ $ $ Loan balance by basis of impairment method: Individually evaluated for impairment $ — $ $ Collectively evaluated for impairment Loan ending balance $ $ $
Impaired Mortgage Loans (Table)	September 30, 2018 Unpaid Recorded principal Related investment balance allowance (in millions) With no related allowance recorded: Residential-first liens $ $ $ — With an allowance recorded: Residential-home equity Residential-first liens Total: Residential $ $ $ December 31, 2017 Unpaid Recorded principal Related investment balance allowance (in millions) With no related allowance recorded: Residential-first liens $ $ $ — With an allowance recorded: Residential-home equity Residential-first liens Total: Residential $ $ $ For the three months ended For the nine months ended September 30, 2018 September 30, 2018 Average Average recorded Interest income recorded Interest income investment recognized investment recognized (in millions) With no related allowance recorded: Residential-first liens $ $ — $ $ — With an allowance recorded: Residential-home equity — Residential-first liens — Total: Residential $ $ — $ $ For the three months ended For the nine months ended September 30, 2017 September 30, 2017 Average Average recorded Interest income recorded Interest income investment recognized investment recognized (in millions) With no related allowance recorded: Residential-first liens $ $ — $ $ — With an allowance recorded: Residential-home equity Residential-first liens — Total: Residential $ $ $ $
Mortgage Loans Modified as a Troubled Debt Restructuring (Table)	For the three months ended September 30, 2017 TDRs TDRs in payment default Number of Recorded Number of Recorded contracts investment contracts investment (in millions) (in millions) Residential-home equity $ — $ — Residential-first liens — — Total $ — $ — For the nine months ended September 30, 2018 TDRs TDRs in payment default Number of Recorded Number of Recorded contracts investment contracts investment (in millions) (in millions) Residential-home equity $ — $ — Residential-first liens — — Total $ — $ — For the nine months ended September 30, 2017 TDRs TDRs in payment default Number of Recorded Number of Recorded contracts investment contracts investment (in millions) (in millions) Residential-home equity $ — $ — Residential-first liens Total $ $
Real Estate Transactions (Table)	The following consolidated statement of financial position line items were most significantly impacted by the transactions, each having a net increase as of September 30, 2017, (in millions): Real estate $ Other investments Cash and cash equivalents Long-term debt Income taxes currently payable Deferred income taxes
Financial Assets Subject to Netting Agreements (Table)	Gross amounts not offset in the consolidated statements of financial position Gross amount of recognized Financial Collateral assets (1) instruments (2) received Net amount (in millions) September 30, 2018 Derivative assets $ $ $ $ Reverse repurchase agreements — — Total $ $ $ $ December 31, 2017 Derivative assets $ $ $ $ Reverse repurchase agreements — — Total $ $ $ $ (1) The gross amount of recognized derivative and reverse repurchase agreement assets are reported with other investments and cash and cash equivalents, respectively, on the consolidated statements of financial position. The above excludes $12.6 million and $17.0 million of derivative assets as of September 30, 2018 and December 31, 2017, respectively, that are not subject to master netting agreements or similar agreements. The gross amounts of derivative and reverse repurchase agreement assets are not netted against offsetting liabilities for presentation on the consolidated statements of financial position. (2) Represents amount of offsetting derivative liabilities that are subject to an enforceable master netting agreement or similar agreement that are not netted against the gross derivative assets for presentation on the consolidated statements of financial position.
Financial Liabilities Subject to Netting Agreements (Table)	Gross amounts not offset in the consolidated statements of financial position Gross amount of recognized Financial Collateral liabilities (1) instruments (2) pledged Net amount (in millions) September 30, 2018 Derivative liabilities $ $ $ $ Total $ $ $ $ December 31, 2017 Derivative liabilities $ $ $ $ Total $ $ $ $ (1) The gross amount of recognized derivative liabilities are reported with other liabilities on the consolidated statements of financial position. The above excludes $151.3 million and $415.6 million of derivative liabilities as of September 30, 2018 and December 31, 2017, respectively, which are primarily embedded derivatives that are not subject to master netting agreements or similar agreements. The gross amount of recognized repurchase agreement liabilities are reported with short-term debt on the consolidated statements of financial position. The gross amounts of derivative and repurchase agreement liabilities are not netted against offsetting assets for presentation on the consolidated statements of financial position. (2) Represents amount of offsetting derivative assets that are subject to an enforceable master netting agreement or similar agreement that are not netted against the gross derivative liabilities for presentation on the consolidated statements of financial position.

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2018
Derivative Financial Instruments
Derivative Financial Instruments, Exposure (Table)	September 30, 2018 December 31, 2017 (in millions) Notional amounts of derivative instruments Interest rate contracts: Interest rate swaps $ $ Interest rate options Interest rate futures Swaptions — Foreign exchange contracts: Currency forwards Currency swaps Currency options Equity contracts: Equity options Equity futures Credit contracts: Credit default swaps Other contracts: Embedded derivatives Total notional amounts at end of period $ $ Credit exposure of derivative instruments Interest rate contracts: Interest rate swaps $ $ Interest rate options Foreign exchange contracts: Currency swaps Currency forwards Currency options Equity contracts: Equity options Credit contracts: Credit default swaps Total gross credit exposure Less: collateral received Net credit exposure $ $
Derivative Financial Instruments, Fair Value Disclosures (Table)	Derivative assets (1) Derivative liabilities (2) September 30, 2018 December 31, 2017 September 30, 2018 December 31, 2017 (in millions) Derivatives designated as hedging instruments Interest rate contracts $ — $ — $ $ Foreign exchange contracts Total derivatives designated as hedging instruments $ $ $ $ Derivatives not designated as hedging instruments Interest rate contracts $ $ $ $ Foreign exchange contracts Equity contracts Credit contracts Other contracts — — Total derivatives not designated as hedging instruments Total derivative instruments $ $ $ $ (1) The fair value of derivative assets is reported with other investments on the consolidated statements of financial position. (2) The fair value of derivative liabilities is reported with other liabilities on the consolidated statements of financial position, with the exception of certain embedded derivative liabilities. Embedded derivatives with a net (asset) liability fair value of $(81.9) million and $160.3 million as of September 30, 2018 and December 31, 2017, respectively, are reported with contractholder funds on the consolidated statements of financial position.
Credit Derivatives Sold (Table)	September 30, 2018 Weighted Maximum average Notional Fair future expected life amount value payments (in years) (in millions) Single name credit default swaps Corporate debt AAA $ $ $ A BBB B Government/municipalities AA Sovereign A BBB Total credit default swap protection sold $ $ $ December 31, 2017 Weighted Maximum average Notional Fair future expected life amount value payments (in years) (in millions) Single name credit default swaps Corporate debt AAA $ $ $ AA A BBB B Government/municipalities AA Sovereign A BBB Total credit default swap protection sold $ $ $
Fair Value Hedges (Table)	Amount of loss Amount of gain recognized in net income on recognized in net income on related hedged item for the derivatives for the three months three months ended Derivatives in fair value hedging ended September 30, (1) Hedged items in fair value September 30, (1) relationships 2018 2017 hedging relationships 2018 2017 (in millions) (in millions) Interest rate contracts $ $ Fixed maturities, available-for-sale $ $ Interest rate contracts — Investment contracts — Total $ $ Total $ $ Amount of gain (loss) Amount of gain (loss) recognized in net income recognized in net income on on related hedged item derivatives for the nine months for the nine months Derivatives in fair value hedging ended September 30, (1) Hedged items in fair value ended September 30, (1) relationships 2018 2017 hedging relationships 2018 2017 (in millions) (in millions) Interest rate contracts $ $ Fixed maturities, available-for-sale $ $ Interest rate contracts — Investment contracts — Total $ $ Total $ $ (1) The gain (loss) on both derivatives and hedged items in fair value relationships is reported in net realized capital gains (losses) on the consolidated statements of operations. The net amount represents the ineffective portion of our fair value hedges.
Fair Value Hedges, Periodic Settlements Disclosures (Table)	Amount of gain (loss) for the three Amount of gain (loss) for the months ended September 30, nine months ended September 30, Hedged item 2018 2017 2018 2017 (in millions) Fixed maturities, available-for-sale (1) $ $ $ $ Investment contracts (2) — — (1) Reported in net investment income on the consolidated statements of operations. (2) Reported in benefits, claims and settlement expenses on the consolidated statements of operations.
Cash Flow Hedges (Table)	Amount of gain (loss) Amount of gain (loss) recognized in AOCI on reclassified from AOCI on derivatives (effective portion) Location of gain (loss) derivatives (effective portion) Derivatives in cash for the three months ended reclassified from AOCI for the three months ended flow hedging September 30, into net income September 30, relationships Related hedged item 2018 2017 (effective portion) 2018 2017 (in millions) (in millions) Interest rate contracts Fixed maturities, available-for-sale $ $ Net investment income $ $ Interest rate contracts Debt — — Operating expense Foreign exchange contracts Fixed maturities, available-for-sale Net realized capital gains (losses) Total $ $ Total $ $ Amount of gain (loss) Amount of gain (loss) recognized in AOCI on reclassified from AOCI on derivatives (effective portion) Location of gain (loss) derivatives (effective portion) Derivatives in cash for the nine months ended reclassified from AOCI for the nine months ended flow hedging September 30, into net income September 30, relationships Related hedged item 2018 2017 (effective portion) 2018 2017 (in millions) (in millions) Interest rate contracts Fixed maturities, available-for-sale $ $ Net investment income $ $ Net realized capital losses — Interest rate contracts Debt — — Operating expense Foreign exchange contracts Fixed maturities, available-for-sale Net realized capital gains Foreign exchange contracts Investment contracts Benefits, claims and settlement expenses — — Total $ $ Total $ $
Cash Flow Hedges, Periodic Settlements Disclosures (Table)	Amount of gain (loss) for the Amount of gain (loss) for the three months ended September 30, nine months ended September 30, Hedged item 2018 2017 2018 2017 (in millions) Fixed maturities, available-for-sale (1) $ $ $ $ Investment contracts (2) — (1) Reported in net investment income on the consolidated statements of operations. (2) Reported in benefits, claims and settlement expenses on the consolidated statements of operations.
Derivatives Not Designated as Hedging Instruments (Table)	Amount of gain (loss) recognized in Amount of gain (loss) recognized in net income on derivatives for the net income on derivatives for the three months ended September 30, nine months ended September 30, Derivatives not designated as hedging instruments 2018 2017 2018 2017 (in millions) Interest rate contracts $ $ $ $ Foreign exchange contracts Equity contracts Credit contracts — Other contracts Total $ $ $ $

Insurance Liabilities (Tables)

Insurance Liabilities (Tables)	9 Months Ended
	Sep. 30, 2018
Insurance Liabilities
Liability for Unpaid Claims (Table)	For the nine months ended September 30, 2018 2017 (in millions) Balance at beginning of period $ $ Less reinsurance recoverable Net balance at beginning of period Incurred: Current year Prior years Total incurred Payments: Current year Prior years Total payments Net balance at end of period Plus reinsurance recoverable Balance at end of period $ $ Amounts not included in the rollforward above: Claim adjustment expense liabilities $ $

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2018
Income Taxes
Reconciliation Between U.S. Corporate Income Tax Rate and Effective Income Tax Rate from Continuing Operations (Table)	For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 U.S. corporate income tax rate % % % % Impact of the Tax Cuts and Jobs Act — — Dividends received deduction Tax credits Impact of equity method presentation — Local country permanent tax adjustments State income taxes Other — Effective income tax rate % % % %
Changes in Unrecognized Tax Benefits (Table)	For the nine months ended For the year ended September 30, 2018 December 31, 2017 (in millions) Balance at beginning of period $ $ Additions based on tax positions related to the current year Additions for tax positions of prior years Reductions for tax positions related to the current year Reductions for tax positions of prior years — Settlements Balance at end of period (1) $ $ (1) Of this amount, $4.8 million, if recognized, would reduce the 2018 effective income tax rate. We recognize interest and penalties related to uncertain tax positions in operating expenses within the consolidated statements of operations.

Employee and Agent Benefits (Ta

Employee and Agent Benefits (Tables)	9 Months Ended
	Sep. 30, 2018
Employee and Agent Benefits
Components of Net Periodic Benefit Cost (Income) (Table)	Other postretirement Pension benefits benefits For the three months ended For the three months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Service cost $ $ $ — $ — Interest cost Expected return on plan assets Amortization of prior service benefit Recognized net actuarial (gain) loss Net periodic benefit cost (income) $ $ $ $ Other postretirement Pension benefits benefits For the nine months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Service cost $ $ $ — $ Interest cost Expected return on plan assets Amortization of prior service benefit Recognized net actuarial (gain) loss Net periodic benefit cost (income) $ $ $ $

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2018
Stockholders' Equity
Reconciliation of Outstanding Shares (Table)	For the nine months ended September 30, 2018 2017 (in millions) Beginning balance Shares issued Treasury stock acquired Ending balance
Other Comprehensive Income (Loss) (Table)	For the three months ended For the nine months ended September 30, 2018 September 30, 2018 Pre-Tax Tax After-Tax Pre-Tax Tax After-Tax (in millions) Net unrealized losses on available-for-sale securities during the period $ $ $ $ $ $ Reclassification adjustment for (gains) losses included in net income (1) Adjustments for assumed changes in amortization patterns Adjustments for assumed changes in policyholder liabilities Net unrealized losses on available- for-sale securities Noncredit component of impairment losses on fixed maturities, available-for-sale during the period Adjustments for assumed changes in amortization patterns Adjustments for assumed changes in policyholder liabilities — — — Noncredit component of impairment losses on fixed maturities, available-for-sale (2) Net unrealized gains on derivative instruments during the period Reclassification adjustment for gains included in net income (3) Adjustments for assumed changes in amortization patterns — Adjustments for assumed changes in policyholder liabilities Net unrealized gains on derivative instruments Foreign currency translation adjustment Amortization of amounts included in net periodic benefit cost (4) Net unrecognized postretirement benefit obligation Other comprehensive loss $ $ $ $ $ $ For the three months ended For the nine months ended September 30, 2017 September 30, 2017 Pre-Tax Tax After-Tax Pre-Tax Tax After-Tax (in millions) Net unrealized gains on available-for-sale securities during the period $ $ $ $ $ $ Reclassification adjustment for losses included in net income (1) Adjustments for assumed changes in amortization patterns Adjustments for assumed changes in policyholder liabilities Net unrealized gains on available- for-sale securities Noncredit component of impairment losses on fixed maturities, available-for-sale during the period Adjustments for assumed changes in amortization patterns Adjustments for assumed changes in policyholder liabilities — Noncredit component of impairment losses on fixed maturities, available-for-sale (2) Net unrealized losses on derivative instruments during the period Reclassification adjustment for gains included in net income (3) Adjustments for assumed changes in amortization patterns Adjustments for assumed changes in policyholder liabilities Net unrealized losses on derivative instruments Foreign currency translation adjustment Amortization of amounts included in net periodic benefit cost (4) Net unrecognized postretirement benefit obligation Other comprehensive income $ $ $ $ $ $ (1) Pre-tax reclassification adjustments relating to available-for-sale securities are reported in net realized capital gains (losses) on the consolidated statements of operations. (2) Represents the net impact of (1) unrealized gains resulting from reclassification of previously recognized noncredit impairment losses from OCI to net realized capital gains (losses) for fixed maturities with bifurcated OTTI that had additional credit losses or fixed maturities that previously had bifurcated OTTI that have now been sold or are intended to be sold and (2) unrealized losses resulting from reclassification of noncredit impairment losses for fixed maturities with bifurcated OTTI from net realized capital gains (losses) to OCI. (3) See Note 4, Derivative Financial Instruments – Cash Flow Hedges, for further details. (4) Amount is comprised of amortization of prior service cost (benefit) and recognized net actuarial (gain) loss, which is reported in operating expenses on the consolidated statements of operations. See Note 8, Employee and Agent Benefits – Components of Net Periodic Benefit Cost, for further details.
Accumulated Other Comprehensive Income (Loss) (Table)	Noncredit Net unrealized component of Net unrealized Foreign Unrecognized Accumulated gains on impairment losses gains currency postretirement other available-for-sale on fixed maturities on derivative translation benefit comprehensive securities available-for-sale instruments adjustment obligation income (loss) (in millions) Balances as of January 1, 2017 $ $ $ $ $ $ Other comprehensive income during the period, net of adjustments — — Amounts reclassified from AOCI — Other comprehensive income Balances as of September 30, 2017 $ $ $ $ $ $ Balances as of January 1, 2018 $ $ $ $ $ $ Other comprehensive loss during the period, net of adjustments — — Amounts reclassified from AOCI — Other comprehensive loss Purchase of subsidiary shares from noncontrolling interest — — — — Effects of implementation of accounting change related to equity investments, net — — — — Effects of implementation of accounting change related to revenue recognition, net — — — — Effects of implementation of accounting change related to the reclassification of certain tax effects, net Balances as of September 30, 2018 $ $ $ $ $ $
Redeemable Noncontrolling Interest (Table)	Following is a reconciliation of the changes in the redeemable noncontrolling interest (in millions): Balance as of January 1, 2017 $ Net income attributable to redeemable noncontrolling interest Redeemable noncontrolling interest of deconsolidated entities (1) Contributions from redeemable noncontrolling interest Distributions to redeemable noncontrolling interest Purchase of subsidiary shares from redeemable noncontrolling interest Change in redemption value of redeemable noncontrolling interest Other comprehensive income attributable to redeemable noncontrolling interest Balance as of September 30, 2017 $ Balance as of January 1, 2018 $ Net income attributable to redeemable noncontrolling interest Redeemable noncontrolling interest of deconsolidated entities (1) Contributions from redeemable noncontrolling interest Distributions to redeemable noncontrolling interest Purchase of subsidiary shares from redeemable noncontrolling interest Change in redemption value of redeemable noncontrolling interest Stock-based compensation attributable to redeemable noncontrolling interest Other comprehensive loss attributable to redeemable noncontrolling interest Balance as of September 30, 2018 $ (1) We deconsolidated certain sponsored investment funds as they no longer met the requirements for consolidation.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Measurements
Fair Value (Table)	September 30, 2018 Assets/ Amount (liabilities) measured at Fair value hierarchy level measured at net asset fair value value (5) Level 1 Level 2 Level 3 (in millions) Assets Fixed maturities, available-for-sale: U.S. government and agencies $ $ — $ $ $ — Non-U.S. governments — States and political subdivisions — — — Corporate — Residential mortgage-backed securities — — — Commercial mortgage-backed securities — — Collateralized debt obligations — — Other debt obligations — — Total fixed maturities, available-for-sale — Fixed maturities, trading — — — Equity securities — — Derivative assets (1) — — Other investments (2) Cash equivalents (3) — — Sub-total excluding separate account assets Separate account assets Total assets $ $ $ $ $ Liabilities Investment contracts (4) $ $ — $ — $ — $ Derivative liabilities (1) — — Other liabilities (4) — — — Total liabilities $ $ — $ — $ $ Net assets $ $ $ $ $ December 31, 2017 Assets/ Amount (liabilities) measured at Fair value hierarchy level measured at net asset fair value value (5) Level 1 Level 2 Level 3 (in millions) Assets Fixed maturities, available-for-sale: U.S. government and agencies $ $ — $ $ $ — Non-U.S. governments — States and political subdivisions — — — Corporate — Residential mortgage-backed securities — — — Commercial mortgage-backed securities — — Collateralized debt obligations — — Other debt obligations — — Total fixed maturities, available-for-sale — Fixed maturities, trading — — — Equity securities, available-for-sale — Equity securities, trading — — Derivative assets (1) — — Other investments (2) Cash equivalents (3) — — Sub-total excluding separate account assets Separate account assets Total assets $ $ $ $ $ Liabilities Investment contracts (4) $ $ — $ — $ — $ Derivative liabilities (1) — — Other liabilities (4) — — — Total liabilities $ $ — $ — $ $ Net assets $ $ $ $ $ (1) Within the consolidated statements of financial position, derivative assets are reported with other investments and derivative liabilities are reported with other liabilities. Refer to Note 4, Derivative Financial Instruments, for further information on fair value by class of derivative instruments. (2) Primarily includes sponsored investment funds, other investment funds, equity method real estate investments reported at fair value and commercial mortgage loans of consolidated VIEs. (3) Includes money market instruments and short-term investments with a maturity date of three months or less when purchased. (4) Includes bifurcated embedded derivatives that are reported at net asset (liability) fair value within the same line item in the consolidated statements of financial position in which the host contract is reported. (5) Certain investments are measured at fair value using the NAV per share (or its equivalent) practical expedient and have not been classified in the fair value hierarchy. Other investments using the NAV practical expedient consist of certain fund interests that are restricted until maturity with unfunded commitments totaling $35.0 million and $46.1 million as of September 30, 2018 and December 31, 2017, respectively. Separate account assets using the NAV practical expedient consist of hedge funds with varying investment strategies that also have a variety of redemption terms and conditions. We do not have unfunded commitments associated with these hedge funds.
Reconciliation for All Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Table)	For the three months ended September 30, 2018 Total realized/unrealized Changes in Beginning gains (losses) Net Ending unrealized asset/ purchases, asset/ gains (losses) (liability) sales, (liability) included in balance Included in issuances balance net income as of Included in other and Transfers Transfers as of relating to June 30, net income comprehensive settlements into out of September 30, positions still 2018 (1) income (3) (4) Level 3 Level 3 2018 held (1) (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ $ — $ — $ $ — $ $ $ — Corporate — Commercial mortgage-backed securities — — — — — Collateralized debt obligations Other debt obligations — — — Total fixed maturities, available-for-sale Fixed maturities, trading — — — — — — Derivative assets — — — Other investments — — — — Separate account assets (2) Liabilities Investment contracts — — Derivative liabilities — — — For the three months ended September 30, 2017 Total realized/unrealized Changes in Beginning gains (losses) Net Ending unrealized asset/ purchases, asset/ gains (losses) (liability) sales, (liability) included in balance Included in Included in issuances balance net income as of net other and Transfers Transfers as of relating to June 30, income comprehensive settlements into out of September 30, positions still 2017 (1) income (3) (4) Level 3 Level 3 2017 held (1) (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ $ $ $ $ — $ — $ $ Corporate — — Commercial mortgage-backed securities Collateralized debt obligations — — Other debt obligations — — — — — Total fixed maturities, available-for-sale Equity securities, available-for-sale — — — — — — Derivative assets — — — Other investments — — — Separate account assets (2) — Liabilities Investment contracts — — — Derivative liabilities — — — For the nine months ended September 30, 2018 Total realized/unrealized Changes in Beginning gains (losses) Net Ending unrealized asset/ purchases, asset/ gains (losses) (liability) sales, (liability) included in balance Included Included in issuances balance net income as of in net other and Transfers Transfers as of relating to December 31, income comprehensive settlements into out of September 30, positions still 2017 (1) income (3) (4) Level 3 Level 3 2018 held (1) (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ $ — $ $ $ — $ $ $ — Corporate Commercial mortgage-backed securities — Collateralized debt obligations Other debt obligations — — — Total fixed maturities, available-for-sale Fixed maturities, trading — — — — — — Equity securities — — — — — Derivative assets — — — Other investments — — — Separate account assets (2) Liabilities Investment contracts — — — Derivative liabilities — — — For the nine months ended September 30, 2017 Total realized/unrealized Changes in Beginning gains (losses) Net Ending unrealized asset/ purchases, asset/ gains (losses) (liability) sales, (liability) included in balance Included Included in issuances balance net income as of in net other and Transfers Transfers as of relating to December 31, income comprehensive settlements into out of September 30, positions still 2016 (1) income (3) (4) Level 3 Level 3 2017 held (1) (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ $ $ $ $ — $ — $ $ Corporate Commercial mortgage-backed securities Collateralized debt obligations — — Other debt obligations — — — Total fixed maturities, available-for-sale Fixed maturities, trading — — — — Equity securities, available-for-sale — — — — — — Equity securities, trading — — — — — — Derivative assets — — — Other investments — — — Separate account assets (2) Liabilities Investment contracts — — Derivative liabilities — — — Other liabilities — — — — — (1) Both realized gains (losses) and mark-to-market unrealized gains (losses) are generally reported in net realized capital gains (losses) within the consolidated statements of operations. Realized and unrealized gains (losses) on certain securities with an investment objective to realize economic value through mark-to-market changes are reported in net investment income within the consolidated statements of operations. (2) Gains and losses for separate account assets do not impact net income as the change in value of separate account assets is offset by a change in value of separate account liabilities. Foreign currency translation adjustments related to the Principal International segment separate account assets are recorded in AOCI and are offset by foreign currency translation adjustments of the corresponding separate account liabilities. (3) Includes foreign currency translation adjustments related to our Principal International segment. (4) Gross purchases, sales, issuances and settlements were: For the three months ended September 30, 2018 Net purchases, sales, issuances Purchases Sales Issuances Settlements and settlements (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ — $ — $ — $ $ Corporate — Collateralized debt obligations — — Other debt obligations — — Total fixed maturities, available-for-sale — Derivative assets — — — Other investments — — — Separate account assets (5) Liabilities Investment contracts — — Derivative liabilities — — For the three months ended September 30, 2017 Net purchases, sales, issuances Purchases Sales Issuances Settlements and settlements (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ $ $ — $ $ Corporate — Commercial mortgage-backed securities — — — Collateralized debt obligations — — Other debt obligations — — — Total fixed maturities, available-for-sale — Derivative assets — — Other investments — — — Separate account assets (5) Liabilities Investment contracts — — Derivative liabilities — — — For the nine months ended September 30, 2018 Net purchases, sales, issuances Purchases Sales Issuances Settlements and settlements (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ — $ — $ — $ $ Corporate — Commercial mortgage-backed securities — — — Collateralized debt obligations — — Other debt obligations — — Total fixed maturities, available-for-sale — Fixed maturities, trading — — — Equity securities — — — Derivative assets — — Other investments — — — Separate account assets (5) Liabilities Investment contracts — — Derivative liabilities — — For the nine months ended September 30, 2017 Net purchases, sales, issuances Purchases Sales Issuances Settlements and settlements (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ $ $ — $ $ Corporate — Commercial mortgage-backed securities — — — Collateralized debt obligations — — Other debt obligations — — — Total fixed maturities, available-for-sale — Fixed maturities, trading — — — Equity securities, trading — — — Derivative assets — — — Other investments — — Separate account assets (5) Liabilities Investment contracts — — Derivative liabilities — — Other liabilities — — — (5) Issuances and settlements include amounts related to mortgage encumbrances associated with real estate in our separate accounts.
Transfers (Table)	For the three months ended September 30, 2018 Transfers out Transfers out Transfers out Transfers out Transfers out Transfers out of Level 1 into of Level 1 into of Level 2 into of Level 2 into of Level 3 into of Level 3 into Level 2 Level 3 Level 1 Level 3 Level 1 Level 2 (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ — $ — $ — $ — $ — $ Corporate — — — — — Collateralized debt obligations — — — — Other debt obligations — — — — — Total fixed maturities, available-for-sale — — — — Fixed maturities, trading — — — — — Separate account assets — — — For the three months ended September 30, 2017 Transfers out Transfers out Transfers out Transfers out Transfers out Transfers out of Level 1 into of Level 1 into of Level 2 into of Level 2 into of Level 3 into of Level 3 into Level 2 Level 3 Level 1 Level 3 Level 1 Level 2 (in millions) Assets Fixed maturities, available-for-sale: Commercial mortgage-backed securities $ — $ — $ — $ $ — $ Collateralized debt obligations — — — — Total fixed maturities, available-for-sale — — — — Separate account assets — — For the nine months ended September 30, 2018 Transfers out Transfers out Transfers out Transfers out Transfers out Transfers out of Level 1 into of Level 1 into of Level 2 into of Level 2 into of Level 3 into of Level 3 into Level 2 Level 3 Level 1 Level 3 Level 1 Level 2 (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ — $ — $ — $ — $ — $ Corporate — — — — Commercial mortgage-backed securities — — — — Collateralized debt obligations — — — — Other debt obligations — — — — — Total fixed maturities, available-for-sale — — — — Fixed maturities, trading — — — — — Separate account assets — For the nine months ended September 30, 2017 Transfers out Transfers out Transfers out Transfers out Transfers out Transfers out of Level 1 into of Level 1 into of Level 2 into of Level 2 into of Level 3 into of Level 3 into Level 2 Level 3 Level 1 Level 3 Level 1 Level 2 (in millions) Assets Fixed maturities, available-for-sale: Corporate $ — $ — $ — $ $ — $ Commercial mortgage-backed securities — — — — Collateralized debt obligations — — — — Other debt obligations — — — — Total fixed maturities, available-for-sale — — — — Fixed maturities, trading — — — — — Equity securities, trading — — — — — Separate account assets — —
Quantitative Information about Level 3 Fair Value Measurements (Table)	September 30, 2018 Assets / (liabilities) measured at Valuation Unobservable Input/range of Weighted fair value technique(s) input description inputs average (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ Discounted cash flow Discount rate (1) Illiquidity premium 50 basis points (“bps”) 50bps Comparability adjustment (25)bps (25)bps Corporate Discounted cash flow Discount rate (1) 3.2%-3.9% Illiquidity premium 0bps-60bps 36bps Commercial mortgage-backed securities Discounted cash flow Discount rate (1) Probability of default Potential loss severity Collateralized debt obligations Discounted cash flow Discount rate (1) 3.0%-3.1% Comparability adjustment 111bps-165bps 118bps Other debt obligations Discounted cash flow Discount rate (1) Illiquidity premium 500bps 500bps Separate account assets Discounted cash flow - mortgage loans Discount rate (1) 3.0%-4.2% Illiquidity premium 0bps-60bps 54bps Credit spread rate 60bps-160bps 128bps Discounted cash flow - real estate Discount rate (1) 5.6%-11.5% Terminal capitalization rate 4.3%-9.3% Average market rent growth rate 1.8%-4.6% Discounted cash flow - real estate debt Loan to value 11.0%-67.5% Market interest rate 3.7%-6.3% September 30, 2018 Assets / (liabilities) measured at Valuation Unobservable Input/range of Weighted fair value technique(s) input description inputs average (in millions) Liabilities Investment contracts (5) Discounted cash flow Long duration interest rate 3.1%-3.2% (2) Long-term equity market volatility 14.0%-28.5% Non-performance risk 0.3%-1.3% Utilization rate See note (3) Lapse rate 1.3%-16.0% Mortality rate See note (4) December 31, 2017 Assets / (liabilities) measured at Valuation Unobservable Input/range of Weighted fair value technique(s) input description inputs average (in millions) Assets Fixed maturities, available-for-sale: Non-U.S. governments $ Discounted cash flow Discount rate (1) Illiquidity premium 50bps 50bps Comparability adjustment (25)bps (25)bps Corporate Discounted cash flow Discount rate (1) 1.9%-7.5% Illiquidity premium 0bps-60bps 21bps Commercial mortgage-backed securities Discounted cash flow Discount rate (1) Probability of default Potential loss severity Other debt obligations Discounted cash flow Discount rate (1) Illiquidity premium 500bps 500bps December 31, 2017 Assets / (liabilities) measured at Valuation Unobservable Input/range of Weighted fair value technique(s) input description inputs average (in millions) Separate account assets Discounted cash flow - mortgage loans Discount rate (1) 2.3%-8.0% Illiquidity premium 0bps-60bps 17bps Credit spread rate 62bps-690bps 293bps Discounted cash flow - real estate Discount rate (1) 5.8%-17.2% Terminal capitalization rate 4.3%-9.3% Average market rent growth rate 0.5%-4.7% Discounted cash flow - real estate debt Loan to value 12.1%-71.4% Market interest rate 3.1%-4.5% Liabilities Investment contracts (5) Discounted cash flow Long duration interest rate 2.5%-2.7% (2) Long-term equity market volatility 18.7%-41.1% Non-performance risk 0.2%-1.2% Utilization rate See note (3) Lapse rate 1.3%-16.0% Mortality rate See note (4) (1) Represents market comparable interest rate or an index adjusted rate used as the base rate in the discounted cash flow analysis prior to any credit spread, illiquidity or other adjustments, where applicable. (2) Represents the range of rate curves used in the valuation analysis that we have determined market participants would use when pricing the instrument. Derived from interpolation between various observable swap rates. (3) This input factor is the number of contractholders taking withdrawals as well as the amount and timing of the withdrawals and a range does not provide a meaningful presentation. (4) This input is based on an appropriate industry mortality table and a range does not provide a meaningful presentation. (5) Includes bifurcated embedded derivatives that are reported at net asset (liability) fair value within the same line item in the consolidated statements of financial position in which the host contract is reported.
Fair Value Option (Table)	September 30, 2018 December 31, 2017 (in millions) Commercial mortgage loans of consolidated VIEs (1) (2) Fair value $ $ Aggregate contractual principal Real estate ventures (1) Fair value Investment funds (1) Fair value — (1) Reported with other investments in the consolidated statements of financial position. (2) None of the loans were more than 90 days past due or in non-accrual status. For the three months ended September 30, For the nine months ended September 30, 2018 2017 2018 2017 (in millions) Commercial mortgage loans of consolidated VIEs Change in fair value pre-tax loss (1) (2) $ $ $ $ Interest income (3) Obligations of consolidated VIEs Change in fair value pre-tax loss - instrument specific credit risk (2) (4) — — — Change in fair value pre-tax loss (2) — — — Interest expense (5) — — — Real estate ventures Change in fair value pre-tax gain (loss) (6) — Investment funds Change in fair value pre-tax gain (6) (7) — — Dividend income (6) — — — (1) None of the change in fair value related to instrument-specific credit risk. (2) Reported in net realized capital gains (losses) on the consolidated statements of operations. (3) Reported in net investment income on the consolidated statements of operations and recorded based on the effective interest rates as determined at the closing of the loan. (4) Estimated based on credit spreads and quality ratings. (5) Reported in operating expenses on the consolidated statements of operations. (6) Reported in net investment income on the consolidated statements of operations. (7) Absent the fair value election, the change in fair value on the investments would be reported in OCI.
Financial Instruments Not Reported at Fair Value (Table)	September 30, 2018 Fair value hierarchy level Carrying amount Fair value Level 1 Level 2 Level 3 (in millions) Assets (liabilities) Mortgage loans $ $ $ — $ — $ Policy loans — — Other investments — Cash and cash equivalents — Investment contracts — Short-term debt — — Long-term debt — Separate account liabilities — — Bank deposits (1) — — Cash collateral payable — — December 31, 2017 Fair value hierarchy level Carrying amount Fair value Level 1 Level 2 Level 3 (in millions) Assets (liabilities) Mortgage loans $ $ $ — $ — $ Policy loans — — Other investments — Cash and cash equivalents — Investment contracts — Short-term debt — — Long-term debt — Separate account liabilities — — Bank deposits (1) — Cash collateral payable — — (1) Deposit liabilities without defined or contractual maturities are no longer in scope of these disclosures upon adoption of authoritative guidance effective January 1, 2018.

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Information
Reconciliation of Assets from Segment to Consolidated (Table)	September 30, 2018 December 31, 2017 (in millions) Assets: Retirement and Income Solutions $ $ Principal Global Investors Principal International U.S. Insurance Solutions Corporate Total consolidated assets $ $
Reconciliation of Operating Revenues and Pre-tax Operating Earnings (Losses) by Segment (Table)	For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Operating revenues by segment: Retirement and Income Solutions: Retirement and Income Solutions – Fee $ $ $ $ Retirement and Income Solutions – Spread Total Retirement and Income Solutions (1) Principal Global Investors (2) Principal International U.S. Insurance Solutions: Specialty Benefits insurance Individual Life insurance Eliminations — — Total U.S. Insurance Solutions Corporate Total segment operating revenues Net realized capital gains (losses), net of related revenue adjustments Adjustments related to equity method investments Total revenues per consolidated statements of operations $ $ $ $ Pre-tax operating earnings (losses) by segment: Retirement and Income Solutions $ $ $ $ Principal Global Investors Principal International U.S. Insurance Solutions Corporate Total segment pre-tax operating earnings Pre-tax net realized capital gains (losses), as adjusted (3) Adjustments related to equity method investments and noncontrolling interest Income before income taxes per consolidated statements of operations $ $ $ $ (1) Reflects inter-segment revenues of $103.9 million and $103.7 million for the three months ended September 30, 2018 and 2017, respectively, $304.5 million and $296.6 million for the nine months ended September 30, 2018 and 2017, respectively. (2) Reflects inter-segment revenues of $69.2 million and $68.2 million for the three months ended September 30, 2018 and 2017, respectively, $199.2 million and $188.7 million for the nine months ended September 30, 2018 and 2017, respectively. (3) Pre-tax net realized capital gains (losses), as adjusted, is derived as follows: For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Net realized capital gains (losses): Net realized capital gains (losses) $ $ $ $ Derivative and hedging-related adjustments Adjustments related to equity method investments Market value adjustments to fee revenues — Adjustments related to sponsored investment funds Recognition of front-end fee revenue Net realized capital gains (losses), net of related revenue adjustments Amortization of deferred acquisition costs and other actuarial balances Capital gains distributed Market value adjustments of embedded derivatives Pre-tax net realized capital gains (losses), as adjusted (a) $ $ $ $ (a) As adjusted before noncontrolling interest capital gains (losses).

Revenues from Contracts with _2

Revenues from Contracts with Customers (Tables)	9 Months Ended
	Sep. 30, 2018
Revenues from Contracts with Customers
Disaggregation of Revenues from Contracts with Customers (Table)	For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Revenue from contracts with customers by segment: Retirement and Income Solutions: Retirement and Income Solutions – Fee $ $ $ $ Retirement and Income Solutions – Spread Total Retirement and Income Solutions Principal Global Investors Principal International U.S. Insurance Solutions: Specialty Benefits insurance Individual Life insurance Eliminations — — Total U.S. Insurance Solutions Corporate Total segment revenue from contracts with customers Adjustments for fees and other revenues not within the scope of revenue recognition guidance (1) Pre-tax other adjustments (2) — Total fees and other revenues per consolidated statements of operations $ $ $ $ (1) Fees and other revenues not within the scope of the revenue recognition guidance primarily represent revenue on contracts accounted for under the financial instruments or insurance contracts standards. (2) Pre-tax other adjustments relate to the recognition of deferred front-end fee revenues for sales charges on retirement and life insurance products and certain market value adjustments to fee revenues.
Retirement and Income Solutions | Retirement and Income Solutions - Fee
Revenues from Contracts with Customers
Disaggregation of Revenues from Contracts with Customers (Table)	For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Administrative service fee revenue $ $ $ $ Other fee revenue Total revenues from contracts with customers Fees and other revenues not within the scope of revenue recognition guidance Total fees and other revenues Premiums and other considerations Net investment income Total operating revenues $ $ $ $
Retirement and Income Solutions | Retirement and Income Solutions - Spread
Revenues from Contracts with Customers
Disaggregation of Revenues from Contracts with Customers (Table)	For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Deposit account fee revenue $ $ $ $ Total revenues from contracts with customers Fees and other revenues not within the scope of revenue recognition guidance Total fees and other revenues Premiums and other considerations Net investment income Total operating revenues $ $ $ $
Principal Global Investors
Revenues from Contracts with Customers
Disaggregation of Revenues from Contracts with Customers (Table)	For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Management fee revenue $ $ $ $ Other fee revenue (1) Total revenues from contracts with customers Fees and other revenues not within the scope of revenue recognition guidance Total fees and other revenues Net investment income Total operating revenues $ $ $ $ (1) During the third quarter of 2018, we recognized a $253.1 million accelerated performance fee resulting from the realignment of a real estate investment team.
Principal International
Revenues from Contracts with Customers
Disaggregation of Revenues from Contracts with Customers (Table)	For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Management fee revenue $ $ $ $ Other fee revenue Total revenues from contracts with customers Fees and other revenues not within the scope of revenue recognition guidance Total fees and other revenues Premiums and other considerations Net investment income Total operating revenues $ $ $ $ Revenues from contracts with customers by region: Latin America $ $ $ $ Asia Principal International corporate / regional offices Eliminations Total revenues from contracts with customers $ $ $ $
U.S. Insurance Solutions
Revenues from Contracts with Customers
Disaggregation of Revenues from Contracts with Customers (Table)	For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Specialty Benefits Insurance: Administrative service fees $ $ $ $ Total revenues from contracts with customers Fees and other revenues not within the scope of revenue recognition guidance Total fees and other revenues Premiums and other considerations Net investment income Total operating revenues $ $ $ $ For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Individual Life Insurance: Administrative service fees $ $ $ $ Commission income Total revenues from contracts with customers Fees and other revenues not within the scope of revenue recognition guidance Total fees and other revenues Premiums and other considerations Net investment income Total operating revenues $ $ $ $
Corporate
Revenues from Contracts with Customers
Disaggregation of Revenues from Contracts with Customers (Table)	For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions) Commission income $ $ $ $ Other fee revenue Eliminations Total revenues from contracts with customers Fees and other revenues not within the scope of revenue recognition guidance Total fees and other revenues Net investment income Total operating revenues $ $ $ $

Stock-Based Compensation Plans

Stock-Based Compensation Plans (Tables)	9 Months Ended
	Sep. 30, 2018
Stock-Based Compensation Plans
Stock-Based Compensation Disclosures (Table)	For the nine months ended September 30, 2018 2017 (in millions) Compensation cost $ $ Related income tax benefit Capitalized as part of an asset
Nonqualified Stock Options Fair Value (Table)	For the nine months ended September 30, 2018 Expected volatility 26.0 % Expected term (in years) 7.0 Risk-free interest rate 2.8 % Expected dividend yield 3.19 % Weighted average estimated fair value per common share $

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Common Share
Earnings Per Common Share (Table)	For the three months ended For the nine months ended September 30, September 30, 2018 2017 2018 2017 (in millions, except per share data) Net income $ $ $ $ Subtract: Net income attributable to noncontrolling interest Total $ $ $ $ Weighted-average shares outstanding: Basic Dilutive effects: Stock options Restricted stock units Performance share awards Diluted Net income per common share: Basic $ $ $ $ Diluted $ $ $ $

Condensed Consolidating Finan_2

Condensed Consolidating Financial Information (Tables)	9 Months Ended
	Sep. 30, 2018
Condensed Consolidating Financial Information
Condensed Consolidating Financial Information, Notes Guarantor (Table)	Condensed Consolidating Statements of Financial Position September 30, 2018 Principal Principal Life Principal Financial Eliminations Principal (in millions) Assets Fixed maturities, available-for-sale $ $ $ $ $ Fixed maturities, trading — Equity securities — — Mortgage loans — Real estate — — Policy loans — — Investment in unconsolidated entities Other investments Cash and cash equivalents Accrued investment income Premiums due and other receivables — Deferred acquisition costs — — Property and equipment — — Goodwill — — Other intangibles — — Separate account assets — — Other assets Total assets $ $ $ $ $ Liabilities Contractholder funds $ — $ $ $ $ Future policy benefits and claims — Other policyholder funds — Short-term debt — — — Long-term debt — Income taxes currently payable — — Deferred income taxes — Separate account liabilities — — Other liabilities Total liabilities Redeemable noncontrolling interest — — — Stockholders’ equity Common stock — Additional paid-in capital Retained earnings Accumulated other comprehensive income (loss) Treasury stock, at cost — — — Total stockholders’ equity attributable to PFG Noncontrolling interest — — — Total stockholders’ equity Total liabilities and stockholders’ equity $ $ $ $ $ (1) PFG sponsors nonqualified benefit plans. Nonqualified benefit plan assets and liabilities held in Rabbi trusts were $687.1 million and $558.4 million, respectively. Condensed Consolidating Statements of Financial Position December 31, 2017 Principal Principal Life Principal Financial Eliminations Principal (in millions) Assets Fixed maturities, available-for-sale $ — $ $ $ $ Fixed maturities, trading — Equity securities — — Mortgage loans — Real estate — — Policy loans — — Investment in unconsolidated entities Other investments Cash and cash equivalents Accrued investment income Premiums due and other receivables — Deferred acquisition costs — — Property and equipment — — Goodwill — — Other intangibles — — Separate account assets — — Other assets Total assets $ $ $ $ $ Liabilities Contractholder funds $ — $ $ $ $ Future policy benefits and claims — Other policyholder funds — Short-term debt — — — Long-term debt — Income taxes currently payable — — Deferred income taxes — Separate account liabilities — — Other liabilities Total liabilities Redeemable noncontrolling interest — — — Stockholders’ equity Common stock — Additional paid-in capital Retained earnings Accumulated other comprehensive income Treasury stock, at cost — — — Total stockholders’ equity attributable to PFG Noncontrolling interest — — Total stockholders’ equity Total liabilities and stockholders’ equity $ $ $ $ $ (1) PFG sponsors nonqualified benefit plans. Nonqualified benefit plan assets and liabilities held in Rabbi trusts were $643.3 million and $524.7 million, respectively. Condensed Consolidating Statements of Operations For the nine months ended September 30, 2018 Principal Principal Life Principal Financial Eliminations Principal (in millions) Revenues Premiums and other considerations $ — $ $ $ — $ Fees and other revenues — Net investment income Net realized capital gains (losses), excluding impairment losses on available-for-sale securities — Net other-than-temporary impairment losses on available-for-sale securities — — Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified from other comprehensive income — — Net impairment losses on available-for-sale securities — — Net realized capital gains (losses) — Total revenues Expenses Benefits, claims and settlement expenses — Dividends to policyholders — — — Operating expenses Total expenses Income (loss) before income taxes Income taxes (benefits) Equity in the net income (loss) of subsidiaries — Net income Net income attributable to noncontrolling interest — — — Net income attributable to PFG $ $ $ $ $ Net income $ $ $ $ $ Other comprehensive loss Comprehensive loss $ $ $ $ $ Condensed Consolidating Statements of Operations For the nine months ended September 30, 2017 Principal Principal Life Principal Financial Eliminations Principal (in millions) Revenues Premiums and other considerations $ — $ $ $ — $ Fees and other revenues Net investment income Net realized capital gains (losses), excluding impairment losses on available-for-sale securities — Net other-than-temporary impairment (losses) recoveries on available-for-sale securities — — Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified from other comprehensive income — — Net impairment losses on available-for-sale securities — — Net realized capital gains (losses) — Total revenues Expenses Benefits, claims and settlement expenses — Dividends to policyholders — — — Operating expenses Total expenses Income (loss) before income taxes Income taxes (benefits) Equity in the net income (loss) of subsidiaries (1) — Net income Net income attributable to noncontrolling interest — — — Net income attributable to PFG $ $ $ $ $ Net income $ $ $ $ $ Other comprehensive income Comprehensive income $ $ $ $ $ (1) Principal Life Insurance Company Only includes income from discontinued operations of $35.5 million related to its sale of Principal Global Investors, LLC to PFS in connection with a corporate reorganization. Condensed Consolidating Statements of Cash Flows For the nine months ended September 30, 2018 Principal Principal Life Principal Financial Eliminations Principal (in millions) Operating activities Net cash provided by (used in) operating activities $ $ $ $ $ Investing activities Fixed maturities available-for-sale and equity securities with operating intent: Purchases Sales — — Maturities — Mortgage loans acquired or originated — Mortgage loans sold or repaid — Real estate acquired — — — Real estate sold — — — Net purchases of property and equipment — — Purchase of interests in subsidiaries, net of cash acquired — — — Dividends and returns of capital received from unconsolidated entities — Net change in other investments Net cash provided by (used in) investing activities Financing activities Issuance of common stock — — — Acquisition of treasury stock — — — Payments for financing element derivatives — — — Purchase of subsidiary shares from noncontrolling interest — — — Dividends to common stockholders — — — Issuance of long-term debt — — Principal repayments of long-term debt — — Net repayments of short-term borrowings — — — Dividends and capital paid to parent — — Investment contract deposits — — Investment contract withdrawals — — Net increase in banking operation deposits — — — Other — — — Net cash provided by (used in) financing activities Net increase (decrease) in cash and cash equivalents Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period $ $ $ $ $ Condensed Consolidating Statements of Cash Flows For the nine months ended September 30, 2017 Principal Principal Life Principal Financial Eliminations Principal (in millions) Operating activities Net cash provided by (used in) operating activities $ $ $ $ $ Investing activities Fixed maturities available-for-sale and equity securities with intent to hold: Purchases — — Sales — Maturities — — Mortgage loans acquired or originated — Mortgage loans sold or repaid — Real estate acquired — — — Real estate sold — — — Net purchases of property and equipment — — Dividends and returns of capital received from unconsolidated entities — Net change in other investments Net cash provided by (used in) investing activities Financing activities Issuance of common stock — — — Acquisition of treasury stock — — — Proceeds from financing element derivatives — — — Payments for financing element derivatives — — — Purchase of subsidiary shares from noncontrolling interest — — Sale of subsidiary shares to noncontrolling interest — — — Dividends to common stockholders — — — Issuance of long-term debt — — — Principal repayments of long-term debt — — Net proceeds from short-term borrowings — — — Dividends and capital paid to parent — — Investment contract deposits — — Investment contract withdrawals — — Net increase in banking operation deposits — — — Other — — — Net cash provided by (used in) financing activities Net increase (decrease) in cash and cash equivalents Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period $ $ $ $ $
Condensed Consolidating Financial Information, Shelf Registration Guarantor (Table)	Condensed Consolidating Statements of Financial Position September 30, 2018 Principal Life Principal Principal Insurance Company Principal Financial Financial and Other Financial Group, Inc. Services, Inc. Subsidiaries Group, Inc. Parent Only Only Combined (1) Eliminations Consolidated (in millions) Assets Fixed maturities, available-for-sale $ $ — $ $ — $ Fixed maturities, trading — — Equity securities — — Mortgage loans — — — Real estate — — — Policy loans — — — Investment in unconsolidated entities Other investments — Cash and cash equivalents Accrued investment income — — Premiums due and other receivables — Deferred acquisition costs — — — Property and equipment — — — Goodwill — — — Other intangibles — — — Separate account assets — — — Other assets Total assets $ $ $ $ $ Liabilities Contractholder funds $ — $ — $ $ — $ Future policy benefits and claims — — — Other policyholder funds — — — Short-term debt — — — Long-term debt Income taxes currently payable — Deferred income taxes — Separate account liabilities — — — Other liabilities Total liabilities Redeemable noncontrolling interest — — — Stockholders’ equity Common stock — Additional paid-in capital Retained earnings Accumulated other comprehensive loss Treasury stock, at cost — Total stockholders’ equity attributable to PFG Noncontrolling interest — — — Total stockholders’ equity Total liabilities and stockholders’ equity $ $ $ $ $ (1) PFG sponsors nonqualified benefit plans. Nonqualified benefit plan assets and liabilities held in Rabbi trusts were $687.1 million and $558.4 million, respectively. Condensed Consolidating Statements of Financial Position December 31, 2017 Principal Life Principal Principal Insurance Company Principal Financial Financial and Other Financial Group, Inc. Services, Inc. Subsidiaries Group, Inc. Parent Only Only Combined (1) Eliminations Consolidated (in millions) Assets Fixed maturities, available-for-sale $ — $ — $ $ — $ Fixed maturities, trading — — Equity securities — — Mortgage loans — — — Real estate — — — Policy loans — — — Investment in unconsolidated entities Other investments — Cash and cash equivalents Accrued investment income — Premiums due and other receivables — Deferred acquisition costs — — — Property and equipment — — — Goodwill — — — Other intangibles — — — Separate account assets — — — Other assets Total assets $ $ $ $ $ Liabilities Contractholder funds $ — $ — $ $ — $ Future policy benefits and claims — — — Other policyholder funds — — — Short-term debt — — — Long-term debt Income taxes currently payable — Deferred income taxes — Separate account liabilities — — — Other liabilities Total liabilities Redeemable noncontrolling interest — — — Stockholders’ equity Common stock — Additional paid-in capital Retained earnings Accumulated other comprehensive income Treasury stock, at cost — Total stockholders’ equity attributable to PFG Noncontrolling interest — — — Total stockholders’ equity Total liabilities and stockholders’ equity $ $ $ $ $ (1) PFG sponsors nonqualified benefit plans. Nonqualified benefit plan assets and liabilities held in Rabbi trusts were $643.3 million and $524.7 million, respectively. Condensed Consolidating Statements of Operations For the nine months ended September 30, 2018 Principal Life Principal Principal Insurance Principal Financial Financial Company and Financial Group, Inc. Services, Inc. Other Subsidiaries Group, Inc. Parent Only Only Combined Eliminations Consolidated (in millions) Revenues Premiums and other considerations $ — $ — $ $ — $ Fees and other revenues — Net investment income (loss) Net realized capital gains (losses), excluding impairment losses on available-for-sale securities — Net other-than-temporary impairment losses on available-for-sale securities — — — Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified from other comprehensive income — — — Net impairment losses on available-for-sale securities — — — Net realized capital gains (losses) — Total revenues Expenses Benefits, claims and settlement expenses — — — Dividends to policyholders — — — Operating expenses Total expenses Income (loss) before income taxes Income taxes (benefits) — Equity in the net income of subsidiaries — — Net income Net income attributable to noncontrolling interest — — — Net income attributable to PFG $ $ $ $ $ Net income $ $ $ $ $ Other comprehensive loss Comprehensive loss $ $ $ $ $ Condensed Consolidating Statements of Operations For the nine months ended September 30, 2017 Principal Life Principal Principal Insurance Principal Financial Financial Company and Financial Group, Inc. Services, Inc. Other Subsidiaries Group, Inc. Parent Only Only Combined Eliminations Consolidated (in millions) Revenues Premiums and other considerations $ — $ — $ $ — $ Fees and other revenues Net investment income (loss) Net realized capital gains, excluding impairment losses on available-for-sale securities — — Net other-than-temporary impairment losses on available-for-sale securities — — — Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified from other comprehensive income — — — Net impairment losses on available-for-sale securities — — — Net realized capital gains — — Total revenues Expenses Benefits, claims and settlement expenses — — — Dividends to policyholders — — — Operating expenses Total expenses Income (loss) before income taxes Income taxes (benefits) Equity in the net income of subsidiaries — — Net income Net income attributable to noncontrolling interest — — — Net income attributable to PFG $ $ $ $ $ Net income $ $ $ $ $ Other comprehensive income Comprehensive income $ $ $ $ $ Condensed Consolidating Statements of Cash Flows For the nine months ended September 30, 2018 Principal Life Principal Principal Insurance Principal Financial Financial Company and Financial Group, Inc. Services, Inc. Other Subsidiaries Group, Inc. Parent Only Only Combined Eliminations Consolidated (in millions) Operating activities Net cash provided by (used in) operating activities $ $ $ $ $ Investing activities Fixed maturities available-for-sale and equity securities with intent to hold: Purchases — — Sales — — — Maturities — — Mortgage loans acquired or originated — — — Mortgage loans sold or repaid — — — Real estate acquired — — — Real estate sold — — — Net purchases of property and equipment — — — Purchase of interests in subsidiaries, net of cash acquired — — — Dividends and returns of capital received from unconsolidated entities — — Net change in other investments Net cash provided by (used in) investing activities Financing activities Issuance of common stock — — — Acquisition of treasury stock — — — Payments for financing element derivatives — — — Purchase of subsidiary shares from noncontrolling interest — — — Dividends to common stockholders — — — Issuance of long-term debt — Principal repayments of long-term debt — Net repayments of short-term borrowings — — — Dividends and capital paid to parent — — Investment contract deposits — — — Investment contract withdrawals — — — Net increase in banking operation deposits — — — Other — — — Net cash provided by (used in) financing activities Net increase (decrease) in cash and cash equivalents Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period $ $ $ $ $ Condensed Consolidating Statements of Cash Flows For the nine months ended September 30, 2017 Principal Life Principal Principal Insurance Principal Financial Financial Company and Financial Group, Inc. Services, Inc. Other Subsidiaries Group, Inc. Parent Only Only Combined Eliminations Consolidated (in millions) Operating activities Net cash provided by (used in) operating activities $ $ $ $ $ Investing activities Fixed maturities available-for-sale and equity securities with intent to hold: Purchases — — — Sales — — — Maturities — — — Mortgage loans acquired or originated — — — Mortgage loans sold or repaid — — — Real estate acquired — — — Real estate sold — — — Net purchases of property and equipment — — — Dividends and returns of capital received from (contributed to) unconsolidated entities — — Net change in other investments Net cash provided by (used in) investing activities Financing activities Issuance of common stock — — — Acquisition of treasury stock — — — Proceeds from financing element derivatives — — — Payments for financing element derivatives — — — Purchase of subsidiary shares from noncontrolling interest — — — Dividends to common stockholders — — — Issuance of long-term debt — — — Principal repayments of long-term debt — Net proceeds from (repayments of) short-term borrowings — — Dividends and capital received from (paid to) parent — — Investment contract deposits — — — Investment contract withdrawals — — — Net increase in banking operation deposits — — — Other — — — Net cash provided by (used in) financing activities Net increase (decrease) in cash and cash equivalents Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period $ $ $ $ $

Nature of Operations and Sign_4

Nature of Operations and Significant Accounting Policies - Recent Accounting Pronouncements (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Recent Accounting Pronouncements
Equity securities, available-for-sale		$ 96
Equity securities, trading		$ 1,770.6
ASU 2016-16 - Intra-entity asset transfer taxes
Recent Accounting Pronouncements
Cumulative effect adjustment, increase to retained earnings	$ 8.7
Cumulative effect adjustment, decrease to other assets	21.1
Cumulative effect adjustment, decrease to deferred income taxes	29.8
Accumulated other comprehensive income (loss) | ASU 2018-02 - Reclassification of certain tax effects
Recent Accounting Pronouncements
Cumulative effect adjustment from adopting guidance	77.6
Accumulated other comprehensive income (loss) | ASU 2016-01 - Equity investments
Recent Accounting Pronouncements
Cumulative effect adjustment from adopting guidance	(1)
Retained earnings (accumulated deficit) | ASU 2018-02 - Reclassification of certain tax effects
Recent Accounting Pronouncements
Cumulative effect adjustment from adopting guidance	(77.6)
Retained earnings (accumulated deficit) | ASU 2016-16 - Intra-entity asset transfer taxes
Recent Accounting Pronouncements
Cumulative effect adjustment, increase to retained earnings	8.7
Retained earnings (accumulated deficit) | ASU 2016-01 - Equity investments
Recent Accounting Pronouncements
Cumulative effect adjustment from adopting guidance	$ 1

Nature of Operations and Sign_5

Nature of Operations and Significant Accounting Policies - Adoption of "Revenue Recognition" Guidance (Details) - USD ($) $ in Millions	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Assets
Deferred acquisition costs	$ 3,671.9		$ 3,540.7
Other assets	1,421.3		1,330.9
Liabilities
Deferred income taxes	911.4		1,092.5
Stockholders' equity
Total stockholders' equity	11,768.7		$ 12,921.9	$ 12,067.3	$ 10,293.8
ASU 2014-09 - Revenue recognition | As adjusted
Assets
Deferred acquisition costs	3,873.3
Other assets	1,279.9
Liabilities
Deferred income taxes	933.3
Stockholders' equity
Total stockholders' equity	11,806.8
ASU 2014-09 - Revenue recognition | Impact of adopting revenue recognition accounting guidance
Assets
Deferred acquisition costs	(201.4)
Other assets	141.4
Liabilities
Deferred income taxes	(21.9)
Stockholders' equity
Total stockholders' equity	$ (38.1)	$ (39.7)

Nature of Operations and Sign_6

Nature of Operations and Significant Accounting Policies - Separate Accounts (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Separate Accounts
Separate account that primarily includes shares of Principal Financial Group, Inc. stock that were allocated and issued to eligible participants of qualified employee benefit plans as part of the 2001 demutualization	$ 131.7	$ 170.5

Variable Interest Entities - Co

Variable Interest Entities - Consolidated VIEs (Details) $ in Millions	Sep. 30, 2018USD ($)item	Dec. 31, 2017USD ($)
Carrying amounts of consolidated VIE assets and liabilities
Total assets	$ 41,266.6	$ 43,154.8
Total liabilities	$ 40,324.5	42,195
Grantor trusts
Consolidated Variable Interest Entity disclosures
Number of consolidated variable interest entities | item	2
Carrying amounts of consolidated VIE assets and liabilities
Total assets	$ 243.1	268.8
Total liabilities	230	253.1
Commercial mortgage-backed securities VIE
Carrying amounts of consolidated VIE assets and liabilities
Total assets	6.9	9.4
Mandatory retirement savings funds
Carrying amounts of consolidated VIE assets and liabilities
Total assets	40,390.3	42,311.4
Total liabilities	40,028.6	41,921.4
Real estate VIE
Carrying amounts of consolidated VIE assets and liabilities
Total assets	368.5	387.1
Total liabilities	64.3	19.5
Sponsored investment funds
Carrying amounts of consolidated VIE assets and liabilities
Total assets	257.8	178.1
Total liabilities	1.6	1
Redeemable noncontrolling interest	$ 75.4	$ 52.4

Variable Interest Entities - Un

Variable Interest Entities - Unconsolidated VIEs (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Money Market Funds
Total assets of unconsolidated money market mutual funds		$ 4,400
Corporate debt securities | Available-for-sale
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	$ 234.2	244.2
Maximum exposure to loss	221.2	224.5
Residential mortgage-backed pass-through securities | Available-for-sale
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	2,363.1	2,523.3
Maximum exposure to loss	2,421.7	2,493.8
Residential mortgage-backed pass-through securities | Trading
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	328.7	366.5
Maximum exposure to loss	328.7	366.5
Commercial mortgage-backed securities | Available-for-sale
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	3,850.2	3,708.3
Maximum exposure to loss	3,950.5	3,734
Commercial mortgage-backed securities | Trading
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	14.1	0.7
Maximum exposure to loss	14.1	0.7
Collateralized debt obligations | Available-for-sale
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	2,368.6	1,359.3
Maximum exposure to loss	2,376.6	1,372.1
Collateralized debt obligations | Trading
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	12
Maximum exposure to loss	12
Other debt obligations | Available-for-sale
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	6,685	5,646.2
Maximum exposure to loss	6,790.8	5,645.1
Other debt obligations | Trading
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	8.7
Maximum exposure to loss	8.7
Equity securities
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	113.5	77.1
Maximum exposure to loss	113.5	77.1
Other investments: Other limited partnership and fund interests
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	731.9	797.4
Maximum exposure to loss	1,445.1	$ 1,438
Fully secured debt of international real estate funds with recourse to the investment manager, included in maximum loss exposure	$ 144.5

Investments - Fixed Maturities

Investments - Fixed Maturities and Equity Securities (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Available-for-sale securities
Amortized cost, fixed maturities	$ 59,937.6	$ 56,562.1
Gross unrealized gains, fixed maturities	1,649.2	3,093.3
Gross unrealized losses, fixed maturities	1,139.6	267
Fair value, fixed maturities	60,447.2	59,388.4
Amortized cost, equity securities		94
Gross unrealized gains, equity securities		7.4
Gross unrealized losses, equity securities		5.4
Fair value, equity securities		96
Other-than-temporary impairments in AOCI	79.1	93.3
Net unrealized gains (losses) on impaired fixed maturities, available-for-sale related to changes in fair value subsequent to the impairment date	86.2	103
U.S. government and agencies
Available-for-sale securities
Amortized cost, fixed maturities	1,342.4	1,314.5
Gross unrealized gains, fixed maturities	5.8	44.9
Gross unrealized losses, fixed maturities	38	7.7
Fair value, fixed maturities	1,310.2	1,351.7
Non-U.S. governments
Available-for-sale securities
Amortized cost, fixed maturities	1,111.1	820.5
Gross unrealized gains, fixed maturities	73.5	84.6
Gross unrealized losses, fixed maturities	12.3	3.6
Fair value, fixed maturities	1,172.3	901.5
States and political subdivisions
Available-for-sale securities
Amortized cost, fixed maturities	6,414.7	6,446.1
Gross unrealized gains, fixed maturities	160.9	371.4
Gross unrealized losses, fixed maturities	127.4	15.9
Fair value, fixed maturities	6,448.2	6,801.6
Corporate debt securities
Available-for-sale securities
Amortized cost, fixed maturities	35,484	34,673
Gross unrealized gains, fixed maturities	1,353.4	2,464.2
Gross unrealized losses, fixed maturities	633.3	104.1
Fair value, fixed maturities	36,204.1	37,033.1
Other-than-temporary impairments in AOCI	0.4	0.5
Residential mortgage-backed pass-through securities
Available-for-sale securities
Amortized cost, fixed maturities	2,421.7	2,493.8
Gross unrealized gains, fixed maturities	19.9	50.8
Gross unrealized losses, fixed maturities	78.5	21.3
Fair value, fixed maturities	2,363.1	2,523.3
Commercial mortgage-backed securities
Available-for-sale securities
Amortized cost, fixed maturities	3,950.5	3,734
Gross unrealized gains, fixed maturities	12.4	32.7
Gross unrealized losses, fixed maturities	112.7	58.4
Fair value, fixed maturities	3,850.2	3,708.3
Other-than-temporary impairments in AOCI	39.8	50.6
Collateralized debt obligations
Available-for-sale securities
Amortized cost, fixed maturities	2,376.6	1,372.1
Gross unrealized gains, fixed maturities	0.2	2.7
Gross unrealized losses, fixed maturities	8.2	15.5
Fair value, fixed maturities	2,368.6	1,359.3
Other-than-temporary impairments in AOCI	1	0.3
Other debt obligations
Available-for-sale securities
Amortized cost, fixed maturities	6,836.6	5,708.1
Gross unrealized gains, fixed maturities	23.1	42
Gross unrealized losses, fixed maturities	129.2	40.5
Fair value, fixed maturities	6,730.5	5,709.6
Other-than-temporary impairments in AOCI	$ 37.9	$ 41.9

Investments - Amortization by E

Investments - Amortization by Expected Maturity (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Amortized cost of fixed maturities available-for-sale
Due in one year or less	$ 2,548.9
Due after one year through five years	11,181.4
Due after five years through ten years	10,316.3
Due after ten years	20,305.6
Subtotal	44,352.2
Mortgage-backed and other asset-backed securities	15,585.4
Amortized cost, fixed maturities	59,937.6	$ 56,562.1
Fair value of fixed maturities available-for-sale
Due in one year or less	2,555.2
Due after one year through five years	11,244.3
Due after five years through ten years	10,251.3
Due after ten years	21,084
Subtotal	45,134.8
Mortgage-backed and other asset-backed securities	15,312.4
Fair value, fixed maturities	$ 60,447.2	$ 59,388.4

Investments - Net Realized Capi

Investments - Net Realized Capital Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Fixed maturities, available-for-sale
Gross gains	$ 32.9	$ 2.1	$ 37.9	$ 12.3
Gross losses	(9.5)	(1.6)	(54.7)	(17.1)
Net impairment (losses) recoveries on available-for-sale securities	(3.6)		(22.5)
Net impairment (losses) recoveries on available-for-sale securities		(16.6)		(59.6)
Hedging, net	(4.7)	(1.2)	(12.7)	(17.2)
Fixed maturities, trading	(0.3)	(3)	(13.7)	(1.2)
Equity securities, trading		14.8		51.2
Equity securities	13.5		17.1
Net realized capital gains (losses)	(5.5)	676.6	36.8	564.1
Unrealized gains (losses) on fixed maturities, trading	(3.4)	(3)	(16.7)	(0.4)
Unrealized gains (losses) on equity securities, trading		9.1		36.6
Unrealized gains (losses) on equity securities, trading reported in net investment income		4.9		32.2
Unrealized gains (losses) on equity securities	8.8		(5.2)
Unrealized gains (losses) on equity securities reported in net investment income	9.6		12.8
Proceeds from sales of investments
Proceeds from sales of investments in fixed maturities, available-for-sale	613.3	163.2	2,351	968.6
Mortgage loans
Fixed maturities, available-for-sale
Realized capital gains (losses)	1.3	1.2	4.2	0.9
Derivatives
Fixed maturities, available-for-sale
Realized capital gains (losses)	41.7	(38.1)	13.7	(148.4)
Other investment types
Fixed maturities, available-for-sale
Realized capital gains (losses)	$ (76.8)	$ 719	$ 67.5	$ 743.2

Investments - Other-Than-Tempor

Investments - Other-Than-Temporary Impairments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Other-than-temporary impairment losses, net of recoveries
Net other-than-temporary impairment (losses) recoveries on available-for-sale securities	$ (1.4)	$ 2.6	$ (8.3)	$ (27.1)
Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified to (from) other comprehensive income	(2.2)	(19.2)	(14.2)	(32.5)
Net impairment (losses) recoveries on available-for-sale securities	(3.6)		(22.5)
Net impairment (losses) recoveries on available-for-sale securities		(16.6)		(59.6)
Fixed maturities
Other-than-temporary impairment losses, net of recoveries
Net other-than-temporary impairment (losses) recoveries on available-for-sale securities	$ (1.4)	$ 2.6	$ (8.3)	$ (27.1)

Investments - Accumulated Credi

Investments - Accumulated Credit Losses for Fixed Maturities with Bifurcated Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Other-Than-Temporary Impairment Credit Losses Recognized in Net Income - Rollforward
Beginning balance	$ (131.1)	$ (154.8)	$ (124.3)	$ (139.9)
Credit losses for which an other-than-temporary impairment was not previously recognized	(1.2)		(11.3)	(14.4)
Credit losses for which an other-than-temporary impairment was previously recognized	(1.2)	(6.5)	(12.9)	(28.7)
Reduction for credit losses previously recognized on fixed maturities now sold, paid down or intended to be sold	12.5	33.6	22.5	50.9
Net reduction (increase) for positive changes in cash flows expected to be collected and amortization	2.5	3.3	7.5	7.8
Foreign currency translation adjustment				(0.1)
Ending balance	$ (118.5)	$ (124.4)	$ (118.5)	$ (124.4)

Investments - Gross Unrealized

Investments - Gross Unrealized Losses for Fixed Maturities and Equity Securities (Details) $ in Millions	Sep. 30, 2018USD ($)item	Dec. 31, 2017USD ($)item
Gross Unrealized Losses for Fixed Maturities and Equity Securities
Fixed maturities, Less than twelve months, Fair value	$ 28,852.9	$ 9,822.3
Fixed maturities, Less than twelve months, Gross unrealized losses	702.2	92.3
Fixed maturities, Greater than or equal to twelve months, Fair value	8,030.8	4,834.9
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	437.4	174.7
Fixed maturities, Total, Fair value	36,883.7	14,657.2
Fixed maturities, Total, Gross unrealized losses	1,139.6	267
U.S. government and agencies
Gross Unrealized Losses for Fixed Maturities and Equity Securities
Fixed maturities, Less than twelve months, Fair value	734.8	294.2
Fixed maturities, Less than twelve months, Gross unrealized losses	20.9	2.2
Fixed maturities, Greater than or equal to twelve months, Fair value	343.3	180.9
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	17.1	5.5
Fixed maturities, Total, Fair value	1,078.1	475.1
Fixed maturities, Total, Gross unrealized losses	38	7.7
Non-U.S. governments
Gross Unrealized Losses for Fixed Maturities and Equity Securities
Fixed maturities, Less than twelve months, Fair value	314.1	111
Fixed maturities, Less than twelve months, Gross unrealized losses	9.2	1.7
Fixed maturities, Greater than or equal to twelve months, Fair value	80.2	22.1
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	3.1	1.9
Fixed maturities, Total, Fair value	394.3	133.1
Fixed maturities, Total, Gross unrealized losses	12.3	3.6
States and political subdivisions
Gross Unrealized Losses for Fixed Maturities and Equity Securities
Fixed maturities, Less than twelve months, Fair value	2,947.7	720
Fixed maturities, Less than twelve months, Gross unrealized losses	85	5
Fixed maturities, Greater than or equal to twelve months, Fair value	688.4	437.7
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	42.4	10.9
Fixed maturities, Total, Fair value	3,636.1	1,157.7
Fixed maturities, Total, Gross unrealized losses	127.4	15.9
Corporate debt securities
Gross Unrealized Losses for Fixed Maturities and Equity Securities
Fixed maturities, Less than twelve months, Fair value	16,519.7	3,871.5
Fixed maturities, Less than twelve months, Gross unrealized losses	471.4	43.4
Fixed maturities, Greater than or equal to twelve months, Fair value	2,470.9	1,644.3
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	161.9	60.7
Fixed maturities, Total, Fair value	18,990.6	5,515.8
Fixed maturities, Total, Gross unrealized losses	633.3	104.1
Residential mortgage-backed pass-through securities
Gross Unrealized Losses for Fixed Maturities and Equity Securities
Fixed maturities, Less than twelve months, Fair value	997.9	354.4
Fixed maturities, Less than twelve months, Gross unrealized losses	24.5	2
Fixed maturities, Greater than or equal to twelve months, Fair value	842.1	734.5
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	54	19.3
Fixed maturities, Total, Fair value	1,840	1,088.9
Fixed maturities, Total, Gross unrealized losses	78.5	21.3
Commercial mortgage-backed securities
Gross Unrealized Losses for Fixed Maturities and Equity Securities
Fixed maturities, Less than twelve months, Fair value	1,741.5	1,342.7
Fixed maturities, Less than twelve months, Gross unrealized losses	32.6	19.9
Fixed maturities, Greater than or equal to twelve months, Fair value	1,461.2	820.3
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	80.1	38.5
Fixed maturities, Total, Fair value	3,202.7	2,163
Fixed maturities, Total, Gross unrealized losses	112.7	58.4
Collateralized debt obligations
Gross Unrealized Losses for Fixed Maturities and Equity Securities
Fixed maturities, Less than twelve months, Fair value	1,818.1	460.9
Fixed maturities, Less than twelve months, Gross unrealized losses	3.9	2.1
Fixed maturities, Greater than or equal to twelve months, Fair value	47.1	38.3
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	4.3	13.4
Fixed maturities, Total, Fair value	1,865.2	499.2
Fixed maturities, Total, Gross unrealized losses	8.2	15.5
Other debt obligations
Gross Unrealized Losses for Fixed Maturities and Equity Securities
Fixed maturities, Less than twelve months, Fair value	3,779.1	2,667.6
Fixed maturities, Less than twelve months, Gross unrealized losses	54.7	16
Fixed maturities, Greater than or equal to twelve months, Fair value	2,097.6	956.8
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	74.5	24.5
Fixed maturities, Total, Fair value	5,876.7	3,624.4
Fixed maturities, Total, Gross unrealized losses	129.2	40.5
Equity securities
Gross Unrealized Losses for Fixed Maturities and Equity Securities
Greater than or equal to twelve months, Fair value		40.4
Greater than or equal to twelve months, Gross unrealized losses		5.4
Total, Fair value		40.4
Total, Gross unrealized losses		5.4
Principal Life Insurance Company
Gross Unrealized Losses for Fixed Maturities and Equity Securities
Fixed maturities, Less than twelve months, Fair value	28,160	9,360.9
Fixed maturities, Less than twelve months, Gross unrealized losses	684.2	75.4
Fixed maturities, Greater than or equal to twelve months, Fair value	7,686.3	4,698.6
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	422.3	164.3
Fixed maturities, Total, Fair value	35,846.3	14,059.5
Fixed maturities, Total, Gross unrealized losses	$ 1,106.5	$ 239.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure
Available-for-sale Securities in Unrealized Loss Positions, Qualitative Disclosure, Percent Investment Grade (as a percent)	97.00%	97.00%
Available-for-sale Securities in Unrealized Loss Positions, Qualitative Disclosure, Average Price (percent of carrying value to amortized cost) | item	97	98
Available-for-sale Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less Than Twelve Months | item	3,276	1,209
Available-for-sale Securities in Unrealized Loss Positions, Average Price, Less Than Twelve Months (percent of carrying value to amortized cost) | item	98	99
Available-for-sale Securities in Unrealized Loss Positions, Percent Investment Grade, Less Than Twelve Months (as a percent)	97.00%	98.00%
Available-for-sale Securities in Unrealized Loss Position, Aggregate Losses On Investment Grade Investments, Less Than Twelve Months	$ 660.2	$ 71.5
Available-for-sale Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Twelve Months or Longer | item	1,215	775
Available-for-sale Securities in Unrealized Loss Positions, Average Price, Twelve Months or Longer (percent of carrying value to amortized cost) | item	95	97
Principal Life Insurance Company | Corporate debt securities
Gross Unrealized Losses for Fixed Maturities and Equity Securities
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	$ 148.5	$ 52.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure
Available-for-sale Securities in Unrealized Loss Positions, Average Price, Twelve Months or Longer (percent of carrying value to amortized cost) | item	94	97
Principal Life Insurance Company | Commercial mortgage-backed securities
Gross Unrealized Losses for Fixed Maturities and Equity Securities
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	$ 79.2	$ 38.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure
Available-for-sale Securities in Unrealized Loss Positions, Average Price, Twelve Months or Longer (percent of carrying value to amortized cost) | item	95	96

Investments - Net Unrealized Ga

Investments - Net Unrealized Gains and Losses on Available-for-Sale Securities and Derivative Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Net Unrealized Gains and Losses on Available-for-Sale Securities and Derivative Instruments
Net unrealized gains (losses) on fixed maturities, available-for-sale	$ 553.9	$ 2,898.5
Noncredit component of impairment losses on fixed maturities, available-for-sale	(79.1)	(93.3)
Net unrealized gains (losses) on equity securities, available-for-sale		2
Adjustments for assumed changes in amortization patterns	3.4	(150.6)
Adjustments for assumed changes in policyholder liabilities	(318.1)	(645.5)
Net unrealized gains (losses) on derivative instruments	109.8	108.2
Net unrealized gains (losses) on equity method subsidiaries and noncontrolling interest adjustments	39.8	31.3
Provision for deferred income tax benefits (taxes)	(65.4)	(695.5)
Net unrealized gains (losses) on available-for-sale securities and derivative instruments	$ 244.3	$ 1,455.1

Investments - Mortgage Loans (D

Investments - Mortgage Loans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 14,948.8	$ 14,064.1	$ 14,948.8	$ 14,064.1		$ 14,183.2
Mortgage loan valuation allowance	(29.1)	(43.7)	(29.1)	(43.7)	$ (30.1)	(32.7)	$ (44.6)	$ (44.9)
Mortgage loans, Total carrying value	14,919.7		14,919.7			14,150.5
Commercial mortgage loans
Mortgage loan disclosures
Mortgage loans, Total amortized cost	13,595.3	12,773.5	13,595.3	12,773.5		12,897.3
Mortgage loan valuation allowance	(25.3)	(28.1)	(25.3)	(28.1)	(25.8)	$ (25.8)	(28)	(27.4)
Mortgage loans, purchased	$ 34.1	41.2	34.1	97.2
Mortgage loans, sold			$ 1.6
Percent of mortgage loans (as a percent)	100.00%		100.00%			100.00%
Commercial mortgage loans | Office
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 4,593		$ 4,593			$ 4,700.2
Percent of mortgage loans (as a percent)	33.80%		33.80%			36.40%
Commercial mortgage loans | Retail
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 2,429		$ 2,429			$ 2,612.7
Percent of mortgage loans (as a percent)	17.90%		17.90%			20.30%
Commercial mortgage loans | Industrial
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 2,220.8		$ 2,220.8			$ 1,881.5
Percent of mortgage loans (as a percent)	16.30%		16.30%			14.60%
Commercial mortgage loans | Apartments
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 3,967.5		$ 3,967.5			$ 3,301.9
Percent of mortgage loans (as a percent)	29.20%		29.20%			25.60%
Commercial mortgage loans | Hotel
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 100.7		$ 100.7			$ 130.9
Percent of mortgage loans (as a percent)	0.70%		0.70%			1.00%
Commercial mortgage loans | Mixed use/other
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 284.3		$ 284.3			$ 270.1
Percent of mortgage loans (as a percent)	2.10%		2.10%			2.10%
Commercial mortgage loans | New England
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 644.4		$ 644.4			$ 591.8
Percent of mortgage loans (as a percent)	4.70%		4.70%			4.60%
Commercial mortgage loans | Middle Atlantic
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 3,932		$ 3,932			$ 3,623
Percent of mortgage loans (as a percent)	29.00%		29.00%			28.10%
Commercial mortgage loans | East North Central
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 612.5		$ 612.5			$ 675.2
Percent of mortgage loans (as a percent)	4.50%		4.50%			5.20%
Commercial mortgage loans | West North Central
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 168.1		$ 168.1			$ 174.9
Percent of mortgage loans (as a percent)	1.20%		1.20%			1.40%
Commercial mortgage loans | South Atlantic
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 2,182.1		$ 2,182.1			$ 2,325.3
Percent of mortgage loans (as a percent)	16.10%		16.10%			18.00%
Commercial mortgage loans | East South Central
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 400.1		$ 400.1			$ 375.7
Percent of mortgage loans (as a percent)	2.90%		2.90%			2.90%
Commercial mortgage loans | West South Central
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 1,134.2		$ 1,134.2			$ 1,072.4
Percent of mortgage loans (as a percent)	8.30%		8.30%			8.30%
Commercial mortgage loans | Mountain
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 992.8		$ 992.8			$ 1,039.3
Percent of mortgage loans (as a percent)	7.30%		7.30%			8.10%
Commercial mortgage loans | Pacific
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 3,336.3		$ 3,336.3			$ 2,849
Percent of mortgage loans (as a percent)	24.60%		24.60%			22.10%
Commercial mortgage loans | International
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 192.8		$ 192.8			$ 170.7
Percent of mortgage loans (as a percent)	1.40%		1.40%			1.30%
Residential mortgage loans
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 1,353.5	1,290.6	$ 1,353.5	1,290.6		$ 1,285.9
Mortgage loan valuation allowance	(3.8)	(15.6)	(3.8)	(15.6)	$ (4.3)	(6.9)	$ (16.6)	$ (17.5)
Mortgage loans, purchased	87.4	68.4	292.2	222.8
Mortgage loans, sold	9.6	$ 17.5	60.9	$ 47.9
Home equity
Mortgage loan disclosures
Mortgage loans, Total amortized cost	17.1		17.1			23
First liens
Mortgage loan disclosures
Mortgage loans, Total amortized cost	$ 1,336.4		$ 1,336.4			$ 1,262.9

Investments - Mortgage Loan Cre

Investments - Mortgage Loan Credit Monitoring (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	$ 14,948.8	$ 14,183.2	$ 14,064.1
Commercial mortgage loans
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	13,595.3	12,897.3	12,773.5
Commercial mortgage loans | A- and above
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	12,532	11,765.2
Commercial mortgage loans | BBB+ thru BBB-
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	1,005.1	1,036.5
Commercial mortgage loans | BB+ thru BB-
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	52.3	89
Commercial mortgage loans | B+ and below
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	5.9	6.6
Brick and mortar
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	13,398.7	12,665.6
Brick and mortar | A- and above
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	12,411.2	11,636.2
Brick and mortar | BBB+ thru BBB-
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	929.4	934.1
Brick and mortar | BB+ thru BB-
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	52.3	89
Brick and mortar | B+ and below
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	5.8	6.3
Credit tenant loans
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	196.6	231.7
Credit tenant loans | A- and above
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	120.8	129
Credit tenant loans | BBB+ thru BBB-
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	75.7	102.4
Credit tenant loans | B+ and below
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	0.1	0.3
Residential mortgage loans
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	1,353.5	1,285.9	$ 1,290.6
Residential mortgage loans | Performing
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	1,332.3	1,267.9
Residential mortgage loans | Non-performing
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	$ 21.2	18
Mortgage loans, Days delinquent to be considered non-performing	90 days
Home equity
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	$ 17.1	23
Home equity | Performing
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	12.1	16.5
Home equity | Non-performing
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	5	6.5
First liens
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	1,336.4	1,262.9
First liens | Performing
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	1,320.2	1,251.4
First liens | Non-performing
Mortgage loan credit quality disclosures
Mortgage loans, Total amortized cost	$ 16.2	$ 11.5

Investments - Mortgage Loans, N

Investments - Mortgage Loans, Non-Accrual and Aging (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	$ 16.2	$ 10.4
Past due	58.7	59.1
Current	14,890.1	14,124.1
Mortgage loans, Total amortized cost	14,948.8	14,183.2	$ 14,064.1
Recorded investment 90 days or more past due and accruing	5	7.6
30 to 59 Days Past Due
Mortgage loan non-accrual and aging disclosures
Past due	34.6	39.1
60 to 89 Days Past Due
Mortgage loan non-accrual and aging disclosures
Past due	8.2	8.6
90 Days or More Past Due
Mortgage loan non-accrual and aging disclosures
Past due	15.9	11.4
Commercial mortgage loans
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Total amortized cost	13,595.3	12,897.3	12,773.5
Brick and mortar
Mortgage loan non-accrual and aging disclosures
Current	13,398.7	12,665.6
Mortgage loans, Total amortized cost	13,398.7	12,665.6
Credit tenant loans
Mortgage loan non-accrual and aging disclosures
Current	196.6	231.7
Mortgage loans, Total amortized cost	196.6	231.7
Residential mortgage loans
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Total amortized cost	1,353.5	1,285.9	$ 1,290.6
Home equity
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	5	6.5
Past due	1.8	3.4
Current	15.3	19.6
Mortgage loans, Total amortized cost	17.1	23
Home equity | 30 to 59 Days Past Due
Mortgage loan non-accrual and aging disclosures
Past due	1	1.9
Home equity | 60 to 89 Days Past Due
Mortgage loan non-accrual and aging disclosures
Past due	0.4	0.7
Home equity | 90 Days or More Past Due
Mortgage loan non-accrual and aging disclosures
Past due	0.4	0.8
First liens
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	11.2	3.9
Past due	56.9	55.7
Current	1,279.5	1,207.2
Mortgage loans, Total amortized cost	1,336.4	1,262.9
Recorded investment 90 days or more past due and accruing	5	7.6
First liens | 30 to 59 Days Past Due
Mortgage loan non-accrual and aging disclosures
Past due	33.6	37.2
First liens | 60 to 89 Days Past Due
Mortgage loan non-accrual and aging disclosures
Past due	7.8	7.9
First liens | 90 Days or More Past Due
Mortgage loan non-accrual and aging disclosures
Past due	$ 15.5	$ 10.6

Investments - Mortgage Loan Val

Investments - Mortgage Loan Valuation Allowance (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Changes in mortgage loan valuation allowance
Beginning balance, Mortgage loan valuation allowance	$ 30.1	$ 44.6	$ 32.7	$ 44.9
Provision: Mortgage loan valuation allowance	(1.4)	(1.1)	(4.2)	(0.5)
Charge-offs: Mortgage loan valuation allowance	(0.3)	(1.2)	(1.9)	(4.3)
Recoveries: Mortgage loan valuation allowance	0.7	1.4	2.5	3.6
Ending balance, Mortgage loan valuation allowance	29.1	43.7	29.1	43.7
Individually evaluated for impairment, Mortgage loan valuation allowance	1.9	4.8	1.9	4.8
Collectively evaluated for impairment, Mortgage loan valuation allowance	27.2	38.9	27.2	38.9
Individually evaluated for impairment, Mortgage loans	10.9	12.8	10.9	12.8
Collectively evaluated for impairment, Mortgage loans	14,937.9	14,051.3	14,937.9	14,051.3
Mortgage loans, Total amortized cost	14,948.8	14,064.1	$ 14,948.8	14,064.1	$ 14,183.2
Commercial mortgage loans
Mortgage loan valuation allowance disclosures
Mortgage loans, Days delinquent to be analyzed for valuation allowance			60 days
Changes in mortgage loan valuation allowance
Beginning balance, Mortgage loan valuation allowance	25.8	28	$ 25.8	27.4
Provision: Mortgage loan valuation allowance	(0.5)	0.1	(0.5)	0.7
Ending balance, Mortgage loan valuation allowance	25.3	28.1	25.3	28.1
Collectively evaluated for impairment, Mortgage loan valuation allowance	25.3	28.1	25.3	28.1
Collectively evaluated for impairment, Mortgage loans	13,595.3	12,773.5	13,595.3	12,773.5
Mortgage loans, Total amortized cost	13,595.3	12,773.5	13,595.3	12,773.5	12,897.3
Residential mortgage loans
Changes in mortgage loan valuation allowance
Beginning balance, Mortgage loan valuation allowance	4.3	16.6	6.9	17.5
Provision: Mortgage loan valuation allowance	(0.9)	(1.2)	(3.7)	(1.2)
Charge-offs: Mortgage loan valuation allowance	(0.3)	(1.2)	(1.9)	(4.3)
Recoveries: Mortgage loan valuation allowance	0.7	1.4	2.5	3.6
Ending balance, Mortgage loan valuation allowance	3.8	15.6	3.8	15.6
Individually evaluated for impairment, Mortgage loan valuation allowance	1.9	4.8	1.9	4.8
Collectively evaluated for impairment, Mortgage loan valuation allowance	1.9	10.8	1.9	10.8
Individually evaluated for impairment, Mortgage loans	10.9	12.8	10.9	12.8
Collectively evaluated for impairment, Mortgage loans	1,342.6	1,277.8	1,342.6	1,277.8
Mortgage loans, Total amortized cost	$ 1,353.5	$ 1,290.6	$ 1,353.5	$ 1,290.6	$ 1,285.9

Investments - Impaired Mortgage

Investments - Impaired Mortgage Loans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Residential mortgage loans
Impaired mortgage loans
Recorded investment in impaired mortgage loans	$ 10.9		$ 10.9		$ 12.5
Unpaid principal balance of impaired mortgage loans	11.9		11.9		13.4
Related allowance for impaired mortgage loans	1.9		1.9		4.5
Average investment in impaired mortgage loans	11	$ 13.1	11.8	$ 16.1
Interest income recognized on impaired mortgage loans		0.1	0.2	0.3
Home equity
Impaired mortgage loans
Recorded investment in impaired mortgage loans with related allowance	6.1		6.1		7.6
Unpaid principal balance of impaired mortgage loans with related allowance	7.2		7.2		8.6
Related allowance for impaired mortgage loans	1.7		1.7		4.3
Average investment in impaired mortgage loans with related allowance	6.4	8.4	6.9	10.6
Interest income recognized on impaired mortgage loans with related allowance		0.1	0.1	0.2
First liens
Impaired mortgage loans
Recorded investment in impaired mortgage loans with no related allowance	1.1		1.1		0.9
Recorded investment in impaired mortgage loans with related allowance	3.7		3.7		4
Unpaid principal balance of impaired mortgage loans with no related allowance	1		1		0.8
Unpaid principal balance of impaired mortgage loans with related allowance	3.7		3.7		4
Related allowance for impaired mortgage loans	0.2		0.2		$ 0.2
Average investment in impaired mortgage loans with no related allowance	0.9	0.6	1	1.1
Average investment in impaired mortgage loans with related allowance	$ 3.7	$ 4.1	3.9	4.4
Interest income recognized on impaired mortgage loans with related allowance			$ 0.1	$ 0.1

Investments - Mortgage Loan Mod

Investments - Mortgage Loan Modifications (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2017USD ($)contract	Sep. 30, 2018USD ($)contract	Sep. 30, 2017USD ($)contract
Mortgage Loan Modifications
Number of mortgage loans modified as a troubled debt restructuring | contract	4	7	11
Recorded investment of mortgage loans modified as a troubled debt restructuring | $	$ 0.2	$ 0.4	$ 0.6
Number of mortgage loans modified as a troubled debt restructuring in payment default | contract			1
Recorded investment of mortgage loans modified as a troubled debt restructuring in payment default | $			$ 0.1
Home equity
Mortgage Loan Modifications
Number of mortgage loans modified as a troubled debt restructuring | contract	3	6	10
Recorded investment of mortgage loans modified as a troubled debt restructuring | $	$ 0.1	$ 0.3	$ 0.5
First liens
Mortgage Loan Modifications
Number of mortgage loans modified as a troubled debt restructuring | contract	1	1	1
Recorded investment of mortgage loans modified as a troubled debt restructuring | $	$ 0.1	$ 0.1	$ 0.1
Number of mortgage loans modified as a troubled debt restructuring in payment default | contract			1
Recorded investment of mortgage loans modified as a troubled debt restructuring in payment default | $			$ 0.1

Investments - Real Estate Trans

Investments - Real Estate Transactions (Details) - Certain real estate joint ventures $ in Millions	1 Months Ended
	Sep. 30, 2017USD ($)
Real Estate Transactions
Net pre-tax realized capital gain	$ 690.9
Net after-tax realized capital gain	410.8
Real estate
Real Estate Transactions
Net increase, assets	293.4
Other investments
Real Estate Transactions
Net increase, assets	222.4
Cash and cash equivalents
Real Estate Transactions
Net increase, assets	219.6
Long-term debt
Real Estate Transactions
Net increase, liabilities	49.4
Income taxes currently payable
Real Estate Transactions
Net increase, liabilities	179.1
Deferred income taxes
Real Estate Transactions
Net increase, liabilities	$ 101

Investments - Securities Posted

Investments - Securities Posted as Collateral (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Securities Posted as Collateral
Commercial mortgage loans and residential first lien mortgages posted as collateral associated with obligation under funding agreements with the Federal Home Loan Bank of Des Moines	$ 3,783.1	$ 2,807.4
Fixed maturities available-for-sale and trading securities posted as collateral for a reinsurance arrangement, derivative credit support annex (collateral) agreements, Futures Commission Merchant agreements, a lending arrangement and an obligation under funding agreements with Federal Home Loan Bank of Des Moines	2,248.4	2,486.2
Securities posted as collateral eligible to be sold or repledged	$ 179.1	$ 173.3

Investments - Balance Sheet Off

Investments - Balance Sheet Offsetting, Assets (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Financial Asset Offsetting
Gross amount of recognized assets subject to netting agreements	$ 225.3	$ 304.6
Amount of liabilities that offset the gross amount of assets subject to netting agreements not offset in statement of financial position	(84.2)	(116.3)
Collateral received, financial assets	(132.1)	(167.1)
Net amount of assets subject to netting agreements	9	21.2
Derivative assets
Financial Asset Offsetting
Gross amount of recognized assets subject to netting agreements	172.5	287
Amount of liabilities that offset the gross amount of assets subject to netting agreements not offset in statement of financial position	(84.2)	(116.3)
Collateral received, financial assets	(79.3)	(149.5)
Net amount of assets subject to netting agreements	9	21.2
Gross amount of assets not subject to netting agreements	12.6	17
Reverse repurchase agreements
Financial Asset Offsetting
Gross amount of recognized assets subject to netting agreements	52.8	17.6
Collateral received, financial assets	$ (52.8)	$ (17.6)

Investments - Balance Sheet O_2

Investments - Balance Sheet Offsetting, Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Financial Liability Offsetting
Gross amount of recognized liabilities subject to netting agreements	$ 257.1	$ 272.5
Amount of assets that offset the gross amount of liabilities subject to netting agreements not offset in statement of financial position	(84.2)	(116.3)
Collateral pledged, financial liabilities	(153.9)	(143.5)
Net amount of liabilities subject to netting agreements	19	12.7
Derivative liabilities
Financial Liability Offsetting
Gross amount of recognized liabilities subject to netting agreements	257.1	272.5
Amount of assets that offset the gross amount of liabilities subject to netting agreements not offset in statement of financial position	(84.2)	(116.3)
Collateral pledged, financial liabilities	(153.9)	(143.5)
Net amount of liabilities subject to netting agreements	19	12.7
Gross amount of liabilities not subject to netting agreements	$ 151.3	$ 415.6

Derivative Financial Instrume_3

Derivative Financial Instruments - Notional Amounts and Credit Exposure (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Derivative Financial Instruments, exposure
Cash and securities posted under collateral arrangements associated with derivative credit support agreements and Futures Commission Merchant agreements	$ 203.6	$ 195
Aggregate fair value of all derivative instruments with credit-risk-related contingent features that were in a liability position	233.2	280.4
Collateral and initial margin posted supporting derivatives with credit-risk-related contingent features that were in a liability position	203.6	195
Additional collateral required to be posted if derivative credit-risk-related contingent features were triggered	20.6
Cash collateral received associated with derivative credit support annex agreements and Futures Commission Merchant agreements	61.6	124.7
Notional amount	51,892.3	40,916.6
Gross credit exposure	191.2	311.4
Less: collateral received	103.5	159.7
Net credit exposure	87.7	151.7
Interest rate swaps
Derivative Financial Instruments, exposure
Cash exchanged under contract	0
Principal payments made under contract	0
Notional amount	35,538.7	23,543.4
Gross credit exposure	84.8	163.4
Interest rate options
Derivative Financial Instruments, exposure
Notional amount	1,127	657
Gross credit exposure	9.8	19.8
Interest rate futures
Derivative Financial Instruments, exposure
Notional amount	172.5	236.5
Swaptions
Derivative Financial Instruments, exposure
Notional amount		14
Currency swaps
Derivative Financial Instruments, exposure
Notional amount	844.5	888.6
Gross credit exposure	69.2	79.1
Currency forwards
Derivative Financial Instruments, exposure
Notional amount	948.8	915.5
Gross credit exposure	1.7	24.3
Currency options
Derivative Financial Instruments, exposure
Notional amount	617.6	583.6
Gross credit exposure	2.1	1.6
Equity options
Derivative Financial Instruments, exposure
Notional amount	2,428.9	3,649.4
Gross credit exposure	20.9	18.2
Equity futures
Derivative Financial Instruments, exposure
Notional amount	116.6	357.8
Credit default swaps
Derivative Financial Instruments, exposure
Notional amount	500	668.5
Gross credit exposure	2.7	5
Embedded derivative financial instruments
Derivative Financial Instruments, exposure
Notional amount	$ 9,597.7	$ 9,402.3

Derivative Financial Instrume_4

Derivative Financial Instruments - Fair Value of Derivatives (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Derivatives, fair value disclosures
Derivative instruments, assets	$ 185.1	$ 304
Derivative instruments, liabilities	408.4	688.1
Fair value of embedded derivative liabilities reported with contractholder funds	(81.9)	160.3
Derivatives designated as hedging instruments
Derivatives, fair value disclosures
Derivative instruments, assets	37.4	39.6
Derivative instruments, liabilities	37.7	59.2
Derivatives not designated as hedging instruments
Derivatives, fair value disclosures
Derivative instruments, assets	147.7	264.4
Derivative instruments, liabilities	370.7	628.9
Interest rate contracts | Derivatives designated as hedging instruments
Derivatives, fair value disclosures
Derivative instruments, liabilities	13.4	22.9
Interest rate contracts | Derivatives not designated as hedging instruments
Derivatives, fair value disclosures
Derivative instruments, assets	87.4	175.2
Derivative instruments, liabilities	40.3	33.6
Foreign exchange contracts | Derivatives designated as hedging instruments
Derivatives, fair value disclosures
Derivative instruments, assets	37.4	39.6
Derivative instruments, liabilities	24.3	36.3
Foreign exchange contracts | Derivatives not designated as hedging instruments
Derivatives, fair value disclosures
Derivative instruments, assets	36.8	66.2
Derivative instruments, liabilities	38.9	26.3
Equity contracts | Derivatives not designated as hedging instruments
Derivatives, fair value disclosures
Derivative instruments, assets	20.9	18.2
Derivative instruments, liabilities	141.7	154.1
Credit contracts | Derivatives not designated as hedging instruments
Derivatives, fair value disclosures
Derivative instruments, assets	2.6	4.8
Derivative instruments, liabilities	1.7	1.5
Other contracts | Derivatives not designated as hedging instruments
Derivatives, fair value disclosures
Derivative instruments, liabilities	$ 148.1	$ 413.4

Derivative Financial Instrume_5

Derivative Financial Instruments - Credit Derivatives Sold (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Credit default swaps
Credit derivatives sold disclosures
Notional amount	$ 405	$ 525
Fair value	1.9	4.2
Maximum future payments	$ 405	$ 525
Weighted average expected life	1 year 4 months 24 days	1 year 3 months 18 days
Single name credit default swaps | Corporate debt securities | AAA
Credit derivatives sold disclosures
Notional amount	$ 30	$ 30
Fair value	0.1	0.3
Maximum future payments	$ 30	$ 30
Weighted average expected life	6 months	1 year 2 months 12 days
Single name credit default swaps | Corporate debt securities | AA
Credit derivatives sold disclosures
Notional amount		$ 30
Fair value		0.1
Maximum future payments		$ 30
Weighted average expected life		6 months
Single name credit default swaps | Corporate debt securities | A
Credit derivatives sold disclosures
Notional amount	$ 15	$ 105
Fair value	0.2	0.5
Maximum future payments	$ 15	$ 105
Weighted average expected life	1 year 2 months 12 days	7 months 6 days
Single name credit default swaps | Corporate debt securities | BBB
Credit derivatives sold disclosures
Notional amount	$ 255	$ 255
Fair value	0.9	2.5
Maximum future payments	$ 255	$ 255
Weighted average expected life	1 year 7 months 6 days	1 year 3 months 18 days
Single name credit default swaps | Corporate debt securities | B
Credit derivatives sold disclosures
Notional amount	$ 20	$ 20
Fair value	(0.3)	(0.5)
Maximum future payments	$ 20	$ 20
Weighted average expected life	1 year 1 month 6 days	1 year 9 months 18 days
Single name credit default swaps | Government/municipalities | AA
Credit derivatives sold disclosures
Notional amount	$ 20	$ 20
Fair value	0.2	0.3
Maximum future payments	$ 20	$ 20
Weighted average expected life	1 year 2 months 12 days	2 years
Single name credit default swaps | Sovereign | A
Credit derivatives sold disclosures
Notional amount	$ 10	$ 10
Fair value	0.1	0.2
Maximum future payments	$ 10	$ 10
Weighted average expected life	1 year	1 year 8 months 12 days
Single name credit default swaps | Sovereign | BBB
Credit derivatives sold disclosures
Notional amount	$ 55	$ 55
Fair value	0.7	0.8
Maximum future payments	$ 55	$ 55
Weighted average expected life	1 year 7 months 6 days	2 years 3 months 18 days

Derivative Financial Instrume_6

Derivative Financial Instruments - Fair Value Hedges (Details) - Fair Value Hedges - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Effect of derivatives in hedging relationships and the related hedged items on the consolidated statements of operations
Amount of gain (loss) recognized in net income on derivatives	$ 2.3	$ 1.2	$ 9.9	$ 1.5
Amount of gain (loss) recognized in net income on related hedged item	(2.4)	(1.2)	(10.2)	(1.8)
Gain (loss) on periodic settlements on interest rate and foreign exchange contracts in fair value hedge of fixed maturities, available-for-sale reported in net investment income	(1.2)	(2.4)	(4.9)	(8.1)
Gain (loss) on periodic settlements on interest rate and foreign exchange contracts in fair value hedge of investment contracts reported in benefits, claims and settlement expenses		0.1		0.9
Interest rate contracts | Fixed maturities, available-for-sale
Effect of derivatives in hedging relationships and the related hedged items on the consolidated statements of operations
Amount of gain (loss) recognized in net income on derivatives	2.3	1.1	9.9	2.1
Amount of gain (loss) recognized in net income on related hedged item	$ (2.4)	(1.1)	$ (10.2)	(2.4)
Interest rate contracts | Investment contracts
Effect of derivatives in hedging relationships and the related hedged items on the consolidated statements of operations
Amount of gain (loss) recognized in net income on derivatives		0.1		(0.6)
Amount of gain (loss) recognized in net income on related hedged item		$ (0.1)		$ 0.6

Derivative Financial Instrume_7

Derivative Financial Instruments - Cash Flow Hedges (Details) - Cash Flow Hedges - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Effect of derivatives in hedging relationships and the related hedged items on the consolidated statements of operations
Maximum length of time hedging exposure to variability in future cash flows for forecasted transactions			1 year 9 months 18 days
Gross unrealized gains (losses) reported in accumulated OCI related to active hedges of forecasted transactions	$ 0		$ 0
Gross unrealized gains (losses) reclassified from AOCI into net capital gains (losses) due to hedged cash flows probable of not occurring			0.2	$ 0
Amount of gain (loss) recognized in accumulated OCI on derivatives (effective portion)	(0.8)	$ (22.2)	37.7	(90.8)
Amount of gain (loss) reclassified from accumulated OCI on derivatives (effective portion)	4.7	2.5	10.4	21
Gain (loss) on periodic settlements on interest rate and foreign exchange contracts in cash flow hedge of fixed maturities, available-for-sale reported in net investment income	1.5	1.9	4.6	5.3
Gain (loss) on periodic settlements on interest rate and foreign exchange contracts in cash flow hedge of investment contracts reported in benefits, claims and settlement expenses		(0.1)	(0.1)	(1)
Net gains (losses) expected to be reclassified from accumulated OCI into net income in the next 12 months			16.7
Net realized capital gains (losses)
Effect of derivatives in hedging relationships and the related hedged items on the consolidated statements of operations
Gain (loss) resulting from the ineffective portion in cash flow hedging relationships	0	0	0	0
Interest rate contracts | Fixed maturities, available-for-sale
Effect of derivatives in hedging relationships and the related hedged items on the consolidated statements of operations
Amount of gain (loss) recognized in accumulated OCI on derivatives (effective portion)	2.4	(5.1)	32.6	(44.2)
Interest rate contracts | Fixed maturities, available-for-sale | Net investment income
Effect of derivatives in hedging relationships and the related hedged items on the consolidated statements of operations
Amount of gain (loss) reclassified from accumulated OCI on derivatives (effective portion)	5.1	5.4	15.8	15.7
Interest rate contracts | Fixed maturities, available-for-sale | Net realized capital gains (losses)
Effect of derivatives in hedging relationships and the related hedged items on the consolidated statements of operations
Amount of gain (loss) reclassified from accumulated OCI on derivatives (effective portion)				(0.7)
Interest rate contracts | Hedged debt | Operating expense
Effect of derivatives in hedging relationships and the related hedged items on the consolidated statements of operations
Amount of gain (loss) reclassified from accumulated OCI on derivatives (effective portion)	(2.7)	(2.8)	(7.9)	(8)
Foreign exchange contracts | Fixed maturities, available-for-sale
Effect of derivatives in hedging relationships and the related hedged items on the consolidated statements of operations
Amount of gain (loss) recognized in accumulated OCI on derivatives (effective portion)	(3.2)	(17.1)	5.2	(46.7)
Foreign exchange contracts | Fixed maturities, available-for-sale | Net realized capital gains (losses)
Effect of derivatives in hedging relationships and the related hedged items on the consolidated statements of operations
Amount of gain (loss) reclassified from accumulated OCI on derivatives (effective portion)	$ 2.3	$ (0.1)	2.5	14
Foreign exchange contracts | Investment contracts
Effect of derivatives in hedging relationships and the related hedged items on the consolidated statements of operations
Amount of gain (loss) recognized in accumulated OCI on derivatives (effective portion)			$ (0.1)	$ 0.1

Derivative Financial Instrume_8

Derivative Financial Instruments - Derivatives Not Designated as Hedging Instruments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Effect of derivatives not designated as hedging instruments on the consolidated statements of operations
Amount of gain (loss) recognized in net income on derivatives	$ 36.1	$ (32.7)	$ 11.8	$ (143.9)
Interest rate contracts
Effect of derivatives not designated as hedging instruments on the consolidated statements of operations
Amount of gain (loss) recognized in net income on derivatives	(33.6)	(2)	(101.4)	(46.2)
Foreign exchange contracts
Effect of derivatives not designated as hedging instruments on the consolidated statements of operations
Amount of gain (loss) recognized in net income on derivatives	(6.4)	28.7	(21.8)	47
Equity contracts
Effect of derivatives not designated as hedging instruments on the consolidated statements of operations
Amount of gain (loss) recognized in net income on derivatives	(46.1)	(63.8)	(104.3)	(162.5)
Credit contracts
Effect of derivatives not designated as hedging instruments on the consolidated statements of operations
Amount of gain (loss) recognized in net income on derivatives		(3.7)	1.3	(16.1)
Other contracts
Effect of derivatives not designated as hedging instruments on the consolidated statements of operations
Amount of gain (loss) recognized in net income on derivatives	$ 122.2	$ 8.1	$ 238	$ 33.9

Insurance Liabilities (Details)

Insurance Liabilities (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Change in unpaid claims
Balance at beginning of period, unpaid claims	$ 2,130.5	$ 2,001.3
Balance at beginning of period, reinsurance recoverables for unpaid claims	375.8	340.3
Net balance at beginning of period, unpaid claims	1,754.7	1,661
Incurred:
Incurred: Current year	939.6	867.2
Incurred: Prior years	11.1	42.2
Total incurred	950.7	909.4
Payments:
Payments: Current year	582.6	527.8
Payments: Prior years	301.4	318.3
Total payments	884	846.1
Net balance at end of period, unpaid claims	1,821.4	1,724.3
Balance at end of period, reinsurance recoverables for unpaid claims	390.9	369.9
Balance at end of period, unpaid claims	2,212.3	2,094.2
Amount not included in the rollforward above:
Claim adjustment expense liabilities	$ 54.1	$ 50.5

Long-Term Debt (Details)

Long-Term Debt (Details) $ in Millions	Mar. 08, 2018USD ($)item
Contingent funding agreements
Long-Term Debt
Number of contingent funding agreements | item	2
Period failure to make payments to trust can be cured before automatic exercise of put options	30 days
Minimum shareholders' equity excluding AOCI and NCI, to avoid automatic exercise of options	$ 4,000
10-year contingent funding agreement | 2028 Trust
Long-Term Debt
Term of contingent funding agreement	10 years
Semi-annual put premium (as a percent)	1.275%
10-year contingent funding agreement | 2028 Trust | Senior Notes due 2028
Long-Term Debt
Amount of notes issuable under option	$ 400
Interest rate (as a percent)	4.111%
30-year contingent funding agreement | 2048 Trust
Long-Term Debt
Term of contingent funding agreement	30 years
Annual put premium (as a percent)	1.58%
30-year contingent funding agreement | 2048 Trust | Senior Notes due 2048
Long-Term Debt
Amount of notes issuable under option	$ 350
Interest rate (as a percent)	4.682%
2028 Trust
Long-Term Debt
Pre-capitalized trust securities sold	$ 400
2048 Trust
Long-Term Debt
Pre-capitalized trust securities sold	$ 350

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reconciliation between the U.S. corporate income tax rate and the effective income tax rate from continuing operations
U.S. corporate income tax rate (as a percent)	21.00%	35.00%	21.00%	35.00%
Impact of the Tax Cuts and Jobs Act (as a percent)	(2.00%)		(3.00%)
Dividends received deduction (as a percent)	(3.00%)	(4.00%)	(3.00%)	(7.00%)
Tax credits (as a percent)	(2.00%)	(2.00%)	(3.00%)	(2.00%)
Impact of equity method presentation (as a percent)		(1.00%)	(1.00%)	(2.00%)
Local country permanent tax adjustments (as a percent)	3.00%	(1.00%)	1.00%	(1.00%)
State income taxes (as a percent)	2.00%	4.00%	1.00%	2.00%
Other income tax rate impacts (as a percent)		(1.00%)	1.00%	(1.00%)
Effective income tax rate (as a percent)	19.00%	30.00%	14.00%	24.00%
Adjustments in income tax related to provisional amounts	$ 5.4		$ 5.4

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Changes in Unrecognized Tax Benefits
Beginning balance, Unrecognized tax benefits	$ 194.1	$ 207.8
Additions based on tax positions related to the current year	0.8	7.2
Additions for tax positions of prior years	47.2	20.2
Reductions for tax positions related to the current year	(10.3)	(3.3)
Reductions for tax positions of prior years		(1.1)
Settlements	(162.8)	(36.7)
Ending balance, Unrecognized tax benefits	69	194.1
Amount of unrecognized tax benefits that would reduce the effective income tax rate, if recognized	4.8
Accumulated pre-tax interest and penalties related to unrecognized tax benefits	$ 1.2	$ 125.5

Employee and Agent Benefits (De

Employee and Agent Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Pension benefits
Components of Net Periodic Benefit Cost (Income)
Service cost	$ 18.3	$ 16.7	$ 54.8	$ 50.3
Interest cost	29.8	31.1	89.6	93.3
Expected return on plan assets	(39.2)	(36)	(117.7)	(108.1)
Amortization of prior service (benefit) cost	(0.8)	(0.6)	(2.5)	(1.7)
Recognized net actuarial (gain) loss	17	17	50.8	51
Net periodic benefit cost (income)	25.1	28.2	75	84.8
Contributions
Contributions made by employer to fund qualified and nonqualified pension plans	92.4		182.2
Pension benefits | Maximum
Contributions
Amount of possible contributions to be made during the current fiscal year to the qualified and nonqualified pension plans combined	200		200
Other postretirement benefits
Components of Net Periodic Benefit Cost (Income)
Service cost				0.1
Interest cost	0.9	1	2.6	3
Expected return on plan assets	(8.4)	(7)	(25.2)	(20.7)
Amortization of prior service (benefit) cost	(3.5)	(8.6)	(10.4)	(25.9)
Recognized net actuarial (gain) loss	(0.4)	(0.1)	(1.1)	(0.1)
Net periodic benefit cost (income)	$ (11.4)	$ (14.7)	$ (34.1)	$ (43.6)

Contingencies, Guarantees and_2

Contingencies, Guarantees and Indemnifications (Details) $ in Millions	Sep. 30, 2018USD ($)
Guarantees to third parties primarily related to former subsidiaries and joint ventures
Guarantees and Indemnifications
Maximum exposure under guarantees	$ 131
Guarantees related to P-Caps contingent funding agreements
Guarantees and Indemnifications
Maximum exposure under guarantees	$ 750

Stockholders' Equity - Reconcil

Stockholders' Equity - Reconciliation of Outstanding Shares (Details) - Common stock - USD ($) shares in Millions, $ in Millions	1 Months Ended			9 Months Ended
	May 31, 2018	May 31, 2017	Feb. 29, 2016	Sep. 30, 2018	Sep. 30, 2017
Reconciliation of Outstanding Common Shares
Outstanding shares at beginning of period				289	287.7
Shares issued				2.3	4.3
Treasury stock acquired				(7.7)	(3.5)
Outstanding shares at end of period				283.6	288.5
Common stock share repurchase disclosures
Share repurchase program, maximum authorized amount (in dollars)	$ 300	$ 250	$ 400

Stockholders' Equity - Other Co

Stockholders' Equity - Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Other Comprehensive Income (Loss)
Other comprehensive income (loss), pre-tax	$ (267.3)	$ 218.1	$ (2,015.4)	$ 1,042.3
Other comprehensive income (loss), tax	58.6	(53)	398.3	(317.4)
Other comprehensive income (loss)	(208.7)	165.1	(1,617.1)	724.9
Net unrealized gains (losses) on available-for-sale securities including NCI
Other Comprehensive Income (Loss)
Other comprehensive income (loss) before reclassifications, pre-tax	(282.9)	137.3	(2,364.4)	1,044.2
Adjustments for assumed changes in amortization patterns, pre-tax	12.1	(0.2)	152.5	(48.4)
Adjustments for assumed changes in policyholder liabilities, pre-tax	41.7	(23.7)	322.4	(167.2)
Other comprehensive income (loss), pre-tax	(248.8)	113.7	(1,862)	878.5
Other comprehensive income (loss) before reclassifications, tax	54.4	(52.6)	492.9	(365.9)
Reclassification from accumulated other comprehensive income, tax	7	0.2	(3)	(17)
Adjustments for assumed changes in amortization patterns, tax	(2.5)	(0.1)	(32)	16.9
Adjustments for assumed changes in policyholder liabilities, tax	(9.3)	8.9	(66.7)	56.6
Other comprehensive income (loss), tax	49.6	(43.6)	391.2	(309.4)
Other comprehensive income (loss) before reclassifications, after-tax	(228.5)	84.7	(1,871.5)	678.3
Reclassification from accumulated other comprehensive income, after-tax	(12.7)	0.5	24.5	32.9
Adjustments for assumed changes in amortization patterns, after-tax	9.6	(0.3)	120.5	(31.5)
Adjustments for assumed changes in policyholder liabilities, after-tax	32.4	(14.8)	255.7	(110.6)
Other comprehensive income (loss)	(199.2)	70.1	(1,470.8)	569.1
Net unrealized gains (losses) on available-for-sale securities including NCI | Net realized capital gains (losses)
Other Comprehensive Income (Loss)
Reclassification from accumulated other comprehensive income, pre-tax	(19.7)	0.3	27.5	49.9
Noncredit component of impairment losses on fixed maturities available-for-sale including NCI
Other Comprehensive Income (Loss)
Other comprehensive income (loss) before reclassifications, pre-tax	2.2	19.2	14.2	32.5
Adjustments for assumed changes in amortization patterns, pre-tax	0.3	(1)	1.6	(2.1)
Adjustments for assumed changes in policyholder liabilities, pre-tax		(0.2)	(0.5)	(0.6)
Other comprehensive income (loss), pre-tax	2.5	18	15.3	29.8
Other comprehensive income (loss) before reclassifications, tax	(0.4)	(5.1)	(3)	(9.8)
Adjustments for assumed changes in amortization patterns, tax	(0.1)	0.4	(0.3)	0.8
Adjustments for assumed changes in policyholder liabilities, tax			0.1	0.2
Other comprehensive income (loss), tax	(0.5)	(4.7)	(3.2)	(8.8)
Other comprehensive income (loss) before reclassifications, after-tax	1.8	14.1	11.2	22.7
Adjustments for assumed changes in amortization patterns, after-tax	0.2	(0.6)	1.3	(1.3)
Adjustments for assumed changes in policyholder liabilities, after-tax		(0.2)	(0.4)	(0.4)
Other comprehensive income (loss)	2	13.3	12.1	21
Net unrealized gains (losses) on derivative instruments including NCI
Other Comprehensive Income (Loss)
Other comprehensive income (loss) before reclassifications, pre-tax	3.7	(17)	12.2	(32.5)
Reclassification from accumulated other comprehensive income, pre-tax	(4.9)	(2.5)	(10.6)	(21)
Adjustments for assumed changes in amortization patterns, pre-tax	(1)	0.6	(0.1)	2.6
Adjustments for assumed changes in policyholder liabilities, pre-tax	1.3	1.9	5.5	6.3
Other comprehensive income (loss), pre-tax	(0.9)	(17)	7	(44.6)
Other comprehensive income (loss) before reclassifications, tax	2.8	5.9	1	11.1
Reclassification from accumulated other comprehensive income, tax	0.8	0.8	1.7	7.2
Adjustments for assumed changes in amortization patterns, tax	0.2	(0.2)		(0.9)
Adjustments for assumed changes in policyholder liabilities, tax	(0.2)	(0.6)	(1.1)	(2.1)
Other comprehensive income (loss), tax	3.6	5.9	1.6	15.3
Other comprehensive income (loss) before reclassifications, after-tax	6.5	(11.1)	13.2	(21.4)
Reclassification from accumulated other comprehensive income, after-tax	(4.1)	(1.7)	(8.9)	(13.8)
Adjustments for assumed changes in amortization patterns, after-tax	(0.8)	0.4	(0.1)	1.7
Adjustments for assumed changes in policyholder liabilities, after-tax	1.1	1.3	4.4	4.2
Other comprehensive income (loss)	2.7	(11.1)	8.6	(29.3)
Foreign currency translation adjustment including NCI
Other Comprehensive Income (Loss)
Other comprehensive income (loss), pre-tax	(32.4)	95.7	(212.5)	155.3
Other comprehensive income (loss), tax	9.5	(7.1)	19.3	(4)
Other comprehensive income (loss)	(22.9)	88.6	(193.2)	151.3
Unrecognized postretirement benefit obligation including NCI
Other Comprehensive Income (Loss)
Other comprehensive income (loss), pre-tax	12.3	7.7	(36.8)	23.3
Reclassification from accumulated other comprehensive income, tax	(3.6)	(3.5)	(10.6)	(10.5)
Other comprehensive income (loss), tax	(3.6)	(3.5)	(10.6)	(10.5)
Reclassification from accumulated other comprehensive income, after-tax	8.7	4.2	26.2	12.8
Other comprehensive income (loss)	8.7	4.2	26.2	12.8
Unrecognized postretirement benefit obligation including NCI | Operating expense
Other Comprehensive Income (Loss)
Reclassification from accumulated other comprehensive income, pre-tax	$ 12.3	$ 7.7	$ 36.8	$ 23.3

Stockholders' Equity - AOCI and

Stockholders' Equity - AOCI and Noncontrolling Interest (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017
Change in accumulated other comprehensive income (loss) rollforward
Balances		$ 12,849.3
Purchase of subsidiary shares from noncontrolling interest	[1]	(23.2)	$ (8.9)
Balances		11,700.8
Change in redeemable noncontrolling interest rollforward
Redeemable noncontrolling interest, balance at beginning of period		101.3	97.5
Net income (loss) attributable to redeemable noncontrolling interest		4.1	6.9
Redeemable noncontrolling interest of deconsolidated entities		(9.7)	(1.4)
Contributions from redeemable noncontrolling interest		89	54.5
Distributions to redeemable noncontrolling interest		(24.8)	(28.2)
Purchase of subsidiary shares from redeemable noncontrolling interest		(7.1)	(4.4)
Change in redemption value of redeemable noncontrolling interest		(2.7)	2.8
Stock-based compensation attributable to redeemable noncontrolling interest		0.1
Other comprehensive income (loss) attributable to redeemable noncontrolling interest		(1.7)	1.4
Redeemable noncontrolling interest, balance at end of period		148.5	129.1
ASU 2014-09 - Revenue recognition
Change in accumulated other comprehensive income (loss) rollforward
Effects of implementation of accounting change		(39.7)
Accumulated other comprehensive income (loss)
Change in accumulated other comprehensive income (loss) rollforward
Balances		165.5	(675.2)
Other comprehensive income (loss) during the period, net of adjustments		(1,667.6)	669.3
Amounts reclassified from accumulated other comprehensive income (loss)		53.9	52.9
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.		(1,613.7)	722.2
Purchase of subsidiary shares from noncontrolling interest	[1]	(1.6)
Balances		(1,347.6)	47
Accumulated other comprehensive income (loss) | ASU 2016-01 - Equity investments
Change in accumulated other comprehensive income (loss) rollforward
Effects of implementation of accounting change		(1)
Accumulated other comprehensive income (loss) | ASU 2014-09 - Revenue recognition
Change in accumulated other comprehensive income (loss) rollforward
Effects of implementation of accounting change		25.6
Accumulated other comprehensive income (loss) | ASU 2018-02 - Reclassification of certain tax effects
Change in accumulated other comprehensive income (loss) rollforward
Effects of implementation of accounting change		77.6
Net unrealized gains (losses) on available-for-sale securities
Change in accumulated other comprehensive income (loss) rollforward
Balances		1,470.7	831.2
Other comprehensive income (loss) during the period, net of adjustments		(1,495.3)	536.2
Amounts reclassified from accumulated other comprehensive income (loss)		24.5	32.9
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.		(1,470.8)	569.1
Balances		248.7	1,400.3
Net unrealized gains (losses) on available-for-sale securities | ASU 2016-01 - Equity investments
Change in accumulated other comprehensive income (loss) rollforward
Effects of implementation of accounting change		(1)
Net unrealized gains (losses) on available-for-sale securities | ASU 2018-02 - Reclassification of certain tax effects
Change in accumulated other comprehensive income (loss) rollforward
Effects of implementation of accounting change		249.8
Noncredit component of impairment losses on fixed maturities available-for-sale
Change in accumulated other comprehensive income (loss) rollforward
Balances		(58.3)	(89.5)
Amounts reclassified from accumulated other comprehensive income (loss)		12.1	21
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.		12.1	21
Balances		(61.4)	(68.5)
Noncredit component of impairment losses on fixed maturities available-for-sale | ASU 2018-02 - Reclassification of certain tax effects
Change in accumulated other comprehensive income (loss) rollforward
Effects of implementation of accounting change		(15.2)
Net unrealized gains (losses) on derivative instruments
Change in accumulated other comprehensive income (loss) rollforward
Balances		42.7	85.3
Other comprehensive income (loss) during the period, net of adjustments		17.5	(15.5)
Amounts reclassified from accumulated other comprehensive income (loss)		(8.9)	(13.8)
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.		8.6	(29.3)
Balances		57	56
Net unrealized gains (losses) on derivative instruments | ASU 2018-02 - Reclassification of certain tax effects
Change in accumulated other comprehensive income (loss) rollforward
Effects of implementation of accounting change		5.7
Foreign currency translation adjustment
Change in accumulated other comprehensive income (loss) rollforward
Balances		(918.5)	(1,093.8)
Other comprehensive income (loss) during the period, net of adjustments		(189.8)	148.6
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.		(189.8)	148.6
Purchase of subsidiary shares from noncontrolling interest		(1.6)
Balances		(1,166.1)	(945.2)
Foreign currency translation adjustment | ASU 2014-09 - Revenue recognition
Change in accumulated other comprehensive income (loss) rollforward
Effects of implementation of accounting change		25.6
Foreign currency translation adjustment | ASU 2018-02 - Reclassification of certain tax effects
Change in accumulated other comprehensive income (loss) rollforward
Effects of implementation of accounting change		(81.8)
Unrecognized postretirement benefit obligation
Change in accumulated other comprehensive income (loss) rollforward
Balances		(371.1)	(408.4)
Amounts reclassified from accumulated other comprehensive income (loss)		26.2	12.8
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.		26.2	12.8
Balances		(425.8)	$ (395.6)
Unrecognized postretirement benefit obligation | ASU 2018-02 - Reclassification of certain tax effects
Change in accumulated other comprehensive income (loss) rollforward
Effects of implementation of accounting change		$ (80.9)
[1]	Excludes amounts attributable to redeemable noncontrolling interest. See Note 10, Stockholders’ Equity, for further details.

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	$ 60,447.2	$ 59,388.4
Fixed maturities, trading	642.1	566
Equity securities	1,885.8	1,866.6
Equity securities, available-for-sale		96
Equity securities, trading		1,770.6
Derivative instruments, assets	185.1	304
Separate account assets	161,302.9	159,272.7
Investment contracts	81.9	(160.3)
Unfunded commitments of investments measured using NAV	$ 35	46.1
Fixed maturities valued using internal pricing models
Fixed maturities classified as Level 3 assets, percent valued using internal pricing models (as a percent)	1.00%
U.S. government and agencies
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	$ 1,310.2	1,351.7
Non-U.S. governments
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	1,172.3	901.5
States and political subdivisions
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	6,448.2	6,801.6
Corporate debt securities
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	36,204.1	37,033.1
Residential mortgage-backed pass-through securities
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	2,363.1	2,523.3
Commercial mortgage-backed securities
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	3,850.2	3,708.3
Collateralized debt obligations
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	2,368.6	1,359.3
Other debt obligations
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	6,730.5	5,709.6
Recurring Fair Value Measurements
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	60,447.2	59,388.4
Fixed maturities, trading	642.1	566
Equity securities	1,885.8
Equity securities, available-for-sale		96
Equity securities, trading		1,770.6
Derivative instruments, assets	185.1	304
Other investments	604.6	498
Cash equivalents	1,803	1,793.3
Sub-total excluding separate account assets	65,567.8	64,416.3
Separate account assets	161,302.9	159,272.7
Total assets	226,870.7	223,689
Investment contracts	81.9	(160.3)
Derivative liabilities	(260.2)	(274.7)
Other liabilities	(230.9)	(253.4)
Total liabilities	(409.2)	(688.4)
Net assets (liabilities)	226,461.5	223,000.6
Recurring Fair Value Measurements | Amount measured at net asset value
Assets (liabilities) measured at fair value on a recurring basis
Other investments	86.2	85.8
Sub-total excluding separate account assets	86.2	85.8
Separate account assets	112.4	120.4
Total assets	198.6	206.2
Net assets (liabilities)	198.6	206.2
Recurring Fair Value Measurements | Fair value hierarchy Level 1
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	920.5	920.4
Equity securities	615.9
Equity securities, available-for-sale		47.4
Equity securities, trading		544
Other investments	141.7	176
Cash equivalents	66.3	46.8
Sub-total excluding separate account assets	1,744.4	1,734.6
Separate account assets	92,838.5	90,090.6
Total assets	94,582.9	91,825.2
Net assets (liabilities)	94,582.9	91,825.2
Recurring Fair Value Measurements | Fair value hierarchy Level 2
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	59,280.3	58,194.7
Fixed maturities, trading	642.1	566
Equity securities	1,269.9
Equity securities, available-for-sale		45.9
Equity securities, trading		1,226.6
Derivative instruments, assets	172.8	279.8
Other investments	359.5	229.7
Cash equivalents	1,736.7	1,746.5
Sub-total excluding separate account assets	63,461.3	62,289.2
Separate account assets	59,866.8	61,410.3
Total assets	123,328.1	123,699.5
Derivative liabilities	(248.9)	(268.6)
Other liabilities	(230.9)	(253.4)
Total liabilities	(479.8)	(522)
Net assets (liabilities)	122,848.3	123,177.5
Recurring Fair Value Measurements | Fair value hierarchy Level 3
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	246.4	273.3
Equity securities, available-for-sale		2.7
Derivative instruments, assets	12.3	24.2
Other investments	17.2	6.5
Sub-total excluding separate account assets	275.9	306.7
Separate account assets	8,485.2	7,651.4
Total assets	8,761.1	7,958.1
Investment contracts	81.9	(160.3)
Derivative liabilities	(11.3)	(6.1)
Total liabilities	70.6	(166.4)
Net assets (liabilities)	8,831.7	7,791.7
Recurring Fair Value Measurements | U.S. government and agencies
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	1,310.2	1,351.7
Recurring Fair Value Measurements | U.S. government and agencies | Fair value hierarchy Level 1
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	898	896.8
Recurring Fair Value Measurements | U.S. government and agencies | Fair value hierarchy Level 2
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	412.2	454.9
Recurring Fair Value Measurements | Non-U.S. governments
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	1,172.3	901.5
Recurring Fair Value Measurements | Non-U.S. governments | Fair value hierarchy Level 1
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	3	2.9
Recurring Fair Value Measurements | Non-U.S. governments | Fair value hierarchy Level 2
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	1,164.4	891.2
Recurring Fair Value Measurements | Non-U.S. governments | Fair value hierarchy Level 3
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	4.9	7.4
Recurring Fair Value Measurements | States and political subdivisions
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	6,448.2	6,801.6
Recurring Fair Value Measurements | States and political subdivisions | Fair value hierarchy Level 2
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	6,448.2	6,801.6
Recurring Fair Value Measurements | Corporate debt securities
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	36,204.1	37,033.1
Recurring Fair Value Measurements | Corporate debt securities | Fair value hierarchy Level 1
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	19.5	20.7
Recurring Fair Value Measurements | Corporate debt securities | Fair value hierarchy Level 2
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	36,119.9	36,884.4
Recurring Fair Value Measurements | Corporate debt securities | Fair value hierarchy Level 3
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	64.7	128
Recurring Fair Value Measurements | Residential mortgage-backed pass-through securities
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	2,363.1	2,523.3
Recurring Fair Value Measurements | Residential mortgage-backed pass-through securities | Fair value hierarchy Level 2
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	2,363.1	2,523.3
Recurring Fair Value Measurements | Commercial mortgage-backed securities
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	3,850.2	3,708.3
Recurring Fair Value Measurements | Commercial mortgage-backed securities | Fair value hierarchy Level 2
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	3,840.4	3,697.7
Recurring Fair Value Measurements | Commercial mortgage-backed securities | Fair value hierarchy Level 3
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	9.8	10.6
Recurring Fair Value Measurements | Collateralized debt obligations
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	2,368.6	1,359.3
Recurring Fair Value Measurements | Collateralized debt obligations | Fair value hierarchy Level 2
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	2,250	1,234.3
Recurring Fair Value Measurements | Collateralized debt obligations | Fair value hierarchy Level 3
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	118.6	125
Recurring Fair Value Measurements | Other debt obligations
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	6,730.5	5,709.6
Recurring Fair Value Measurements | Other debt obligations | Fair value hierarchy Level 2
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	6,682.1	5,707.3
Recurring Fair Value Measurements | Other debt obligations | Fair value hierarchy Level 3
Assets (liabilities) measured at fair value on a recurring basis
Fixed maturities, available-for-sale	$ 48.4	$ 2.3

Fair Value Measurements - Chang

Fair Value Measurements - Changes in Level 3 Fair Value Measurements (Details) - Recurring Fair Value Measurements - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Investment contracts
Changes in Level 3 fair value measurements rollforward, assets and liabilities
Beginning balance, liabilities	$ (42.8)	$ (146.6)	$ (160.3)	$ (176.5)
Total realized/unrealized gains (losses) included in net income, liabilities	122	8	237.7	31.5
Total realized/unrealized gains (losses) included in other comprehensive income, liabilities	(0.1)			0.3
Net purchases, sales, issuances and settlements, liabilities	2.8	0.4	4.5	6.5
Ending balance, liabilities	81.9	(138.2)	81.9	(138.2)
Changes in unrealized gains (losses) included in net income relating to positions still held, liabilities	121.6	7.6	237.7	28.9
Gross purchases, sales, issuances and settlements
Issuances, liabilities	1.4	(0.3)	1.6	0.1
Settlements, liabilities	1.4	0.7	2.9	6.4
Net purchases, sales, issuances and settlements, liabilities	2.8	0.4	4.5	6.5
Derivative liabilities
Changes in Level 3 fair value measurements rollforward, assets and liabilities
Beginning balance, liabilities	(10.6)	(12.6)	(6.1)	(22.6)
Total realized/unrealized gains (losses) included in net income, liabilities	(1.3)	4.4	(5.7)	15.5
Net purchases, sales, issuances and settlements, liabilities	0.6	0.5	0.5	(0.6)
Ending balance, liabilities	(11.3)	(7.7)	(11.3)	(7.7)
Changes in unrealized gains (losses) included in net income relating to positions still held, liabilities	(1.4)	4.3	(5.9)	13.7
Gross purchases, sales, issuances and settlements
Purchases, liabilities	(0.1)		(1.3)	(1.2)
Sales, liabilities	0.7	0.5	1.8	0.6
Net purchases, sales, issuances and settlements, liabilities	0.6	0.5	0.5	(0.6)
Other liabilities
Changes in Level 3 fair value measurements rollforward, assets and liabilities
Beginning balance, liabilities				(59.9)
Total realized/unrealized gains (losses) included in net income, liabilities				(0.1)
Net purchases, sales, issuances and settlements, liabilities				60
Gross purchases, sales, issuances and settlements
Settlements, liabilities				60
Net purchases, sales, issuances and settlements, liabilities				60
Fixed maturities | Available-for-sale
Changes in Level 3 fair value measurements rollforward, assets and liabilities
Beginning balance, assets	277.7	460.4	273.3	517.4
Total realized/unrealized gains (losses) included in net income, assets	(1)	(4.5)	(3)	(12.2)
Total realized/unrealized gains (losses) included in other comprehensive income, assets	(0.8)	8.5	0.1	17.4
Net purchases, sales, issuances and settlements, assets	55.8	26.9	146	(3.1)
Transfers into Level 3, assets	42.5	61.5	58.1	190.1
Transfers out of Level 3, assets	(127.8)	(77.3)	(228.1)	(234.1)
Ending balance, assets	246.4	475.5	246.4	475.5
Changes in unrealized gains (losses) included in net income relating to positions still held, assets	(1.1)	(4.3)	(1.7)	(4.8)
Gross purchases, sales, issuances and settlements
Purchases, assets	70.5	94.1	205	161.5
Sales, assets	(5.7)	(37.5)	(9.9)	(106.6)
Settlements, assets	(9)	(29.7)	(49.1)	(58)
Net purchases, sales, issuances and settlements, assets	55.8	26.9	146	(3.1)
Fixed maturities | Trading
Changes in Level 3 fair value measurements rollforward, assets and liabilities
Beginning balance, assets	3.7			92.9
Total realized/unrealized gains (losses) included in net income, assets				(2.4)
Net purchases, sales, issuances and settlements, assets			3.7	(92.4)
Transfers into Level 3, assets				1.9
Transfers out of Level 3, assets	(3.7)		(3.7)
Gross purchases, sales, issuances and settlements
Purchases, assets			3.7
Settlements, assets				(92.4)
Net purchases, sales, issuances and settlements, assets			3.7	(92.4)
Non-U.S. governments | Available-for-sale
Changes in Level 3 fair value measurements rollforward, assets and liabilities
Beginning balance, assets	6.6	65.1	7.4	62.1
Total realized/unrealized gains (losses) included in net income, assets		(0.1)		(0.2)
Total realized/unrealized gains (losses) included in other comprehensive income, assets		(0.1)	(0.1)	0.1
Net purchases, sales, issuances and settlements, assets	(0.4)	(10.7)	(1.1)	(7.8)
Transfers out of Level 3, assets	(1.3)		(1.3)
Ending balance, assets	4.9	54.2	4.9	54.2
Changes in unrealized gains (losses) included in net income relating to positions still held, assets		(0.1)		(0.2)
Gross purchases, sales, issuances and settlements
Purchases, assets		18.9		40.7
Sales, assets		(29.3)		(47.5)
Settlements, assets	(0.4)	(0.3)	(1.1)	(1)
Net purchases, sales, issuances and settlements, assets	(0.4)	(10.7)	(1.1)	(7.8)
Corporate debt securities | Available-for-sale
Changes in Level 3 fair value measurements rollforward, assets and liabilities
Beginning balance, assets	86	202.9	128	259.1
Total realized/unrealized gains (losses) included in net income, assets	(0.8)	(0.3)	0.3	(2.2)
Total realized/unrealized gains (losses) included in other comprehensive income, assets	0.2	3.7	(0.1)	3.3
Net purchases, sales, issuances and settlements, assets	(11.2)	35.8	(14.8)	(3)
Transfers into Level 3, assets			1	22.2
Transfers out of Level 3, assets	(9.5)		(49.7)	(37.3)
Ending balance, assets	64.7	242.1	64.7	242.1
Changes in unrealized gains (losses) included in net income relating to positions still held, assets	(1)	(0.2)	(1)	(0.6)
Gross purchases, sales, issuances and settlements
Purchases, assets	0.6	65.3	12.6	97.9
Sales, assets	(5.7)	(8.2)	(9.9)	(59.1)
Settlements, assets	(6.1)	(21.3)	(17.5)	(41.8)
Net purchases, sales, issuances and settlements, assets	(11.2)	35.8	(14.8)	(3)
Commercial mortgage-backed securities | Available-for-sale
Changes in Level 3 fair value measurements rollforward, assets and liabilities
Beginning balance, assets	10.1	61.5	10.6	71.1
Total realized/unrealized gains (losses) included in net income, assets		(4.1)	(2.5)	(9.8)
Total realized/unrealized gains (losses) included in other comprehensive income, assets	(0.3)	1.4	0.2	11.2
Net purchases, sales, issuances and settlements, assets		(0.2)	(0.1)	(0.7)
Transfers into Level 3, assets		6.1	2.5	24.1
Transfers out of Level 3, assets		(50)	(0.9)	(81.2)
Ending balance, assets	9.8	14.7	9.8	14.7
Changes in unrealized gains (losses) included in net income relating to positions still held, assets		(4)		(4)
Gross purchases, sales, issuances and settlements
Settlements, assets		(0.2)	(0.1)	(0.7)
Net purchases, sales, issuances and settlements, assets		(0.2)	(0.1)	(0.7)
Collateralized debt obligations | Available-for-sale
Changes in Level 3 fair value measurements rollforward, assets and liabilities
Beginning balance, assets	80.2	128.1	125	33.6
Total realized/unrealized gains (losses) included in net income, assets	(0.2)		(0.8)
Total realized/unrealized gains (losses) included in other comprehensive income, assets	(0.2)	3.5	0.4	2.8
Net purchases, sales, issuances and settlements, assets	64.4	2.2	66.7	9.1
Transfers into Level 3, assets	42.5	55.4	54.6	143.7
Transfers out of Level 3, assets	(68.1)	(27.3)	(127.3)	(27.3)
Ending balance, assets	118.6	161.9	118.6	161.9
Changes in unrealized gains (losses) included in net income relating to positions still held, assets	(0.1)		(0.7)
Gross purchases, sales, issuances and settlements
Purchases, assets	65.5	9.9	93.6	22.9
Settlements, assets	(1.1)	(7.7)	(26.9)	(13.8)
Net purchases, sales, issuances and settlements, assets	64.4	2.2	66.7	9.1
Other debt obligations | Available-for-sale
Changes in Level 3 fair value measurements rollforward, assets and liabilities
Beginning balance, assets	94.8	2.8	2.3	91.5
Total realized/unrealized gains (losses) included in other comprehensive income, assets	(0.5)		(0.3)
Net purchases, sales, issuances and settlements, assets	3	(0.2)	95.3	(0.7)
Transfers into Level 3, assets				0.1
Transfers out of Level 3, assets	(48.9)		(48.9)	(88.3)
Ending balance, assets	48.4	2.6	48.4	2.6
Gross purchases, sales, issuances and settlements
Purchases, assets	4.4		98.8
Settlements, assets	(1.4)	(0.2)	(3.5)	(0.7)
Net purchases, sales, issuances and settlements, assets	3	(0.2)	95.3	(0.7)
Equity securities
Changes in Level 3 fair value measurements rollforward, assets and liabilities
Beginning balance, assets			2.7
Total realized/unrealized gains (losses) included in net income, assets			12.9
Net purchases, sales, issuances and settlements, assets			(15.6)
Gross purchases, sales, issuances and settlements
Sales, assets			(15.6)
Net purchases, sales, issuances and settlements, assets			(15.6)
Equity securities | Available-for-sale
Changes in Level 3 fair value measurements rollforward, assets and liabilities
Beginning balance, assets		2.7		2.7
Ending balance, assets		2.7		2.7
Equity securities | Trading
Changes in Level 3 fair value measurements rollforward, assets and liabilities
Net purchases, sales, issuances and settlements, assets				(0.7)
Transfers into Level 3, assets				0.7
Gross purchases, sales, issuances and settlements
Settlements, assets				(0.7)
Net purchases, sales, issuances and settlements, assets				(0.7)
Derivative assets
Changes in Level 3 fair value measurements rollforward, assets and liabilities
Beginning balance, assets	16	31.6	24.2	33.9
Total realized/unrealized gains (losses) included in net income, assets	(3.9)	(3)	(15.6)	(7.1)
Net purchases, sales, issuances and settlements, assets	0.2	0.7	3.7	2.5
Ending balance, assets	12.3	29.3	12.3	29.3
Changes in unrealized gains (losses) included in net income relating to positions still held, assets	(3.6)	(2.4)	(14.4)	(6)
Gross purchases, sales, issuances and settlements
Purchases, assets		0.3	3.1	2.5
Sales, assets	0.2	0.4	0.6
Net purchases, sales, issuances and settlements, assets	0.2	0.7	3.7	2.5
Other investments
Changes in Level 3 fair value measurements rollforward, assets and liabilities
Beginning balance, assets	13.2	35.2	6.5	36.9
Total realized/unrealized gains (losses) included in net income, assets	(0.1)	(0.4)	1.7	1.5
Net purchases, sales, issuances and settlements, assets	4.1	0.1	9	(3.5)
Ending balance, assets	17.2	34.9	17.2	34.9
Changes in unrealized gains (losses) included in net income relating to positions still held, assets		(0.3)	1.8	1.6
Gross purchases, sales, issuances and settlements
Purchases, assets	4.1	0.1	9	0.6
Sales, assets				(4.1)
Net purchases, sales, issuances and settlements, assets	4.1	0.1	9	(3.5)
Separate account assets
Changes in Level 3 fair value measurements rollforward, assets and liabilities
Beginning balance, assets	8,291.5	7,412.9	7,651.4	7,354.8
Total realized/unrealized gains (losses) included in net income, assets	315.6	234.9	725.4	593.1
Total realized/unrealized gains (losses) included in other comprehensive income, assets	0.4		(0.2)	(0.9)
Net purchases, sales, issuances and settlements, assets	(88.4)	(171)	142.9	(449.9)
Transfers into Level 3, assets	2.3	0.5	2.3	2.6
Transfers out of Level 3, assets	(36.2)	(14)	(36.6)	(36.4)
Ending balance, assets	8,485.2	7,463.3	8,485.2	7,463.3
Changes in unrealized gains (losses) included in net income relating to positions still held, assets	304.4	183.1	696	510.3
Gross purchases, sales, issuances and settlements
Purchases, assets	42	79.7	613.8	259
Sales, assets	(276)	(193.8)	(504.5)	(575.2)
Issuances, assets	(28)	(61.1)	(133.5)	(196.8)
Settlements, assets	173.6	4.2	167.1	63.1
Net purchases, sales, issuances and settlements, assets	$ (88.4)	$ (171)	$ 142.9	$ (449.9)

Fair Value Measurements - Trans

Fair Value Measurements - Transfers (Details) - Recurring Fair Value Measurements - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Fixed maturities | Available-for-sale
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3	$ 42.5	$ 61.5	$ 58.1	$ 190.1
Transfers out of Level 3 into Level 2	127.8	77.3	228.1	234.1
Fixed maturities | Trading
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3				1.9
Transfers out of Level 3 into Level 2	3.7		3.7
Non-U.S. governments | Available-for-sale
Fair Value Hierarchy Levels Transfers
Transfers out of Level 3 into Level 2	1.3		1.3
Corporate debt securities | Available-for-sale
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3			1	22.2
Transfers out of Level 3 into Level 2	9.5		49.7	37.3
Commercial mortgage-backed securities | Available-for-sale
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3		6.1	2.5	24.1
Transfers out of Level 3 into Level 2		50	0.9	81.2
Collateralized debt obligations | Available-for-sale
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3	42.5	55.4	54.6	143.7
Transfers out of Level 3 into Level 2	68.1	27.3	127.3	27.3
Other debt obligations | Available-for-sale
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3				0.1
Transfers out of Level 3 into Level 2	48.9		48.9	88.3
Equity securities | Trading
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3				0.7
Separate account assets
Fair Value Hierarchy Levels Transfers
Transfers out of Level 1 into Level 2	0.7	5.9	293.2	12.3
Transfers out of Level 2 into Level 1		5.4	0.8	5.6
Transfers out of Level 2 into Level 3	2.3	0.5	2.3	2.6
Transfers out of Level 3 into Level 1			0.2
Transfers out of Level 3 into Level 2	$ 36.2	$ 14	$ 36.4	$ 36.4

Fair Value Measurements - Quant

Fair Value Measurements - Quantitative Information for Level 3 Measurements (Details) - Recurring Fair Value Measurements $ in Millions	Sep. 30, 2018USD ($)item	Dec. 31, 2017USD ($)item
Unobservable inputs
Assets measured at fair value | $	$ 226,870.7	$ 223,689
Liabilities measured at fair value | $	(409.2)	(688.4)
Fair value hierarchy Level 3
Unobservable inputs
Assets measured at fair value | $	8,761.1	7,958.1
Liabilities measured at fair value | $	70.6	(166.4)
Fair value hierarchy Level 3 | Investment contracts
Unobservable inputs
Liabilities measured at fair value | $	$ 81.9	$ (160.3)
Embedded derivative, Valuation technique	us-gaap:ValuationTechniqueDiscountedCashFlowMember	us-gaap:ValuationTechniqueDiscountedCashFlowMember
Fair value hierarchy Level 3 | Investment contracts | Long duration interest rate | Minimum
Unobservable inputs
Embedded derivative, Input	0.031	0.025
Fair value hierarchy Level 3 | Investment contracts | Long duration interest rate | Maximum
Unobservable inputs
Embedded derivative, Input	0.032	0.027
Fair value hierarchy Level 3 | Investment contracts | Long-term equity market volatility | Minimum
Unobservable inputs
Embedded derivative, Input	0.140	0.187
Fair value hierarchy Level 3 | Investment contracts | Long-term equity market volatility | Maximum
Unobservable inputs
Embedded derivative, Input	0.285	0.411
Fair value hierarchy Level 3 | Investment contracts | Non-performance risk | Minimum
Unobservable inputs
Embedded derivative, Input	0.003	0.002
Fair value hierarchy Level 3 | Investment contracts | Non-performance risk | Maximum
Unobservable inputs
Embedded derivative, Input	0.013	0.012
Fair value hierarchy Level 3 | Investment contracts | Lapse rate | Minimum
Unobservable inputs
Embedded derivative, Input	0.013	0.013
Fair value hierarchy Level 3 | Investment contracts | Lapse rate | Maximum
Unobservable inputs
Embedded derivative, Input	0.160	0.160
Fair value hierarchy Level 3 | Non-U.S. governments | Available-for-sale
Unobservable inputs
Assets measured at fair value | $	$ 4.9	$ 6.1
Fixed maturities, available-for-sale, Valuation technique	us-gaap:ValuationTechniqueDiscountedCashFlowMember	us-gaap:ValuationTechniqueDiscountedCashFlowMember
Fair value hierarchy Level 3 | Non-U.S. governments | Available-for-sale | Discount rate
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.036	0.027
Fair value hierarchy Level 3 | Non-U.S. governments | Available-for-sale | Discount rate | Weighted average input
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.036	0.027
Fair value hierarchy Level 3 | Non-U.S. governments | Available-for-sale | Illiquidity premium
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.0050	0.0050
Fair value hierarchy Level 3 | Non-U.S. governments | Available-for-sale | Illiquidity premium | Weighted average input
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.0050	0.0050
Fair value hierarchy Level 3 | Non-U.S. governments | Available-for-sale | Comparability adjustment
Unobservable inputs
Fixed maturities, available-for-sale, Input	(0.0025)	(0.0025)
Fair value hierarchy Level 3 | Non-U.S. governments | Available-for-sale | Comparability adjustment | Weighted average input
Unobservable inputs
Fixed maturities, available-for-sale, Input	(0.0025)	(0.0025)
Fair value hierarchy Level 3 | Corporate debt securities | Available-for-sale
Unobservable inputs
Assets measured at fair value | $	$ 25.5	$ 51
Fixed maturities, available-for-sale, Valuation technique	us-gaap:ValuationTechniqueDiscountedCashFlowMember	us-gaap:ValuationTechniqueDiscountedCashFlowMember
Fair value hierarchy Level 3 | Corporate debt securities | Available-for-sale | Discount rate | Minimum
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.032	0.019
Fair value hierarchy Level 3 | Corporate debt securities | Available-for-sale | Discount rate | Maximum
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.039	0.075
Fair value hierarchy Level 3 | Corporate debt securities | Available-for-sale | Discount rate | Weighted average input
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.037	0.046
Fair value hierarchy Level 3 | Corporate debt securities | Available-for-sale | Illiquidity premium | Minimum
Unobservable inputs
Fixed maturities, available-for-sale, Input	0	0
Fair value hierarchy Level 3 | Corporate debt securities | Available-for-sale | Illiquidity premium | Maximum
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.0060	0.0060
Fair value hierarchy Level 3 | Corporate debt securities | Available-for-sale | Illiquidity premium | Weighted average input
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.0036	0.0021
Fair value hierarchy Level 3 | Commercial mortgage-backed securities | Available-for-sale
Unobservable inputs
Assets measured at fair value | $	$ 0.5	$ 0.5
Fixed maturities, available-for-sale, Valuation technique	us-gaap:ValuationTechniqueDiscountedCashFlowMember	us-gaap:ValuationTechniqueDiscountedCashFlowMember
Fair value hierarchy Level 3 | Commercial mortgage-backed securities | Available-for-sale | Discount rate
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.250	0.060
Fair value hierarchy Level 3 | Commercial mortgage-backed securities | Available-for-sale | Discount rate | Weighted average input
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.250	0.060
Fair value hierarchy Level 3 | Commercial mortgage-backed securities | Available-for-sale | Probability of default
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.950	0.850
Fair value hierarchy Level 3 | Commercial mortgage-backed securities | Available-for-sale | Probability of default | Weighted average input
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.950	0.850
Fair value hierarchy Level 3 | Commercial mortgage-backed securities | Available-for-sale | Potential loss severity
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.280	0.320
Fair value hierarchy Level 3 | Commercial mortgage-backed securities | Available-for-sale | Potential loss severity | Weighted average input
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.280	0.320
Fair value hierarchy Level 3 | Collateralized debt obligations | Comparability adjustment | Minimum
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.0111
Fair value hierarchy Level 3 | Collateralized debt obligations | Comparability adjustment | Maximum
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.0165
Fair value hierarchy Level 3 | Collateralized debt obligations | Comparability adjustment | Weighted average input
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.0118
Fair value hierarchy Level 3 | Collateralized debt obligations | Available-for-sale
Unobservable inputs
Assets measured at fair value | $	$ 65.4
Fixed maturities, available-for-sale, Valuation technique	us-gaap:ValuationTechniqueDiscountedCashFlowMember
Fair value hierarchy Level 3 | Collateralized debt obligations | Available-for-sale | Discount rate | Minimum
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.030
Fair value hierarchy Level 3 | Collateralized debt obligations | Available-for-sale | Discount rate | Maximum
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.031
Fair value hierarchy Level 3 | Collateralized debt obligations | Available-for-sale | Discount rate | Weighted average input
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.030
Fair value hierarchy Level 3 | Other debt obligations | Available-for-sale
Unobservable inputs
Assets measured at fair value | $	$ 1.8	$ 2.3
Fixed maturities, available-for-sale, Valuation technique	us-gaap:ValuationTechniqueDiscountedCashFlowMember	us-gaap:ValuationTechniqueDiscountedCashFlowMember
Fair value hierarchy Level 3 | Other debt obligations | Available-for-sale | Discount rate
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.050	0.050
Fair value hierarchy Level 3 | Other debt obligations | Available-for-sale | Discount rate | Weighted average input
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.050	0.050
Fair value hierarchy Level 3 | Other debt obligations | Available-for-sale | Illiquidity premium
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.0500	0.0500
Fair value hierarchy Level 3 | Other debt obligations | Available-for-sale | Illiquidity premium | Weighted average input
Unobservable inputs
Fixed maturities, available-for-sale, Input	0.0500	0.0500
Fair value hierarchy Level 3 | Separate account assets
Unobservable inputs
Assets measured at fair value | $	$ 8,303.2	$ 7,484.6
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, mortgage loans | Discount rate | Minimum
Unobservable inputs
Separate account assets, input	0.030	0.023
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, mortgage loans | Discount rate | Maximum
Unobservable inputs
Separate account assets, input	0.042	0.080
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, mortgage loans | Discount rate | Weighted average input
Unobservable inputs
Separate account assets, input	0.041	0.048
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, mortgage loans | Illiquidity premium | Minimum
Unobservable inputs
Separate account assets, input	0	0
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, mortgage loans | Illiquidity premium | Maximum
Unobservable inputs
Separate account assets, input	0.0060	0.0060
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, mortgage loans | Illiquidity premium | Weighted average input
Unobservable inputs
Separate account assets, input	0.0054	0.0017
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, mortgage loans | Credit spread rate | Minimum
Unobservable inputs
Separate account assets, input	0.0060	0.0062
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, mortgage loans | Credit spread rate | Maximum
Unobservable inputs
Separate account assets, input	0.0160	0.0690
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, mortgage loans | Credit spread rate | Weighted average input
Unobservable inputs
Separate account assets, input	0.0128	0.0293
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, real estate | Discount rate | Minimum
Unobservable inputs
Separate account assets, input	0.056	0.058
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, real estate | Discount rate | Maximum
Unobservable inputs
Separate account assets, input	0.115	0.172
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, real estate | Discount rate | Weighted average input
Unobservable inputs
Separate account assets, input	0.068	0.069
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, real estate | Terminal capitalization rate | Minimum
Unobservable inputs
Separate account assets, input	0.043	0.043
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, real estate | Terminal capitalization rate | Maximum
Unobservable inputs
Separate account assets, input	0.093	0.093
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, real estate | Terminal capitalization rate | Weighted average input
Unobservable inputs
Separate account assets, input	0.058	0.061
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, real estate | Average market rent growth rate | Minimum
Unobservable inputs
Separate account assets, input	0.018	0.005
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, real estate | Average market rent growth rate | Maximum
Unobservable inputs
Separate account assets, input	0.046	0.047
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, real estate | Average market rent growth rate | Weighted average input
Unobservable inputs
Separate account assets, input	0.030	0.029
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, real estate debt | Loan to value | Minimum
Unobservable inputs
Separate account assets, input	0.110	0.121
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, real estate debt | Loan to value | Maximum
Unobservable inputs
Separate account assets, input	0.675	0.714
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, real estate debt | Loan to value | Weighted average input
Unobservable inputs
Separate account assets, input	0.458	0.458
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, real estate debt | Market interest rate | Minimum
Unobservable inputs
Separate account assets, input	0.037	0.031
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, real estate debt | Market interest rate | Maximum
Unobservable inputs
Separate account assets, input	0.063	0.045
Fair value hierarchy Level 3 | Separate account assets | Discounted cash flow, real estate debt | Market interest rate | Weighted average input
Unobservable inputs
Separate account assets, input	0.043	0.038

Fair Value Measurements - Ass_2

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Nonrecurring Basis (Details) - Nonrecurring Fair Value Measurements - Fair value hierarchy Level 3 - Mortgage loans - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Assets and liabilities measured at fair value on a nonrecurring basis
Fair value of assets measured on nonrecurring basis	$ 6.1	$ 0.8	$ 6.1	$ 0.8
Net realized capital gains (losses)
Assets and liabilities measured at fair value on a nonrecurring basis
Net (gain) loss due to change in fair value of assets measured on nonrecurring basis	$ 0.1	$ 0	$ 0.7	$ 0.3

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value Option on Consolidated VIEs and Equity Method Investments (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)item	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)item	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)item
Commercial Mortgage Loans of Consolidated VIEs
Fair Value Option, Quantitative Disclosures
Fair value of assets for which fair value option was elected	$ 6.9		$ 6.9		$ 9.3
Contractual principal amounts of assets for which the fair value option was elected	$ 7		$ 7		$ 9.2
Number of loans which are more than 90 days past due or in nonaccrual status | item	0		0		0
Pre-tax gain (loss) due to change in fair value of assets and liabilities for which the fair value option was elected	$ (0.1)	$ (0.1)	$ (0.2)	$ (0.3)
Interest income	0.1	0.2	0.5	0.7
Obligations of Consolidated VIEs
Fair Value Option, Quantitative Disclosures
Credit risk portion of pre-tax gain (loss) due to change in fair value of liabilities for which the fair value option was elected				(0.1)
Pre-tax gain (loss) due to change in fair value of assets and liabilities for which the fair value option was elected				(0.1)
Interest expense				0.3
Real Estate Ventures
Fair Value Option, Quantitative Disclosures
Fair value of assets for which fair value option was elected	$ 17.2		17.2		$ 6.5
Pre-tax gain (loss) due to change in fair value of assets and liabilities for which the fair value option was elected		(0.3)	$ 1.8	1.6
Investment Funds
Fair Value Option, Quantitative Disclosures
Fair value of assets for which fair value option was elected					$ 45.2
Pre-tax gain (loss) due to change in fair value of assets and liabilities for which the fair value option was elected		$ 0.4		0.6
Dividend income				$ 1.9

Fair Value Measurements - Finan

Fair Value Measurements - Financial Instruments Not Reported at Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Assets (liabilities)
Mortgage loans	$ 14,919.7	$ 14,150.5
Policy loans	804.4	808.3
Short-term debt	(36.1)	(39.5)
Long-term debt	(3,245.5)	(3,178.4)
Carrying amount
Assets (liabilities)
Mortgage loans	14,919.7	14,150.5
Policy loans	804.4	808.3
Other investments	247.4	236.8
Cash and cash equivalents not required to be reported at fair value	1,123.7	677.5
Investment contracts	(32,863.9)	(31,003)
Short-term debt	(36.1)	(39.5)
Long-term debt	(3,245.5)	(3,178.4)
Separate account liabilities	(147,429.4)	(145,552.5)
Bank deposits	(515.4)	(2,336.4)
Cash collateral payable	(61.6)	(125.8)
Assets (liabilities) measured at fair value
Assets (liabilities)
Mortgage loans	14,855.1	14,443.2
Policy loans	939.2	998.4
Other investments	239.7	234
Cash and cash equivalents not required to be reported at fair value	1,123.7	677.5
Investment contracts	(31,651.5)	(30,468.8)
Short-term debt	(36.1)	(39.5)
Long-term debt	(3,275.5)	(3,442.5)
Separate account liabilities	(146,205.9)	(144,300.5)
Bank deposits	(502.5)	(2,328.9)
Cash collateral payable	(61.6)	(125.8)
Assets (liabilities) measured at fair value | Fair value hierarchy Level 1
Assets (liabilities)
Cash and cash equivalents not required to be reported at fair value	1,070.9	659.9
Bank deposits		(1,780.3)
Cash collateral payable	(61.6)	(125.8)
Assets (liabilities) measured at fair value | Fair value hierarchy Level 2
Assets (liabilities)
Other investments	156.5	159.4
Cash and cash equivalents not required to be reported at fair value	52.8	17.6
Investment contracts	(4,647)	(4,736.1)
Short-term debt	(36.1)	(39.5)
Long-term debt	(3,161.5)	(3,393.5)
Bank deposits	(502.5)	(548.6)
Assets (liabilities) measured at fair value | Fair value hierarchy Level 3
Assets (liabilities)
Mortgage loans	14,855.1	14,443.2
Policy loans	939.2	998.4
Other investments	83.2	74.6
Investment contracts	(27,004.5)	(25,732.7)
Long-term debt	(114)	(49)
Separate account liabilities	$ (146,205.9)	$ (144,300.5)

Segment Information - Reconcili

Segment Information - Reconciliation of Segment Assets to Consolidated (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Segment Information: Assets
Total assets	$ 258,758.3	$ 253,941.2
Retirement and Income Solutions
Segment Information: Assets
Total assets	176,653.1	169,757.8
Principal Global Investors
Segment Information: Assets
Total assets	2,362.7	2,322.9
Principal International
Segment Information: Assets
Total assets	49,706.7	51,684
U.S. Insurance Solutions
Segment Information: Assets
Total assets	25,507.5	25,092.9
Corporate
Segment Information: Assets
Total assets	$ 4,528.3	$ 5,083.6

Segment Information - Reconci_2

Segment Information - Reconciliation of Segment Operating Revenues and Earnings to Consolidated (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating Revenue And Profit (Loss) From Segments To Consolidated
Net realized capital gains (losses), net of related revenue adjustments	$ (20.2)	$ 668.7	$ (11.8)	$ 525.5
Total revenues	4,348.1	4,627.8	10,466.6	10,855.5
Pre-tax net realized capital gains (losses), as adjusted	(27.9)	720.7	(2.9)	570.6
Income (loss) before income taxes	569.1	1,157.8	1,541.5	1,937.4
Retirement and Income Solutions
Operating Revenue And Profit (Loss) From Segments To Consolidated
Inter-segment revenues	103.9	103.7	304.5	296.6
Principal Global Investors
Operating Revenue And Profit (Loss) From Segments To Consolidated
Inter-segment revenues	69.2	68.2	199.2	188.7
Operating Segments
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	4,366.7	3,978.2	10,520.1	10,392.4
Pre-tax operating earnings (losses)	593.4	452.9	1,575.6	1,420.2
Operating Segments | Retirement and Income Solutions
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	2,438.6	2,370.8	5,071.5	5,537.2
Pre-tax operating earnings (losses)	259.8	210.1	709.3	698.1
Operating Segments | Retirement and Income Solutions | Retirement and Income Solutions - Fee
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	469.2	455.3	1,385.6	1,357.2
Operating Segments | Retirement and Income Solutions | Retirement and Income Solutions - Spread
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	1,969.4	1,915.5	3,685.9	4,180
Operating Segments | Principal Global Investors
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	632.8	367.5	1,380.9	1,068.9
Pre-tax operating earnings (losses)	215.4	130.2	452.7	345.6
Operating Segments | Principal International
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	287.4	274.7	1,060.1	915.4
Pre-tax operating earnings (losses)	32.4	72.4	201.5	251.7
Operating Segments | U.S. Insurance Solutions
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	1,029.3	985.5	3,046	2,912.5
Pre-tax operating earnings (losses)	118.2	83.2	336	273.8
Operating Segments | U.S. Insurance Solutions | Specialty Benefits insurance
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	592.6	550.1	1,731.5	1,615.9
Operating Segments | U.S. Insurance Solutions | Individual Life insurance
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	436.7	435.4	1,314.6	1,296.7
Operating Segments | U.S. Insurance Solutions | U.S. Insurance Solutions Eliminations
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues			(0.1)	(0.1)
Operating Segments | Corporate
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	(21.4)	(20.3)	(38.4)	(41.6)
Pre-tax operating earnings (losses)	(32.4)	(43)	(123.9)	(149)
Reconciling Items
Operating Revenue And Profit (Loss) From Segments To Consolidated
Net realized capital gains (losses), net of related revenue adjustments	(20.2)	668.7	(11.8)	525.5
Revenue adjustments related to equity method investments	1.6	(19.1)	(41.7)	(62.4)
Pre-tax net realized capital gains (losses), as adjusted	(27.9)	720.7	(2.9)	570.6
Earnings adjustments related to equity method investments and noncontrolling interest	$ 3.6	$ (15.8)	$ (31.2)	$ (53.4)

Segment Information - Net Reali

Segment Information - Net Realized Capital Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Information: Net realized capital gains (losses), as adjusted
Net realized capital gains (losses)	$ (5.5)	$ 676.6	$ 36.8	$ 564.1
Derivative and hedging-related adjustments	(15.8)	(10.8)	(48.5)	(45.3)
Market value adjustments to fee revenues		(0.1)	0.1	(0.1)
Adjustments related to equity method investments	(0.9)	1.3	(4.9)	2.4
Adjustments related to sponsored investment funds	2.9	1.6	8	4.5
Recognition of front-end fee revenue	(0.9)	0.1	(3.3)	(0.1)
Net realized capital gains (losses), net of related revenue adjustments	(20.2)	668.7	(11.8)	525.5
Amortization of deferred acquisition costs and other actuarial balances	5.9	23.4	12.7	41.5
Capital (gains) losses distributed	(17.7)	(11.5)	(15.4)	(39.6)
Market value adjustments of embedded derivatives	4.1	40.1	11.6	43.2
Pre-tax net realized capital gains (losses), as adjusted	$ (27.9)	$ 720.7	$ (2.9)	$ 570.6

Revenues from Contracts with _3

Revenues from Contracts with Customers - Disaggregation by Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues from Contracts with Customers - Disaggregation of Revenues
Total fees and other revenues per consolidated statements of operations	$ 1,261.8	$ 987.1	$ 3,285.7	$ 2,882.8
Operating Segments
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	862.7	584	2,079.8	1,703.1
Operating Segments | Retirement and Income Solutions
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	66.5	65.7	200.5	198.9
Operating Segments | Principal Global Investors
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	623.4	359.9	1,354.8	1,044.2
Fees and other revenues not within the scope of revenue recognition guidance	8.4	6.8	22.4	21.4
Total fees and other revenues per consolidated statements of operations	631.8	366.7	1,377.2	1,065.6
Operating Segments | Principal International
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	118	109	362.2	315.5
Fees and other revenues not within the scope of revenue recognition guidance	1.7	1.7	5.5	5.1
Total fees and other revenues per consolidated statements of operations	119.7	110.7	367.7	320.6
Operating Segments | U.S. Insurance Solutions
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	14.6	12.3	41.2	37.8
Operating Segments | Corporate
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	40.2	37.1	121.1	106.7
Fees and other revenues not within the scope of revenue recognition guidance	(84.3)	(80.5)	(241.6)	(215.7)
Total fees and other revenues per consolidated statements of operations	(44.1)	(43.4)	(120.5)	(109)
Operating Segments | Retirement and Income Solutions - Fee | Retirement and Income Solutions
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	63.7	63.2	192.3	191.4
Fees and other revenues not within the scope of revenue recognition guidance	288.3	282.7	857.5	821.2
Total fees and other revenues per consolidated statements of operations	352	345.9	1,049.8	1,012.6
Operating Segments | Retirement and Income Solutions - Spread | Retirement and Income Solutions
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	2.8	2.5	8.2	7.5
Fees and other revenues not within the scope of revenue recognition guidance	3.4	3.9	9	11.9
Total fees and other revenues per consolidated statements of operations	6.2	6.4	17.2	19.4
Operating Segments | Specialty Benefits insurance | U.S. Insurance Solutions
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	3.6	3.4	11.1	10.3
Fees and other revenues not within the scope of revenue recognition guidance	5.2	5.2	15.6	16
Total fees and other revenues per consolidated statements of operations	8.8	8.6	26.7	26.3
Operating Segments | Individual Life insurance | U.S. Insurance Solutions
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	11	8.9	30.2	27.6
Fees and other revenues not within the scope of revenue recognition guidance	177.3	183.3	540.7	520
Total fees and other revenues per consolidated statements of operations	188.3	192.2	570.9	547.6
Operating Segments | U.S. Insurance Solutions Eliminations | U.S. Insurance Solutions
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers			(0.1)	(0.1)
Reconciling Items
Revenues from Contracts with Customers - Disaggregation of Revenues
Fees and other revenues not within the scope of revenue recognition guidance	400	$ 403.1	1,209.1	1,179.9
Pre-tax other adjustments	$ (0.9)		$ (3.2)	$ (0.2)

Revenues from Contracts with _4

Revenues from Contracts with Customers - Disaggregation within Segments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues from Contracts with Customers - Disaggregation of Revenues
Total fees and other revenues	$ 1,261.8	$ 987.1	$ 3,285.7	$ 2,882.8
Premiums and other considerations	2,172.4	2,126.1	4,433.4	4,826.8
Net investment income (loss)	919.4	838	2,710.7	2,581.8
Operating Segments
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	862.7	584	2,079.8	1,703.1
Total operating revenues	4,366.7	3,978.2	10,520.1	10,392.4
Operating Segments | Retirement and Income Solutions
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	66.5	65.7	200.5	198.9
Total operating revenues	2,438.6	2,370.8	5,071.5	5,537.2
Operating Segments | Retirement and Income Solutions | Retirement and Income Solutions - Fee
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	63.7	63.2	192.3	191.4
Fees and other revenues not within the scope of revenue recognition guidance	288.3	282.7	857.5	821.2
Total fees and other revenues	352	345.9	1,049.8	1,012.6
Premiums and other considerations	1.1	0.8	3.5	2.6
Net investment income (loss)	116.1	108.6	332.3	342
Total operating revenues	469.2	455.3	1,385.6	1,357.2
Operating Segments | Retirement and Income Solutions | Retirement and Income Solutions - Fee | Administrative service fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	63.2	62.6	191.1	190.2
Operating Segments | Retirement and Income Solutions | Retirement and Income Solutions - Fee | Other fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	0.5	0.6	1.2	1.2
Operating Segments | Retirement and Income Solutions | Retirement and Income Solutions - Spread
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	2.8	2.5	8.2	7.5
Fees and other revenues not within the scope of revenue recognition guidance	3.4	3.9	9	11.9
Total fees and other revenues	6.2	6.4	17.2	19.4
Premiums and other considerations	1,495.7	1,495.3	2,339.1	2,932.9
Net investment income (loss)	467.5	413.8	1,329.6	1,227.7
Total operating revenues	1,969.4	1,915.5	3,685.9	4,180
Operating Segments | Retirement and Income Solutions | Retirement and Income Solutions - Spread | Deposit account fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	2.8	2.5	8.2	7.5
Operating Segments | Principal Global Investors
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	623.4	359.9	1,354.8	1,044.2
Fees and other revenues not within the scope of revenue recognition guidance	8.4	6.8	22.4	21.4
Total fees and other revenues	631.8	366.7	1,377.2	1,065.6
Net investment income (loss)	1	0.8	3.7	3.3
Total operating revenues	632.8	367.5	1,380.9	1,068.9
Operating Segments | Principal Global Investors | Management fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	317.6	309.1	946.1	901.3
Operating Segments | Principal Global Investors | Other fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	305.8	50.8	408.7	142.9
Performance fee recognized resulting from realignment of a real estate investment team	253.1
Operating Segments | Principal International
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	118	109	362.2	315.5
Fees and other revenues not within the scope of revenue recognition guidance	1.7	1.7	5.5	5.1
Total fees and other revenues	119.7	110.7	367.7	320.6
Premiums and other considerations	55.6	43.3	255.1	150.7
Net investment income (loss)	112.1	120.7	437.3	444.1
Total operating revenues	287.4	274.7	1,060.1	915.4
Operating Segments | Principal International | Latin America
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	92	81.7	281	236.6
Operating Segments | Principal International | Asia
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	26	27.4	81.4	79.3
Operating Segments | Principal International | Principal International Corporate / Regional Office
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	0.2	0.2	0.8	0.6
Operating Segments | Principal International | Geographical Eliminations
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	(0.2)	(0.3)	(1)	(1)
Operating Segments | Principal International | Management fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	117.2	106.5	359.1	306.4
Operating Segments | Principal International | Other fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	0.8	2.5	3.1	9.1
Operating Segments | U.S. Insurance Solutions
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	14.6	12.3	41.2	37.8
Total operating revenues	1,029.3	985.5	3,046	2,912.5
Operating Segments | U.S. Insurance Solutions | Specialty Benefits insurance
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	3.6	3.4	11.1	10.3
Fees and other revenues not within the scope of revenue recognition guidance	5.2	5.2	15.6	16
Total fees and other revenues	8.8	8.6	26.7	26.3
Premiums and other considerations	539.2	505.1	1,583.9	1,474.2
Net investment income (loss)	44.6	36.4	120.9	115.4
Total operating revenues	592.6	550.1	1,731.5	1,615.9
Operating Segments | U.S. Insurance Solutions | Specialty Benefits insurance | Administrative service fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	3.6	3.4	11.1	10.3
Operating Segments | U.S. Insurance Solutions | Individual Life insurance
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	11	8.9	30.2	27.6
Fees and other revenues not within the scope of revenue recognition guidance	177.3	183.3	540.7	520
Total fees and other revenues	188.3	192.2	570.9	547.6
Premiums and other considerations	80.8	81.6	251.8	266.4
Net investment income (loss)	167.6	161.6	491.9	482.7
Total operating revenues	436.7	435.4	1,314.6	1,296.7
Operating Segments | U.S. Insurance Solutions | Individual Life insurance | Administrative service fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	5.6	5.4	17.2	16
Operating Segments | U.S. Insurance Solutions | Individual Life insurance | Commission income
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	5.4	3.5	13	11.6
Operating Segments | Corporate
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	40.2	37.1	121.1	106.7
Fees and other revenues not within the scope of revenue recognition guidance	(84.3)	(80.5)	(241.6)	(215.7)
Total fees and other revenues	(44.1)	(43.4)	(120.5)	(109)
Net investment income (loss)	22.7	23.1	82.1	67.4
Total operating revenues	(21.4)	(20.3)	(38.4)	(41.6)
Operating Segments | Corporate | Other fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	8.8	7.5	26	22
Operating Segments | Corporate | Commission income
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	78.7	72.5	236.2	223.8
Operating Segments | Corporate | Revenue by type - Eliminations
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	$ (47.3)	$ (42.9)	$ (141.1)	$ (139.1)

Revenues from Contracts with _5

Revenues from Contracts with Customers - Contract Costs (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2018USD ($)
Contract costs
Contract cost asset	$ 141.4	$ 141.4
Practical expedient, incremental costs of obtaining a contract		true
Amortization expense of contract cost asset	$ 6.1	$ 17.7
Impairment loss for contract cost asset		$ 0

Stock-Based Compensation Plan_2

Stock-Based Compensation Plans - Stock-Based Awards (Details) - USD ($) shares in Millions, $ in Millions	9 Months Ended		153 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	May 20, 2014
Stock-Based Compensation Plans
Stock-Based Compensation Plans - Disclosures
Compensation cost	$ 60.7	$ 61.5
Related income tax benefit	13.2	20.9
Capitalized as part of an asset	$ 1.5	$ 1.6
Amended and Restated 2010 Stock Incentive Plan and 2005 Directors Stock Plan
Stock-Based Compensation Plans - Disclosures
Number of shares that will be granted				0
Stock Incentive Plan and Directors Stock Plan
Stock-Based Compensation Plans - Disclosures
Options granted (in shares)			0
Awards or units granted (in shares)			0
2014 Stock Incentive Plan and 2014 Directors Stock Plan
Stock-Based Compensation Plans - Disclosures
Maximum number of new shares of common stock available for grant (in shares)	7.3		7.3

Stock-Based Compensation Plan_3

Stock-Based Compensation Plans - Nonqualified Stock Options (Details) - Nonqualified Stock Options $ / shares in Units, shares in Millions, $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)$ / sharesshares
Stock-Based Compensation Plans - Disclosures
Options granted (in shares) | shares	0.8
Assumptions used to estimate fair value of stock options granted during period
Weighted-average expected volatility (as a percent)	26.00%
Weighted-average expected term	7 years
Weighted-average risk-free interest rate (as a percent)	2.80%
Weighted-average expected dividend yield (as a percent)	3.19%
Weighted-average estimated fair value of stock options granted (in dollars per share) | $ / shares	$ 14.85
Other nonqualified stock option disclosures
Unrecognized compensation costs | $	$ 4.5
Weighted-average service period over which unrecognized compensation costs will be recognized	1 year 2 months 12 days

Stock-Based Compensation Plan_4

Stock-Based Compensation Plans - Performance Share Awards and Restricted Stock Units (Details) $ / shares in Units, shares in Millions, $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)$ / sharesshares
Performance Share Awards
Change in nonvested units outstanding
Awards or units granted (in shares) | shares	0.2
Awards or units granted weighted-average grant-date fair value (in dollars per share) | $ / shares	$ 63.98
Other award and unit disclosures
Lower limit multiple of initial target awards (as a percent)	0.00%
Upper limit multiple of initial target awards (as a percent)	150.00%
Unrecognized compensation costs | $	$ 5
Weighted-average service period over which unrecognized compensation costs will be recognized	1 year 1 month 6 days
Restricted Stock Units
Change in nonvested units outstanding
Awards or units granted (in shares) | shares	0.8
Awards or units granted weighted-average grant-date fair value (in dollars per share) | $ / shares	$ 63.70
Other award and unit disclosures
Unrecognized compensation costs | $	$ 55
Weighted-average service period over which unrecognized compensation costs will be recognized	1 year 9 months 18 days

Stock-Based Compensation Plan_5

Stock-Based Compensation Plans - Employee Stock Purchase Plan (Details) - Employee Stock Purchase Plan shares in Millions	9 Months Ended
	Sep. 30, 2018$ / sharesshares
Stock-Based Compensation Plans - Disclosures
Share purchases under employee stock purchase plan (in shares)	0.5
Weighted-average fair value of discount on employee stock purchase plan (in dollars per share) | $ / shares	$ 10.02
Shares available to be issued under employee stock purchase plan (in shares)	2.4

Earnings Per Common Share (Deta

Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net income (loss)	$ 460	$ 813.2	$ 1,322	$ 1,481.6
Subtract:
Net income (loss) attributable to noncontrolling interest	3.7	3	12	13
Total	$ 456.3	$ 810.2	$ 1,310	$ 1,468.6
Weighted-average shares outstanding:
Basic	284.9	289.3	286.9	288.8
Dilutive effects:
Diluted	287.8	293.1	290	292.7
Net income (loss) per common share:
Basic	$ 1.60	$ 2.80	$ 4.57	$ 5.08
Diluted	$ 1.59	$ 2.76	$ 4.52	$ 5.02
Nonqualified Stock Options
Dilutive effects:
Stock-based compensation awards	0.9	1.7	1.1	1.8
Restricted Stock Units
Dilutive effects:
Stock-based compensation awards	1.7	1.9	1.7	1.9
Performance Share Awards
Dilutive effects:
Stock-based compensation awards	0.3	0.2	0.3	0.2

Condensed Consolidating Finan_3

Condensed Consolidating Financial Information - Guarantor, Statements of Financial Position (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Assets
Fixed maturities, available-for-sale	$ 60,447.2	$ 59,388.4
Fixed maturities, trading	642.1	566
Equity securities	1,885.8	1,866.6
Mortgage loans	14,919.7	14,150.5
Real estate	1,699.7	1,736.7
Policy loans	804.4	808.3
Investment in unconsolidated entities	846.6	820.6
Other investments	2,761.7	2,765.6
Cash and cash equivalents	2,926.7	2,470.8	$ 2,795	$ 2,719.6
Accrued investment income	660.7	610.6
Premiums due and other receivables	1,514.4	1,469.8
Deferred acquisition costs	3,671.9	3,540.7
Property and equipment	770.6	759.5
Goodwill	1,128.7	1,068.8
Other intangibles	1,353.9	1,314.7
Separate account assets	161,302.9	159,272.7
Other assets	1,421.3	1,330.9
Total assets	258,758.3	253,941.2
Liabilities
Contractholder funds	39,813.2	38,082.5
Future policy benefits and claims	34,818.3	33,019.3
Other policyholder funds	849.4	922.3
Short-term debt	36.1	39.5
Long-term debt	3,245.5	3,178.4
Income taxes currently payable	29.3	16.7
Deferred income taxes	911.4	1,092.5
Separate account liabilities	161,302.9	159,272.7
Other liabilities	5,835	5,294.1
Total liabilities	246,841.1	240,918
Redeemable noncontrolling interest	148.5	101.3	129.1	97.5
Stockholders' equity
Common stock	4.8	4.7
Additional paid-in capital	10,026.2	9,925.2
Retained earnings (accumulated deficit)	10,207.9	9,482.9
Accumulated other comprehensive income (loss)	(1,347.6)	165.5
Treasury stock, at cost	(7,190.5)	(6,729)
Total stockholders' equity attributable to Principal Financial Group, Inc.	11,700.8	12,849.3
Noncontrolling interest	67.9	72.6
Total stockholders' equity	11,768.7	12,921.9	12,067.3	10,293.8
Total liabilities and stockholders' equity	258,758.3	253,941.2
Principal Financial Group, Inc. Parent Only
Assets
Fixed maturities, available-for-sale	200.4
Fixed maturities, trading	314.5	351.8
Investment in unconsolidated entities	14,127.1	15,063.2
Other investments	10.5	10.2
Cash and cash equivalents	310.5	842.8	618.1	882.6
Accrued investment income	1.2	1.1
Other assets	414.2	389.7
Total assets	15,378.4	16,658.8
Liabilities
Long-term debt	3,129.3	3,128.1
Other liabilities	548.3	681.4
Total liabilities	3,677.6	3,809.5
Stockholders' equity
Common stock	4.8	4.7
Additional paid-in capital	10,026.2	9,925.2
Retained earnings (accumulated deficit)	10,207.9	9,482.9
Accumulated other comprehensive income (loss)	(1,347.6)	165.5
Treasury stock, at cost	(7,190.5)	(6,729)
Total stockholders' equity attributable to Principal Financial Group, Inc.	11,700.8	12,849.3
Total stockholders' equity	11,700.8	12,849.3
Total liabilities and stockholders' equity	15,378.4	16,658.8
Principal Life Insurance Company Only
Assets
Fixed maturities, available-for-sale	53,579	52,632.1
Fixed maturities, trading	168	49.1
Equity securities	93.3	100.1
Mortgage loans	14,133.1	13,389.6
Real estate	1.9	3
Policy loans	758.9	765.7
Investment in unconsolidated entities	2,554.1	2,658.2
Other investments	4,641.1	4,986
Cash and cash equivalents	1,311.2	426.7	781.3	675.1
Accrued investment income	587.3	538.8
Premiums due and other receivables	1,864.7	1,720.1
Deferred acquisition costs	3,657.7	3,331.5
Property and equipment	664.6	653.3
Goodwill	54.3	54.3
Other intangibles	20.2	21.6
Separate account assets	121,171.6	117,300.8
Other assets	1,150.9	1,177.5
Total assets	206,411.9	199,808.4
Liabilities
Contractholder funds	36,981.6	35,330.2
Future policy benefits and claims	29,515.6	27,794
Other policyholder funds	692.8	794.5
Deferred income taxes	344.5	731.6
Separate account liabilities	121,171.6	117,300.8
Other liabilities	8,698.1	7,910.9
Total liabilities	197,404.2	189,862
Stockholders' equity
Common stock	2.5	2.5
Additional paid-in capital	6,325.2	6,346
Retained earnings (accumulated deficit)	2,491.4	2,238.1
Accumulated other comprehensive income (loss)	188.6	1,359.8
Total stockholders' equity attributable to Principal Financial Group, Inc.	9,007.7	9,946.4
Total stockholders' equity	9,007.7	9,946.4
Total liabilities and stockholders' equity	206,411.9	199,808.4
Principal Financial Services, Inc. and Other Subsidiaries Combined
Assets
Fixed maturities, available-for-sale	7,035.2	7,120.3
Fixed maturities, trading	159.6	165.1
Equity securities	1,792.5	1,766.5
Mortgage loans	1,542.3	1,449.6
Real estate	1,697.8	1,733.7
Policy loans	45.5	42.6
Investment in unconsolidated entities	6,761.4	7,491.4
Other investments	2,262.1	2,231.9
Cash and cash equivalents	1,752.7	1,526.4	2,160.3	2,082.8
Accrued investment income	75.4	77.7
Premiums due and other receivables	3,663.2	3,362.4
Deferred acquisition costs	14.2	209.2
Property and equipment	106	106.2
Goodwill	1,074.4	1,014.5
Other intangibles	1,333.7	1,293.1
Separate account assets	40,131.3	41,971.9
Other assets	4,453.9	4,346
Total assets	73,901.2	75,908.5
Liabilities
Contractholder funds	3,180.9	3,092.8
Future policy benefits and claims	6,385.4	6,155
Other policyholder funds	158.6	128.6
Short-term debt	36.1	39.5
Long-term debt	839.1	710.4
Income taxes currently payable	185.4	166.2
Deferred income taxes	1,088.2	986.9
Separate account liabilities	40,131.3	41,971.9
Other liabilities	7,681.4	7,533.6
Total liabilities	59,686.4	60,784.9
Redeemable noncontrolling interest	148.5	101.3
Stockholders' equity
Additional paid-in capital	9,077.8	9,053.5
Retained earnings (accumulated deficit)	5,811.6	5,311.7
Accumulated other comprehensive income (loss)	(891)	579.4
Total stockholders' equity attributable to Principal Financial Group, Inc.	13,998.4	14,944.6
Noncontrolling interest	67.9	77.7
Total stockholders' equity	14,066.3	15,022.3
Total liabilities and stockholders' equity	73,901.2	75,908.5
Principal Financial Services, Inc. and Other Subsidiaries Combined | Nonqualified benefit plans
Stockholders' equity
Assets held in Rabbi trusts	687.1	643.3
Liabilities held in Rabbi trusts	558.4	524.7
Eliminations, Notes Guarantor
Assets
Fixed maturities, available-for-sale	(367.4)	(364)
Mortgage loans	(755.7)	(688.7)
Investment in unconsolidated entities	(22,596)	(24,392.2)
Other investments	(4,152)	(4,462.5)
Cash and cash equivalents	(447.7)	(325.1)	$ (764.7)	$ (920.9)
Accrued investment income	(3.2)	(7)
Premiums due and other receivables	(4,013.5)	(3,612.7)
Other assets	(4,597.7)	(4,582.3)
Total assets	(36,933.2)	(38,434.5)
Liabilities
Contractholder funds	(349.3)	(340.5)
Future policy benefits and claims	(1,082.7)	(929.7)
Other policyholder funds	(2)	(0.8)
Long-term debt	(722.9)	(660.1)
Income taxes currently payable	(156.1)	(149.5)
Deferred income taxes	(521.3)	(626)
Other liabilities	(11,092.8)	(10,831.8)
Total liabilities	(13,927.1)	(13,538.4)
Stockholders' equity
Common stock	(2.5)	(2.5)
Additional paid-in capital	(15,403)	(15,399.5)
Retained earnings (accumulated deficit)	(8,303)	(7,549.8)
Accumulated other comprehensive income (loss)	702.4	(1,939.2)
Total stockholders' equity attributable to Principal Financial Group, Inc.	(23,006.1)	(24,891)
Noncontrolling interest		(5.1)
Total stockholders' equity	(23,006.1)	(24,896.1)
Total liabilities and stockholders' equity	$ (36,933.2)	$ (38,434.5)

Condensed Consolidating Finan_4

Condensed Consolidating Financial Information - Guarantor, Statements of Operations (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues
Premiums and other considerations	$ 2,172.4	$ 2,126.1	$ 4,433.4	$ 4,826.8
Fees and other revenues	1,261.8	987.1	3,285.7	2,882.8
Net investment income (loss)	919.4	838	2,710.7	2,581.8
Net realized capital gains (losses), excluding impairment losses on available-for-sale securities	(1.9)	693.2	59.3	623.7
Net other-than-temporary impairment (losses) recoveries on available-for-sale securities	(1.4)	2.6	(8.3)	(27.1)
Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified to (from) other comprehensive income	(2.2)	(19.2)	(14.2)	(32.5)
Net impairment (losses) recoveries on available-for-sale securities	(3.6)		(22.5)
Net impairment (losses) recoveries on available-for-sale securities		(16.6)		(59.6)
Net realized capital gains (losses)	(5.5)	676.6	36.8	564.1
Total revenues	4,348.1	4,627.8	10,466.6	10,855.5
Expenses
Benefits, claims and settlement expenses	2,642.1	2,504.6	5,752.4	6,020.7
Dividends to policyholders	31.9	32.6	92.6	92.7
Operating expenses	1,105	932.8	3,080.1	2,804.7
Total expenses	3,779	3,470	8,925.1	8,918.1
Income (loss) before income taxes	569.1	1,157.8	1,541.5	1,937.4
Income taxes (benefits)	109.1	344.6	219.5	455.8
Net income (loss)	460	813.2	1,322	1,481.6
Net income (loss) attributable to noncontrolling interest	3.7	3	12	13
Net income (loss) attributable to Principal Financial Group, Inc.	456.3	810.2	1,310	1,468.6
Net income (loss)	460	813.2	1,322	1,481.6
Other comprehensive income (loss)	(208.7)	165.1	(1,617.1)	724.9
Comprehensive income (loss)	$ 251.3	$ 978.3	(295.1)	2,206.5
Principal Financial Group, Inc. Parent Only
Revenues
Fees and other revenues				7.8
Net investment income (loss)			16.8	7.4
Net realized capital gains (losses), excluding impairment losses on available-for-sale securities			(11.3)
Net realized capital gains (losses)			(11.3)
Total revenues			5.5	15.2
Expenses
Operating expenses			143.7	152.1
Total expenses			143.7	152.1
Income (loss) before income taxes			(138.2)	(136.9)
Income taxes (benefits)			(52.6)	(57.2)
Equity in the net income (loss) of subsidiaries			1,395.6	1,548.3
Net income (loss)			1,310	1,468.6
Net income (loss) attributable to Principal Financial Group, Inc.			1,310	1,468.6
Net income (loss)			1,310	1,468.6
Other comprehensive income (loss)			(1,605.4)	719.9
Comprehensive income (loss)			(295.4)	2,188.5
Principal Life Insurance Company Only
Revenues
Premiums and other considerations			3,996.4	4,512.5
Fees and other revenues			1,632.2	1,584.2
Net investment income (loss)			1,957.6	1,883.5
Net realized capital gains (losses), excluding impairment losses on available-for-sale securities			(114.7)	(119.2)
Net other-than-temporary impairment (losses) recoveries on available-for-sale securities			(5.9)	(27.8)
Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified to (from) other comprehensive income			(13.6)	(26.1)
Net impairment (losses) recoveries on available-for-sale securities			(19.5)
Net impairment (losses) recoveries on available-for-sale securities				(53.9)
Net realized capital gains (losses)			(134.2)	(173.1)
Total revenues			7,452	7,807.1
Expenses
Benefits, claims and settlement expenses			5,095.7	5,529.9
Dividends to policyholders			92.6	92.7
Operating expenses			1,665	1,570.2
Total expenses			6,853.3	7,192.8
Income (loss) before income taxes			598.7	614.3
Income taxes (benefits)			13.9	34.1
Equity in the net income (loss) of subsidiaries			456.1	566.5
Net income (loss)			1,040.9	1,146.7
Net income (loss) attributable to Principal Financial Group, Inc.			1,040.9	1,146.7
Net income (loss)			1,040.9	1,146.7
Other comprehensive income (loss)			(1,413.4)	495.8
Comprehensive income (loss)			(372.5)	1,642.5
Income (loss) from discontinued operations, net of related income taxes				35.5
Principal Financial Services, Inc. and Other Subsidiaries Combined
Revenues
Premiums and other considerations			437	314.3
Fees and other revenues			1,944.9	1,607.2
Net investment income (loss)			1,770.2	1,836.6
Net realized capital gains (losses), excluding impairment losses on available-for-sale securities			185.3	743.6
Net other-than-temporary impairment (losses) recoveries on available-for-sale securities			(2.4)	0.7
Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified to (from) other comprehensive income			(0.6)	(6.4)
Net impairment (losses) recoveries on available-for-sale securities			(3)
Net impairment (losses) recoveries on available-for-sale securities				(5.7)
Net realized capital gains (losses)			182.3	737.9
Total revenues			4,334.4	4,496
Expenses
Benefits, claims and settlement expenses			664.8	498.9
Operating expenses			1,541.6	1,345.8
Total expenses			2,206.4	1,844.7
Income (loss) before income taxes			2,128	2,651.3
Income taxes (benefits)			259.4	481.9
Equity in the net income (loss) of subsidiaries			(471.1)	(613.1)
Net income (loss)			1,397.5	1,556.3
Net income (loss) attributable to noncontrolling interest			12	13
Net income (loss) attributable to Principal Financial Group, Inc.			1,385.5	1,543.3
Net income (loss)			1,397.5	1,556.3
Other comprehensive income (loss)			(1,740.8)	750.1
Comprehensive income (loss)			(343.3)	2,306.4
Eliminations, Notes Guarantor
Revenues
Fees and other revenues			(291.4)	(316.4)
Net investment income (loss)			(1,033.9)	(1,145.7)
Net realized capital gains (losses), excluding impairment losses on available-for-sale securities				(0.7)
Net realized capital gains (losses)				(0.7)
Total revenues			(1,325.3)	(1,462.8)
Expenses
Benefits, claims and settlement expenses			(8.1)	(8.1)
Operating expenses			(270.2)	(263.4)
Total expenses			(278.3)	(271.5)
Income (loss) before income taxes			(1,047)	(1,191.3)
Income taxes (benefits)			(1.2)	(3)
Equity in the net income (loss) of subsidiaries			(1,380.6)	(1,501.7)
Net income (loss)			(2,426.4)	(2,690)
Net income (loss) attributable to Principal Financial Group, Inc.			(2,426.4)	(2,690)
Net income (loss)			(2,426.4)	(2,690)
Other comprehensive income (loss)			3,142.5	(1,240.9)
Comprehensive income (loss)			$ 716.1	$ (3,930.9)

Condensed Consolidating Finan_5

Condensed Consolidating Financial Information - Guarantor, Statements of Cash Flows (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating activities
Net cash provided by (used in) operating activities	$ 3,713.9	$ 3,628.7
Investing activities
Fixed maturities available-for-sale and equity securities with intent to hold: Purchases	(10,992.3)	(10,425.7)
Fixed maturities available-for-sale and equity securities with intent to hold: Sales	2,900.4	1,011.2
Fixed maturities available-for-sale and equity securities with intent to hold: Maturities	4,703.5	6,577.2
Mortgage loans acquired or originated	(2,347.4)	(2,036.5)
Mortgage loans sold or repaid	1,567.6	1,297.4
Real estate acquired	(53.7)	(113.6)
Real estate sold	63.5	457.1
Net (purchases) sales of property and equipment	(73.4)	(133.3)
Purchase of interests in subsidiaries, net of cash acquired	(184.7)
Net change in other investments	7.8	48.5
Net cash provided by (used in) investing activities	(4,408.7)	(3,317.7)
Financing activities
Issuance of common stock	52.4	143.1
Acquisition of treasury stock	(461.5)	(218.1)
Proceeds from financing element derivatives		0.1
Payments for financing element derivatives	(53.7)	(59.5)
Purchase of subsidiary shares from noncontrolling interest	(30.3)	(13.3)
Dividends to common stockholders	(446.5)	(398.5)
Issuance of long-term debt	66.8
Principal repayments of long-term debt	(1)	(56.2)
Net proceeds from (repayments of) short-term borrowings	(0.8)	4.9
Investment contract deposits	6,228.5	8,244.4
Investment contract withdrawals	(4,361.6)	(7,963.1)
Net increase (decrease) in banking operation deposits	159.5	79.8
Other	(1.1)	0.8
Net cash provided by (used in) financing activities	1,150.7	(235.6)
Net increase (decrease) in cash and cash equivalents	455.9	75.4
Cash and cash equivalents at beginning of period	2,470.8	2,719.6
Cash and cash equivalents at end of period	2,926.7	2,795
Principal Financial Group, Inc. Parent Only
Operating activities
Net cash provided by (used in) operating activities	(164.6)	(36.7)
Investing activities
Fixed maturities available-for-sale and equity securities with intent to hold: Purchases	(200.8)
Fixed maturities available-for-sale and equity securities with intent to hold: Maturities	1.6
Dividends and returns of capital received from (contributed to) unconsolidated entities	686.6	250.1
Net change in other investments	0.5	(4.4)
Net cash provided by (used in) investing activities	487.9	245.7
Financing activities
Issuance of common stock	52.4	143.1
Acquisition of treasury stock	(461.5)	(218.1)
Dividends to common stockholders	(446.5)	(398.5)
Net cash provided by (used in) financing activities	(855.6)	(473.5)
Net increase (decrease) in cash and cash equivalents	(532.3)	(264.5)
Cash and cash equivalents at beginning of period	842.8	882.6
Cash and cash equivalents at end of period	310.5	618.1
Principal Life Insurance Company Only
Operating activities
Net cash provided by (used in) operating activities	3,686	4,946.3
Investing activities
Fixed maturities available-for-sale and equity securities with intent to hold: Purchases	(9,301.2)	(9,431.3)
Fixed maturities available-for-sale and equity securities with intent to hold: Sales	1,978.3	731.7
Fixed maturities available-for-sale and equity securities with intent to hold: Maturities	4,288	5,964.6
Mortgage loans acquired or originated	(2,126.7)	(2,078.4)
Mortgage loans sold or repaid	1,379.6	1,244.6
Net (purchases) sales of property and equipment	(42.3)	(92.9)
Dividends and returns of capital received from (contributed to) unconsolidated entities	43.2	32
Net change in other investments	12.6	58.3
Net cash provided by (used in) investing activities	(3,768.5)	(3,571.4)
Financing activities
Proceeds from financing element derivatives		0.1
Payments for financing element derivatives	(53.7)	(59.5)
Capital received from (dividends and capital paid to) parent	(601.6)	(1,243.5)
Investment contract deposits	5,923.4	7,976.5
Investment contract withdrawals	(4,300)	(7,943.1)
Other	(1.1)	0.8
Net cash provided by (used in) financing activities	967	(1,268.7)
Net increase (decrease) in cash and cash equivalents	884.5	106.2
Cash and cash equivalents at beginning of period	426.7	675.1
Cash and cash equivalents at end of period	1,311.2	781.3
Principal Financial Services, Inc. and Other Subsidiaries Combined
Operating activities
Net cash provided by (used in) operating activities	688.9	(1,094.7)
Investing activities
Fixed maturities available-for-sale and equity securities with intent to hold: Purchases	(1,496.7)	(994.4)
Fixed maturities available-for-sale and equity securities with intent to hold: Sales	922.1	292.4
Fixed maturities available-for-sale and equity securities with intent to hold: Maturities	413.9	612.6
Mortgage loans acquired or originated	(326.4)	(278.2)
Mortgage loans sold or repaid	223.3	200.5
Real estate acquired	(53.7)	(113.6)
Real estate sold	63.5	457.1
Net (purchases) sales of property and equipment	(31.1)	(40.4)
Purchase of interests in subsidiaries, net of cash acquired	(184.7)
Dividends and returns of capital received from (contributed to) unconsolidated entities	601.6	1,243.5
Net change in other investments	(365.1)	(354.2)
Net cash provided by (used in) investing activities	(233.3)	1,025.3
Financing activities
Purchase of subsidiary shares from noncontrolling interest	(30.3)	(14.6)
Sale of subsidiary shares to noncontrolling interest		1.3
Issuance of long-term debt	164.9	313.5
Principal repayments of long-term debt	(36.3)	(203.8)
Net proceeds from (repayments of) short-term borrowings	(0.8)	4.9
Capital received from (dividends and capital paid to) parent	(729.8)	(282.1)
Investment contract deposits	305.1	267.9
Investment contract withdrawals	(61.6)	(20)
Net increase (decrease) in banking operation deposits	159.5	79.8
Net cash provided by (used in) financing activities	(229.3)	146.9
Net increase (decrease) in cash and cash equivalents	226.3	77.5
Cash and cash equivalents at beginning of period	1,526.4	2,082.8
Cash and cash equivalents at end of period	1,752.7	2,160.3
Eliminations, Notes Guarantor
Operating activities
Net cash provided by (used in) operating activities	(496.4)	(186.2)
Investing activities
Fixed maturities available-for-sale and equity securities with intent to hold: Purchases	6.4
Fixed maturities available-for-sale and equity securities with intent to hold: Sales		(12.9)
Mortgage loans acquired or originated	105.7	320.1
Mortgage loans sold or repaid	(35.3)	(147.7)
Dividends and returns of capital received from (contributed to) unconsolidated entities	(1,331.4)	(1,525.6)
Net change in other investments	359.8	348.8
Net cash provided by (used in) investing activities	(894.8)	(1,017.3)
Financing activities
Purchase of subsidiary shares from noncontrolling interest		1.3
Sale of subsidiary shares to noncontrolling interest		(1.3)
Issuance of long-term debt	(98.1)	(313.5)
Principal repayments of long-term debt	35.3	147.6
Capital received from (dividends and capital paid to) parent	1,331.4	1,525.6
Net cash provided by (used in) financing activities	1,268.6	1,359.7
Net increase (decrease) in cash and cash equivalents	(122.6)	156.2
Cash and cash equivalents at beginning of period	(325.1)	(920.9)
Cash and cash equivalents at end of period	$ (447.7)	$ (764.7)

Condensed Consolidating Finan_6

Condensed Consolidating Financial Information - Shelf Registration Guarantor, Statements of Financial Position (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Assets
Fixed maturities, available-for-sale	$ 60,447.2	$ 59,388.4
Fixed maturities, trading	642.1	566
Equity securities	1,885.8	1,866.6
Mortgage loans	14,919.7	14,150.5
Real estate	1,699.7	1,736.7
Policy loans	804.4	808.3
Investment in unconsolidated entities	846.6	820.6
Other investments	2,761.7	2,765.6
Cash and cash equivalents	2,926.7	2,470.8	$ 2,795	$ 2,719.6
Accrued investment income	660.7	610.6
Premiums due and other receivables	1,514.4	1,469.8
Deferred acquisition costs	3,671.9	3,540.7
Property and equipment	770.6	759.5
Goodwill	1,128.7	1,068.8
Other intangibles	1,353.9	1,314.7
Separate account assets	161,302.9	159,272.7
Other assets	1,421.3	1,330.9
Total assets	258,758.3	253,941.2
Liabilities
Contractholder funds	39,813.2	38,082.5
Future policy benefits and claims	34,818.3	33,019.3
Other policyholder funds	849.4	922.3
Short-term debt	36.1	39.5
Long-term debt	3,245.5	3,178.4
Income taxes currently payable	29.3	16.7
Deferred income taxes	911.4	1,092.5
Separate account liabilities	161,302.9	159,272.7
Other liabilities	5,835	5,294.1
Total liabilities	246,841.1	240,918
Redeemable noncontrolling interest	148.5	101.3	129.1	97.5
Stockholders' equity
Common stock	4.8	4.7
Additional paid-in capital	10,026.2	9,925.2
Retained earnings (accumulated deficit)	10,207.9	9,482.9
Accumulated other comprehensive income (loss)	(1,347.6)	165.5
Treasury stock, at cost	(7,190.5)	(6,729)
Total stockholders' equity attributable to Principal Financial Group, Inc.	11,700.8	12,849.3
Noncontrolling interest	67.9	72.6
Total stockholders' equity	11,768.7	12,921.9	12,067.3	10,293.8
Total liabilities and stockholders' equity	258,758.3	253,941.2
Principal Financial Group, Inc. Parent Only
Assets
Fixed maturities, available-for-sale	200.4
Fixed maturities, trading	314.5	351.8
Investment in unconsolidated entities	14,127.1	15,063.2
Other investments	10.5	10.2
Cash and cash equivalents	310.5	842.8	618.1	882.6
Accrued investment income	1.2	1.1
Other assets	414.2	389.7
Total assets	15,378.4	16,658.8
Liabilities
Long-term debt	3,129.3	3,128.1
Other liabilities	548.3	681.4
Total liabilities	3,677.6	3,809.5
Stockholders' equity
Common stock	4.8	4.7
Additional paid-in capital	10,026.2	9,925.2
Retained earnings (accumulated deficit)	10,207.9	9,482.9
Accumulated other comprehensive income (loss)	(1,347.6)	165.5
Treasury stock, at cost	(7,190.5)	(6,729)
Total stockholders' equity attributable to Principal Financial Group, Inc.	11,700.8	12,849.3
Total stockholders' equity	11,700.8	12,849.3
Total liabilities and stockholders' equity	15,378.4	16,658.8
Principal Financial Services, Inc. Only
Assets
Equity securities	5.7	5.7
Investment in unconsolidated entities	14,523	15,449.7
Other investments	102.3	131.3
Cash and cash equivalents	706.4	617.4	1,282	1,203.4
Accrued investment income		0.2
Premiums due and other receivables	0.4	2
Other assets	77.8	94.8
Total assets	15,415.6	16,301.1
Liabilities
Long-term debt	383	412.7
Income taxes currently payable	3.7	37.3
Deferred income taxes	13.5	12.4
Other liabilities	1,017	894.1
Total liabilities	1,417.2	1,356.5
Stockholders' equity
Additional paid-in capital	9,077.8	9,053.5
Retained earnings (accumulated deficit)	5,811.6	5,311.7
Accumulated other comprehensive income (loss)	(891)	579.4
Total stockholders' equity attributable to Principal Financial Group, Inc.	13,998.4	14,944.6
Total stockholders' equity	13,998.4	14,944.6
Total liabilities and stockholders' equity	15,415.6	16,301.1
Principal Life Insurance Company and Other Subsidiaries Combined
Assets
Fixed maturities, available-for-sale	60,246.8	59,388.4
Fixed maturities, trading	327.6	214.2
Equity securities	1,880.1	1,860.9
Mortgage loans	14,919.7	14,150.5
Real estate	1,699.7	1,736.7
Policy loans	804.4	808.3
Investment in unconsolidated entities	711	706.7
Other investments	2,648.9	2,624.1
Cash and cash equivalents	3,033.3	2,001.1	2,561.4	2,114.8
Accrued investment income	659.5	609.3
Premiums due and other receivables	1,896.6	1,880.3
Deferred acquisition costs	3,671.9	3,540.7
Property and equipment	770.6	759.5
Goodwill	1,128.7	1,068.8
Other intangibles	1,353.9	1,314.7
Separate account assets	161,302.9	159,272.7
Other assets	1,592.6	1,619.4
Total assets	258,648.2	253,556.3
Liabilities
Contractholder funds	39,813.2	38,082.5
Future policy benefits and claims	34,818.3	33,019.3
Other policyholder funds	849.4	922.3
Short-term debt	36.1	39.5
Long-term debt	116.1	50.3
Income taxes currently payable	160.2	105.9
Deferred income taxes	1,417.7	1,705.1
Separate account liabilities	161,302.9	159,272.7
Other liabilities	5,309.1	4,760.7
Total liabilities	243,823	237,958.3
Redeemable noncontrolling interest	148.5	101.3
Stockholders' equity
Common stock	11	11
Additional paid-in capital	11,715.8	11,336
Retained earnings (accumulated deficit)	3,601.1	3,394.1
Accumulated other comprehensive income (loss)	(717.1)	685
Treasury stock, at cost	(2)	(2)
Total stockholders' equity attributable to Principal Financial Group, Inc.	14,608.8	15,424.1
Noncontrolling interest	67.9	72.6
Total stockholders' equity	14,676.7	15,496.7
Total liabilities and stockholders' equity	258,648.2	253,556.3
Principal Life Insurance Company and Other Subsidiaries Combined | Nonqualified benefit plans
Stockholders' equity
Assets held in Rabbi trusts	687.1	643.3
Liabilities held in Rabbi trusts	558.4	524.7
Eliminations, Shelf Registration Debt Guarantor
Assets
Investment in unconsolidated entities	(28,514.5)	(30,399)
Cash and cash equivalents	(1,123.5)	(990.5)	$ (1,666.5)	$ (1,481.2)
Premiums due and other receivables	(382.6)	(412.5)
Other assets	(663.3)	(773)
Total assets	(30,683.9)	(32,575)
Liabilities
Long-term debt	(382.9)	(412.7)
Income taxes currently payable	(134.6)	(126.5)
Deferred income taxes	(519.8)	(625)
Other liabilities	(1,039.4)	(1,042.1)
Total liabilities	(2,076.7)	(2,206.3)
Stockholders' equity
Common stock	(11)	(11)
Additional paid-in capital	(20,793.6)	(20,389.5)
Retained earnings (accumulated deficit)	(9,412.7)	(8,705.8)
Accumulated other comprehensive income (loss)	1,608.1	(1,264.4)
Treasury stock, at cost	2	2
Total stockholders' equity attributable to Principal Financial Group, Inc.	(28,607.2)	(30,368.7)
Total stockholders' equity	(28,607.2)	(30,368.7)
Total liabilities and stockholders' equity	$ (30,683.9)	$ (32,575)

Condensed Consolidating Finan_7

Condensed Consolidating Financial Information - Shelf Registration Guarantor, Statements of Operations (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues
Premiums and other considerations	$ 2,172.4	$ 2,126.1	$ 4,433.4	$ 4,826.8
Fees and other revenues	1,261.8	987.1	3,285.7	2,882.8
Net investment income (loss)	919.4	838	2,710.7	2,581.8
Net realized capital gains (losses), excluding impairment losses on available-for-sale securities	(1.9)	693.2	59.3	623.7
Net other-than-temporary impairment (losses) recoveries on available-for-sale securities	(1.4)	2.6	(8.3)	(27.1)
Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified to (from) other comprehensive income	(2.2)	(19.2)	(14.2)	(32.5)
Net impairment (losses) recoveries on available-for-sale securities	(3.6)		(22.5)
Net impairment (losses) recoveries on available-for-sale securities		(16.6)		(59.6)
Net realized capital gains (losses)	(5.5)	676.6	36.8	564.1
Total revenues	4,348.1	4,627.8	10,466.6	10,855.5
Expenses
Benefits, claims and settlement expenses	2,642.1	2,504.6	5,752.4	6,020.7
Dividends to policyholders	31.9	32.6	92.6	92.7
Operating expenses	1,105	932.8	3,080.1	2,804.7
Total expenses	3,779	3,470	8,925.1	8,918.1
Income (loss) before income taxes	569.1	1,157.8	1,541.5	1,937.4
Income taxes (benefits)	109.1	344.6	219.5	455.8
Net income (loss)	460	813.2	1,322	1,481.6
Net income (loss) attributable to noncontrolling interest	3.7	3	12	13
Net income (loss) attributable to Principal Financial Group, Inc.	456.3	810.2	1,310	1,468.6
Net income (loss)	460	813.2	1,322	1,481.6
Other comprehensive income (loss)	(208.7)	165.1	(1,617.1)	724.9
Comprehensive income (loss)	$ 251.3	$ 978.3	(295.1)	2,206.5
Principal Financial Group, Inc. Parent Only
Revenues
Fees and other revenues				7.8
Net investment income (loss)			16.8	7.4
Net realized capital gains (losses), excluding impairment losses on available-for-sale securities			(11.3)
Net realized capital gains (losses)			(11.3)
Total revenues			5.5	15.2
Expenses
Operating expenses			143.7	152.1
Total expenses			143.7	152.1
Income (loss) before income taxes			(138.2)	(136.9)
Income taxes (benefits)			(52.6)	(57.2)
Equity in the net income (loss) of subsidiaries			1,395.6	1,548.3
Net income (loss)			1,310	1,468.6
Net income (loss) attributable to Principal Financial Group, Inc.			1,310	1,468.6
Net income (loss)			1,310	1,468.6
Other comprehensive income (loss)			(1,605.4)	719.9
Comprehensive income (loss)			(295.4)	2,188.5
Principal Financial Services, Inc. Only
Revenues
Fees and other revenues			2.5	0.2
Net investment income (loss)			(4.9)	(2)
Net realized capital gains (losses), excluding impairment losses on available-for-sale securities			1.3	4.5
Net realized capital gains (losses)			1.3	4.5
Total revenues			(1.1)	2.7
Expenses
Operating expenses			23.1	38.5
Total expenses			23.1	38.5
Income (loss) before income taxes			(24.2)	(35.8)
Income taxes (benefits)			6.2	(15.3)
Equity in the net income (loss) of subsidiaries			1,415.9	1,563.8
Net income (loss)			1,385.5	1,543.3
Net income (loss) attributable to Principal Financial Group, Inc.			1,385.5	1,543.3
Net income (loss)			1,385.5	1,543.3
Other comprehensive income (loss)			(1,645.1)	686.1
Comprehensive income (loss)			(259.6)	2,229.4
Principal Life Insurance Company and Other Subsidiaries Combined
Revenues
Premiums and other considerations			4,433.4	4,826.8
Fees and other revenues			3,295.3	2,881.9
Net investment income (loss)			2,687.5	2,572
Net realized capital gains (losses), excluding impairment losses on available-for-sale securities			69.3	619.2
Net other-than-temporary impairment (losses) recoveries on available-for-sale securities			(8.3)	(27.1)
Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified to (from) other comprehensive income			(14.2)	(32.5)
Net impairment (losses) recoveries on available-for-sale securities			(22.5)
Net impairment (losses) recoveries on available-for-sale securities				(59.6)
Net realized capital gains (losses)			46.8	559.6
Total revenues			10,463	10,840.3
Expenses
Benefits, claims and settlement expenses			5,752.4	6,020.7
Dividends to policyholders			92.6	92.7
Operating expenses			2,924.2	2,620.6
Total expenses			8,769.2	8,734
Income (loss) before income taxes			1,693.8	2,106.3
Income taxes (benefits)			265.9	529.5
Net income (loss)			1,427.9	1,576.8
Net income (loss) attributable to noncontrolling interest			12	13
Net income (loss) attributable to Principal Financial Group, Inc.			1,415.9	1,563.8
Net income (loss)			1,427.9	1,576.8
Other comprehensive income (loss)			(1,668.9)	688.9
Comprehensive income (loss)			(241)	2,265.7
Eliminations, Shelf Registration Debt Guarantor
Revenues
Fees and other revenues			(12.1)	(7.1)
Net investment income (loss)			11.3	4.4
Total revenues			(0.8)	(2.7)
Expenses
Operating expenses			(10.9)	(6.5)
Total expenses			(10.9)	(6.5)
Income (loss) before income taxes			10.1	3.8
Income taxes (benefits)				(1.2)
Equity in the net income (loss) of subsidiaries			(2,811.5)	(3,112.1)
Net income (loss)			(2,801.4)	(3,107.1)
Net income (loss) attributable to Principal Financial Group, Inc.			(2,801.4)	(3,107.1)
Net income (loss)			(2,801.4)	(3,107.1)
Other comprehensive income (loss)			3,302.3	(1,370)
Comprehensive income (loss)			$ 500.9	$ (4,477.1)

Condensed Consolidating Finan_8

Condensed Consolidating Financial Information - Shelf Registration Guarantor, Statements of Cash Flows (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating activities
Net cash provided by (used in) operating activities	$ 3,713.9	$ 3,628.7
Investing activities
Fixed maturities available-for-sale and equity securities with intent to hold: Purchases	(10,992.3)	(10,425.7)
Fixed maturities available-for-sale and equity securities with intent to hold: Sales	2,900.4	1,011.2
Fixed maturities available-for-sale and equity securities with intent to hold: Maturities	4,703.5	6,577.2
Mortgage loans acquired or originated	(2,347.4)	(2,036.5)
Mortgage loans sold or repaid	1,567.6	1,297.4
Real estate acquired	(53.7)	(113.6)
Real estate sold	63.5	457.1
Net (purchases) sales of property and equipment	(73.4)	(133.3)
Purchase of interests in subsidiaries, net of cash acquired	(184.7)
Net change in other investments	7.8	48.5
Net cash provided by (used in) investing activities	(4,408.7)	(3,317.7)
Financing activities
Issuance of common stock	52.4	143.1
Acquisition of treasury stock	(461.5)	(218.1)
Proceeds from financing element derivatives		0.1
Payments for financing element derivatives	(53.7)	(59.5)
Dividends to common stockholders	(446.5)	(398.5)
Purchase of subsidiary shares from noncontrolling interest	(30.3)	(13.3)
Issuance of long-term debt	66.8
Principal repayments of long-term debt	(1)	(56.2)
Net proceeds from (repayments of) short-term borrowings	(0.8)	4.9
Investment contract deposits	6,228.5	8,244.4
Investment contract withdrawals	(4,361.6)	(7,963.1)
Net increase (decrease) in banking operation deposits	159.5	79.8
Other	(1.1)	0.8
Net cash provided by (used in) financing activities	1,150.7	(235.6)
Net increase (decrease) in cash and cash equivalents	455.9	75.4
Cash and cash equivalents at beginning of period	2,470.8	2,719.6
Cash and cash equivalents at end of period	2,926.7	2,795
Principal Financial Group, Inc. Parent Only
Operating activities
Net cash provided by (used in) operating activities	(164.6)	(36.7)
Investing activities
Fixed maturities available-for-sale and equity securities with intent to hold: Purchases	(200.8)
Fixed maturities available-for-sale and equity securities with intent to hold: Maturities	1.6
Dividends and returns of capital received from (contributed to) unconsolidated entities	686.6	250.1
Net change in other investments	0.5	(4.4)
Net cash provided by (used in) investing activities	487.9	245.7
Financing activities
Issuance of common stock	52.4	143.1
Acquisition of treasury stock	(461.5)	(218.1)
Dividends to common stockholders	(446.5)	(398.5)
Net cash provided by (used in) financing activities	(855.6)	(473.5)
Net increase (decrease) in cash and cash equivalents	(532.3)	(264.5)
Cash and cash equivalents at beginning of period	842.8	882.6
Cash and cash equivalents at end of period	310.5	618.1
Principal Financial Services, Inc. Only
Operating activities
Net cash provided by (used in) operating activities	420.9	449.3
Investing activities
Dividends and returns of capital received from (contributed to) unconsolidated entities	546.9	(37)
Net change in other investments	(162.5)	(70.5)
Net cash provided by (used in) investing activities	384.4	(107.5)
Financing activities
Issuance of long-term debt	8.5	6.4
Principal repayments of long-term debt	(38.2)	(19.5)
Capital received from (dividends and capital paid to) parent	(686.6)	(250.1)
Net cash provided by (used in) financing activities	(716.3)	(263.2)
Net increase (decrease) in cash and cash equivalents	89	78.6
Cash and cash equivalents at beginning of period	617.4	1,203.4
Cash and cash equivalents at end of period	706.4	1,282
Principal Life Insurance Company and Other Subsidiaries Combined
Operating activities
Net cash provided by (used in) operating activities	3,810.4	3,721
Investing activities
Fixed maturities available-for-sale and equity securities with intent to hold: Purchases	(10,791.5)	(10,425.7)
Fixed maturities available-for-sale and equity securities with intent to hold: Sales	2,900.4	1,011.2
Fixed maturities available-for-sale and equity securities with intent to hold: Maturities	4,701.9	6,577.2
Mortgage loans acquired or originated	(2,347.4)	(2,036.5)
Mortgage loans sold or repaid	1,567.6	1,297.4
Real estate acquired	(53.7)	(113.6)
Real estate sold	63.5	457.1
Net (purchases) sales of property and equipment	(73.4)	(133.3)
Purchase of interests in subsidiaries, net of cash acquired	(184.7)
Net change in other investments	(20.3)	(106.6)
Net cash provided by (used in) investing activities	(4,237.6)	(3,472.8)
Financing activities
Proceeds from financing element derivatives		0.1
Payments for financing element derivatives	(53.7)	(59.5)
Purchase of subsidiary shares from noncontrolling interest	(30.3)	(13.3)
Issuance of long-term debt	66.8
Principal repayments of long-term debt	(1)	(56.2)
Net proceeds from (repayments of) short-term borrowings	(0.8)	(71.6)
Capital received from (dividends and capital paid to) parent	(546.9)	37
Investment contract deposits	6,228.5	8,244.4
Investment contract withdrawals	(4,361.6)	(7,963.1)
Net increase (decrease) in banking operation deposits	159.5	79.8
Other	(1.1)	0.8
Net cash provided by (used in) financing activities	1,459.4	198.4
Net increase (decrease) in cash and cash equivalents	1,032.2	446.6
Cash and cash equivalents at beginning of period	2,001.1	2,114.8
Cash and cash equivalents at end of period	3,033.3	2,561.4
Eliminations, Shelf Registration Debt Guarantor
Operating activities
Net cash provided by (used in) operating activities	(352.8)	(504.9)
Investing activities
Dividends and returns of capital received from (contributed to) unconsolidated entities	(1,233.5)	(213.1)
Net change in other investments	190.1	230
Net cash provided by (used in) investing activities	(1,043.4)	16.9
Financing activities
Issuance of long-term debt	(8.5)	(6.4)
Principal repayments of long-term debt	38.2	19.5
Net proceeds from (repayments of) short-term borrowings		76.5
Capital received from (dividends and capital paid to) parent	1,233.5	213.1
Net cash provided by (used in) financing activities	1,263.2	302.7
Net increase (decrease) in cash and cash equivalents	(133)	(185.3)
Cash and cash equivalents at beginning of period	(990.5)	(1,481.2)
Cash and cash equivalents at end of period	$ (1,123.5)	$ (1,666.5)