Janus Henderson (JHG) 10-K 27 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 22, 2018	Jun. 30, 2017
Document and Entity Information
Entity Registrant Name	Janus Henderson Group plc
Entity Central Index Key	1,274,173
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float			$ 6,635,447,229.18
Entity Common Stock, Shares Outstanding		200,406,138
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Fees and other receivables	$ 419.6	$ 165.5
OEIC and unit trust receivables	239.9	142.1
Other current assets	75.9	28.5
Total current assets	2,242.6	1,060.7
Non-current assets:
Property, equipment and software, net	70.6	41.2
Intangible assets, net	3,204.8	401.3
Goodwill	1,533.9	741.5
Retirement benefit asset, net	199.3	180.2
Other non-current assets	21.5	8.5
Total assets	7,272.7	2,433.4
Current liabilities:
Accounts payable and accrued liabilities	292.9	141.7
Current portion of accrued compensation, benefits and staff costs	398.7	147
Current portion of long-term debt	57.2
OEIC and unit trust payables	234.8	137.9
Total current liabilities	1,005.1	452.8
Non-current liabilities:
Accrued compensation, benefits and staff costs	23	8.7
Long-term debt	322
Deferred tax liabilities, net	752.6	70.7
Retirement benefit obligations, net	4.6	11.9
Other non-current liabilities	99.6	39
Total liabilities	2,206.9	583.1
Commitments and contingencies (See Note 18)
REDEEMABLE NONCONTROLLING INTERESTS	190.3	158
EQUITY
Common stock ( $1.50 par and 0.125 par, 480,000,000 and 2,194,910,776 shares authorized; 200,406,138 and 1,131,842,109 shares issued and outstanding, respectively)	300.6	234.4
Additional paid-in-capital	3,842.9	1,237.9
Treasury shares ( 4,071,284 and 38,848,749 shares held, respectively)	(155.8)	(155.1)
Accumulated other comprehensive loss, net of tax	(301.8)	(434.5)
Retained earnings	1,151.4	764.8
Total shareholders' equity	4,837.3	1,647.5
Nonredeemable noncontrolling interests	38.2	44.8
Total equity	4,875.5	1,692.3
Total liabilities, redeemable noncontrolling interests and equity	7,272.7	2,433.4
Consolidated excluding VIEs
Current assets:
Cash and cash equivalents	760.1	279
Investment securities	280.4	79.6
Current liabilities:
Accounts payable and accrued liabilities	292.9	141.7
Consolidated VIEs
Current assets:
Cash and cash equivalents	34.1	44.2
Investment securities	419.7	313.7
Other current assets	12.9	8.1
Current liabilities:
Accounts payable and accrued liabilities	$ 21.5	$ 26.2

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical)	Dec. 31, 2017$ / sharesshares	Dec. 31, 2017£ / sharesshares	Dec. 31, 2016£ / sharesshares
CONSOLIDATED BALANCE SHEETS
Common stock, par (in dollars/pounds per share) | (per share)	$ 1.50	£ 1.50	£ 0.125
Common stock, shares authorized	480,000,000	480,000,000	2,194,910,776
Common stock, shares issued	200,406,138	200,406,138	1,131,842,109
Common stock, shares outstanding	200,406,138	200,406,138	1,131,842,109
Treasury shares (in shares)	4,071,284	4,071,284	38,848,749

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Management fees	$ 1,465.1	$ 867.8	$ 914.7
Performance fees	103.9	54.8	150.8
Shareowner servicing fees	71.5
Other revenue	103.2	77.3	89.6
Total revenue	1,743.7	999.9	1,155.1
Operating expenses:
Employee compensation and benefits	543.3	273.5	317.1
Long-term incentive plans	150.8	87.5	85.9
Distribution expenses	277.3	209.1	235.6
Investment administration	43.8	46.2	48.3
Marketing	31.2	13.9	14.2
General, administrative and occupancy	202.2	109.8	113.3
Depreciation and amortization	52.8	27.8	23.4
Total operating expenses	1,301.4	767.8	837.8
Operating income	442.3	232.1	317.3
Interest expense	(11.9)	(6.6)	(20.1)
Investment gains (losses), net	18	(11.7)	39.7
Other non-operating income (expenses), net	(1)	(1.9)	0.6
Income before taxes	447.4	211.9	337.5
Income tax provision	211	(34.6)	(6.1)
Net income	658.4	177.3	331.4
Net loss (income) attributable to noncontrolling interests	(2.9)	11.7	(1.6)
Net income attributable to JHG	$ 655.5	$ 189	$ 329.8
Earnings per share attributable to JHG common shareholders:
Basic (in dollars per share)	$ 3.97	$ 1.69	$ 2.93
Diluted (in dollars per share)	$ 3.93	$ 1.66	$ 2.78
Other comprehensive income (loss), net of tax:
Foreign currency translation gains (losses)	$ 125	$ (247.1)	$ (94.5)
Net unrealized losses on available-for-sale securities	(2)	(0.4)	(13.3)
Actuarial gains (losses)	(11.1)	15	(0.7)
Other comprehensive income (loss ), net of tax	111.9	(232.5)	(108.5)
Other comprehensive loss (income) attributable to noncontrolling interests	20.8	(12.4)	0.4
Other comprehensive income (loss) attributable to JHG	132.7	(244.9)	(108.1)
Total Comprehensive income (loss)	770.3	(55.2)	222.9
Total comprehensive loss (income) attributable to noncontrolling interests	17.9	(0.7)	(1.2)
Total comprehensive income (loss) attributable to JHG	$ 788.2	$ (55.9)	$ 221.7

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net income	$ 658.4	$ 177.3	$ 331.4
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	52.8	27.8	23.4
Deferred income taxes	(355.6)	2	(8.1)
Stock-based compensation plan expense	67.4	37.3	43.6
Gains (losses) from equity-method investments, net	0.6	3.1	(17.9)
Investment gains (losses), net	18	(11.7)	39.7
Contributions to pension plans in excess of costs recognized	(20.9)	(4.6)	(3.7)
Other, net	7.2	18.1	2.3
Changes in operating assets and liabilities:
OEIC and unit trust receivables and payables	(0.9)	(4.4)
Other assets	(117.8)	(6.1)	43.8
Other accruals and liabilities	170.9	(14.2)	(9.1)
Net operating activities	444.1	235.1	388.9
Investing activities:
Cash acquired from acquisition of JCG	417.2
Acquisition of subsidiaries, net of cash acquired			(57.8)
Proceeds from:
Proceeds from Investment securities - VIEs, net	122.4
Investment securities - seed capital, net	26.5	31.6	14.9
Purchases of:
Investment securities - VIEs, net	(827.5)	(81.6)	(40.3)
Property, equipment and software	(17.7)	(14.2)	(12.1)
Intangibles			(4)
Investment income received by consolidated funds	7.9	6.5
Cash movement on deconsolidation of consolidated funds	(11.2)	(8.4)
Net cash paid on settled hedges	(23.7)	(47.9)
Dividends received from equity-method investments	0.2	0.7	2.4
Dividends attributable to noncontrolling interests	(2.6)
Proceeds from sale of interests in equity-method investments, net			122.7
Proceeds from sale of Volantis	0.5
Net investing activities	519.5	(108.3)	56.8
Financing activities:
Settlement of convertible note hedge	59.3
Settlement of stock warrant	(47.8)
Proceeds from issuance of options	25.7
Proceeds from stock-based compensation plans	6	11	15.6
Purchase of common stock for stock-based compensation plans	(52.1)	(54.3)	(96.3)
Dividends paid to shareholders	(256)	(157.5)	(161)
Repurchase of common stock			(38.2)
Repayment of long-term debt	(92.5)	(203.4)
Distributions to noncontrolling interests	(5)
Third-party sales (redemptions) in consolidated seeded investment products, net	(141.4)	65.6	58.4
Principal payments under capital lease obligations	(0.9)
Net financing activities	(504.7)	(338.6)	(221.5)
Cash and cash equivalents:
Effect of foreign exchange rate changes	12.1	(48.7)	(19)
Net change	471	(260.5)	205.2
At beginning of year	323.2	583.7	378.5
At end of year	794.2	323.2	583.7
Supplemental cash flow information:
Cash paid for interest	8	7.3	16.7
Cash paid for income taxes, net of refunds	113.1	40.7	14.4
Reconciliation of cash and cash equivalents:
Cash and cash equivalents	323.2	583.7	378.5
Consolidated excluding VIEs
Cash and cash equivalents:
At beginning of year	279	530.9
At end of year	760.1	279	530.9
Reconciliation of cash and cash equivalents:
Cash and cash equivalents	279	530.9	530.9
Consolidated VIEs
Purchases of:
Investment securities - VIEs, net		(76.6)	(9.3)
Cash and cash equivalents:
At beginning of year	44.2	52.8
At end of year	34.1	44.2	52.8
Reconciliation of cash and cash equivalents:
Cash and cash equivalents	$ 44.2	$ 52.8	$ 52.8

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions	Common stock	Additional paid-in-capital	Treasury shares	Accumulated other comprehensive loss	Retained earnings	Nonredeemable noncontrolling interests	Total
Balance at Dec. 31, 2014	$ 235.8	$ 1,231.8	$ (156.6)	$ (81.5)	$ 652	$ 42.9	$ 1,924.4
Balance (in shares) at Dec. 31, 2014	1,139,200,000
Increase (Decrease) in Stockholders' Equity
Net income					329.8	1.6	331.4
Other comprehensive income (loss)				(108.1)		(0.4)	(108.5)
Dividends paid to shareholders					(161)		(161)
Purchase of common stock for stock-based compensation plans			(96.3)				(96.3)
Vesting of stock-based compensation plans			84		(84)
Issuance for common stock for stock-based compensation plans	$ 0.3	6.1	(6.4)
Issuance for common stock for stock-based compensation plans (in shares)	1,600,000
Stock-based compensation plan expense					43.6		43.6
Proceeds from stock-based compensation plans					15.6		15.6
Repurchase of common stock	$ (1.7)				(36.5)		(38.2)
Repurchase of common stock (in shares)	(9,000,000)
Balance at Dec. 31, 2015	$ 234.4	1,237.9	(175.3)	(189.6)	759.5	44.1	1,911
Balance (in shares) at Dec. 31, 2015	1,131,800,000
Increase (Decrease) in Stockholders' Equity
Net income					189	(11.7)	177.3
Other comprehensive income (loss)				(244.9)		12.4	(232.5)
Dividends paid to shareholders					(157.5)		(157.5)
Purchase of common stock for stock-based compensation plans			(54.3)				(54.3)
Vesting of stock-based compensation plans			74.5		(74.5)
Stock-based compensation plan expense					37.3		37.3
Proceeds from stock-based compensation plans					11		11
Balance at Dec. 31, 2016	$ 234.4	1,237.9	(155.1)	(434.5)	764.8	44.8	$ 1,692.3
Balance (in shares) at Dec. 31, 2016	1,131,800,000						1,131,842,109
Increase (Decrease) in Stockholders' Equity
Share consolidation (in shares)	(1,018,600,000)
Net income					655.5	1.5	$ 657
Other comprehensive income (loss)				132.7		(20.8)	111.9
Dividends paid to shareholders		0.1			(256)		(255.9)
Distributions to noncontrolling interests						(0.6)	(0.6)
Derivative instruments acquired on acquisition		31.4					31.4
NCI recognized on acquisition of JCG						13.3	13.3
Fair value adjustments to redeemable noncontrolling interests					(0.4)		(0.4)
Adjust consideration for post combination services under unvested stock-based compensation plans		(51.8)					(51.8)
Redemptions of convertible debt and settlement of derivative instruments		(22.3)					(22.3)
Tax impact of convertible debt redemptions and settlement of derivative instruments		(2.7)					(2.7)
Purchase of common stock for stock-based compensation plans			(52.1)				(52.1)
Issuance of common stock	$ 130.8	2,551.2					2,682
Issuance of common stock (in shares)	87,200,000
Redenomination and reduction of par value of stock	$ (64.6)	64.6
Vesting of stock-based compensation plans		(29)	51.4		(22.4)
Stock-based compensation plan expense		57.5			9.9		67.4
Proceeds from stock-based compensation plans		6					6
Balance at Dec. 31, 2017	$ 300.6	$ 3,842.9	$ (155.8)	$ (301.8)	$ 1,151.4	$ 38.2	$ 4,875.5
Balance (in shares) at Dec. 31, 2017	200,400,000						200,406,138

Description of the Business

Description of the Business	12 Months Ended
	Dec. 31, 2017
Description of the Business
Description of the Business	Note 1 — Description of the Business The Group is an independent global asset manager, specializing in active investment across all major asset classes. JHG actively manages a broad range of investment products for institutional and retail investors across five capabilities: Equities, Quantitative Equities, Fixed Income, Multi-Asset and Alternatives. On the Closing Date, JCG and Henderson completed the Merger. As a result of the Merger, JCG and its consolidated subsidiaries became subsidiaries of Henderson, which was renamed to Janus Henderson Group plc. See Note 4 — Acquisitions, for more information on the Merger. JHG is a public limited company incorporated in Jersey, Channel Islands, and is tax resident and domiciled in the UK. JHG's ordinary shares are traded on the NYSE and the Company's CDIs are traded on the ASX.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	Note 2 — Summary of Significant Accounting Policies Basis of Presentation The consolidated financial statements have been prepared according to GAAP. The Group's consolidated financial statements include all majority owned subsidiaries and consolidated seeded investment products, and intercompany accounts and transactions have been eliminated in consolidation. Events subsequent to the balance sheet date have been evaluated for inclusion in the accompanying consolidated financial statements through the issuance date. Prior to the Merger, Henderson's functional currency was GBP. After consideration of numerous factors, such as the denomination of the shares, payment of dividends, and the Group's main economic environment, management concluded that the post-Merger functional currency of JHG is USD. All values are rounded to the nearest $100,000 USD, except when otherwise indicated. Certain balances from prior years have been reclassified in order to conform to the current year presentation. This has included reclassifications between line items within the investing cash flow category of the Consolidated Statements of Cash Flows. Accounting Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates and the differences could be material. JHG's significant estimates relate to investment securities, acquisition accounting, goodwill and intangible assets, retirement benefit assets and obligations, contingent consideration, equity compensation and income taxes. Segment Information JHG is a global asset manager and manages a range of investment products, operating across various product lines, distribution channels and geographic regions. However, information is reported to the chief operating decision-makers, the Co-CEOs, on an aggregated basis. Strategic and financial management decisions are determined centrally by the Co-CEOs and, on this basis, the Group operates as a single segment investment management business. Consolidation of Investment Products The Group performs periodic consolidation analyses of its seeded investment products to determine if the product is a VIE or a voting rights entity ("VRE"). Factors considered in this assessment include the entity's legal organization, the entity's capital structure and equity ownership, and any de facto agent implications of the Group's involvement with the entity. Investment products that are determined to be VIEs are consolidated if the Group is the primary beneficiary of the entity. VREs are consolidated if the Group holds the majority voting interest. Upon the occurrence of certain events (such as contributions and redemptions, either by JHG or third parties, or amendments to the governing documents of the Group's investment products), management reviews and reconsiders its previous conclusion regarding the status of an entity as a VIE or a VRE. Additionally, management continually reconsiders whether JHG is considered a VIE's primary beneficiary, and thus consolidates such entity. Variable Interest Entities Certain investment products for which a controlling financial interest is achieved through arrangements that do not involve or are not directly linked to voting interests are considered VIEs. JHG reviews factors, including whether or not (i) the entity has equity that is sufficient to permit it to finance its activities without additional subordinated support from other parties and (ii) the equity holders at risk have the obligation to absorb losses, the right to receive residual returns and the right to direct the activities of the product that most significantly impact the entity's economic performance, to determine if the investment product is a VIE. The Group re-evaluates such factors as facts and circumstances change. The Group consolidates a VIE if JHG is the VIE's primary beneficiary. The primary beneficiary of a VIE is defined as the variable interest holder that has a controlling financial interest in the VIE. A controlling financial interest is defined as (i) the power to direct the activities of the VIE that most significantly impact its economic performance and (ii) the obligation to absorb losses of the entity or the right to receive benefits from the entity that potentially could be significant to the VIE. JHG is the manager of various types of seeded investment products, which may be considered VIEs. The Group's involvement in financing the operations of the VIEs is generally limited to its investments in the entities. VIEs are generally subject to consolidation by the Company at lower ownership percentages compared to the 50% threshold applied to VREs and are also subject to specific disclosure requirements. Voting Rights Entities The Group consolidates seeded investment products accounted for as VREs when it is considered to control such products, which generally exists if JHG has a greater than 50% voting equity interest. Property, Equipment and Software Property, equipment and software is recorded at cost. Depreciation is recorded using the straight-line method over the estimated useful life of the related assets (or the lease term, if shorter). Depreciation expense totaled $24.6 million, $8.2 million and $7.9 million for the years ended December 31, 2017, 2016 and 2015, respectively. Property, equipment and software are summarized as follows (in millions): Depreciation 2017 2016 Furniture, fixtures and computer equipment 3-10 years $ $ Leasehold improvements Over the shorter of 20 years or the period of the lease Computer software 3-7 years ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Property, equipment and software, gross $ $ Accumulated depreciation ​ ​ ) ​ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Property, equipment and software, net $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Internally generated software is recorded at cost and depreciated over its estimated useful life. Internal and external costs incurred in connection with researching or obtaining software for internal use are expensed as incurred during the preliminary project stage, as are training and maintenance costs. Internal and external costs incurred for internal use software during the application development stage are capitalized until such time that the software is substantially complete and ready for its intended use. Application development stage costs are depreciated on a straight-line basis over the estimated useful life of the software. JHG evaluates its property, equipment and software assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. The evaluation is based on an estimate of the future cash flows expected to result from the use of the asset and its eventual disposal. If expected future undiscounted cash flows are less than the carrying amount of the asset, an impairment loss is recognized in an amount equal to the excess of the carrying amount of the asset over the fair value of the asset. There were no impairments of property, equipment and software for the years ended December 31, 2017, 2016 and 2015. Deferred Commissions Initial sales commissions paid to and received from financial intermediaries on sales of certain wholesale products are deferred and amortized over various periods, not exceeding four years. The amortization period is based on the average expected life of the product on which the commission is received. Deferred commissions are recognized as components of other current assets, and of accounts payable and of accrued liabilities on the Consolidated Balance Sheets. Equity Method Investments The Group's investment in equity method investees, where the Group does not control the investee but can exert significant influence over the financial and operating policies (generally considered to be ownership between 20% and 50%), as well as in joint ventures where there is joint control (and in both cases, where it is not the primary beneficiary of a VIE), are accounted for using the equity method of accounting. Investments are initially recognized at cost when purchased for cash, or at the fair value of shares received where acquired as part of a wider transaction. The investments are subsequently carried at cost adjusted for the Group's share of net income or loss and other changes in comprehensive income of the equity method investee, less any dividends or distributions received by the Group. The Consolidated Statements of Comprehensive Income includes the Group's share of net income or loss for the year, or period of ownership, if shorter, within other non-operating income (expenses), net. Financial Instruments Financial assets are recognized at fair value in the Consolidated Balance Sheets when the Group becomes party to the contractual provisions of an instrument. The fair value recognized is adjusted for transaction costs, except for financial assets classified as trading where transaction costs are recognized immediately in net income. Financial assets are derecognized when the rights to receive cash flows from the investments have expired or where they have been transferred and the Group has also transferred substantially all the risks and reward of ownership. Purchases and sales of financial assets are recognized at the trade date. Delivery and settlement terms are usually determined by established practices in the market concerned. Debt securities, equity securities and holdings in pooled funds are designated as either trading or available-for-sale and are measured at subsequent reporting dates at fair value. The Group determines the classification of its financial assets on initial recognition. Unrealized gains and losses represent the difference between the fair value of the financial asset at the reporting date and cost or, if these have been previously revalued, the fair value at the last reporting date. Realized gains and losses on financial assets are calculated as the difference between the net sales proceeds and cost or amortized cost using the specific identification method. Financial liabilities, excluding deferred consideration, derivatives, fund deferral liabilities and redeemable noncontrolling interests in consolidated funds which are stated at fair value, are stated at amortized cost using the effective interest rate method. Financial liabilities stated at amortized cost include the Group's long term debt. Amortized cost is calculated by taking into account any issue costs and any discount or premium on settlement. Financial liabilities cease to be recognized when the obligation under the liability has been discharged or cancelled or has expired. Trading Securities Financial assets classified as trading are carried on the Group's Consolidated Balance Sheets at fair value. These comprise: the Group's manager box position representing the Group's holding in various OEICs and unit trusts used to cover any net shortfall in units created or liquidated for clients after the funds are priced; investments in the Group's fund products held by employee benefit trusts; certain investments in unconsolidated seed capital investments; and certain investments in consolidated funds. Gains and losses arising from changes in the fair value of financial assets classified as trading securities are included within investments gains (losses), net in the Consolidated Statements of Comprehensive Income. Where investments in the Group's fund products are held against outstanding deferred compensation liabilities, any movement in the fair value of these assets and corresponding movements in the deferred compensation liability are recognized in the Consolidated Statements of Comprehensive Income. Available-for-Sale Securities Financial assets classified as available-for-sale consist of certain unconsolidated seed capital investments and certain investments in consolidated funds. Available-for-sale securities are carried at fair value on the Consolidated Balance Sheet s , with changes in fair value recorded as a component of other comprehensive income within the Group's Consolidated Statements of Comprehensive Income until realized. When an asset is disposed of, the cumulative change in fair value, previously recognized in other comprehensive income, is reclassified to net income in the current accounting period. Seeded Investment Products The Group periodically adds new investment strategies to its investment product offerings by providing the initial cash investment or "seeding." The primary purpose of seeded investment products is to generate an investment performance track record in a product to attract third-party investors. JHG's initial investment in a new product represents 100% ownership in that product. Seeded investment products are initially consolidated and the individual securities within the portfolio are accounted for as trading securities. The change in fair value of seeded investment products is recorded in investment gains (losses), net on JHG's Consolidated Statements of Comprehensive Income. Noncontrolling interests in seeded investment products represent third-party ownership interests and are part of investment securities on JHG's Consolidated Balance Sheets. These assets are not available for general corporate purposes and may be redeemed by the third parties at any time. Refer to the consolidation discussion in this note for information regarding the consolidation of certain seeded investment products. JHG may redeem invested seed capital for a variety of reasons, including when third-party investments in the relevant product are sufficient to sustain the given investment strategy. The length of time JCG holds a majority interest in a product varies based on a number of factors, including, but not limited to, market demand, market conditions and investment performance. Investments in Advised Mutual Funds and Investments Related to the Economic Hedging of Deferred Compensation JHG grants mutual fund share awards to employees that are indexed to certain funds managed by JHG. Upon vesting, participants receive the value of the mutual fund share awards adjusted for gains or losses attributable to the mutual funds to which the award was indexed, subject to tax withholding, or participants receive shares in the mutual fund. When investments in the Group's fund products are purchased and held against deferred compensation liabilities, any movement in the fair value of the assets and corresponding movements in the deferred compensation liability are recognized in the Consolidated Statements of Comprehensive Income. The Group maintains deferred compensation plans for certain highly compensated employees and members of its Board of Directors. Eligible participants may defer a portion of their compensation and have the ability to earn a return by indexing their deferrals to mutual funds managed by the Group and its subsidiaries. The Group makes no contributions to the plan. To protect against market variability of the liability, the Group creates an economic hedge by investing in mutual funds that are consistent with the deferred amounts and mutual fund elections of the participants. Such investments remain assets of JHG. Changes in market value of the liability to participants are recognized as long-term incentive compensation in JHG's Consolidated Statements of Comprehensive Income, and changes in the market value of the mutual fund securities are recognized in investment gains (losses), net on JHG's Consolidated Statements of Comprehensive Income. Impairment Evaluation The Group periodically evaluates the carrying value of equity method investments and investment securities classified as available-for-sale for potential impairment. In determining if an impairment exists, the Group considers the duration, extent and circumstances of any decline in fair value. Where a fall in the value of an investment is prolonged or significant, it is considered an indication of impairment. The Group evaluates the securities in an unrealized loss position in the available for sale portfolio for OTTI on the basis of the duration of the decline in value of the security and severity of that decline as well as the Group's intent and ability to hold these securities for a period of time sufficient to allow for any anticipated recovery in the market value. For equity method investments, if circumstances indicate that an OTTI may exist, the investments are evaluated using market values where available, or the expected future cash flows of the investment. If it is determined that the impairment on an equity security is other than temporary, the investment is written down to fair value. An impairment loss equal to the difference between the carrying value of the security and its fair value is recognized as an impairment charge within investment gains (losses), net in the Group's Consolidated Statements of Comprehensive Income. For available-for-sale investments, any amounts previously recognized in other comprehensive income in respect of cumulative changes in fair value are taken to net income on impairment. No impairment charges were recognized on investment securities for the years ended December 31, 2017, 2016 and 2015. Trade Receivables Trade receivables, which generally have 30 day payment terms, are initially recognized at fair value, normally equivalent to the invoice amount. When the time value of money is material, the fair value is discounted. Provision for specific doubtful accounts is made when there is evidence that the Group may not be able to recover balances in full. Balances are written off when the receivable amount is deemed uncollectable. OEIC and Unit Trust Receivables and Payables OEIC and unit trust receivables and payables are in relation to the purchase of units/shares (by investors) and the liquidation of units/shares (owned by trustees). The amounts are dependent on the level of trading and fund switches in the four working days leading up to the end of the period. Since they are held with different counterparties, the amounts are presented gross on the Group's Consolidated Balance Sheets. Cash and Cash Equivalents Cash and cash equivalents primarily consist of cash held at banks, on demand deposits, highly liquid short term government securities and investments in money market instruments with a maturity date of three months or less. Cash balances maintained by consolidated VREs are not considered legally restricted and are included in cash and cash equivalents on the Consolidated Balance Sheets. Cash balances held by consolidated VIEs are disclosed separately as a component of assets of consolidated VIEs on the Consolidated Balance Sheets. Derivative Instruments The Group may, from time to time, use derivative financial instruments to mitigate price, interest rate, foreign currency and credit risk. The Group does not designate derivative instruments as hedges for accounting purposes, with the exception of certain foreign currency forward contracts used for net investment hedging. Derivative instruments are measured at fair value and classified as either other current assets or accounts payable and accrued liabilities on the Group's Consolidated Balance Sheets. Changes in the fair value of derivative instruments are recorded within investment gains (losses), net in the Group's Consolidated Statements of Comprehensive Income. Changes in fair value of foreign currency forward contracts designated as hedges for accounting purposes are recognized in accumulated other comprehensive income under net investment hedge accounting. The Group's consolidated seed investments may also be party to derivative instruments. These derivative instruments are disclosed separately from the Group's corporate derivative instruments. Refer to Note 6 — Investment Securities. Noncontrolling Interests and Redeemable Noncontrolling Interests Noncontrolling interests that are not subject to redemption rights are classified in permanent equity. Redeemable noncontrolling interests are classified outside of permanent equity on the Consolidated Balance Sheets and are measured at the estimated fair value as of the balance sheet date. Noncontrolling interests in consolidated seed investments are classified as redeemable noncontrolling interests where there is an obligation on the fund to repurchase units at the investor's request. Refer to Note 13 — Noncontrolling Interests for further information. Fair Value Measurements Fair value is the price that would be received to sell an asset or transfer a liability in an orderly transaction between market participants at the measurement date. The fair value of financial instruments traded in active markets (such as publicly traded securities and derivatives) is based on quoted market prices at the reporting date. The quoted market price used for financial instruments is the last traded market price for both financial assets and financial liabilities where the last traded price falls within the bid ask spread. In circumstances where the last traded price is not within the bid ask spread, management will determine the point within the bid ask spread that is most representative of fair value current bid price. The fair value of financial instruments that are not traded in an active market is determined using valuation techniques commonly used by market participants, including the use of comparable recent arm's length transactions, discounted cash flow analysis and option pricing models. Estimating fair value requires significant management judgment, including benchmarking to similar instruments with observable market data and applying appropriate discounts that reflect differences between the securities that the Group is valuing and the selected benchmark. Measurements of fair value are classified within a hierarchy that prioritizes the inputs to valuation techniques used to measure fair value based on whether the inputs to those valuation techniques are observable or unobservable. The valuation hierarchy contains three levels: • Level 1 — Valuation inputs are unadjusted quoted market prices for identical assets or liabilities in active markets. • Level 2 — Valuation inputs are quoted market prices for identical assets or liabilities in markets that are not active, quoted market prices for similar assets and liabilities in active markets, and other observable inputs directly or indirectly related to the asset or liability being measured. • Level 3 — Valuation inputs are unobservable and significant to the fair value measurement. The valuation of an asset or liability may involve inputs from more than one level of the hierarchy. The level in the fair value hierarchy within which a fair value measurement in its entirety falls is determined based on the lowest level input that is significant to the fair value measurement. Level 1 Fair Value Measurements JHG's Level 1 fair value measurements consist mostly of seeded investment products, investments in advised mutual funds, cash equivalents and investments related to deferred compensation plans with quoted market prices in active markets. The fair value level of consolidated seeded investment products is determined by the underlying securities of the product. The fair value level of unconsolidated seeded investment products is determined using the respective NAV of each product. Level 2 Fair Value Measurements JHG's Level 2 fair value measurements consist mostly of consolidated seeded investment products and JHG's long-term debt. The fair value of consolidated seeded investment products is determined by the underlying securities of the product. The fair value of JHG's long-term debt is determined using broker quotes and recent trading activity, which are considered Level 2 inputs. Level 3 Fair Value Measurements JHG's assets and liabilities measured at Level 3 are primarily private equity investments, redeemable noncontrolling interests, contingent deferred consideration and deferred compensation liabilities which are held against investments in the Group's fund products, where the significant valuation inputs are unobservable. Private equity investments are valued using a combination of the enterprise value / EBITDA multiple method and the discounted cash flow method. Significant unobservable inputs include discount rates, EBITDA multiple, and price-earnings ratio, taking into account management's experience and knowledge of market conditions of the specific industries. The fair value of redeemable noncontrolling interests in consolidated funds is primarily driven by the fair value of the investments in consolidated funds. Details of inputs used to calculate the fair value of contingent deferred consideration can be found in Note 9 — Fair Value Measurements. Nonrecurring Fair Value Measurements Nonrecurring Level 3 fair value measurements include goodwill and intangible assets. The Group measures the fair value of goodwill and intangible assets on initial recognition using discounted cash flow analysis that requires assumptions regarding projected future earnings and discount rates. Because of the significance of the unobservable inputs in the fair value measurements of these assets and liabilities, such measurements are classified as Level 3. See the 'Goodwill and Intangible Assets, net' accounting policy set forth within Note 2 — Summary of Significant Accounting Policies for further information. Income Taxes The Group provides for current tax expense according to the tax laws in each jurisdiction in which it operates, using tax rates and laws that have been enacted by the Balance Sheet date. Deferred income tax assets and liabilities are recorded for temporary differences between the financial statement and income tax basis of assets and liabilities as measured by the enacted income tax rates that may be in effect when these differences reverse. The effect of changes in tax rates on the Group's deferred tax assets and liabilities is recognized as income tax within net income in the period that includes the enactment date. Significant management judgment is required in developing the Group's provision for income taxes, including the valuation allowances that might be required against deferred tax assets and the evaluation of unrecognized tax benefits resulting from uncertain tax positions taken or expected to be taken in a tax return. The Group periodically assesses the recoverability of its deferred tax assets and the need for valuation allowances on these assets. The Group makes these assessments based on the weight of available evidence regarding possible sources of future taxable income and estimates relating to the future performance of the business that results in taxable income. In evaluating uncertain tax positions, the Group considers the probability that the tax benefit can be sustained on examination by a taxing authority on the basis of its technical merits ('the recognition threshold'). For tax positions meeting this threshold, the amount recognized in the financial statements is the benefit expected to be realized upon settlement with the taxing authority on the basis of a cumulative-probability assessment of the possible outcomes. For tax positions not meeting the recognition threshold, no financial statement benefit is recognized. The Group recognizes the accrual of interest and penalties on uncertain tax positions as a component of the income tax provision. Revenue Recognition Revenue includes management fees and performance fees, net of rebates. Management fees are recognized in the accounting period in which the associated investment management service is provided. Performance fees for all fund ranges and separate accounts are recognized on crystallization and are therefore accounted for when the prescribed performance hurdles are achieved and it is probable that a fee will be collected as a result. There are no performance fee contracts where revenue can be reversed or clawed back. There are no cumulative revenues recognized that would be reversed if all of the existing investments became worthless. Management fees are generally based upon a percentage of the market value of AUM and are calculated as a percentage of either the daily, month-end or quarter-end average asset balance in accordance with contractual agreements. Performance fees are specified in certain fund and client contracts and are based on investment performance either on an absolute basis or compared to an established index over a specified period of time. This is often subject to a hurdle rate. Management fees are primarily received monthly or quarterly while performance fees are usually received monthly, quarterly or annually by the Group, although the frequency of receipt varies between agreements. Management and performance fee revenue not yet received is recognized within fees and other receivables in the Consolidated Balance Sheets. U.S. Mutual Fund Performance Fees The investment management fee paid by each U.S. mutual fund subject to a performance fee is the base management fee plus or minus a performance fee adjustment as determined by the relative investment performance of the fund compared to a specified benchmark index. Under the performance-based fee structure, the investment advisory fee paid by each fund consists of two components: (1) a base fee calculated by applying the contractual fixed rate of the advisory fee to the fund's average daily net assets during the previous month, plus or minus (2) a performance fee adjustment calculated by applying a variable rate of up to 0.15% to the fund's average daily net assets during the performance measurement period. The performance measurement period begins as a trailing period ranging from 12 to 18 months, and each subsequent month is added to each successive performance measurement period until a 36-month period is achieved. At that point, the measurement period becomes a rolling 36-month period. When current fund net assets vary from fund net assets over the performance measurement period, the performance fee adjustment, as a percentage of fund current assets, may vary significantly. Under circumstances involving underperformance by a rapidly shrinking fund, the dollar amount of the negative performance fee adjustment could be more than the dollar amount of the positive base fee. The addition of performance fees to all funds without such fees is subject to the approval of both a majority of the shareholders of such Funds and the Funds' Independent Board of Trustees. Commissions Commissions on management fees are accounted for on an accrual basis and are recognized in the accounting period in which the associated management fee is earned. Operating Expenses Operating expenses are accrued and recognized as incurred. Stock-Based Compensation The Group issues stock-based awards to employees, all of which are classified as equity settled stock-based payments. Equity settled stock-based payments are measured at the fair value of the shares at the grant date. The awards are expensed, with a corresponding increase in reserves, on either a straight-line basis or a graded basis (depending on vesting conditions) over the vesting period. Forfeitures are recognized as they occur. The grant date fair value for stock options is determined using the Black-Scholes option pricing model, and the grant date fair value of restricted stock is determined from the market price on the date of grant. The Black-Scholes model requires management to determine certain variables; the assumptions used in the Black-Scholes option pricing model include dividend yield, expected volatility, risk free interest rate and expected life. The dividend yield and expected volatility are determined using historical Group data. The risk free interest rate for options granted is based on the three year UK treasury coupon at the time of the grant. The expected life of the stock options is the same as the service conditions applicable to all Group awards. The Group generally uses the Monte Carlo model to determine the fair value of performance-based awards. The assumptions used in the Monte Carlo model include dividend yield, share price volatility and discount rate. The Group had $9.9 million and $37.3 million of stock-based compensation costs and nil and $11.0 million of proceeds from stock-based compensation plans included in retained earnings during the years ended December 31, 2017 and 2016, respectively.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	12 Months Ended
	Dec. 31, 2017
Recent Accounting Pronouncements
Recent Accounting Pronouncements	Note 3 — Recent Accounting Pronouncements Revenue Recognition In May 2014, the Financial Accounting Standards Board ("FASB") issued a new revenue recognition standard. The standard's core principle is that a company will recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In addition, the standard specifies the accounting for certain costs to obtain or fulfill a contract with a customer and expands disclosure requirements for revenue recognition. The revenue standard is effective for annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period. The Company is evaluating the effect of adopting this new accounting standard, including the amending Accounting Standards Update ("ASU"). Management reviewed the terms and conditions of its revenue contracts and does not expect a significant change in the timing of revenue recognition for its management fees, performance fees, servicing fees and its other revenue upon adoption of the new guidance. However, the Group's evaluation is not complete. In March 2016, the FASB issued an amendment to its principal-versus-agent guidance in the FASB's new revenue standard. The key provisions of the amendment are assessing the nature of the entity's promise to the customer, identifying the specified goods or services, and applying the control principle and indicators of control. The amendment is effective for annual reporting periods beginning after December 15, 2017, including interim periods within those annual reporting periods. In addition, entities are required to adopt the amendment by using the same transition method they used to adopt the new revenue standard. The Company's principal-versus-agent assessment focused on treatment of distribution fees collected from mutual fund assets and whether such fees should be reported as revenue (1) on a gross basis or (2) on a net basis, where such fees are reduced by distribution fees paid by the Company to intermediaries. Currently, certain distribution fees are presented on a gross basis, while others are presented on a net basis, with respective presentations dictated by the terms of the underlying distribution agreements. Presentation of distribution fees will be made on a gross basis upon adoption of the accounting guidance. The Company currently expects such presentation to increase annual revenue by approximately $97 million with a corresponding increase in annual expense based on respective annualized figures in 2017. The guidance will be adopted on a retrospective basis. The retrospective basis will require the restatement of prior period revenue and expense amounts, but will not impact operating income or net income figures. Financial Instruments In January 2016, the FASB issued amendments to its financial instruments standard, including changes relating to the accounting for equity investments and the presentation and disclosure requirements for financial instruments. Under the amended guidance, all equity investments in unconsolidated entities (other than those accounted for using the equity method of accounting) will generally be measured at fair value through earnings. There will no longer be an available-for-sale classification (changes in fair value reported in other comprehensive income) for equity securities with readily determinable fair values. The amended guidance also requires financial assets and financial liabilities to be presented separately in the notes to the consolidated financial statements, grouped by measurement category (e.g., fair value, amortized cost, lower of cost or market value) and form of financial asset (e.g., loans, securities). The standard is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. As of December 31, 2017, the Group has available-for-sale investment securities that have been measured at fair value through other comprehensive income. Upon adoption of the standard in 2018, changes in fair value related to these securities will be recorded to investment gains (losses), net on JHG's Consolidated Statements of Comprehensive Income. In addition, a cumulative effect adjustment will be recorded to the 2018 retained earnings beginning balance to remove the accumulated balance in other comprehensive income. Adoption of the standard will not have a material impact on JHG's results of operations or cash flows. Leases In February 2016, the FASB issued a new standard on accounting for leases. The new standard represents a significant change to lease accounting and introduces a lessee model that brings most leases on to the balance sheet. The standard also aligns certain of the underlying principles of the new lessor model with those in the FASB's new revenue recognition standard. Furthermore, the new standard addresses other concerns related to the current leases model. The standard is effective for calendar periods beginning after December 15, 2018. The Group is evaluating the effect of adopting this new accounting standard. Statement of Cash Flows In August 2016, the FASB issued an ASU to clarify guidance on the classification of certain cash receipts and cash payments in the statements of cash flows. The FASB issued the ASU with the intent of reducing diversity in practice regarding eight types of cash flows. The ASU is effective for annual reporting periods beginning after December 15, 2017, including interim periods within those annual reporting periods. Management does not expect the adoption to have a material impact on the Consolidated Statements of Cash Flows. In November 2016, the FASB issued an ASU to clarify guidance on the classification and presentation of restricted cash in the statements of cash flows. The ASU is effective for annual reporting periods beginning after December 15, 2017, including interim periods within those annual reporting periods. Management does not expect the adoption to have a material impact on the Consolidated Statements of Cash Flows. Goodwill Impairment Testing In January 2017, the FASB issued an ASU which simplifies the accounting for goodwill impairments by eliminating step two from the goodwill impairment test. The ASU requires goodwill impairments to be measured on the basis of the fair value of the reporting unit relative to the reporting unit's carrying amount rather than on the basis of the implied amount of goodwill relative to the goodwill balance of the reporting unit. The ASU is effective for annual and interim impairment tests for periods beginning after December 15, 2021. Early adoption is allowed for annual and interim impairment tests occurring after January 1, 2017. The Group early adopted the guidance effective January 1, 2017, and applied the guidance to its annual impairment tests in 2017. Hedge Accounting In August 2017, the FASB issued an ASU that amends hedge accounting. The ASU expands the strategies eligible for hedge accounting, changes how companies assess hedge effectiveness and will require new disclosures and presentation. The ASU is effective on January 1, 2019, for calendar year-end companies; however, early adoption is permitted. The Group is evaluating the effect of adopting this new accounting standard. Retirement Benefit Plans In March 2017, the FASB issued an ASU that requires the bifurcation of net periodic pension costs. The service cost component will be presented with other employee compensation costs in operating income, while the other components of net periodic pension costs will be presented separately outside of operations. The guidance is effective for annual reporting periods beginning after December 15, 2017, and interim periods within that reporting period. The Group anticipates reclassifying approximately $2.7 million of other components excluding service costs outside of operating expenses on an annualized basis.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2017
Acquisitions
Acquisitions	Note 4 — Acquisitions Merger with JCG On the Closing Date, pursuant to the Agreement and Plan of Merger dated as of October 3, 2016 (the "Merger Agreement"), by and among JCG, a Delaware corporation, Henderson, a company incorporated in Jersey, and Horizon Orbit Corp., a Delaware corporation and a direct and wholly owned subsidiary of Henderson ("Merger Sub"), Merger Sub merged with and into JCG, with JCG surviving such merger as a direct and wholly owned subsidiary of Henderson. Upon closing of the Merger, Henderson became the parent holding company for the combined group and was renamed Janus Henderson Group plc. Upon closing of the Merger, holders of JCG common stock received 0.47190 fully paid and non-assessable JHG ordinary shares with a par value of $1.50 per share (the "Ordinary Shares") for each share of JCG common stock held, plus cash in lieu of any fractional shares based on prevailing market prices. Effective immediately prior to the closing of the Merger, Henderson implemented a share consolidation of ordinary shares at a ratio of one Ordinary Share (or CDI, as applicable) for every 10 ordinary shares (or CDIs, as applicable) outstanding. The fair value of consideration transferred to JCG common stockholders was $2,630.2 million, representing 87.2 million shares of JHG transferred at a share price of $30.75 each as of the Closing Date, adjusted for a post-combination stock-based compensation charge for unvested shares in relation to JCG share plans. The issuance of JHG shares in connection with the Merger was registered under the Securities Act of 1933, as amended, pursuant to JHG's registration statement on Form F- 4 (File No. 333- 216824) filed with the SEC on March 20, 2017 (the "Registration Statement"). Fair Values of Assets Acquired and Liabilities Assumed Preliminary estimates of fair values of the assets acquired and liabilities assumed were based on information available as of the closing of the Merger. The Group evaluated the underlying inputs and assumptions used in its valuations and finalized its purchase price allocation as of December 31, 2017. Certain adjustments were recorded to goodwill, deferred tax liabilities, other non-current liabilities and noncontrolling interests. The final allocation of the consideration transferred to the assets acquired and liabilities assumed are presented in the following table (in millions): Preliminary purchase Adjustments Final purchase Assets: ​ ​ ​ Cash and cash equivalents $ $ — $ Investment securities ​ ​ — ​ Fees and other receivables — Other current assets, net ​ ​ — ​ Property, equipment and software — Intangible assets ​ ​ — ​ Goodwill Other non-current assets, net ​ ​ ​ ​ Liabilities: Long-term debt ​ ​ — ​ Deferred tax liabilities Accounts payable and accrued liabilities ​ ​ — ​ Other non-current liabilities Noncontrolling interests ​ ​ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net assets acquired $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Goodwill Goodwill primarily represents the value JHG expects to obtain from growth opportunities and synergies for the combined operations. Goodwill is not deductible for tax purposes. Intangible Assets Acquired intangible assets include the value of investment advisory agreements for mutual funds, separate accounts and ETPs. Also included are the values of acquired trademarks, which include trademarks for Janus Capital Management LLC, Intech, Kapstream, Perkins and VelocityShares. Acquired intangible assets and their weighted-average estimated useful lives are presented in the following table (in millions): Fair value Useful Investment management contracts: ​ Mutual funds $ Indefinite Separate accounts ​ ETNs ETFs ​ Indefinite Trademarks Indefinite ​ ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Debt The fair value of JHG's debt was valued using broker quotes and recent trading activity, which are considered fair value Level 2 inputs. The acquired 2018 Convertible Notes may be wholly or partially settled in cash, and thereby the liability and conversion feature components are accounted for separately. The $115.2 million liability component at the Closing Date was determined by discounting future contractual cash flows at a 1.9% rate, which is consistent with the estimated market interest rate for similar senior notes with no conversion option. The liability component will accrete up to the face value of $116.6 million, through interest expense, over the remaining term of the notes. The $42.9 million equity component was determined as the difference between the liability component and the fair value of the 2018 Convertible Notes at the Closing Date. The 2025 Senior Notes were recorded at their fair value of $323.7 million at the time of the Merger. The 2025 Senior Notes include unamortized debt premium, net at December 31, 2017, of $22.0 million, which will be amortized over the remaining life of the 2025 Senior Notes through interest expense. The unamortized debt premium is recorded as a liability within long-term debt on JHG's Consolidated Balance Sheets. Deferred Tax Liabilities, Net Deferred income taxes primarily relate to deferred income tax balances acquired from JCG and the deferred tax impact of fair value adjustments to the assets and liabilities acquired from JCG, including intangible assets and long-term debt. Deferred income taxes were provisionally estimated based on statutory tax rates in the jurisdictions of the legal entities where the acquired assets and liabilities are taxed. Tax rates used are continually assessed, and updates to deferred income tax estimates are based on any changes to provisional valuations of the related assets and liabilities and refinement of the effective tax rates, which could result in changes to these provisional values. Pro Forma Results of Operations The following table presents summarized unaudited supplemental pro forma operating results as if the Merger had occurred at the beginning of each of the periods presented (in millions): Year ended December 31, 2017 2016 2015 Revenue $ $ $ Net income attributable to JHG $ $ $ JCG Results of Operations Unaudited revenue (inclusive of revenue from certain mandates transferred to JCG from Henderson after the Merger) and net income of JCG from the Closing Date through the end of December 31, 2017, included in JHG's Consolidated Statements of Comprehensive Income are presented in the following table (in millions): Closing Date — Revenue $ Net income attributable to JCG $ Options On the Closing Date of the Merger, JHG sold 20 tranches of conditional options to Dai-ichi, with each tranche allowing Dai-ichi to purchase 500,000 JHG ordinary shares at a strike price of £29.972 per share (the terms of such options having been adjusted in accordance with the terms of the Dai-ichi Option Agreement to take account of the effect of the share consolidation). The cash consideration received for the options was £19.8 million ($25.7 million). The options can be exercised by Dai-ichi during the period from the Closing Date of the Merger until October 3, 2018. As of December 31, 2017, the fair value of the options was $26.1 million. Contingent Consideration Acquisitions prior to the Merger included contingent consideration. Refer to Note 9 — Fair Value Measurements for a detailed discussion of the terms of the contingent consideration.

Consolidation

Consolidation	12 Months Ended
	Dec. 31, 2017
Consolidation
Consolidation	Note 5 — Consolidation Variable Interest Entities Consolidated Variable Interest Entities JHG's consolidated VIEs as of December 31, 2017, include certain consolidated seeded investment products in which the Group has an investment and acts as the investment manager. The assets of these VIEs are not available to JHG or the creditors of JHG. JHG may not, under any circumstances, access cash and cash equivalents held by consolidated VIEs to use in its operating activities or otherwise. In addition, the investors in these VIEs have no recourse to the credit of the Group. Consolidated VIE assets and liabilities, presented after intercompany eliminations, at December 31, 2017 and 2016, are as follows (in millions): December 31, December 31, Investment securities $ $ Cash and cash equivalents Other current assets ​ ​ Accounts payable and accrued liabilities ) ) ​ ​ ​ ​ ​ ​ ​ ​ Total ​ ​ Redeemable noncontrolling interests in consolidated VIEs ) ) Nonredeemable noncontrolling interests in consolidated VIEs ​ ) ​ ) ​ ​ ​ ​ ​ ​ ​ ​ JHG's net interest in consolidated VIEs $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unconsolidated Variable Interest Entities At December 31, 2017 and 2016, JHG's carrying value of investment securities included on the Consolidated Balance Sheets pertaining to unconsolidated VIEs was $6.2 million and nil, respectively. JHG's total exposure to unconsolidated VIEs represents the value of its economic ownership interest in the investment securities. Voting Rights Entities Consolidated Voting Rights Entities The following table presents the balances related to consolidated VREs that were recorded on JHG's Consolidated Balance Sheets, including JHG's net interest in these products (in millions): December 31, December 31, Investment securities $ $ Cash and cash equivalents — Other current assets ​ ​ — Accounts payable and accrued liabilities ) — ​ ​ ​ ​ ​ ​ ​ ​ Total ​ ​ Redeemable noncontrolling interests in consolidated VREs ) — ​ ​ ​ ​ ​ ​ ​ ​ JHG's net interest in consolidated VREs $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ JHG's total exposure to consolidated VREs represents the value of its economic ownership interest in these seeded investment products. JHG may not, under any circumstances, access cash and cash equivalents held by consolidated VREs to use in its operating activities or for any other purpose. Unconsolidated Variable Rights Entities At December 31, 2017 and 2016, JHG's carrying value of investment securities included on the Consolidated Balance Sheets pertaining to unconsolidated VREs was $50.0 million and $4.9 million, respectively. JHG's total exposure to unconsolidated VIEs represents the value of its economic ownership interest in the investment securities.

Investment Securities

Investment Securities	12 Months Ended
	Dec. 31, 2017
Investment Securities
Investment Securities	Note 6 — Investment Securities JHG's investment securities as of December 31, 2017 and 2016, are summarized as follows (in millions): December 31, 2017 2016 Trading securities: ​ ​ Seeded investment products: Consolidated VIEs $ $ Consolidated VREs Unconsolidated VIEs and VREs ​ ​ Separate accounts — Pooled investment funds ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ Total seeded investment products Investments related to deferred compensation plans ​ ​ Other investments ​ ​ ​ ​ ​ ​ ​ ​ Total trading securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Available-for-sale securities: Seeded investment products: ​ ​ Consolidated VIEs Unconsolidated VIEs and VREs ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total available-for-sale securities ​ ​ ​ ​ ​ ​ ​ ​ Total investment securities $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Trading Securities Net unrealized gains (losses) on trading securities held as of December 31, 2017, 2016 and 2015, are summarized as follows (in millions): Year ended December 31, 2017 2016 2015 Trading securities still held at period end $ $ $ ) Available-for-Sale Securities The following is a summary of available-for-sale securities as of December 31, 2017 and 2016 (in millions): Gross Foreign Cost Gains Losses Fair value December 31, 2017: ​ ​ ​ ​ ​ Available-for-sale securities $ $ $ — $ $ December 31, 2016: ​ ​ ​ ​ ​ Available-for-sale securities $ $ $ — $ $ Derivative Instruments JHG maintains an economic hedge program that uses derivative instruments to hedge against market volatility of certain seeded investments by using index and commodity futures ("futures"), credit default swaps, index swaps and total return swaps ("TRSs"). Certain foreign currency exposures associated with the Group's seeded investment products are also hedged by using foreign currency forward contracts. JHG was party to the following derivative instruments as of December 31, 2017 and 2016 (in millions): Notional Value December 31, December 31, Futures $ $ Credit default swaps — Index swaps ​ ​ Total return swaps Foreign currency forward contracts ​ ​ The derivative instruments are not designated as hedges for accounting purposes, with the exception of foreign currency forward contracts used for net investment hedging. Changes in fair value of the futures, index swaps, TRSs and credit default swaps are recognized in investment gains (losses), net in JHG's Consolidated Statements of Comprehensive Income. Changes in the fair value of the foreign currency forward contracts designated as hedges for accounting purposes are recognized in other comprehensive income (loss), net of tax on JHG's Consolidated Statements of Comprehensive Income. The value of the individual derivative contracts are recognized on a gross basis and included in other current assets or accounts payable and accrued liabilities on the Consolidated Balance Sheets. The Group has entered into netting arrangements with certain counterparties. The impacts of any potential netting are shown below. The following tables illustrate the effect of offsetting derivative instruments on JHG's Consolidated Balance Sheets as of December 31, 2017 and 2016 (in millions): December 31, 2017 Gross amounts Gross amounts Gross amounts Net amounts Assets: ​ ​ ​ ​ Futures $ $ ) $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets $ $ ) $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: Futures $ ) $ $ — $ ) Foreign currency forward contracts ) — ) Total return swaps ​ ) ​ — ​ ​ — Index swaps ) — — Credit default swaps ​ ) ​ — ​ ​ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total liabilities $ ) $ $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2016 Gross amounts Gross amounts Gross amounts Net amounts Liabilities: ​ ​ ​ ​ Total return swaps $ ) $ — $ $ — Index swaps ​ ) ​ — ​ ​ ) Foreign currency forward contracts ) — — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total liabilities $ ) $ — $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The Group recognized the following net foreign currency translation gains (losses) on hedged seed investments denominated in currencies other than the Group's functional currency and net gains (losses) associated with foreign currency forward contracts under net investment hedge accounting for the years ended December 31, 2017, 2016 and 2015 (in millions): Year ended December 31, 2017 2016 2015 Foreign currency translation $ ) $ $ Foreign currency forward contracts ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ — $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The foreign currency translation gains and losses on foreign currency forward contracts associated with the net investment hedge are recognized in other comprehensive income (loss), net of tax in JHG's Consolidated Statements of Comprehensive Income. Derivative Instruments in Consolidated Seeded Investment Products Certain of the Group's consolidated seeded investment products utilize derivative instruments to contribute to the achievement of defined investment objectives. These derivative instruments are classified within other current assets or accounts payable and accrued liabilities on JHG's Consolidated Balance Sheets. Gains and losses on these derivative instruments are classified within investment gains (losses), net in JHG's Consolidated Statements of Comprehensive Income. JHG's consolidated seeded investment products were party to the following derivative instruments as of December 31, 2017 and 2016 (in millions): Notional Value December 31, December 31, Futures $ $ Contracts for differences Credit default swaps ​ ​ Total return swaps — Interest rate swaps ​ ​ Options Swaptions ​ ​ Foreign currency forward contracts The following table illustrates the effect of offsetting derivative instruments within consolidated seeded investment products on JHG's Consolidated Balance Sheets as of December 31, 2017 (in millions): December 31, 2017 Gross amounts Gross amounts Gross amounts Net amounts Assets: ​ ​ ​ ​ Futures $ $ ) $ — $ Contracts for differences ​ ​ — ​ — ​ Interest rate swaps ) — Total return swaps ​ ​ — ​ — ​ Credit default swaps ) — — Options ​ ​ ) ​ — ​ Swaptions — — Foreign currency forward contracts ​ ​ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ ) $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: ​ ​ ​ ​ Futures $ ) $ $ — $ — Interest rate swaps ​ ) ​ ​ — ​ ) Credit default swaps ) — ) Options ​ ) ​ ​ — ​ — Foreign currency forward contracts ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ ) $ $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The following table illustrates the effect of offsetting derivative instruments within consolidated seeded investment products on JHG's Consolidated Balance Sheets as of December 31, 2016 (in millions): December 31, 2016 Gross amounts Gross amounts Gross amounts Net amounts Assets: ​ ​ ​ ​ Futures $ $ ) $ — $ Contracts for differences ​ ​ ) ​ — ​ Interest rate swaps ) — — Options ​ ​ ) ​ — ​ Foreign currency forward contracts — ) — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets $ $ ) $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: Futures $ ) $ $ — $ — Contracts for differences ) — — Interest rate swaps ​ ) ​ ​ — ​ — Credit default swaps ) — — ) Options ​ ) ​ ​ — ​ — Foreign currency forward contracts ) — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total liabilities $ ) $ $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2017 and 2016, certain consolidated seeded investment products sold credit protection through the use of credit default swap contracts. The contracts provide alternative credit risk exposure to individual companies and countries outside of traditional bond markets. The terms of the credit default swap contracts range from one to five years. As sellers in credit default swap contracts, the consolidated seeded investment products would be required to pay the notional value of a referenced debt obligation to the counterparty in the event of a default on the debt obligation by the issuer. The notional value represents the estimated maximum potential undiscounted amount of future payments required upon the occurrence of a credit default event. As of December 31, 2017 and 2016, the notional values of the agreements totaled $4.0 million and nil, respectively. The credit default swap contracts include recourse provisions that allow for recovery of a certain percentage of amounts paid upon the occurrence of a credit default event. As of December 31, 2017 and 2016, the fair value of the credit default swap contracts selling protection was $0.1 million and nil respectively. Investment Gains (Losses), Net Investment gains (losses), net on JHG's Consolidated Statements of Comprehensive Income included the following for the years ended December 31, 2017, 2016 and 2015 (in millions): Year ended December 31, 2017 2016 2015 Seeded investment products $ $ $ Fair value movements on derivatives ) ) Gain on sale of equity method investments ​ — ​ — ​ Gain on sale of Volantis — — Other ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Investment gains (losses), net $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Purchases, Sales, Settlements and Maturities Cash flows related to investment securities for the years ended December 31, 2017, 2016 and 2015, are summarized as follows (in millions): Year ended December 31, 2017 2016 2015 Purchases Sales, Purchases Sales, Purchases Sales, Trading securities $ ) $ $ ) $ $ ) $ Available-for-sale securities ) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total cash flows $ ) $ $ ) $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets
Goodwill and Intangible Assets	Note 7 — Goodwill and Intangible Assets JHG's goodwill and intangible assets are summarized below (in millions): December 31, Merger Amortization Foreign December 31, Indefinite-lived intangible assets: ​ ​ ​ ​ ​ Investment management agreements $ $ $ — $ $ Trademarks ​ — ​ ​ — ​ ​ Definite-lived intangible assets: Client relationships ​ ​ ​ — ​ ​ Accumulated amortization ) — ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net intangible assets $ $ $ ) $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Goodwill $ $ $ — $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Indefinite-lived intangible assets represent certain investment management contracts where the Group expects both the renewal of the contracts and the cash flows generated by them to continue indefinitely. Trademarks primarily relate to JCG and were acquired as a result of the Merger. Definite-lived intangible assets represent client relationships, which are amortized over their estimated lives using the straight-line method. The estimated weighted-average life of the client relationships is approximately 13 years. The opening goodwill balance originates from the various acquisitions the Group has undertaken. The Merger goodwill balance represents goodwill recorded at the Closing Date of the Merger. Refer to Note 4 — Acquisitions, for additional information on goodwill and intangible assets acquired from the Merger. Foreign currency translation movements in the table primarily relate to the translation of the intangible assets and goodwill balances denominated in non-USD currencies to the Group's functional and presentational currency of USD using the closing foreign currency exchange rate at the end of each reporting period. Expected future amortization expense related to definite-lived intangible assets is summarized below (in millions): Year ended December 31, Amount 2018 $ 2019 2020 ​ 2021 2022 ​ Thereafter ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Impairment Testing The Group elected to perform a qualitative assessment of the valuation of goodwill and indefinite-lived intangible assets for its 2017 impairment test and concluded it is more likely than not that the fair values of the Group's reporting unit and the specific intangible assets exceed their carrying values. The 2016 impairment test of indefinite-lived intangible assets indicated an impairment loss of $4.9 million which was recognized within depreciation and amortization on the Group's Consolidated Statement of Comprehensive Income for the year ended December 31, 2016. No goodwill impairment losses were identified during the 2015 impairment test. Definite-lived intangible assets are tested for impairment if there is an indication of impairment. No indicators of impairment were identified.

Equity Method Investments

Equity Method Investments	12 Months Ended
	Dec. 31, 2017
Equity Method Investments
Equity Method Investments	Note 8 — Equity Method Investments Equity method investments of $5.9 million and $0.2 million were recognized on the Group's Consolidated Balance Sheets within 'other non-current assets' as at December 31, 2017 and 2016, respectively. The Group holds interests in the following equity method investments including joint ventures managed through shareholder agreements with third-party investors, accounted for under the equity method: Country of Functional 2017 2016 Long Tail Alpha USA USD ​ % ​ % Optimum Investment Management Limited UK GBP % % Northern Pines Henderson Capital GP LLC USA USD ​ — % ​ % Northern Pines Henderson Capital LLC USA USD — % % The Group's share of net loss from equity method investments recognized within net income was $0.6 million and $3.1 million at December 31, 2017 and 2016, respectively. During 2016, the Group received a share of profit from its equity method investments of $0.7 million. An impairment loss of $3.8 million was also recognized in relation to the Group's shareholding in Northern Pines as a result of the decision to wind up this joint venture.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Measurements
Fair Value Measurements	Note 9 — Fair Value Measurements The following table presents assets, liabilities and redeemable noncontrolling interests presented in the consolidated financial statements or disclosed in the notes to the consolidated financial statements at fair value on a recurring basis as of December 31, 2017 (in millions): Fair value measurements using: Quoted prices in Significant other Significant Total Assets: ​ ​ ​ ​ Cash equivalents $ $ — $ — $ Investment securities: ​ ​ ​ ​ Consolidated VIEs — trading Other — trading ​ ​ ​ ​ Consolidated VIEs — available-for-sale — — Other — available-for-sale ​ ​ — ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total investment securities Seed hedge derivatives ​ ​ — ​ — ​ Derivatives in consolidated seeded investment products — Contingent consideration ​ — ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets $ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: ​ ​ ​ ​ Derivatives in consolidated seeded investment products $ $ $ — $ Financial liabilities in consolidated seeded investment ​ ​ ​ ​ products — — Seed hedge derivatives ​ ​ ​ — ​ Current portion of long-term debt (1) — — Long-term debt (1) ​ — ​ ​ — ​ Deferred bonuses — — Contingent consideration ​ — ​ — ​ ​ Dai-ichi options — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total liabilities $ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Redeemable noncontrolling interests: Consolidated seeded investment products $ — $ — $ $ Intech — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total redeemable noncontrolling interests $ — $ — $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Carried at amortized cost and disclosed at fair value. The following table presents assets, liabilities and redeemable noncontrolling interests presented in the consolidated financial statements or disclosed in the notes to the consolidated financial statements at fair value on a recurring basis as of December 31, 2016 (in millions): Fair value measurements using: Quoted prices in Significant other Significant Total Assets: ​ ​ ​ ​ Investment securities: Consolidated VIEs — trading $ $ $ $ Other — trading — Consolidated VIEs — available-for-sale ​ ​ ​ — ​ Other — available-for-sale — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total investment securities ​ ​ ​ ​ Derivatives in consolidated seeded investment products — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets $ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: Derivatives in consolidated seeded investment products $ $ $ — $ Financial liabilities in consolidated seeded investment products — — Contingent consideration ​ — ​ — ​ ​ Deferred bonuses — — Seed hedge derivatives ​ — ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total liabilities $ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total redeemable noncontrolling interests in consolidated seeded investment products $ — $ — $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Level 1 Fair Value Measurements JHG's Level 1 fair value measurements consist mostly of seeded investment products, investments in advised mutual funds, cash equivalents and investments related to deferred compensation plans with quoted market prices in active markets. The fair value level of consolidated seeded investment products is determined by the underlying securities of the product. The fair value level of unconsolidated seeded investment products is determined using the respective NAV of each product. Level 2 Fair Value Measurements JHG's Level 2 fair value measurements consist mostly of consolidated seeded investment products and JHG's long-term debt. The fair value of consolidated seeded investment products is determined by the underlying securities of the product. The fair value of JHG's long-term debt is determined using broker quotes and recent trading activity, which are considered Level 2 inputs. Level 3 Fair Value Measurements Investment Products As of December 31, 2017, and December 31, 2016, certain securities within consolidated VIEs were valued using significant unobservable inputs, resulting in Level 3 classification. Disposal of Volantis On April 1, 2017, the Group completed the sale of Volantis. Consideration for the sale was a 10% share of the management and performance fees generated by Volantis for a period of three years. The fair value of the Volantis contingent consideration is estimated at each reporting date by forecasting revenues over the contingency period of three years. Significant unobservable inputs used in the valuation are limited to forecast revenues, which factor in expected growth in AUM based on performance and industry trends. Increases in forecast revenue increase the fair value of the consideration, while decreases in forecast revenue decrease the fair value. The forecasted share of revenues is then discounted back to the valuation date using an 11.8% discount rate. As of December 31, 2017, the fair value of the Volantis contingent consideration asset was $9.0 million. Contingent Consideration Acquisition of Geneva The consideration payable on the acquisition of Geneva Capital Management LLC ("Geneva") in 2014 included two contingent tranches of up to $45.4 million and $25.0 million, payable over six years. There was a $3.0 million fair value adjustment in the year ended December 31, 2017. As of December 31, 2017 and 2016, the contingent consideration had a fair value of $19.3 million and $20.3 million, respectively, and was included in other non-current liabilities on JHG's Consolidated Balance Sheets. The fair value of the Geneva contingent consideration is estimated at each reporting date by forecasting revenue, as defined by the sale and purchase agreement, over the contingency period and by determining whether targets will be met. Significant unobservable inputs used in the valuation are limited to forecast revenues, which factor in expected growth in AUM based on performance and industry trends. Acquisition of Perennial The consideration payable on the acquisition of Perennial Fixed Interest Partners Pty Ltd and Perennial Growth Management Pty Ltd (together "Perennial") included contingent consideration payable in 2017 and 2019 if revenues of the Perennial equities business meet certain targets. The total maximum payment over the remaining contingent consideration period is $5.9 million as of December 31, 2017. In addition, there is a maximum amount of $41.2 million payable in two tranches in 2019 and 2020, which have employee service conditions attached ("earn-out"). The earn-out is accrued over the service period as compensation expense and is based on net management fee revenue. Fair value adjustments to the consideration during the year ended December 31, 2017, resulted in a $1.8 million decrease to the liability. As of December 31, 2017 and 2016, the contingent consideration and earn-out had a combined fair value of $7.0 million and $5.2 million, respectively, which is included in other non-current liabilities on JHG's Consolidated Balance Sheets. The fair value of the Perennial contingent consideration and earn-out is calculated at each reporting date by forecasting Perennial revenues over the contingency period and determining whether the forecasted amounts meet the defined targets. The significant unobservable input used in the valuation is forecasted revenue. Acquisition of Kapstream JCG's acquisition of Kapstream was a two-stage acquisition. The original acquisition of 51% in July 2015 had contingent consideration payable at 18 and 36 months after acquisition if certain Kapstream AUM reach defined targets. The purchase of the remaining 49% had contingent consideration of up to $43.8 million. Payment of the contingent consideration is subject to all Kapstream products and certain products advised by the Group, reaching defined revenue targets on the first, second and third anniversaries of January 31, 2017. The contingent consideration will be payable in three equal installments on the anniversary dates and is indexed to the performance of the premier share class of the Kapstream Absolute Return Income Fund. Upon achieving the defined revenue targets, the holders receive the value of the contingent consideration adjusted for gains or losses attributable to the mutual fund to which the contingent consideration is indexed, subject to tax withholding. On January 31, 2018, the first anniversary of the acquisition, Kapstream reached defined revenue targets and the Group paid $15.3 million in February 2018. No fair value adjustment was necessary in the year ended December 31, 2017. As of December 31, 2017, the aggregate contingent consideration had a fair value of $44.2 million; $18.8 million is included in accounts payable and accrued liabilities, and $25.4 million is included in other non-current liabilities on JHG's Consolidated Balance Sheets. As of December 31, 2017, the total maximum payment over the remaining contingent consideration period (first, second and third anniversaries) is $48.6 million. The total maximum payment includes fair value adjustments associated with the consideration, which is indexed to the performance of a certain fund. The fair value of the Kapstream contingent consideration is calculated at each reporting date by forecasting certain Kapstream AUM or defined revenue over the contingency period and determining whether the forecasted amounts meet the defined targets. Significant unobservable inputs used in the valuation are limited to forecasted Kapstream AUM and performance against defined revenue targets. Acquisition of VelocityShares JCG's acquisition of VelocityShares in 2014 included contingent consideration. The remaining contingent consideration is payable on the third and fourth anniversaries of the acquisition, in amounts up to $8.0 million each. The payments are contingent on certain VelocityShares' ETPs reaching defined net revenue targets. VelocityShares ETPs reached defined net revenue targets in November 2017, the third anniversary of the acquisition, and the Group paid contingent consideration of $3.6 million in January 2018. The total remaining maximum payment for the fourth and final contingent consideration payment is $8.0 million. Fair value adjustments to the consideration during the year ended December 31, 2017, resulted in a $0.8 million decrease to the liability. As of December 31, 2017, the contingent consideration had a fair value of $6.1 million. The fair value is included in accounts payable and accrued liabilities on JHG's Consolidated Balance Sheets. The fair value of the VelocityShares contingent consideration is calculated at each reporting date by forecasting net ETP revenue, as defined by the purchase agreement, over the contingency period and by determining whether net forecasted ETP revenue targets are achieved. Significant unobservable inputs used in the valuation are considered non-public data and limited to forecasted gross revenues and certain expense items, which are deducted from these revenues. Deferred Bonuses Deferred bonuses represent liabilities to employees over the vesting period that will be settled by investments in JHG products. Dai-ichi Options As of December 31, 2017, the fair value of the options sold to Dai-ichi was $26.1 million. The fair value was determined using a Black-Scholes option pricing model. The Black-Scholes model requires management to estimate certain variables, primarily the volatility of the underlying shares. Changes in the fair value of the options are recognized in other non-operating income (expense), net in JHG's Consolidated Statements of Comprehensive Income. Redeemable Noncontrolling Interests in Intech Intech became a subsidiary of the Group as a result of the Merger. Redeemable noncontrolling interests in Intech are measured at fair value on a quarterly basis or more frequently if events or circumstances indicate that a material change in the fair value of Intech has occurred. The fair value of Intech is determined using a valuation methodology that incorporates observable metrics from publicly traded peer companies as valuation comparables and adjustments related to investment performance and changes in AUM. Redeemable Noncontrolling Interests in Consolidated Seeded Investment Products Redeemable noncontrolling interests in consolidated seeded investment products are measured at fair value. Their fair values are primarily driven by the fair value of the investments in consolidated funds. The fair value of redeemable noncontrolling interests may also fluctuate from period to period based on changes in the Group's relative ownership percentage of seed investments. Changes in Fair Value Changes in fair value of JHG's Level 3 assets for the years ended December 31, 2017 and 2016, are as follows (in millions): Year ended December 31, 2017 2016 Beginning of year fair value $ $ Balance acquired from the Merger — Additions ​ ​ Settlements ) — Transfers to Level 2 ​ ) ​ — Movement recognized in net income ) Movements recognized in other comprehensive income ​ ​ Foreign currency translation ) ​ ​ ​ ​ ​ ​ ​ ​ End of year fair value $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Changes in fair value of JHG's individual Level 3 liabilities and redeemable noncontrolling interests for the years ended December 31, 2017 and 2016, are as follows (in millions): Year ended December 31, 2017 2016 Contingent Deferred Dai-ichi Redeemable Contingent Deferred Redeemable Beginning of year fair value $ $ $ — $ $ $ $ Balances acquired from the Merger — — — — — Additions ​ — ​ — ​ ​ — ​ ​ — ​ — Changes in ownership — — — — — Net movement in bonus deferrals ​ — ​ ​ — ​ — ​ — ​ ​ — Fair value adjustments — ) — — — Unrealized gains (losses) ​ — ​ — ​ — ​ ) ​ — ​ — ​ Amortization of Intech appreciation rights — — — — — — Distributions ​ — ​ — ​ — ​ ) ​ — ​ — ​ — Foreign currency translation ) ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ End of year fair value $ $ $ $ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Significant Unobservable Inputs Valuation techniques and significant unobservable inputs used in the valuation of JHG's material Level 3 asset, the Group's private equity investment included within consolidated VIEs, as of December 31, 2017, and December 31, 2016, are as follows (in millions): As of December 31, 2017 Fair Valuation Significant Range Investment securities of consolidated VIEs — trading $ Discounted cash flow Discount rate EBITDA multiple Price-earnings ratio 12.0%-15.0% (14.3)% 11.6-15.1 (14.3) 22.6-61.3 (52.4) As of December 31, 2016 Fair Valuation Significant Range Investment securities of consolidated VIEs — trading $ Discounted cash flow Discount rate EBITDA multiple Price-earnings ratio 12.0%-30.0% (16.3)% 8.7-11.0 (9.1) 17.2-24.0 (18.4) Nonrecurring Fair Value Measurements Nonrecurring Level 3 fair value measurements include goodwill and intangible assets. The Group measures the fair value of goodwill and intangible assets on initial recognition using discounted cash flow analysis that requires assumptions regarding projected future earnings and discount rates. Due to the significance of the unobservable inputs in the fair value measurements of these assets, such measurements are classified as Level 3. Goodwill and intangible assets were part of the preliminary allocation of the consideration transferred to the assets acquired and liabilities assumed from the Merger. Refer to Note 4 — Acquisitions for additional information. Transfers between Fair Value Levels The underlying securities of funds and separate accounts may trade on a foreign stock exchange. In some cases, the closing price of such securities may be adjusted to capture the effects of any post-closing activity affecting the markets in which they trade. Security prices are adjusted based upon historical impacts for similar post-close activity. These adjustments result in the securities being classified as Level 2 and may also result in movements of securities between Level 1 and Level 2. Transfers are recognized at the end of each reporting period. Transfers from Level 3 to Level 2 were $1.1 million for the year ended December 31, 2017. There were no transfers between Level 1 and Level 2 for the year ended December 31, 2017.

Debt

Debt	12 Months Ended
	Dec. 31, 2017
Debt
Debt	Note 10 — Debt Debt as of December 31, 2017 and 2016, consisted of the following (in millions): December 31, December 31, Carrying Fair Carrying Fair 4.875% Senior Notes due 2025 $ $ $ — $ — 0.750% Convertible Senior Notes due 2018 — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total debt ​ ​ ​ — ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Less: Current portion of long-term debt — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total long-term debt $ $ $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 4.875% Senior Notes Due 2025 As a result of the Merger, the Group assumed 2025 Senior Notes with a principal value of $300.0 million, which pay interest at 4.875% semiannually on February 1 and August 1 of each year and mature on August 1, 2025. The 2025 Senior Notes were recorded at their fair value of $323.7 million at the time of the Merger. The 2025 Senior Notes include unamortized debt premium, net at December 31, 2017, of $22.0 million, which will be amortized over the remaining life of the 2025 Senior Notes. The unamortized debt premium is recorded as a liability within long-term debt on JHG's Consolidated Balance Sheets. 0.750% Convertible Senior Notes Due 2018 As a result of the Merger, the Group assumed 2018 Convertible Notes with a principal value of $116.6 million. The 2018 Convertible Notes pay interest at 0.750% semiannually on January 15 and July 15 of each year and mature on July 15, 2018. The 2018 Convertible Notes had a fair value of $158.1 million at the time of the Merger. The 2018 Convertible Notes may be wholly or partially settled in cash at the election of JHG and thereby the liability and conversion feature components of the 2018 Convertible Notes were accounted for separately. The $115.2 million liability component at the Closing Date was determined by discounting future contractual cash flows at a 1.9% rate, which is consistent with the estimated market interest rate for similar senior notes with no conversion option. The $42.9 million equity component was determined as the difference between the liability component and the fair value of 2018 Convertible Notes at the Closing Date. The fair value as of December 31, 2017, in the table above represents the fair value of the liability component. Upon closing of the Merger, JHG fully and unconditionally guaranteed the obligations of JCG in relation to the 2018 Convertible Notes and 2025 Senior Notes. Holders of the 2018 Convertible Notes may convert the notes during a particular calendar quarter if the last reported sale price of JHG's common stock is greater than or equal to 130% of the applicable conversion price for at least 20 trading days during a period of 30 consecutive trading days ending on the last trading day of the preceding quarter. During the year ended December 31, 2017, $59.1 million of principal was redeemed and settled with cash for a total cash outlay of $92.5 million. Additional conversion notices were received in 2018; refer to Note 22 — Subsequent Events for additional information. As of December 31, 2017, the face value of the 2018 Convertible Notes was $57.5 million. As of January 1, 2018, the 2018 Convertible Notes met the conversion criteria and are convertible during the first quarter 2018 at a conversion rate of 45.1535 shares of JHG common stock per $1,000 principal amount of the 2018 Convertible Notes, which is equivalent to a conversion price of approximately $22.15 per share of common stock. Convertible Note Hedge and Warrants Prior to the Merger, JCG entered into convertible note hedge and warrant transactions. The instruments were intended to reduce the potential for future dilution to shareholders by effectively increasing the initial conversion price of the 2018 Convertible Notes. The convertible note hedge and warrants were terminated by the Group in June 2017, and JHG received $59.3 million and paid $47.8 million to settle the contracts. The net proceeds from the settlements were recorded in additional paid-in-capital on the Group's Consolidated Balance Sheets. 7.25% Senior Notes due 2016 In March 2011, Henderson issued £150.0 million ($240.4 million) of 2016 Senior Notes which were unsecured, unrated and repayable in full on March 24, 2016. The 2016 Senior Notes paid interest at 7.25% semi-annually on March 24 and September 24. The interest on the 2016 Senior Notes was amortized over the five year term to interest expense in the Consolidated Statements of Comprehensive Income. The 2016 Senior Notes were repaid in full at their maturity on March 24, 2016. The Group was in compliance with all covenants attached to the 2016 Senior Notes up to the date of repayment. The covenants included the requirement to provide notice of any actual or potential default event and the preparation of audited accounts for each accounting period. Credit Facility At December 31, 2017, JHG had a $200 million, unsecured, revolving credit facility ("Credit Facility") with Bank of America Merrill Lynch International Limited, as coordinator, book runner and mandated lead arranger. JHG and its subsidiaries can use the Credit Facility for general corporate purposes. The rate of interest for each interest period is the aggregate of the applicable margin, which is based on JHG's long-term credit rating and the London Interbank Offered Rate ("LIBOR"); the Euro Interbank Offered Rate ("EURIBOR") in relation to any loan in euro ("EUR"); or in relation to any loan in Australian dollar ("AUD"), the benchmark rate for that currency. JHG is required to pay a quarterly commitment fee on any unused portion of the Credit Facility, which is also based on JHG's long-term credit rating. Under the Credit Facility, the financing leverage ratio cannot exceed 3.00x EBITDA. At December 31, 2017, JHG was in compliance with all covenants, and there were no borrowings under the Credit Facility at December 31, 2017, or from inception of the Credit Facility. The Credit Facility had a maturity date of February 16, 2022, with two one-year extension options that can be exercised at the discretion of JHG with the lender's consent on the first and second anniversary of the date of the agreement, respectively. On the first anniversary of the date of the agreement, the Group exercised the option to extend the term of the Credit Facility by one year. The revised maturity date of the Credit Facility is February 16, 2023.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Taxes
Income Taxes	Note 11 — Income Taxes The components of the Group's provision for income taxes for the years ended December 31, 2017, 2016 and 2015, are as follows (in millions): Year ended December 31, 2017 2016 2015 Current: ​ ​ ​ UK $ $ $ U.S. including state and local ​ ​ ​ International ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total current income taxes ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred: UK ​ ​ ) ​ ) U.S. including state and local ) ) International ​ ) ​ ​ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total deferred income taxes (benefits) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total income tax expense $ ) $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The components of the Group's total income before taxes for the years ended December 31, 2017, 2016 and 2015, are as follows (in millions): Year ended December 31, 2017 2016 2015 UK $ $ $ U.S. ) International ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total income before taxes $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The Group's top holding company is tax resident in the UK and is subject to the tax laws and regulations of that country. The following is a reconciliation between the UK statutory corporation tax rate and the effective tax rate on the Group's income from operations. Year ended 2017 2016 2015 UK statutory corporation tax rate ​ % ​ % ​ % Effect of foreign tax rates ) ) Impact of Property disposal (1) ​ — ​ — ​ ) Equity-based compensation ) ) Finalization of positions with HMRC (2) ​ ​ ) ​ ) Tax adjustments Non-deductible costs associated with the Merger ​ ​ ​ — Impact of changes in statutory tax rates on deferred taxes ) ) ) Taxes applicable to prior years ​ ) ​ ​ ) Other, net ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Effective income tax rate, controlling interest ​ )% ​ % ​ % Net income attributable to noncontrolling interests ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total effective income tax rate ​ )% ​ % ​ % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) This incorporates the tax impact of the disposal of THRE during 2015. (2) Her Majesty's Revenue and Customs ('HMRC'), tax authority of the UK. The Group operates in several taxing jurisdictions around the world, each with its own statutory tax rate and set of tax laws and regulations. As a result, the future blended average statutory tax rate is dependent on changes to such laws and regulations and the mix of profits and losses of the Group's subsidiaries. The Group's blended average statutory tax rate increased subsequent to the Merger with JCG. Tax Legislation The Group has significant tax expense and tax current and deferred payable impact associated with the Act enacted on December 22, 2017, which resulted in an income tax benefit of $340.7 million. The Act includes significant changes to the U.S. corporate income tax system: it reduces the U.S. federal corporate tax rate from 35.0% to 21.0% as of January 1, 2018; it shifts the U.S. to a modified territorial tax regime which requires companies to pay a one-time mandatory tax on earnings of certain foreign subsidiaries that were previously tax deferred; and it creates new taxes on certain foreign-sourced earnings. Income tax effects resulting from changes in tax laws are accounted for by the Group in accordance with the authoritative guidance, which requires that these tax effects be recognized in the period in which the law is enacted and the effects are recorded as a component of provision for income taxes from continuing operations. On December 22, 2017, the SEC issued guidance under Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act ("SAB 118") directing taxpayers to consider the impact of the Act as "provisional" when they do not have the necessary information available, prepared or analyzed (including computations) in reasonable detail to complete their accounting for the change in tax law. In accordance with SAB 118, the estimated income tax benefit of $340.7 million represents the Group's best estimate based on interpretation of the Act as the Group is still accumulating data to finalize the underlying calculations, or in certain cases, the U.S. Treasury is expected to issue further guidance on the application of certain provisions of the Act. In accordance with SAB 118, the additional estimated income tax benefit related to the revaluation of deferred tax assets and liabilities of $345.4 million and tax expense related to the one-time tax on the previously deferred earnings of foreign subsidiaries of $4.7m is considered provisional and will be finalized before December 22, 2018. During 2016, tax legislation enacted in the UK to reduce the corporation tax rate in future years resulted in a $4.0 million net non cash benefit (2015: $8.1 million benefit) related to the revaluation of certain deferred tax assets and liabilities. The UK corporation tax rate reduced from 20% to 19% with effect from April 1, 2017 and then to 17% with effect from April 1, 2020. Deferred Taxes The significant components of the Group's deferred tax assets and liabilities as of December 31, 2017 and 2016, are as follows (in millions): December 31, 2017 2016 Deferred tax assets: ​ ​ Compensation and staff benefits $ $ Loss carryforwards ​ ​ Accrued liabilities Debt premium ​ ​ — Other ​ ​ ​ ​ ​ ​ ​ ​ Gross deferred tax assets ​ ​ Valuation allowance ) ) ​ ​ ​ ​ ​ ​ ​ ​ Deferred tax assets, net of valuation allowance $ $ ​ ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities: Retirement benefits $ ) $ ) Goodwill and acquired intangible assets ) ) Other ​ ) ​ ) ​ ​ ​ ​ ​ ​ ​ ​ Gross deferred tax liabilities ) ) ​ ​ ​ ​ ​ ​ ​ ​ Net deferred tax (liabilities) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred tax assets and liabilities that relate to the same jurisdiction are recorded net on the Group's Consolidated Balance Sheets as non-current balances and as of December 31, 2017 and 2016, are as follows (in millions): December 31, 2017 2016 Deferred tax assets, net (included in other non-current assets) $ — $ Deferred tax liabilities, net ) ) ​ ​ ​ ​ ​ ​ ​ ​ Net deferred tax (liabilities) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ A valuation allowance has been established against the deferred tax assets related to the Group's tax loss carryforward where a history of losses in the respective tax jurisdiction makes it unlikely that the deferred tax asset will be realized or where it is unlikely that the Group would generate sufficient taxable income of the appropriate character to realize the full benefit of the deferred tax asset. The valuation allowance for deferred tax assets increased by $38.4 million in 2017. The increase is primarily attributable to foreign net operating losses and capital losses. The Group has made no provision for income taxes on undistributed earnings of foreign subsidiaries as most dividends distributed by foreign subsidiaries to their direct parent and ultimately to the Group's top holding company attract no additional tax. The U.S subsidiaries evaluated liquidity requirements in the U.S. and the capital requirements of the Group's foreign subsidiaries and concluded that foreign earnings be indefinitely reinvested. Unrecognized Tax Benefits The Group operates in several tax jurisdictions and a number of years may elapse before an uncertain tax position, for which the Group has unrecognized tax benefits, is finally resolved. A reconciliation of the beginning and ending liability for the years ended December 31, 2017, 2016 and 2015, is as follows (in millions): Year ended December 31, 2017 2016 2015 Balance, as of January 1 $ $ $ Balance acquired from the Merger — — Additions for tax positions of current year ​ ​ — ​ Additions/(reduction) for tax positions of prior years — ) Reduction due to settlement with taxing authorities ​ ) ​ ) ​ — Reduction due to statute expirations ) — — Foreign currency translation ​ ​ ) ​ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance, as of December 31 $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The entire unrecognized tax benefits, if recognized, would favorably affect the Group's effective tax rate in future periods. The Group recognizes interest and penalties on uncertain tax positions as a component of the income tax provision. At December 31, 2017, 2016 and 2015 the total accrued interest balance relating to uncertain tax positions was $1.5 million, $0.7 million and $1.2 million, respectively. Potential penalties at December 31, 2017, 2016 and 2015 were insignificant and have not been accrued. The Group is subject to U.S. federal income tax, state and local income tax, UK income tax and income tax in several other jurisdictions, all of which can be examined by the relevant taxing authorities. For the Group's major tax jurisdictions, the tax years that remain open to examination by the taxing authorities at December 31, 2017 are 2014 and onwards for U.S. Federal tax and a number of State tax. A handful of States have open years from 2008 and onwards. The tax years from 2015 and onwards remain open for the UK. The Internal Revenue Service ("IRS") is examining the Henderson U.S. federal tax filing for the year ended December 31, 2014. In addition, a number of tax years from 2005 onwards remain open for a limited number of subsidiaries in the UK while cases involving other taxpayers are being litigated through the judicial system, the results of which will resolve the Group's position for these open years. While examination outcomes are subject to significant uncertainty, they are not expected to be material as the Group has recognized a tax benefit only for those positions that meet the more likely than not recognition threshold. It is reasonably possible that the total amounts of unrecognized tax benefits will change within the next 12 months due to completion of tax authorities' exams or the expiration of statutes of limitations. Management estimates that the existing liability for uncertain tax positions could decrease by approximately $1.1 million within the next 12 months, ignoring changes due to foreign currency translation.

Other Financial Statement Capti

Other Financial Statement Captions	12 Months Ended
	Dec. 31, 2017
Other Financial Statement Captions
Other Financial Statement Captions	Note 12 — Other Financial Statement Captions Other current assets on JHG's Consolidated Balance Sheets at December 31, 2017 and 2016, are composed of the following (in millions): December 31, 2017 2016 Prepaid expenses $ $ Deferred acquisition costs Current corporation tax ​ ​ Other current assets ​ ​ ​ ​ ​ ​ ​ ​ Total other current assets $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other non-current assets on the Consolidated Balance Sheets of $21.5 million as of December 31, 2017, primarily relate to deferred consideration for Volantis and equity-method investments. The $8.5 million balance as of December 31, 2016, primarily relates to deferred tax assets. Accounts payable and accrued liabilities on JHG's Consolidated Balance Sheets at December 31, 2017 and 2016, comprise the following (in millions): December 31, 2017 2016 Accrued commissions $ $ Accrued rebates Other accrued liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total other accrued liabilities $ $ ​ ​ ​ ​ ​ ​ ​ ​ Current corporation tax ​ ​ Contingent consideration — Dai-ichi option ​ ​ — Derivatives — Other current liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total accounts payable and accrued liabilities $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other non-current liabilities on JHG's Consolidated Balance Sheets at December 31, 2017 and 2016, comprise the following (in millions): December 31, 2017 2016 Non-current tax liabilities $ $ Other creditors — Deferred consideration ​ ​ Other non-current accrued liabilities ​ ​ ​ ​ ​ ​ ​ ​ Total other non-current liabilities $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other creditors included within other non-current liabilities primarily comprise the non current portion of onerous lease obligations as of December 31, 2017 and 2016. As a result of historic acquisitions, the Group became party to three material operating leases in respect of 1 Knightsbridge Green, London, 8 Lancelot Place, London and Rex House, Queen Street, London. At the reporting date, the lease in respect of 1 Knightsbridge Green had expired and the onerous leases in respect of the other two offices run for a further period of six years and nine years respectively. At the cease use date of these properties a loss contingency, net of expected sub lease rental income, was recognized in respect of these properties as an accrued liability on the Group's Consolidated Balance Sheets at the net present value of the net expected future cash outflows. Other non-current accrued liabilities primarily represent deferred consideration payable on the acquisition of Geneva and Perennial.

Noncontrolling Interests

Noncontrolling Interests	12 Months Ended
	Dec. 31, 2017
Noncontrolling Interests
Noncontrolling Interests	Note 13 — Noncontrolling Interests Redeemable Noncontrolling Interests Redeemable noncontrolling interests as of December 31, 2017 and 2016, consisted of the following (in millions): December 31, 2017 2016 Consolidated seeded investment products $ $ Intech: Appreciation rights ​ ​ — Founding member ownership interests — ​ ​ ​ ​ ​ ​ ​ ​ Total redeemable noncontrolling interests $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consolidated Seeded Investment Products Noncontrolling interests in consolidated seeded investment products are classified as redeemable noncontrolling interests when there is an obligation to repurchase units at the investor's request. Redeemable noncontrolling interests in consolidated seed investment products may fluctuate from period to period and are impacted by changes in JHG's relative ownership, changes in the amount of third-party investment in seeded products and volatility in the market value of the seeded products' underlying securities. Third-party redemption of investments is redeemed from the respective product's net assets and cannot be redeemed from the assets of other seeded products or from the assets of JHG. The following table presents the movement in redeemable noncontrolling interests in consolidated seeded investment products for the years ended December 31, 2017, 2016 and 2015 (in millions): Year ended December 31, 2017 2016 2015 Opening balance $ $ $ Balance acquired from the Merger — — Changes in market value ​ ) ​ ​ ) Changes in ownership Foreign currency translation ​ ) ​ ) ​ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Closing balance $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Changes in ownership reflect third-party investment in consolidated seeded investment products, additional seed capital investment or seed capital redemptions. Intech Intech became a subsidiary of the Group as a result of the Merger. Intech ownership interests held by a founding member had an estimated fair value of $4.4 million as of December 31, 2017, representing an approximate 1.1% ownership of Intech. This founding member is entitled to retain his remaining Intech interests until his death and has the option to require JHG to purchase his ownership interests of Intech at fair value. Intech appreciation rights are being amortized on a graded vesting method over the respective vesting period. The appreciation rights are exercisable upon termination of employment from Intech to the extent vested. Upon exercise, the appreciation rights are settled in Intech equity. Nonredeemable Noncontrolling Interests Nonredeemable noncontrolling interests as of December 31, 2017 and 2016, are as follows (in millions): December 31, 2017 2016 Nonredeemable noncontrolling interests in: ​ ​ Seed capital investments $ $ Intech ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ Total nonredeemable noncontrolling interests $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Long-Term Incentive Compensatio

Long-Term Incentive Compensation	12 Months Ended
	Dec. 31, 2017
Long-Term Incentive Compensation
Long-Term Incentive Compensation	Note 14 — Long-Term Incentive Compensation The Group operates the following stock-based compensation plans: Restricted Share Plan, Employee Share Ownership Plan, Long-Term Incentive Plan, Deferred Equity Plan, Buy As You Earn Share Plan, Company Share Option Plan, Executive Shared Ownership Plan, Sharesave Plan, Restricted Stock Awards, Price Vesting Units, Mutual Fund Share Awards and Profits Interests and Other Awards. Further details on the material plans in operation during 2017 are set out below: Deferred Equity Plan ("DEP") Employees who receive cash-based incentive awards over a preset threshold, have an element deferred. The deferred awards are deferred into the Company's shares, or into Group managed funds. The DEP trustee purchases Company shares and units or shares in Group managed funds and holds them in trust. Awards are deferred for up to three years and vest in three equal tranches if employees satisfy employment conditions at each vesting date The expense of deferred short-term incentive awards is recognized in net income over the period of deferral on a graded basis, the fair value of which is determined by prevailing share price or unit price at grant date. Restricted Share Plan ("RSP") The RSP allows employees to receive shares in the Group for nil consideration at a future point, usually after three years, and are recognized in net income on a graded basis. The awards are typically granted for staff recruitment and retention purposes — all awards have employment conditions and larger awards generally have performance hurdles. The Compensation Committee approves all awards to Code Staff (employees who perform a significant influence function, senior management and individuals whose professional activities could have a material impact on a firm's risk profile), any awards over £500,000 and award vestings that exceed £50,000. The fair value of the shares granted is the average intra trading price of the preceding five business days. Buy As You Earn Share Plan ("BAYE") The BAYE is a HMRC approved plan. Eligible employees purchase shares in the Group by investing monthly, up to £150 (annual limit £1,800), which is deducted from their gross salary. For each share purchased ('partnership share'), for no additional payment, two free matching shares are awarded. Matching shares will be forfeited if purchased shares are withdrawn from the trust within one year. The non-UK version of the BAYE operates on a similar basis to that of the UK, but each purchased share is matched with one partnership share, which is not subject to forfeiture. Sharesave Plan ("SAYE") The SAYE is a HMRC approved plan. UK employees may participate in more than one scheme but only up to a maximum of £500 per month across all schemes. Employees who participate in the SAYE contribute a monthly amount from their net salary to a savings account. The SAYE vesting period is three years for UK employees. At the end of the three year vesting period, the employees in the 2017 SAYE can exercise their share options using the funds in their savings account, to subscribe for shares at a pre-set price. The pre-set price was £18.40 per share for 2017 (2016 SAYE: £20.60 and 2015 SAYE: £22.70), a 20% discount to the average share price five business days prior to the award. Employees have up to six months after the three year vesting period to exercise their options and subscribe for shares. Forfeiture provisions apply in the case of approved and unapproved leavers. The U.S. Employee Share Purchase Plan ('ESPP') operates on the same principles as the UK SAYE, but has a two year savings period and a lower discount at 15%. In 2017, ESPP was not offered to U.S. employees. The pre-set option price of prior year awards were $31.20 for 2016 ESPP and $35.50 for 2015 ESPP. Employees may participate in more than one plan, but only up to a plan maximum of $312.50 per month across all plans. Company Share Option Plan ("CSOP") CSOP is a HMRC approved share option plan with the maximum value of unvested options at any time limited to £30,000 for UK employees. No such restrictions apply for overseas employees. Employees can buy Group shares after a three year vesting period at an option price fixed at the start of the scheme. There are no Group performance conditions attached to the options, only employment conditions that must be satisfied, and the exercise period is two years, while U.S. employees have three months to exercise. Executive Directors are not eligible to participate in the CSOP, but they may hold awards made prior to their executive appointment. The CSOP plans are valued using the Black Scholes Option Pricing Model and recognized in net income on a straight line basis. The 2017 CSOP option price was £22.80 (2016 CSOP: £26.10 and 2015 CSOP: £28.48). The 2014 CSOP became exercisable for UK employees in April 2017; the option price was £26.71. The 2015 CSOP became available to exercise for U.S. employees in April 2017 as the U.S. CSOP is a two year plan. Executive Shared Ownership Plan ("ExSOP") The ExSOP is an employee share ownership plan and is aimed at encouraging employee share ownership at middle management level. Executive Directors do not participate in the ExSOP. Certain employees are invited to acquire jointly, with an employee benefit trust, the beneficial interest in a number of Company shares under the terms of a joint ownership agreement ('JOA'). Under a JOA, the employee will benefit from any growth in value in excess of a hurdle price fixed at the time of the award subject to employment conditions being satisfied on the vesting date. The ExSOP scheme is valued using the Black Scholes Option Pricing Model and is recognized in net income on a straight line basis. For the 2017 ExSOP, the market price at grant was £22.62 (ExSOP 2016: £25.00 and ExSOP 2015: £28.21) per share. The hurdle price was set at £24.90 (2016: £28.45 and 2015: £31.05) per share. The shares have a three year vesting period with a subsequent two year exercise period. The 2014 ExSOP became exercisable for employees in April 2017 with a market price at grant of £26.81 and a hurdle price at £29.22. Restricted Stock Awards ("RSA") Restricted Stock Awards are generally issued as part of annual variable compensation and for recruitment and retention purposes in accordance with Amended and Restated 2010 LTI Plan, the JCG 2005 Long Term Incentive Stock Plan and the 2012 EIA Plan. Awards generally vest over a three- or four-year period. Price-Vesting Units JCG granted 137,178 price-vesting units to its Chief Executive Officer on December 31, 2014, valued at $2.2 million. At the Closing Date, the price-vesting units were converted to JHG price-vesting units with a value of $2.3 million and were measured based on operating profit margin performance and converted into a time-based award vesting on December 31, 2017. On December 31, 2017, 75,634 price-vesting units vested. JCG granted 138,901 price-vesting units to its Chief Executive Officer on December 31, 2015, valued at $1.9 million. These price-vesting units may or may not vest in whole or in part, three years after the date of grant, depending on JHG's three-year Total Shareholder Return ("TSR") performance relative to a peer group during the vesting period. At the Closing Date, the price-vesting units were converted to 65,548 JHG price-vesting units with a value of $2.0 million. The performance criteria will remain in place post-Merger through the life of the price-vesting units. JCG granted 134,666 price-vesting units to its Chief Executive Officer on December 31, 2016, valued at $1.8 million. These price-vesting units may or may not vest in whole or in part, three years after the date of grant, depending on JHG's three-year TSR performance relative to a peer group during the vesting period. At the Closing Date, the price-vesting units were converted to 63,549 JHG price-vesting units with a value of $2.0 million. The performance criteria will remain in place post-Merger through the life of the price-vesting units. Mutual Fund Share Awards ("MFSA") Mutual Fund Share Awards are generally issued as part of annual variable compensation and for recruitment and retention purposes. At December 31, 2017, the cost basis of unvested mutual fund share awards totaled $57.8 million ($49.8 million are time-based and $8.0 million are performance-based). The awards are indexed to certain mutual funds managed by the Group. Upon vesting, participants receive the value of the award adjusted for gains or losses attributable to the mutual funds to which the award was indexed, subject to tax withholding. Time-based awards generally vest four years from the grant date. The performance-based mutual fund share awards vest five years after the grant date if certain performance criteria are achieved. Perkins Senior Profits Interests Awards On November 18, 2013, Perkins granted senior profits interests awards, which fully vest on December 31, 2018, and are entitled to a total of 10% of Perkins' annual taxable income. The entitlement to a percentage of Perkins' annual taxable income over the vesting period is tiered and starts at 2% in 2015 and increases 2% each year thereafter until reaching 10% after fully vesting on December 31, 2018. In addition, these awards have a formula-driven terminal value based on Perkins' revenue. JHG can call and terminate any or all of the awards on December 31, 2018, and each year thereafter. Holders of such interests can require JHG to purchase the interests in exchange for the then-applicable formula price on December 31, 2018. The senior profits interests are also subject to termination at premiums or discounts to the formula at the option of JHG or certain employees, as applicable, upon certain corporate or employment-related events affecting Perkins or certain employees. As of December 31, 2017, the formula-driven value was zero and there was no liability on JHG's Consolidated Balance Sheets. Intech Long-Term Incentive Awards In October 2014, Intech granted long-term incentive awards to retain and incentivize employees. The awards consisted of appreciation rights, profits interests and phantom interests, and are designed to give recipients and equity-like stake in Intech. Upon the Closing Date of the Merger, the appreciation rights had fair value of $13.3 million which is being amortized on a graded basis over the 10-year vesting schedule. The appreciation rights are exercisable upon termination of employment from Intech and to the extent vested. Upon exercise, the appreciation rights are settled in Intech equity. The profits interests and phantom interests awards entitle recipients to 9.2% of Intech's pre-incentive profits. Additional appreciation rights were granted in February 2015 and March 2016. Upon the closing date of the Merger, the 2015 and 2016 appreciation rights had fair value of $0.9 million and $1.8 million, respectively, which is being amortized on a graded basis over the remaining vesting schedule. The appreciation rights are exercisable upon termination of employment from Intech and to the extent vested. Upon exercise, the appreciation rights are settled in Intech equity. The fair values of the appreciation rights were estimated using the Black-Scholes option pricing model with the following assumptions: Assumptions October 2014 February 2015 March 2016 Dividend yield ​ % ​ % ​ % Expected volatility % % % Risk-free interest rate ​ % ​ % ​ % Expected life (in years) Grant date fair value (in millions) $ $ $ Merger date fair value (in millions) $ $ $ The dividend yield and expected volatility were determined using historical data from publicly traded peers. The risk-free interest rate for the 2014 grant is based on the 10-year U.S. Treasury note at the time of the grant while the risk-free interest rates for the 2015 and 2016 grants are based on the average of the five-year and seven-year U.S. Treasury notes at the time of the grant. The expected life of the appreciation rights was estimated based upon the assumption that recipients terminate upon vesting and exercise a certain percentage of their rights each year over the following four years. Intech profits interests and phantom interests entitle holders to periodic distributions of a portion of Intech operating income. Distributions are made during employment and, for profits interests, post-employment for up to 10 years. Phantom interests are entitled to a one-time distribution at termination of employment. Compensation expense for post-employment distributions is based upon the present value of expected future distributions and will be recognized pro rata over the 10-year vesting schedule for profits interests and five years for phantom interests. The present value of these payments was determined using a 2% discount rate, which represents the interest rate on a 20-year U.S. Treasury note. As of December 31, 2017, the total undiscounted estimated post-employment payments for profits interests and phantom interests was $49.8 million (the majority will not be paid until 10 to 20 years after the grant date). The estimated post-employment payments will be evaluated and adjusted quarterly, as necessary, with changes recorded in results of operations. As of December 31, 2017, the carrying value of the liability associated with the Intech profits interests and phantom interests was $13.6 million and is included in other non-current assets on JHG's Consolidated Balance Sheets. Long-Term Incentive Plan ("LTIP") LTIP awards provide selected employees restricted shares or nil cost options that have employment and performance conditions. Employees who have been awarded such options have five years to exercise their options following the three year vesting period for 2013 LTIP and five and four years to exercise their options following the three and four year vesting periods (respectively) for 2014 LTIP. For 2014 LTIP, if the Group TSR is between the 50th and 75th percentiles, the amount vesting will increase on a linear basis. The Compensation Committee must also be satisfied the Group TSR reflects the underlying performance of the Group. The performance hurdle was 95% relative to Group TSR and 5% on risk and sustainability metrics. Employees must also satisfy employment conditions at each anniversary date for the shares to vest. Two-thirds of the 2015 and 2016 LTIP can be exercised from the end of year three and one-third from the end of year four. The 2015 and 2016 LTIP award vesting and release of the award are subject to performance against the following performance conditions measured (as appropriate) over, or at the end of, the relevant three or four year performance period (in respect of the first and second tranche of the award respectively): 2015 and 2016 awards criteria (pre-Merger) Weighting Market conditions ​ FTSE 350 % ASX 100 ​ % Non-Market Net Fund Flows Condition ​ % Investment Performance Condition % Operating Margin Condition ​ % People Strategy Condition % Following the completion of the Merger with JCG, the Compensation Committee reviewed the performance metrics under the existing LTIP plans and proposed changes to ensure that the metrics remain relevant and appropriate for the objectives and goals of the combined Group. 2014 LTIP vesting conditions remain unchanged and the existing performance metrics were measured as at May 30, 2017 to determine the appropriate level of vesting. The vested portion of the 2015 and 2016 LTIP awards remain subject to the original metrics (measured at the Merger completion date) while the new criteria were applied to the unvested portion: 2015 and 2016 awards criteria (post-Merger) Weighting Market conditions ​ Relative TSR % Non-Market ​ Relative investment performance % Relative net income before tax growth ​ % In respect of the first tranche of the award, an additional holding period of two years shall apply commencing on the relevant vesting date, during which time the participant may not sell, pledge, charge, assign, dispose of or otherwise transfer ownership of the underlying share pertaining to the award, other than to meet mandatory liabilities to tax and/or social security contributions. In respect of the second tranche of the award, an additional holding period of one year shall apply commencing on the relevant vesting date with similar conditions. The performance period for the first tranche of 2014 LTIP was completed on December 31, 2016 and 3% of awards vested in April 2017. The performance period for the second tranche of 2014 LTIP was completed on December 31, 2017 and 3% of awards will vest in April 2018. The Monte Carlo model was used to value the options of the 2015 and 2016 plans. The performance period for the first tranche of 2015 LTIP was completed on December 31, 2017. 25% of the pre-Merger awards and 74.6% of the post-Merger awards will vest in April 2018. The components of the Group's long-term incentive compensation expense for the years ended December 31, 2017, 2016 and 2015 are summarized as follows (in millions): Year ended December 31, 2017 2016 2015 DEP $ $ $ LTIP RSP ​ ​ ​ BAYE ExSOP ​ ​ ​ CSOP SAYE ​ ​ ​ RSA — — ESOP ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stock-based payments expense ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ DEP Funds — liability settled ​ ​ ​ MFSA — liability settled — — Profits interests and other ​ ​ — ​ — Social Security costs ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total charge to the Consolidated Statements of Comprehensive Income $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ At December 31, 2017, unrecognized and unearned compensation, based on vesting outcomes as of December 31, 2017 on the 2017 LTIP, and the weighted-average number of years over which the compensation cost will be recognized is summarized as follows (in millions): Unrecognized Weighted- DEP $ ​ LTIP RSP ​ ​ BAYE ExSOP ​ ​ CSOP SAYE ​ ​ RSA ​ ​ ​ ​ ​ ​ ​ ​ Stock-based payments expense ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ DEP Funds — Liability settled MFSA — liability settled ​ ​ Profits interests and other Social Security costs ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total remaining charge to the Consolidated Statements of Comprehensive Income $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The Group generally grants annual long-term incentive awards in March and April in relation to annual awards but also throughout the year due to seasonality of performance fee bonuses. Stock Options Stock options were granted to employees in 2017, 2016 and 2015. The fair value of stock options granted to the Group's employees in 2017 was estimated on the date of each grant using the Black-Scholes option pricing model and a Monte Carlo Model, with the following assumptions: Black-Scholes Options Pricing Model Year ended December 31, 2017 2016 CSOP U.S. CSOP ExSOP SAYE CSOP U.S. CSOP ExSOP SAYE U.S. SAYE Fair value of options granted (pence) ​ ​ ​ ​ ​ ​ ​ ​ ​ Assumptions: Dividend yield ​ % ​ % ​ % ​ % ​ % ​ % ​ % ​ % ​ % Expected volatility % % % % % % % % % Risk-free interest rate ​ % ​ % ​ % ​ % ​ % ​ % ​ % ​ % ​ % Expected life (years) Monte Carlo Model — LTIP 2015 Year ended December 31, 2017 % Allocation Tranche 1 Tranche 2 Fair Values: ​ Relative TSR % 118.96p 124.11p Relative investment performance ​ % 209.76p 206.59p Relative net income before tax growth % 209.76p 206.59p Assumptions: ​ Date of grant May 1, 2015 May 1, 2015 Start of performance period ​ ​ January 1, 2015 January 1, 2015 End of performance period December 31, 2017 December 31, 2018 Vesting date ​ ​ May 1, 2018 May 1, 2019 Date of modification ("DoM") May 1, 2017 May 1, 2017 Share price at DoM ​ ​ 233.7p 233.7p Risk free discount rate 0.1% pa 0.1%pa Dividend yield ​ ​ 4.5% pa 4.5% pa Share price volatility in GBP 30% pa 30% pa Holding period adjustment ​ ​ Percentage based on pre-modification performance conditions Monte Carlo Model — LTIP 2016 Year Ended December 31, 2017 % allocation Tranche 1 Tranche 2 Fair values: ​ Relative TSR % 120.98p 123.64p Relative investment performance ​ % 200.42p 197.39p Relative net income before tax growth % 200.42p 197.39p Assumptions: ​ Date of grant May 1, 2016 May 1, 2016 Start of performance period ​ ​ January 1, 2016 January 1, 2016 End of performance period December 31, 2018 December 31, 2019 Vesting date ​ ​ March 24, 2019 March 24, 2020 Date of modification ("DoM") May 30, 2017 May 30, 2017 Share price at DoM ​ ​ 233.7p 233.7p Risk free discount rate 0.1% pa 0.1%pa Dividend yield ​ ​ 4.5% pa 4.5% pa Share price volatility in GBP 30% pa 30% pa Holding period adjustment ​ ​ Expected volatility was determined using an average of Henderson's historical volatility. Expected life was determined using the vesting periods of each grant. The risk-free interest rate for periods within the contractual life of the options is based on the UK Treasury 3 year coupon rate and 2 year coupon rate respectively at grant date. The table below summarizes the Group's outstanding options, exercisable options and options vested or expected to vest for the years ended December 31, 2017, 2016 and 2015: 2017 2016 2015 Shares Weighted- Shares Weighted- Shares Weighted- Outstanding at January 1 ​ $ ​ £ ​ £ Share consolidation ) $ — £ — — £ — Acquired from Merger ​ $ ​ — £ — ​ — £ — Granted $ £ £ Exercised ​ ) $ ​ ) £ ​ ) £ Forfeited ) $ ) £ ) £ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Outstanding at December 31 ​ $ ​ £ ​ £ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Exercisable (1) $ £ £ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Vested or expected to vest ​ $ ​ £ ​ £ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Included in the above table is the Group's nil cost LTIP options which constitute the majority of forfeitures. (1) The number of exercisable options represents instruments for which all vesting criteria have been satisfied and whose exercise price was below the closing price of the Group's common stock as of the end of the period. The following table summarizes the intrinsic value of exercised, outstanding and exercisable options at December 31, 2017, 2016 and 2015 (in millions): December 31, 2017 2016 2015 Exercised $ £ £ Outstanding $ £ £ Exercisable $ £ £ Deferred Equity Plan The table below summarizes DEP unvested stock awards for the years ended December 31, 2017, 2016 and 2015: 2017 2016 2015 Shares Weighted- Shares Weighted- Shares Weighted- Outstanding at January 1 ​ $ ​ £ ​ £ Share consolidation ) $ — £ — — £ — Adjustment ​ $ ​ — £ — ​ £ Granted $ £ £ Exercised ​ ) $ ​ ) £ ​ ) £ Forfeited ) $ ) £ ) £ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unvested at December 31 ​ $ ​ £ ​ £ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Restricted Stock Awards The table below summarizes unvested restricted stock awards for the year ended December 31, 2017: 2017 Shares Weighted- Outstanding at January 1 ​ — $ — Acquired from the Merger $ Granted ​ $ Exercised ) $ Forfeited ​ ) $ ​ ​ ​ ​ ​ ​ ​ ​ Unvested at December 31 $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Retirement Benefit Plans

Retirement Benefit Plans	12 Months Ended
	Dec. 31, 2017
Retirement Benefit Plans
Retirement Benefit Plans	Note 15 — Retirement Benefit Plans Defined Contribution Plans The Group operates two separate defined contribution retirement benefit plans; a 401(k) plan for U.S. employees and a separate plan for international employees. Substantially all U.S. full-time employees of JHG are eligible to participate in a company-sponsored 401(k) plan. During the year ended December 31, 2017, JHG matched 5.0% of employee-eligible compensation in the 401(k) Plan. Expenses related to the 401(k) plan are included in employee compensation and benefits on JHG's Consolidated Statements of Comprehensive Income and were $8.6 million during the year ended December 31, 2017. The assets of the plan are held separately from those of the Group in trustee administered funds. Substantially all non-U.S. full-time employees of JHG are eligible to participate in company-sponsored defined contribution plans. The total amounts charged to the Consolidated Statements of Comprehensive Income for the years ended December 31, 2017, 2016 and 2015 in respect of the non-U.S. defined contribution plan was $11.8 million, $11.6 million and $11.7 million, respectively, which represents contributions paid or payable to this plan by the Group. Defined Benefit Plans The main defined benefit pension plan sponsored by the Group is the defined benefit section of the Janus Henderson Group UK Pension Scheme ("JHGPS" or the "Plan"), previously the Henderson Group Pension Scheme, which closed to new members on November 15, 1999. The JHGPS is funded by contributions to a separately administered fund. Benefits in the defined benefit section of the JHGPS are based on service and final salary. The plan is approved by HMRC for tax purposes and is operated separately from the Group and managed by an independent Trustee board. The Trustee is responsible for payment of the benefits and management of the JHGPS assets. The Group also has a contractual obligation to provide certain members of the JHGPS with additional defined benefits on an unfunded basis. The JHGPS is subject to UK regulations, which require the Group and the Trustee to agree to a funding strategy and contribution schedule for the scheme. The Group's latest triennial valuation of the JHGPS has resulted in a deficit on a technical provisions basis of $39.2 million (£29.0 million). The Group agreed with the trustees of the plan to make contributions of $11.4 million (£8.4 million) per year for four years starting from 2017 to recover the deficit. Plan assets and benefit obligations The Plan assets and defined benefit obligations of the JHGPS and the unapproved pension plan were valued as of December 31, 2017. The Group's plan assets, benefit obligations and funded status as at the December 31 measurement date are as follows (in millions): December 31, 2017 2016 Change in plan assets: ​ ​ Fair value of plan assets as of January 1 $ $ Return on plan assets ​ ​ Employer contributions Benefits paid ​ ) ​ ) Settlements ) — Foreign currency translation ​ ​ ) ​ ​ ​ ​ ​ ​ ​ ​ Fair value of plan assets as of December 31 ​ ​ ​ ​ ​ ​ ​ ​ Change in benefit obligation: ​ ​ Benefit obligation as of January 1 ) ) Service cost ​ ) ​ ) Interest cost ) ) Settlements ​ ​ — Benefits paid Actuarial loss ​ ) ​ ) Foreign currency translation ) ​ ​ ​ ​ ​ ​ ​ ​ Benefit obligation as of December 31 ​ ) ​ ) ​ ​ ​ ​ ​ ​ ​ ​ Funded status as at year end ​ ​ ​ ​ ​ ​ ​ ​ Tax at source ​ ) ​ ) ​ ​ ​ ​ ​ ​ ​ ​ Net retirement benefit asset recognized in the Consolidated Balance Sheets $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amounts recognized on the Consolidated Balance Sheet, net of tax at source as at December 31, 2017 and 2016, consist of the following (in millions): December 31, 2017 2016 Retirement benefit assets recognized in the Consolidated Balance Sheets: ​ ​ Janus Henderson Group UK Pension Scheme $ $ Retirement benefit obligations recognized in the Consolidated Balance Sheets: ​ ​ Janus Henderson Group unapproved pension scheme ) ) ​ ​​ ​ ​ ​​ ​ ​ ​ Net retirement benefit asset recognized in the Consolidated Balance Sheets: $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The following key assumptions were used in determining the defined benefit obligation as at December 31, 2017 and 2016: December 31, 2017 2016 Discount rate ​ % ​ % Inflation — salaries % % Inflation — RPI ​ % ​ % Inflation — CPI % % Pension increases (RPI capped at 5% p.a.) ​ % ​ % Pension increases (RPI capped at 2.5% p.a.) % % Life expectancy of male aged 60 at accounting date ​ ​ Life expectancy of male aged 60 in 15 years time The discount rate applied to the plan obligations is based on AA-rated corporate bond yields with similar maturities. Plan assets The fair values of the JHGPS plan assets as at December 31, 2017 and 2016, by major asset class, are as follows (in millions): December 31, 2017 2016 Cash and cash equivalents $ $ Money market instruments — Forward foreign exchange contracts ​ ​ ) Bond assets Equity investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets at fair value $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2017, $231.1 million of JHGPS assets were held in JHG managed funds. The assets of the JHGPS are allocated to a growth portfolio and to bond assets. The majority of the growth portfolio is invested in pooled diversified funds, with the objective of achieving a level of growth greater than the bond portfolio. The bond portfolio is managed on a segregated basis, with the primary objective of meeting the cash flows as they mature. The strategic allocation as at December 31, 2017 and 2016 was broadly 25% growth portfolio and 75% bond assets. As of December 31, 2017, $232.8 million of the JHGPS plan assets held were classified as Level 2 in the fair value hierarchy, with the remainder classified as Level 1. The following table shows a reconciliation of the beginning and ending fair value measurement for Level 3 assets (in millions): December 31, 2017 2016 Fair value of Level 3 assets at beginning of year $ — $ Losses recognized in the period — ) Purchases, sales and settlements, net ​ — ​ ) ​ ​ ​ ​ ​ ​ ​ ​ Fair value of Level 3 assets at end of year $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The expected rate of return on assets for the financial period ending December 31, 2017 was 2.6% p.a. based on financial conditions as at December 31, 2016 (2016: 3.4% p.a.). This rate is derived by taking the weighted average of the long-term expected rate of return on each of the asset classes in JHGPS's target asset allocation. The expected rate of return has been determined based on yields on either long-dated government bonds or relevant corporate bonds, dependent on the class of asset in question, adjusted where appropriate based on the individual characteristics of each asset class. Actuarial gains and losses Cumulative amounts recognized in accumulated other comprehensive income and the actuarial gain, net of tax deducted at source, credited to other comprehensive income for the years ended December 31, 2017 and 2016 are shown below (in millions): December 31, 2017 2016 Opening accumulated unamortized actuarial gain $ $ Current year actuarial gain (loss) ) Tax at source on current year actuarial gain (loss) ​ ​ ) Release of actuarial gain due to settlement event ) — Release of tax at source due to settlement event ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ Closing accumulated unamortized actuarial gain $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ No actuarial gains were amortized from accumulated other comprehensive income during the year ended December 31, 2017 (2016: nil). No actuarial gains are expected to be amortized from accumulated other comprehensive income into net periodic benefit cost during 2018. Net periodic benefit cost The components of net periodic benefit cost in respect of defined benefit plans for the years ended December 31, 2017, 2016 and 2015 include the following (in millions): December 31, 2017 2016 2015 Service cost $ ) $ ) $ ) Settlement gain — — Interest cost ​ ) ​ ) ​ ) Expected return on plan assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net periodic benefit credit ​ ​ ​ Contributions to money purchase section ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total cost $ ) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The following key assumptions were used in determining the net periodic benefit cost for the years ended December 31, 2017, 2016 and 2015 (in millions): December 31, 2017 2016 2015 Discount rate ​ % ​ % ​ % Inflation — salaries % % % Inflation — RPI ​ % ​ % ​ % Inflation — CPI % % % Pension increases (RPI capped at 5% p.a.) ​ % ​ % ​ % Pension increases (RPI capped at 2.5% p.a.) % % % Expected return on plan assets ​ % ​ % ​ % Amortization period for net actuarial gains/losses at beginning of the year Cash flows Employer contributions of $20.5 million were paid in relation to the Group's defined benefit pension plans during 2017 (excluding credits to members' Money Purchase accounts). The Group expects to contribute approximately $12.9 million to the JHGPS (excluding credits to members' Money purchase accounts) in the year ended December 31, 2018. This includes the additional contributions agreed with the Trustees. The expected future benefit payments for the Group's pension plan are as follows (in millions): 2018 $ 2019 $ 2020 $ 2021 $ 2022 $ 2023-2027 $

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	12 Months Ended
	Dec. 31, 2017
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Loss	Note 16 — Accumulated Other Comprehensive Loss Changes in accumulated other comprehensive loss, net of tax, for the years ended December 31, 2017 and 2016, are as follows (in millions): Year ended December 31, 2017 2016 Foreign Available- Retirement Total Foreign Available- Retirement Total Beginning balance $ ) $ $ $ ) $ ) $ $ $ ) Other comprehensive income (loss) before reclassifications ) ) ) Amounts reclassified from accumulated other comprehensive income (loss) ​ — ​ ) ​ ) ​ ) ​ — ​ ) ​ — ​ ) Total other comprehensive income (loss) ) ) ) ) ) Less: other comprehensive loss (income) attributable to noncontrolling interests ​ ​ ) ​ — ​ ​ ) ​ — ​ — ​ ) ​ ​ ​ ​ ​​ ​ ​ ​​ ​ ​ ​​ ​ ​ ​​ ​ ​ ​​ ​ ​ ​​ ​ ​ ​​ ​ ​ ​ Ending balance $ ) $ $ $ ) $ ) $ $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The components of other comprehensive income (loss), net of tax for the years ended December 31, 2017, 2016 and 2015, are as follows (in millions): Year ended December 31, 2017 Pre-tax Tax Net Net unrealized losses on available-for-sale securities $ $ — $ Foreign currency translation adjustments — Retirement benefit asset, net ​ ) ​ ) ​ ) Reclassifications to net income ) — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total other comprehensive income $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, 2016 Pre-tax Tax Net Net unrealized gains on available-for-sale securities $ $ — $ Foreign currency translation adjustments ) ) Retirement benefit asset, net ​ ​ ​ Reclassifications to net income ) — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total other comprehensive income loss $ ) $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, 2015 Pre-tax Tax Net Net unrealized gains on available-for-sale securities $ $ — $ Foreign currency translation adjustments ) — ) Retirement benefit asset, net ​ ) ​ ) ​ ) Reclassifications to net income ) — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total other comprehensive income loss $ ) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Earnings and Dividends Per Shar

Earnings and Dividends Per Share	12 Months Ended
	Dec. 31, 2017
Earnings and Dividends Per Share
Earnings and Dividends Per Share	Note 17 — Earnings and Dividends Per Share Earnings Per Share The following is a summary of the earnings per share calculation for the years ended December 31, 2017, 2016 and 2015 (in millions, except per share data): Year ended December 31, 2017 2016 2015 Net income attributable to JHG $ $ $ Less: Allocation of earnings to participating stock-based awards ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income attributable to JHG common shareholders $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average common shares outstanding — basic Dilutive effect of non-participating stock-based awards ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average diluted common shares outstanding — diluted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Earnings per share: ​ ​ ​ Basic $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted (two class) $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The share numbers in the table above have been updated to reflect the share consolidation on April 26, 2017. Refer to Note 2 — Summary of Significant Accounting Policies, for additional information on the share consolidation. The potential dilutive effect of redemptions of the Group's 2018 Convertible Notes has been excluded from the calculations above. Redemptions to date have been settled wholly in cash, and the Group has the ability and intent to settle future redemptions wholly in cash. The following instruments are anti-dilutive and have not been included in the weighted-average diluted shares outstanding calculation (in millions): Year ended 2017 2016 2015 Unvested nonparticipating stock awards ​ ​ ​ Dai-ichi options — — Dividends Per Share The payment of cash dividends is within the discretion of JHG's Board of Directors and depends on many factors, including, but not limited to, the Group's results of operations, financial condition, capital requirements, and general business conditions and legal requirements. From the Closing Date, the Group intends to declare dividends quarterly in USD; prior to the Merger, the Group declared dividends in GBP on a semi-annual basis, with an extraordinary first quarter 2017 dividend declared on April 19, 2017. The following is a summary of cash dividends declared and paid for the years ended December 31, 2017, 2016 and 2015, in GBP and USD: Year ended December 31, 2017 2016 2015 Dividends paid per share — pre-Merger — in GBP £ £ £ Dividends paid per share — post-Merger — in USD $ $ — $ — The pre-Merger share numbers in the table above have not been updated to reflect the share consolidation on April 26, 2017. Refer to Note 2 — 'Summary of Significant Accounting Policies', for additional information on the share consolidation.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies
Commitments and Contingencies	Note 18 — Commitments and Contingencies Commitments and contingencies may arise in the normal course of business. Commitments and contingencies as of December 31, 2017 are discussed below. Operating and Capital Leases As of December 31, 2017, future minimum rental commitments under non-cancelable operating and capital leases are as follows (in millions): Year ended December 31, Amount 2018 $ 2019 2020 ​ 2021 2022 ​ Thereafter ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Litigation and Other Regulatory Matters JHG is periodically involved in various legal proceedings and other regulatory matters. Although there can be no assurances, based on information currently available, management believes that it is probable that the ultimate outcome of matters that are pending or threatened will not have a material effect on JHG's consolidated financial statements.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions
Related Party Transactions	Note 19 — Related Party Transactions Disclosures relating to equity method investments and the Group pension scheme can be found in Note 8 and Note 15 respectively. Transactions between JHG and its controlled subsidiaries have been eliminated on consolidation and are not disclosed in this note. Certain managed funds are deemed to be related parties of the Group under the related party guidance. The Group earns fees from the funds for which it acts as investment manager and the balance sheet includes amount due from these managed funds. During the years ended December 31, 2017, 2016 and 2015, the Group recognized revenues of $1,473.5 million, $885.0 million and $1,082.8 million, respectively, from the funds it manages that are related parties and not consolidated, in the Consolidated Statements of Comprehensive Income. The following table reflects amounts in the Consolidated Balance Sheets relating to fees receivable from managed funds which are deemed to be related parties (in millions): Year ended 2017 2016 12b-1 plan fees (1) $ $ — As of December 31 2017 2016 Accrued income $ $ Accounts receivable (1) The annual marketing or distribution fees on a mutual fund. Dai-ichi is a significant shareholder of the Group. Investment management fees (included in the revenue figure above) for the years ended December 31, 2017 and 2016, were $11.0 million and nil, respectively. Seed investments held in managed funds are disclosed in Note 5 — Consolidation.

Geographic Information

Geographic Information	12 Months Ended
	Dec. 31, 2017
Geographic Information
Geographic Information	Note 20 — Geographic Information The following summary provides information concerning the Group's principal geographic areas for the years ended and as of December 31, 2017, 2016 and 2015 (in millions): Year ended December 31, Operating revenues 2017 2016 2015 U.S. $ $ $ UK Luxembourg ​ ​ ​ International ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating revenues are attributed to countries based on the location in which revenues are earned. As of Long-lived assets 2017 2016 UK $ $ U.S. Australia ​ ​ — Other ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Long-lived assets include property, equipment, software and intangible assets.

Selected Quarterly Financial Da

Selected Quarterly Financial Data	12 Months Ended
	Dec. 31, 2017
Selected Quarterly Financial Data
Selected Quarterly Financial Data	Note 21 — Selected Quarterly Financial Data (Unaudited) 2017 (in millions, except per share amounts) First Second Third Fourth Full Operating revenue $ $ $ $ $ Operating income Net income ​ ​ ​ ​ ​ Net income attributable to noncontrolling interests — ) ) ) Net income attributable to JHG ​ ​ ​ ​ ​ Basic earnings per share attributable to JHG common shareholders $ $ $ $ $ Diluted earnings per share attributable to JHG common shareholders $ $ $ $ $ 2016 (in millions, except per share amounts) First Second Third Fourth Full Operating revenue $ $ $ $ $ Operating income Net income ​ ​ ​ ​ ​ Net income attributable to noncontrolling interests ) ) Net income attributable to JHG ​ ​ ​ ​ ​ Basic earnings per share attributable to JHG common shareholders $ $ $ $ $ Diluted earnings per share attributable to JHG common shareholders $ $ $ $ $

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events
Subsequent Events	Note 22 — Subsequent Events BNP Paribas Securities Services On October 19, 2017, the Group signed an agreement with BNP Paribas. BNP Paribas will assume responsibility for the majority of JHG's back-office (including fund administration and fund accounting), middle-office and custody functions in the U.S. BNP Paribas will pay JHG net consideration of approximately $36 million for the operations upon closing, which is anticipated for March 2018. 0.750% Convertible Senior Notes Due 2018 Holders of the 2018 Convertible Notes may convert the notes during a particular calendar quarter if the last reported sale price of JHG's common stock is greater than or equal to 130% of the applicable conversion price for at least 20 trading days during a period of 30 consecutive trading days ending on the last trading day of the preceding quarter. As of January 1, 2018, the 2018 Convertible Notes met the conversion criteria and are convertible during the first quarter 2018 at a conversion rate of 45.1535 shares of JHG common stock per $1,000 principal amount of the 2018 Convertible Notes, which is equivalent to a conversion price of approximately $22.15 per share of common stock. During the period from January 1, 2018 to February 22, 2018, an additional $22.5 million in principal was redeemed and settled with cash for a total cash outlay of $39.1 million, and additional conversion notices amounting to $25.4 million in principal had been received. JHG intends to settle the conversion notices with cash during the first quarter 2018. Dividend On February 5, 2018, JHG's Board of Directors declared a fourth quarter 2017 cash dividend of $0.32 per share. The dividend will be paid on March 2, 2018, to shareholders of record at the close of business on February 16, 2018.

Summary of Significant Accoun29

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation The consolidated financial statements have been prepared according to GAAP. The Group's consolidated financial statements include all majority owned subsidiaries and consolidated seeded investment products, and intercompany accounts and transactions have been eliminated in consolidation. Events subsequent to the balance sheet date have been evaluated for inclusion in the accompanying consolidated financial statements through the issuance date. Prior to the Merger, Henderson's functional currency was GBP. After consideration of numerous factors, such as the denomination of the shares, payment of dividends, and the Group's main economic environment, management concluded that the post-Merger functional currency of JHG is USD. All values are rounded to the nearest $100,000 USD, except when otherwise indicated. Certain balances from prior years have been reclassified in order to conform to the current year presentation. This has included reclassifications between line items within the investing cash flow category of the Consolidated Statements of Cash Flows.
Accounting Estimates	Accounting Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates and the differences could be material. JHG's significant estimates relate to investment securities, acquisition accounting, goodwill and intangible assets, retirement benefit assets and obligations, contingent consideration, equity compensation and income taxes.
Segment Information	Segment Information JHG is a global asset manager and manages a range of investment products, operating across various product lines, distribution channels and geographic regions. However, information is reported to the chief operating decision-makers, the Co-CEOs, on an aggregated basis. Strategic and financial management decisions are determined centrally by the Co-CEOs and, on this basis, the Group operates as a single segment investment management business.
Consolidation of Investment Products	Consolidation of Investment Products The Group performs periodic consolidation analyses of its seeded investment products to determine if the product is a VIE or a voting rights entity ("VRE"). Factors considered in this assessment include the entity's legal organization, the entity's capital structure and equity ownership, and any de facto agent implications of the Group's involvement with the entity. Investment products that are determined to be VIEs are consolidated if the Group is the primary beneficiary of the entity. VREs are consolidated if the Group holds the majority voting interest. Upon the occurrence of certain events (such as contributions and redemptions, either by JHG or third parties, or amendments to the governing documents of the Group's investment products), management reviews and reconsiders its previous conclusion regarding the status of an entity as a VIE or a VRE. Additionally, management continually reconsiders whether JHG is considered a VIE's primary beneficiary, and thus consolidates such entity. Variable Interest Entities Certain investment products for which a controlling financial interest is achieved through arrangements that do not involve or are not directly linked to voting interests are considered VIEs. JHG reviews factors, including whether or not (i) the entity has equity that is sufficient to permit it to finance its activities without additional subordinated support from other parties and (ii) the equity holders at risk have the obligation to absorb losses, the right to receive residual returns and the right to direct the activities of the product that most significantly impact the entity's economic performance, to determine if the investment product is a VIE. The Group re-evaluates such factors as facts and circumstances change. The Group consolidates a VIE if JHG is the VIE's primary beneficiary. The primary beneficiary of a VIE is defined as the variable interest holder that has a controlling financial interest in the VIE. A controlling financial interest is defined as (i) the power to direct the activities of the VIE that most significantly impact its economic performance and (ii) the obligation to absorb losses of the entity or the right to receive benefits from the entity that potentially could be significant to the VIE. JHG is the manager of various types of seeded investment products, which may be considered VIEs. The Group's involvement in financing the operations of the VIEs is generally limited to its investments in the entities. VIEs are generally subject to consolidation by the Company at lower ownership percentages compared to the 50% threshold applied to VREs and are also subject to specific disclosure requirements. Voting Rights Entities The Group consolidates seeded investment products accounted for as VREs when it is considered to control such products, which generally exists if JHG has a greater than 50% voting equity interest.
Property, Equipment and Software	Property, Equipment and Software Property, equipment and software is recorded at cost. Depreciation is recorded using the straight-line method over the estimated useful life of the related assets (or the lease term, if shorter). Depreciation expense totaled $24.6 million, $8.2 million and $7.9 million for the years ended December 31, 2017, 2016 and 2015, respectively. Property, equipment and software are summarized as follows (in millions): Depreciation December 31, 2017 2016 Furniture, fixtures and computer equipment 3-10 years $ $ Leasehold improvements Over the shorter of 20 years or the period of the lease Computer software 3-7 years ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Property, equipment and software, gross $ $ Accumulated depreciation ​ ​ ) ​ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Property, equipment and software, net $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Internally generated software is recorded at cost and depreciated over its estimated useful life. Internal and external costs incurred in connection with researching or obtaining software for internal use are expensed as incurred during the preliminary project stage, as are training and maintenance costs. Internal and external costs incurred for internal use software during the application development stage are capitalized until such time that the software is substantially complete and ready for its intended use. Application development stage costs are depreciated on a straight-line basis over the estimated useful life of the software. JHG evaluates its property, equipment and software assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. The evaluation is based on an estimate of the future cash flows expected to result from the use of the asset and its eventual disposal. If expected future undiscounted cash flows are less than the carrying amount of the asset, an impairment loss is recognized in an amount equal to the excess of the carrying amount of the asset over the fair value of the asset. There were no impairments of property, equipment and software for the years ended December 31, 2017, 2016 and 2015.
Deferred Commissions	Deferred Commissions Initial sales commissions paid to and received from financial intermediaries on sales of certain wholesale products are deferred and amortized over various periods, not exceeding four years. The amortization period is based on the average expected life of the product on which the commission is received. Deferred commissions are recognized as components of other current assets, and of accounts payable and of accrued liabilities on the Consolidated Balance Sheets.
Equity Method Investments	Equity Method Investments The Group's investment in equity method investees, where the Group does not control the investee but can exert significant influence over the financial and operating policies (generally considered to be ownership between 20% and 50%), as well as in joint ventures where there is joint control (and in both cases, where it is not the primary beneficiary of a VIE), are accounted for using the equity method of accounting. Investments are initially recognized at cost when purchased for cash, or at the fair value of shares received where acquired as part of a wider transaction. The investments are subsequently carried at cost adjusted for the Group's share of net income or loss and other changes in comprehensive income of the equity method investee, less any dividends or distributions received by the Group. The Consolidated Statements of Comprehensive Income includes the Group's share of net income or loss for the year, or period of ownership, if shorter, within other non-operating income (expenses), net.
Financial Instruments	Financial Instruments Financial assets are recognized at fair value in the Consolidated Balance Sheets when the Group becomes party to the contractual provisions of an instrument. The fair value recognized is adjusted for transaction costs, except for financial assets classified as trading where transaction costs are recognized immediately in net income. Financial assets are derecognized when the rights to receive cash flows from the investments have expired or where they have been transferred and the Group has also transferred substantially all the risks and reward of ownership. Purchases and sales of financial assets are recognized at the trade date. Delivery and settlement terms are usually determined by established practices in the market concerned. Debt securities, equity securities and holdings in pooled funds are designated as either trading or available-for-sale and are measured at subsequent reporting dates at fair value. The Group determines the classification of its financial assets on initial recognition. Unrealized gains and losses represent the difference between the fair value of the financial asset at the reporting date and cost or, if these have been previously revalued, the fair value at the last reporting date. Realized gains and losses on financial assets are calculated as the difference between the net sales proceeds and cost or amortized cost using the specific identification method. Financial liabilities, excluding deferred consideration, derivatives, fund deferral liabilities and redeemable noncontrolling interests in consolidated funds which are stated at fair value, are stated at amortized cost using the effective interest rate method. Financial liabilities stated at amortized cost include the Group's long term debt. Amortized cost is calculated by taking into account any issue costs and any discount or premium on settlement. Financial liabilities cease to be recognized when the obligation under the liability has been discharged or cancelled or has expired. Trading Securities Financial assets classified as trading are carried on the Group's Consolidated Balance Sheets at fair value. These comprise: the Group's manager box position representing the Group's holding in various OEICs and unit trusts used to cover any net shortfall in units created or liquidated for clients after the funds are priced; investments in the Group's fund products held by employee benefit trusts; certain investments in unconsolidated seed capital investments; and certain investments in consolidated funds. Gains and losses arising from changes in the fair value of financial assets classified as trading securities are included within investments gains (losses), net in the Consolidated Statements of Comprehensive Income. Where investments in the Group's fund products are held against outstanding deferred compensation liabilities, any movement in the fair value of these assets and corresponding movements in the deferred compensation liability are recognized in the Consolidated Statements of Comprehensive Income. Available-for-Sale Securities Financial assets classified as available-for-sale consist of certain unconsolidated seed capital investments and certain investments in consolidated funds. Available-for-sale securities are carried at fair value on the Consolidated Balance Sheet s , with changes in fair value recorded as a component of other comprehensive income within the Group's Consolidated Statements of Comprehensive Income until realized. When an asset is disposed of, the cumulative change in fair value, previously recognized in other comprehensive income, is reclassified to net income in the current accounting period. Seeded Investment Products The Group periodically adds new investment strategies to its investment product offerings by providing the initial cash investment or "seeding." The primary purpose of seeded investment products is to generate an investment performance track record in a product to attract third-party investors. JHG's initial investment in a new product represents 100% ownership in that product. Seeded investment products are initially consolidated and the individual securities within the portfolio are accounted for as trading securities. The change in fair value of seeded investment products is recorded in investment gains (losses), net on JHG's Consolidated Statements of Comprehensive Income. Noncontrolling interests in seeded investment products represent third-party ownership interests and are part of investment securities on JHG's Consolidated Balance Sheets. These assets are not available for general corporate purposes and may be redeemed by the third parties at any time. Refer to the consolidation discussion in this note for information regarding the consolidation of certain seeded investment products. JHG may redeem invested seed capital for a variety of reasons, including when third-party investments in the relevant product are sufficient to sustain the given investment strategy. The length of time JCG holds a majority interest in a product varies based on a number of factors, including, but not limited to, market demand, market conditions and investment performance. Investments in Advised Mutual Funds and Investments Related to the Economic Hedging of Deferred Compensation JHG grants mutual fund share awards to employees that are indexed to certain funds managed by JHG. Upon vesting, participants receive the value of the mutual fund share awards adjusted for gains or losses attributable to the mutual funds to which the award was indexed, subject to tax withholding, or participants receive shares in the mutual fund. When investments in the Group's fund products are purchased and held against deferred compensation liabilities, any movement in the fair value of the assets and corresponding movements in the deferred compensation liability are recognized in the Consolidated Statements of Comprehensive Income. The Group maintains deferred compensation plans for certain highly compensated employees and members of its Board of Directors. Eligible participants may defer a portion of their compensation and have the ability to earn a return by indexing their deferrals to mutual funds managed by the Group and its subsidiaries. The Group makes no contributions to the plan. To protect against market variability of the liability, the Group creates an economic hedge by investing in mutual funds that are consistent with the deferred amounts and mutual fund elections of the participants. Such investments remain assets of JHG. Changes in market value of the liability to participants are recognized as long-term incentive compensation in JHG's Consolidated Statements of Comprehensive Income, and changes in the market value of the mutual fund securities are recognized in investment gains (losses), net on JHG's Consolidated Statements of Comprehensive Income. Impairment Evaluation The Group periodically evaluates the carrying value of equity method investments and investment securities classified as available-for-sale for potential impairment. In determining if an impairment exists, the Group considers the duration, extent and circumstances of any decline in fair value. Where a fall in the value of an investment is prolonged or significant, it is considered an indication of impairment. The Group evaluates the securities in an unrealized loss position in the available for sale portfolio for OTTI on the basis of the duration of the decline in value of the security and severity of that decline as well as the Group's intent and ability to hold these securities for a period of time sufficient to allow for any anticipated recovery in the market value. For equity method investments, if circumstances indicate that an OTTI may exist, the investments are evaluated using market values where available, or the expected future cash flows of the investment. If it is determined that the impairment on an equity security is other than temporary, the investment is written down to fair value. An impairment loss equal to the difference between the carrying value of the security and its fair value is recognized as an impairment charge within investment gains (losses), net in the Group's Consolidated Statements of Comprehensive Income. For available-for-sale investments, any amounts previously recognized in other comprehensive income in respect of cumulative changes in fair value are taken to net income on impairment. No impairment charges were recognized on investment securities for the years ended December 31, 2017, 2016 and 2015. Trade Receivables Trade receivables, which generally have 30 day payment terms, are initially recognized at fair value, normally equivalent to the invoice amount. When the time value of money is material, the fair value is discounted. Provision for specific doubtful accounts is made when there is evidence that the Group may not be able to recover balances in full. Balances are written off when the receivable amount is deemed uncollectable. OEIC and Unit Trust Receivables and Payables OEIC and unit trust receivables and payables are in relation to the purchase of units/shares (by investors) and the liquidation of units/shares (owned by trustees). The amounts are dependent on the level of trading and fund switches in the four working days leading up to the end of the period. Since they are held with different counterparties, the amounts are presented gross on the Group's Consolidated Balance Sheets. Cash and Cash Equivalents Cash and cash equivalents primarily consist of cash held at banks, on demand deposits, highly liquid short term government securities and investments in money market instruments with a maturity date of three months or less. Cash balances maintained by consolidated VREs are not considered legally restricted and are included in cash and cash equivalents on the Consolidated Balance Sheets. Cash balances held by consolidated VIEs are disclosed separately as a component of assets of consolidated VIEs on the Consolidated Balance Sheets.
Derivative Instruments	Derivative Instruments The Group may, from time to time, use derivative financial instruments to mitigate price, interest rate, foreign currency and credit risk. The Group does not designate derivative instruments as hedges for accounting purposes, with the exception of certain foreign currency forward contracts used for net investment hedging. Derivative instruments are measured at fair value and classified as either other current assets or accounts payable and accrued liabilities on the Group's Consolidated Balance Sheets. Changes in the fair value of derivative instruments are recorded within investment gains (losses), net in the Group's Consolidated Statements of Comprehensive Income. Changes in fair value of foreign currency forward contracts designated as hedges for accounting purposes are recognized in accumulated other comprehensive income under net investment hedge accounting. The Group's consolidated seed investments may also be party to derivative instruments. These derivative instruments are disclosed separately from the Group's corporate derivative instruments. Refer to Note 6 — Investment Securities.
Noncontrolling Interests and Redeemable Noncontrolling Interests	Noncontrolling Interests and Redeemable Noncontrolling Interests Noncontrolling interests that are not subject to redemption rights are classified in permanent equity. Redeemable noncontrolling interests are classified outside of permanent equity on the Consolidated Balance Sheets and are measured at the estimated fair value as of the balance sheet date. Noncontrolling interests in consolidated seed investments are classified as redeemable noncontrolling interests where there is an obligation on the fund to repurchase units at the investor's request. Refer to Note 13 — Noncontrolling Interests for further information.
Fair Value Measurements	Fair Value Measurements Fair value is the price that would be received to sell an asset or transfer a liability in an orderly transaction between market participants at the measurement date. The fair value of financial instruments traded in active markets (such as publicly traded securities and derivatives) is based on quoted market prices at the reporting date. The quoted market price used for financial instruments is the last traded market price for both financial assets and financial liabilities where the last traded price falls within the bid ask spread. In circumstances where the last traded price is not within the bid ask spread, management will determine the point within the bid ask spread that is most representative of fair value current bid price. The fair value of financial instruments that are not traded in an active market is determined using valuation techniques commonly used by market participants, including the use of comparable recent arm's length transactions, discounted cash flow analysis and option pricing models. Estimating fair value requires significant management judgment, including benchmarking to similar instruments with observable market data and applying appropriate discounts that reflect differences between the securities that the Group is valuing and the selected benchmark. Measurements of fair value are classified within a hierarchy that prioritizes the inputs to valuation techniques used to measure fair value based on whether the inputs to those valuation techniques are observable or unobservable. The valuation hierarchy contains three levels: • Level 1 — Valuation inputs are unadjusted quoted market prices for identical assets or liabilities in active markets. • Level 2 — Valuation inputs are quoted market prices for identical assets or liabilities in markets that are not active, quoted market prices for similar assets and liabilities in active markets, and other observable inputs directly or indirectly related to the asset or liability being measured. • Level 3 — Valuation inputs are unobservable and significant to the fair value measurement. The valuation of an asset or liability may involve inputs from more than one level of the hierarchy. The level in the fair value hierarchy within which a fair value measurement in its entirety falls is determined based on the lowest level input that is significant to the fair value measurement. Level 1 Fair Value Measurements JHG's Level 1 fair value measurements consist mostly of seeded investment products, investments in advised mutual funds, cash equivalents and investments related to deferred compensation plans with quoted market prices in active markets. The fair value level of consolidated seeded investment products is determined by the underlying securities of the product. The fair value level of unconsolidated seeded investment products is determined using the respective NAV of each product. Level 2 Fair Value Measurements JHG's Level 2 fair value measurements consist mostly of consolidated seeded investment products and JHG's long-term debt. The fair value of consolidated seeded investment products is determined by the underlying securities of the product. The fair value of JHG's long-term debt is determined using broker quotes and recent trading activity, which are considered Level 2 inputs. Level 3 Fair Value Measurements JHG's assets and liabilities measured at Level 3 are primarily private equity investments, redeemable noncontrolling interests, contingent deferred consideration and deferred compensation liabilities which are held against investments in the Group's fund products, where the significant valuation inputs are unobservable. Private equity investments are valued using a combination of the enterprise value / EBITDA multiple method and the discounted cash flow method. Significant unobservable inputs include discount rates, EBITDA multiple, and price-earnings ratio, taking into account management's experience and knowledge of market conditions of the specific industries. The fair value of redeemable noncontrolling interests in consolidated funds is primarily driven by the fair value of the investments in consolidated funds. Details of inputs used to calculate the fair value of contingent deferred consideration can be found in Note 9 — Fair Value Measurements. Nonrecurring Fair Value Measurements Nonrecurring Level 3 fair value measurements include goodwill and intangible assets. The Group measures the fair value of goodwill and intangible assets on initial recognition using discounted cash flow analysis that requires assumptions regarding projected future earnings and discount rates. Because of the significance of the unobservable inputs in the fair value measurements of these assets and liabilities, such measurements are classified as Level 3. See the 'Goodwill and Intangible Assets, net' accounting policy set forth within Note 2 — Summary of Significant Accounting Policies for further information.
Income Taxes	Income Taxes The Group provides for current tax expense according to the tax laws in each jurisdiction in which it operates, using tax rates and laws that have been enacted by the Balance Sheet date. Deferred income tax assets and liabilities are recorded for temporary differences between the financial statement and income tax basis of assets and liabilities as measured by the enacted income tax rates that may be in effect when these differences reverse. The effect of changes in tax rates on the Group's deferred tax assets and liabilities is recognized as income tax within net income in the period that includes the enactment date. Significant management judgment is required in developing the Group's provision for income taxes, including the valuation allowances that might be required against deferred tax assets and the evaluation of unrecognized tax benefits resulting from uncertain tax positions taken or expected to be taken in a tax return. The Group periodically assesses the recoverability of its deferred tax assets and the need for valuation allowances on these assets. The Group makes these assessments based on the weight of available evidence regarding possible sources of future taxable income and estimates relating to the future performance of the business that results in taxable income. In evaluating uncertain tax positions, the Group considers the probability that the tax benefit can be sustained on examination by a taxing authority on the basis of its technical merits ('the recognition threshold'). For tax positions meeting this threshold, the amount recognized in the financial statements is the benefit expected to be realized upon settlement with the taxing authority on the basis of a cumulative-probability assessment of the possible outcomes. For tax positions not meeting the recognition threshold, no financial statement benefit is recognized. The Group recognizes the accrual of interest and penalties on uncertain tax positions as a component of the income tax provision.
Revenue Recognition	Revenue Recognition Revenue includes management fees and performance fees, net of rebates. Management fees are recognized in the accounting period in which the associated investment management service is provided. Performance fees for all fund ranges and separate accounts are recognized on crystallization and are therefore accounted for when the prescribed performance hurdles are achieved and it is probable that a fee will be collected as a result. There are no performance fee contracts where revenue can be reversed or clawed back. There are no cumulative revenues recognized that would be reversed if all of the existing investments became worthless. Management fees are generally based upon a percentage of the market value of AUM and are calculated as a percentage of either the daily, month-end or quarter-end average asset balance in accordance with contractual agreements. Performance fees are specified in certain fund and client contracts and are based on investment performance either on an absolute basis or compared to an established index over a specified period of time. This is often subject to a hurdle rate. Management fees are primarily received monthly or quarterly while performance fees are usually received monthly, quarterly or annually by the Group, although the frequency of receipt varies between agreements. Management and performance fee revenue not yet received is recognized within fees and other receivables in the Consolidated Balance Sheets. U.S. Mutual Fund Performance Fees The investment management fee paid by each U.S. mutual fund subject to a performance fee is the base management fee plus or minus a performance fee adjustment as determined by the relative investment performance of the fund compared to a specified benchmark index. Under the performance-based fee structure, the investment advisory fee paid by each fund consists of two components: (1) a base fee calculated by applying the contractual fixed rate of the advisory fee to the fund's average daily net assets during the previous month, plus or minus (2) a performance fee adjustment calculated by applying a variable rate of up to 0.15% to the fund's average daily net assets during the performance measurement period. The performance measurement period begins as a trailing period ranging from 12 to 18 months, and each subsequent month is added to each successive performance measurement period until a 36-month period is achieved. At that point, the measurement period becomes a rolling 36-month period. When current fund net assets vary from fund net assets over the performance measurement period, the performance fee adjustment, as a percentage of fund current assets, may vary significantly. Under circumstances involving underperformance by a rapidly shrinking fund, the dollar amount of the negative performance fee adjustment could be more than the dollar amount of the positive base fee. The addition of performance fees to all funds without such fees is subject to the approval of both a majority of the shareholders of such Funds and the Funds' Independent Board of Trustees.
Commissions	Commissions Commissions on management fees are accounted for on an accrual basis and are recognized in the accounting period in which the associated management fee is earned.
Operating Expenses	Operating Expenses Operating expenses are accrued and recognized as incurred.
Stock-Based Compensation	Stock-Based Compensation The Group issues stock-based awards to employees, all of which are classified as equity settled stock-based payments. Equity settled stock-based payments are measured at the fair value of the shares at the grant date. The awards are expensed, with a corresponding increase in reserves, on either a straight-line basis or a graded basis (depending on vesting conditions) over the vesting period. Forfeitures are recognized as they occur. The grant date fair value for stock options is determined using the Black-Scholes option pricing model, and the grant date fair value of restricted stock is determined from the market price on the date of grant. The Black-Scholes model requires management to determine certain variables; the assumptions used in the Black-Scholes option pricing model include dividend yield, expected volatility, risk free interest rate and expected life. The dividend yield and expected volatility are determined using historical Group data. The risk free interest rate for options granted is based on the three year UK treasury coupon at the time of the grant. The expected life of the stock options is the same as the service conditions applicable to all Group awards. The Group generally uses the Monte Carlo model to determine the fair value of performance-based awards. The assumptions used in the Monte Carlo model include dividend yield, share price volatility and discount rate. The Group had $9.9 million and $37.3 million of stock-based compensation costs and nil and $11.0 million of proceeds from stock-based compensation plans included in retained earnings during the years ended December 31, 2017 and 2016, respectively. Prior to the Group's Extraordinary General Meeting ("EGM") on April 26, 2017, the Group's articles of association did not allow the Group to recognize these items in additional paid-in-capital. A change in the Group's articles of association was approved at the EGM and from April 26, 2017, all costs in relation to stock-based compensation will be recognized in additional paid-in-capital. The accumulated balance in relation to stock-based compensation plans within retained earnings as of December 31, 2017 and 2016, was $(105.4) million and $(92.9) million, respectively.
Earnings Per Share	Earnings Per Share Basic earnings per share attributable to JHG shareholders is calculated by dividing net income (adjusted for the allocation of earnings to participating restricted stock awards) by the weighted average number of shares outstanding. JHG has calculated earnings per share using the two class method. There are some participating restricted stock awards which are paid non forfeitable dividends. Under the two class method, net income attributable to JHG is adjusted for the allocation of earnings to participating restricted stock awards. Diluted earnings per share is calculated in a similar way to basic earnings per share, but is adjusted for the effect of potential common shares unless they are anti-dilutive.
Contingent Consideration	Contingent Consideration Contingent consideration, resulting from business combinations, is recognized at fair value at the acquisition date as part of the business combination and discounted where the time value of money is material. The determination of the fair value is based on discounted cash flows, with the key assumptions being the probability of meeting each performance target and the discount factor applied. When the contingent consideration meets the definition of a financial liability, it is subsequently remeasured to fair value at each reporting date through net income. Finance charges, where discounting has been applied, are also recognized through net income. See Note 9 — Fair Value Measurement for further information about contingent consideration on acquisitions taking place during the reporting period.
Goodwill and Intangible Assets, Net	Goodwill and Intangible Assets, Net Goodwill represents the excess of cost over the fair value of the identifiable net assets of acquired companies and is capitalized in the Consolidated Balance Sheets. Intangible assets consist primarily of investment management contracts and trademarks acquired as part of business combinations. Investment management contracts have been identified as separately identifiable intangible assets arising on the acquisition of subsidiaries or businesses. Such contracts are recognized at the present value of the expected future cash flows of the investment management contracts at the date of acquisition. Investment management contracts may be classified as either indefinite lived investment management contracts or finite lived client relationships. Indefinite-lived intangible assets comprise of investment management agreements where the agreements are with investment companies themselves and not with underlying investors. Such contracts are typically renewed indefinitely and therefore the Group considers the contract life to be indefinite and, as a result, the contracts are not amortized. Definite lived intangible assets comprise of investment management agreements where the agreements are with the underlying investor. Indefinite-lived intangible assets and goodwill are not amortized. Finite-lived client relationships are amortized on a straight-line basis over their remaining useful lives. Goodwill is reviewed for impairment annually or more frequently if changes in circumstances indicate that the carrying value may be impaired. The Group has determined that it has one reporting unit for goodwill impairment testing purposes, which is consistent with internal management reporting and management's oversight of operations. The Group may first assess goodwill for qualitative factors to determine whether it is necessary to perform a quantitative impairment test. The qualitative analysis considers entity-specific and macroeconomic factors and their potential impact on the key assumptions used in the determination of the fair value of the reporting unit. A quantitative impairment test is performed if the results of the qualitative assessment indicate that it is more likely than not that the fair value of the related reporting unit is less than its carrying value, or if a qualitative assessment is not performed. Where the fair value is less than the carrying amount, an impairment is recognized. Any impairment is recognized immediately through net income and cannot subsequently be reversed. Intangible assets subject to amortization are tested for impairment whenever events or circumstances indicate that the carrying value may not be recoverable and indefinite-lived assets are tested for impairment annually or more frequently if changes in circumstances indicate that the carrying value may be impaired. Goodwill and intangible assets require significant management estimates and judgment, including the valuation and expected life determination in connection with the initial purchase price allocation and the ongoing evaluation for impairment.
Foreign Currency	Foreign Currency Transactions in foreign currencies are recorded at the appropriate exchange rate prevailing at the date of the transaction. Foreign currency monetary balances at the reporting date are converted at the prevailing exchange rate. Foreign currency non-monetary balances carried at fair value or cost are translated at the rates prevailing at the date when the fair value or cost is determined. Gains and losses arising on retranslation are recognized as a component of net income, except for available for sale financial assets where the unhedged changes in fair value are recognized in other comprehensive income. On consolidation, the assets and liabilities of the Group's operations whose functional currency is not USD are translated at exchange rates prevailing at the reporting date. Income and expense items are recognized at an average monthly exchange rate. Exchange differences arising, if any, are taken through other comprehensive income to accumulated other comprehensive income. Where net investment hedge accounting is applied using foreign currency forward contracts, the fair value movement on these contracts is also recognized within accumulated other comprehensive income. In the period in which an operation is disposed of, translation differences previously recognized in accumulated other comprehensive income are recognized as a component of net income.
Post Employment Retirement Benefits	Post Employment Retirement Benefits The Group provides employees with retirement benefits through both defined benefit and defined contribution plans. The assets of these plans are held separately from the Group's general assets, in trustee administered funds. Contributions to the defined contribution plan are expensed to employee compensation and benefits on the Consolidated Statements of Comprehensive Income when they become payable. Defined benefit obligations and the cost of providing benefits are determined annually by independent qualified actuaries using the projected unit credit method. The Group's annual measurement date of the defined benefit plan is December 31. The defined benefit obligation is measured as the present value of the estimated future cash outflows using a discount rate based on AA rated corporate bond yields of appropriate duration. The plan assets are recognized at fair value. The funded status of the defined benefit pension plans (the resulting surplus or deficit of defined benefit assets less liabilities) is recognized in the Consolidated Balance Sheets, net of any taxes that would be deducted at source. Actuarial gains and losses arise as a result of the difference between actual experience and actuarial assumptions. The '10% corridor' method for recognizing actuarial gains and losses has been adopted by the Group. This means that cumulative actuarial gains or losses up to an amount equal to 10% of the higher of the liabilities or assets of the scheme ('the corridor') have no immediate impact on net income and are instead recognized through other comprehensive income. Cumulative gains or losses greater than the corridor are amortized to net income over the average remaining future working lifetime of the active members in the plan. Net periodic benefit cost is recorded as a component of net income in the Consolidated Statements of Comprehensive Income and includes service cost, interest cost, expected return on plan assets and any actuarial gains and losses previously recognized as a component of other comprehensive income which have been amortized in the period. Net periodic benefit costs are recognized as an operating expense. See Note 15 — Retirement Benefit Plans for further discussion of the Group's pension plans.
Common Stock	Common Stock JHG's common stock, par value $1.50 per share is classified as equity instruments. Equity shares issued by JHG are recorded at the fair value of the proceeds received or the market price on the day of issue. Direct issue costs, net of tax, are deducted from additional paid-in-capital within equity. Treasury shares held are equity shares of JHG acquired by or issued to employee benefit trusts. Treasury shares held are recorded at cost and are deducted from equity. No gain or loss is recognized in the Consolidated Statements of Comprehensive Income on the purchase, issue, sale or cancellation of JHG's own equity shares. Share Redenomination and Consolidation On April 26, 2017, Henderson redenominated its ordinary shares from GBP to USD, resulting in a change in par value from £0.125 to $0.1547 per share. At that time, Henderson had 1,131,842,110 shares in issue and as a result the ordinary share nominal capital became $175.1 million. The difference between the revised ordinary share nominal capital balance of $175.1 million and the previously stated ordinary share nominal capital balance of $234.4 million (converted at the historic exchange rate rather than the rate required for the redenomination under Jersey company law) was recognized as a component of additional paid-in-capital. Consequently, the additional paid-in-capital balance was adjusted from $1,237.9 million to $1,297.2 million. Additionally, in accordance with a special resolution passed by the shareholders on May 3, 2017, the par value of the shares of Henderson was reduced to $0.15 per share, from $0.1547 per share, and the total ordinary share nominal capital became $169.8 million. In accordance with that resolution, the reduction in the total ordinary share nominal capital of $5.3 million was credited to the additional paid-in-capital account, which moved from $1,297.2 million to $1,302.5 million. On April 26, 2017, the shareholders approved a 10-to-1 share consolidation, which took effect on May 30, 2017. As a result of the share consolidation, the number of shares in issue was reduced by a factor of 10, and the par value of the shares became $1.50.

Summary of Significant Accoun30

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Summary of Significant Accounting Policies
Schedule of property, equipment and software	Property, equipment and software are summarized as follows (in millions): Depreciation December 31, 2017 2016 Furniture, fixtures and computer equipment 3-10 years $ $ Leasehold improvements Over the shorter of 20 years or the period of the lease Computer software 3-7 years ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Property, equipment and software, gross $ $ Accumulated depreciation ​ ​ ) ​ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Property, equipment and software, net $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2017
Acquisitions
Summary of final allocation of the consideration transferred to the assets acquired and liabilities assumed	The final allocation of the consideration transferred to the assets acquired and liabilities assumed are presented in the following table (in millions): Preliminary purchase Adjustments Final purchase Assets: ​ ​ ​ Cash and cash equivalents $ $ — $ Investment securities ​ ​ — ​ Fees and other receivables — Other current assets, net ​ ​ — ​ Property, equipment and software — Intangible assets ​ ​ — ​ Goodwill Other non-current assets, net ​ ​ ​ ​ Liabilities: Long-term debt ​ ​ — ​ Deferred tax liabilities Accounts payable and accrued liabilities ​ ​ — ​ Other non-current liabilities Noncontrolling interests ​ ​ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net assets acquired $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Summary of acquired intangible assets and weighted-average estimated useful lives	Acquired intangible assets and their weighted-average estimated useful lives are presented in the following table (in millions): Fair value Useful Investment management contracts: ​ Mutual funds $ Indefinite Separate accounts ​ ETNs ETFs ​ Indefinite Trademarks Indefinite ​ ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Summary of unaudited supplemental pro forma operating results and JCG results of operations included in JHG's Condensed Consolidated Statements of Comprehensive Income	Pro Forma Results of Operations The following table presents summarized unaudited supplemental pro forma operating results as if the Merger had occurred at the beginning of each of the periods presented (in millions): Year ended December 31, 2017 2016 2015 Revenue $ $ $ Net income attributable to JHG $ $ $ JCG Results of Operations Unaudited revenue (inclusive of revenue from certain mandates transferred to JCG from Henderson after the Merger) and net income of JCG from the Closing Date through the end of December 31, 2017, included in JHG's Consolidated Statements of Comprehensive Income are presented in the following table (in millions): Closing Date — Revenue $ Net income attributable to JCG $

Consolidation (Tables)

Consolidation (Tables)	12 Months Ended
	Dec. 31, 2017
Consolidation
Schedule of assets and liabilities	Consolidated VIE assets and liabilities, presented after intercompany eliminations, at December 31, 2017 and 2016, are as follows (in millions): December 31, December 31, Investment securities $ $ Cash and cash equivalents Other current assets ​ ​ Accounts payable and accrued liabilities ) ) ​ ​ ​ ​ ​ ​ ​ ​ Total ​ ​ Redeemable noncontrolling interests in consolidated VIEs ) ) Nonredeemable noncontrolling interests in consolidated VIEs ​ ) ​ ) ​ ​ ​ ​ ​ ​ ​ ​ JHG's net interest in consolidated VIEs $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of consolidated voting right entities (VREs)	The following table presents the balances related to consolidated VREs that were recorded on JHG's Consolidated Balance Sheets, including JHG's net interest in these products (in millions): December 31, December 31, Investment securities $ $ Cash and cash equivalents — Other current assets ​ ​ — Accounts payable and accrued liabilities ) — ​ ​ ​ ​ ​ ​ ​ ​ Total ​ ​ Redeemable noncontrolling interests in consolidated VREs ) — ​ ​ ​ ​ ​ ​ ​ ​ JHG's net interest in consolidated VREs $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Investment Securities (Tables)

Investment Securities (Tables)	12 Months Ended
	Dec. 31, 2017
Summary of investment securities	JHG's investment securities as of December 31, 2017 and 2016, are summarized as follows (in millions): December 31, 2017 2016 Trading securities: ​ ​ Seeded investment products: Consolidated VIEs $ $ Consolidated VREs Unconsolidated VIEs and VREs ​ ​ Separate accounts — Pooled investment funds ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ Total seeded investment products Investments related to deferred compensation plans ​ ​ Other investments ​ ​ ​ ​ ​ ​ ​ ​ Total trading securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Available-for-sale securities: Seeded investment products: ​ ​ Consolidated VIEs Unconsolidated VIEs and VREs ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total available-for-sale securities ​ ​ ​ ​ ​ ​ ​ ​ Total investment securities $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of net unrealized gains (losses) on trading securities	Net unrealized gains (losses) on trading securities held as of December 31, 2017, 2016 and 2015, are summarized as follows (in millions): Year ended December 31, 2017 2016 2015 Trading securities still held at period end $ $ $ )
Summary of available-for-sale securities	The following is a summary of available-for-sale securities as of December 31, 2017 and 2016 (in millions): Gross Foreign Cost Gains Losses Fair value December 31, 2017: ​ ​ ​ ​ ​ Available-for-sale securities $ $ $ — $ $ December 31, 2016: ​ ​ ​ ​ ​ Available-for-sale securities $ $ $ — $ $
Schedule of gross and offsetting amounts for derivative instruments	The following tables illustrate the effect of offsetting derivative instruments on JHG's Consolidated Balance Sheets as of December 31, 2017 and 2016 (in millions): December 31, 2017 Gross amounts Gross amounts Gross amounts Net amounts Assets: ​ ​ ​ ​ Futures $ $ ) $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets $ $ ) $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: Futures $ ) $ $ — $ ) Foreign currency forward contracts ) — ) Total return swaps ​ ) ​ — ​ ​ — Index swaps ) — — Credit default swaps ​ ) ​ — ​ ​ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total liabilities $ ) $ $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2016 Gross amounts Gross amounts Gross amounts Net amounts Liabilities: ​ ​ ​ ​ Total return swaps $ ) $ — $ $ — Index swaps ​ ) ​ — ​ ​ ) Foreign currency forward contracts ) — — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total liabilities $ ) $ — $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of net foreign currency translation gains (losses) on hedged seed investments denominated in foreign currencies and net gains (losses) associated with foreign currency forward contracts under net investment hedging	The Group recognized the following net foreign currency translation gains (losses) on hedged seed investments denominated in currencies other than the Group's functional currency and net gains (losses) associated with foreign currency forward contracts under net investment hedge accounting for the years ended December 31, 2017, 2016 and 2015 (in millions): Year ended December 31, 2017 2016 2015 Foreign currency translation $ ) $ $ Foreign currency forward contracts ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ — $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of offsetting derivative instruments within consolidated seeded investment products	The following table illustrates the effect of offsetting derivative instruments within consolidated seeded investment products on JHG's Consolidated Balance Sheets as of December 31, 2017 (in millions): December 31, 2017 Gross amounts Gross amounts Gross amounts Net amounts Assets: ​ ​ ​ ​ Futures $ $ ) $ — $ Contracts for differences ​ ​ — ​ — ​ Interest rate swaps ) — Total return swaps ​ ​ — ​ — ​ Credit default swaps ) — — Options ​ ​ ) ​ — ​ Swaptions — — Foreign currency forward contracts ​ ​ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ ) $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: ​ ​ ​ ​ Futures $ ) $ $ — $ — Interest rate swaps ​ ) ​ ​ — ​ ) Credit default swaps ) — ) Options ​ ) ​ ​ — ​ — Foreign currency forward contracts ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ ) $ $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The following table illustrates the effect of offsetting derivative instruments within consolidated seeded investment products on JHG's Consolidated Balance Sheets as of December 31, 2016 (in millions): December 31, 2016 Gross amounts Gross amounts Gross amounts Net amounts Assets: ​ ​ ​ ​ Futures $ $ ) $ — $ Contracts for differences ​ ​ ) ​ — ​ Interest rate swaps ) — — Options ​ ​ ) ​ — ​ Foreign currency forward contracts — ) — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets $ $ ) $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: Futures $ ) $ $ — $ — Contracts for differences ) — — Interest rate swaps ​ ) ​ ​ — ​ — Credit default swaps ) — — ) Options ​ ) ​ ​ — ​ — Foreign currency forward contracts ) — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total liabilities $ ) $ $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of investment gains (losses), net in Consolidated Statements of Comprehensive Income	Investment gains (losses), net on JHG's Consolidated Statements of Comprehensive Income included the following for the years ended December 31, 2017, 2016 and 2015 (in millions): Year ended December 31, 2017 2016 2015 Seeded investment products $ $ $ Fair value movements on derivatives ) ) Gain on sale of equity method investments ​ — ​ — ​ Gain on sale of Volantis — — Other ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Investment gains (losses), net $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Cash flows related to investment securities	Cash flows related to investment securities for the years ended December 31, 2017, 2016 and 2015, are summarized as follows (in millions): Year ended December 31, 2017 2016 2015 Purchases Sales, Purchases Sales, Purchases Sales, Trading securities $ ) $ $ ) $ $ ) $ Available-for-sale securities ) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total cash flows $ ) $ $ ) $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Not Designated as Hedging Instrument
Schedule of derivative instruments	JHG was party to the following derivative instruments as of December 31, 2017 and 2016 (in millions): Notional Value December 31, December 31, Futures $ $ Credit default swaps — Index swaps ​ ​ Total return swaps Foreign currency forward contracts ​ ​
Seeded investment products
Schedule of derivative instruments	JHG's consolidated seeded investment products were party to the following derivative instruments as of December 31, 2017 and 2016 (in millions): Notional Value December 31, December 31, Futures $ $ Contracts for differences Credit default swaps ​ ​ Total return swaps — Interest rate swaps ​ ​ Options Swaptions ​ ​ Foreign currency forward contracts

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets
Summary of goodwill and intangible assets	JHG's goodwill and intangible assets are summarized below (in millions): December 31, Merger Amortization Foreign December 31, Indefinite-lived intangible assets: ​ ​ ​ ​ ​ Investment management agreements $ $ $ — $ $ Trademarks ​ — ​ ​ — ​ ​ Definite-lived intangible assets: Client relationships ​ ​ ​ — ​ ​ Accumulated amortization ) — ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net intangible assets $ $ $ ) $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Goodwill $ $ $ — $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of expected future amortization	Expected future amortization expense related to definite-lived intangible assets is summarized below (in millions): Year ended December 31, Amount 2018 $ 2019 2020 ​ 2021 2022 ​ Thereafter ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Equity Method Investments (Tabl

Equity Method Investments (Tables)	12 Months Ended
	Dec. 31, 2017
Equity Method Investments
Summary of Equity Method Investments	Country of Functional 2017 2016 Long Tail Alpha USA USD ​ % ​ % Optimum Investment Management Limited UK GBP % % Northern Pines Henderson Capital GP LLC USA USD ​ — % ​ % Northern Pines Henderson Capital LLC USA USD — % %

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Measurements
Schedule of assets, liabilities and redeemable noncontrolling interests presented in the financial statements or disclosed in the notes to the financial statements at fair value on a recurring basis	The following table presents assets, liabilities and redeemable noncontrolling interests presented in the consolidated financial statements or disclosed in the notes to the consolidated financial statements at fair value on a recurring basis as of December 31, 2017 (in millions): Fair value measurements using: Quoted prices in Significant other Significant Total Assets: ​ ​ ​ ​ Cash equivalents $ $ — $ — $ Investment securities: ​ ​ ​ ​ Consolidated VIEs — trading Other — trading ​ ​ ​ ​ Consolidated VIEs — available-for-sale — — Other — available-for-sale ​ ​ — ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total investment securities Seed hedge derivatives ​ ​ — ​ — ​ Derivatives in consolidated seeded investment products — Contingent consideration ​ — ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets $ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: ​ ​ ​ ​ Derivatives in consolidated seeded investment products $ $ $ — $ Financial liabilities in consolidated seeded investment ​ ​ ​ ​ products — — Seed hedge derivatives ​ ​ ​ — ​ Current portion of long-term debt (1) — — Long-term debt (1) ​ — ​ ​ — ​ Deferred bonuses — — Contingent consideration ​ — ​ — ​ ​ Dai-ichi options — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total liabilities $ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Redeemable noncontrolling interests: Consolidated seeded investment products $ — $ — $ $ Intech — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total redeemable noncontrolling interests $ — $ — $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Carried at amortized cost and disclosed at fair value. The following table presents assets, liabilities and redeemable noncontrolling interests presented in the consolidated financial statements or disclosed in the notes to the consolidated financial statements at fair value on a recurring basis as of December 31, 2016 (in millions): Fair value measurements using: Quoted prices in Significant other Significant Total Assets: ​ ​ ​ ​ Investment securities: Consolidated VIEs — trading $ $ $ $ Other — trading — Consolidated VIEs — available-for-sale ​ ​ ​ — ​ Other — available-for-sale — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total investment securities ​ ​ ​ ​ Derivatives in consolidated seeded investment products — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets $ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: Derivatives in consolidated seeded investment products $ $ $ — $ Financial liabilities in consolidated seeded investment products — — Contingent consideration ​ — ​ — ​ ​ Deferred bonuses — — Seed hedge derivatives ​ — ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total liabilities $ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total redeemable noncontrolling interests in consolidated seeded investment products $ — $ — $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of changes in fair value of the recurring Level 3 fair value measurements for collective items	Changes in fair value of JHG's Level 3 assets for the years ended December 31, 2017 and 2016, are as follows (in millions): Year ended December 31, 2017 2016 Beginning of year fair value $ $ Balance acquired from the Merger — Additions ​ ​ Settlements ) — Transfers to Level 2 ​ ) ​ — Movement recognized in net income ) Movements recognized in other comprehensive income ​ ​ Foreign currency translation ) ​ ​ ​ ​ ​ ​ ​ ​ End of year fair value $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of changes in fair value of the recurring Level 3 fair value measurements for individual items	Changes in fair value of JHG's individual Level 3 liabilities and redeemable noncontrolling interests for the years ended December 31, 2017 and 2016, are as follows (in millions): Year ended December 31, 2017 2016 Contingent Deferred Dai-ichi Redeemable Contingent Deferred Redeemable Beginning of year fair value $ $ $ — $ $ $ $ Balances acquired from the Merger — — — — — Additions ​ — ​ — ​ ​ — ​ ​ — ​ — Changes in ownership — — — — — Net movement in bonus deferrals ​ — ​ ​ — ​ — ​ — ​ ​ — Fair value adjustments — ) — — — Unrealized gains (losses) ​ — ​ — ​ — ​ ) ​ — ​ — ​ Amortization of Intech appreciation rights — — — — — — Distributions ​ — ​ — ​ — ​ ) ​ — ​ — ​ — Foreign currency translation ) ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ End of year fair value $ $ $ $ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Summary of valuation techniques and significant unobservable inputs used in the valuation of the company's private equity investments	Valuation techniques and significant unobservable inputs used in the valuation of JHG's material Level 3 asset, the Group's private equity investment included within consolidated VIEs, as of December 31, 2017, and December 31, 2016, are as follows (in millions): As of December 31, 2017 Fair Valuation Significant Range Investment securities of consolidated VIEs — trading $ Discounted cash flow Discount rate EBITDA multiple Price-earnings ratio 12.0%-15.0% (14.3)% 11.6-15.1 (14.3) 22.6-61.3 (52.4) As of December 31, 2016 Fair Valuation Significant Range Investment securities of consolidated VIEs — trading $ Discounted cash flow Discount rate EBITDA multiple Price-earnings ratio 12.0%-30.0% (16.3)% 8.7-11.0 (9.1) 17.2-24.0 (18.4)

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt
Components of debt	Debt as of December 31, 2017 and 2016, consisted of the following (in millions): December 31, December 31, Carrying Fair Carrying Fair 4.875% Senior Notes due 2025 $ $ $ — $ — 0.750% Convertible Senior Notes due 2018 — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total debt ​ ​ ​ — ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Less: Current portion of long-term debt — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total long-term debt $ $ $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Taxes
Schedule of provision for income taxes	The components of the Group's provision for income taxes for the years ended December 31, 2017, 2016 and 2015, are as follows (in millions): Year ended December 31, 2017 2016 2015 Current: ​ ​ ​ UK $ $ $ U.S. including state and local ​ ​ ​ International ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total current income taxes ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred: UK ​ ​ ) ​ ) U.S. including state and local ) ) International ​ ) ​ ​ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total deferred income taxes (benefits) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total income tax expense $ ) $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of components of income before taxes and equity earnings	The components of the Group's total income before taxes for the years ended December 31, 2017, 2016 and 2015, are as follows (in millions): Year ended December 31, 2017 2016 2015 UK $ $ $ U.S. ) International ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total income before taxes $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of differences between effective income tax rate and statutory federal income tax rate	Year ended 2017 2016 2015 UK statutory corporation tax rate ​ % ​ % ​ % Effect of foreign tax rates ) ) Impact of Property disposal (1) ​ — ​ — ​ ) Equity-based compensation ) ) Finalization of positions with HMRC (2) ​ ​ ) ​ ) Tax adjustments Non-deductible costs associated with the Merger ​ ​ ​ — Impact of changes in statutory tax rates on deferred taxes ) ) ) Taxes applicable to prior years ​ ) ​ ​ ) Other, net ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Effective income tax rate, controlling interest ​ )% ​ % ​ % Net income attributable to noncontrolling interests ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total effective income tax rate ​ )% ​ % ​ % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) This incorporates the tax impact of the disposal of THRE during 2015. (2) Her Majesty's Revenue and Customs ('HMRC'), tax authority of the UK.
Schedule of Significant components of deferred tax assets and liabilities	The significant components of the Group's deferred tax assets and liabilities as of December 31, 2017 and 2016, are as follows (in millions): December 31, 2017 2016 Deferred tax assets: ​ ​ Compensation and staff benefits $ $ Loss carryforwards ​ ​ Accrued liabilities Debt premium ​ ​ — Other ​ ​ ​ ​ ​ ​ ​ ​ Gross deferred tax assets ​ ​ Valuation allowance ) ) ​ ​ ​ ​ ​ ​ ​ ​ Deferred tax assets, net of valuation allowance $ $ ​ ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities: Retirement benefits $ ) $ ) Goodwill and acquired intangible assets ) ) Other ​ ) ​ ) ​ ​ ​ ​ ​ ​ ​ ​ Gross deferred tax liabilities ) ) ​ ​ ​ ​ ​ ​ ​ ​ Net deferred tax (liabilities) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of balance sheet classification of deferred income tax assets and liabilities	Deferred tax assets and liabilities that relate to the same jurisdiction are recorded net on the Group's Consolidated Balance Sheets as non-current balances and as of December 31, 2017 and 2016, are as follows (in millions): December 31, 2017 2016 Deferred tax assets, net (included in other non-current assets) $ — $ Deferred tax liabilities, net ) ) ​ ​ ​ ​ ​ ​ ​ ​ Net deferred tax (liabilities) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Reconciliation of beginning and ending tax contingencies liability	A reconciliation of the beginning and ending liability for the years ended December 31, 2017, 2016 and 2015, is as follows (in millions): Year ended December 31, 2017 2016 2015 Balance, as of January 1 $ $ $ Balance acquired from the Merger — — Additions for tax positions of current year ​ ​ — ​ Additions/(reduction) for tax positions of prior years — ) Reduction due to settlement with taxing authorities ​ ) ​ ) ​ — Reduction due to statute expirations ) — — Foreign currency translation ​ ​ ) ​ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance, as of December 31 $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Other Financial Statement Cap39

Other Financial Statement Captions (Tables)	12 Months Ended
	Dec. 31, 2017
Other Financial Statement Captions
Other current assets	Other current assets on JHG's Consolidated Balance Sheets at December 31, 2017 and 2016, are composed of the following (in millions): December 31, 2017 2016 Prepaid expenses $ $ Deferred acquisition costs Current corporation tax ​ ​ Other current assets ​ ​ ​ ​ ​ ​ ​ ​ Total other current assets $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Accounts payable and accrued liabilities	Accounts payable and accrued liabilities on JHG's Consolidated Balance Sheets at December 31, 2017 and 2016, comprise the following (in millions): December 31, 2017 2016 Accrued commissions $ $ Accrued rebates Other accrued liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total other accrued liabilities $ $ ​ ​ ​ ​ ​ ​ ​ ​ Current corporation tax ​ ​ Contingent consideration — Dai-ichi option ​ ​ — Derivatives — Other current liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total accounts payable and accrued liabilities $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Other non-current liabilities	Other non-current liabilities on JHG's Consolidated Balance Sheets at December 31, 2017 and 2016, comprise the following (in millions): December 31, 2017 2016 Non-current tax liabilities $ $ Other creditors — Deferred consideration ​ ​ Other non-current accrued liabilities ​ ​ ​ ​ ​ ​ ​ ​ Total other non-current liabilities $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Noncontrolling Interests (Table

Noncontrolling Interests (Tables)	12 Months Ended
	Dec. 31, 2017
Noncontrolling Interests
Summary of redeemable noncontrolling interests	Redeemable noncontrolling interests as of December 31, 2017 and 2016, consisted of the following (in millions): December 31, 2017 2016 Consolidated seeded investment products $ $ Intech: Appreciation rights ​ ​ — Founding member ownership interests — ​ ​ ​ ​ ​ ​ ​ ​ Total redeemable noncontrolling interests $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of movement in redeemable noncontrolling interests in consolidated seeded investment products	The following table presents the movement in redeemable noncontrolling interests in consolidated seeded investment products for the years ended December 31, 2017, 2016 and 2015 (in millions): Year ended December 31, 2017 2016 2015 Opening balance $ $ $ Balance acquired from the Merger — — Changes in market value ​ ) ​ ​ ) Changes in ownership Foreign currency translation ​ ) ​ ) ​ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Closing balance $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Summary of nonredeemable noncontrolling interests	Nonredeemable noncontrolling interests as of December 31, 2017 and 2016, are as follows (in millions): December 31, 2017 2016 Nonredeemable noncontrolling interests in: ​ ​ Seed capital investments $ $ Intech ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ Total nonredeemable noncontrolling interests $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Long-Term Incentive Compensat41

Long-Term Incentive Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Summary of long term incentive plan weighting	2015 and 2016 awards criteria (pre-Merger) Weighting Market conditions ​ FTSE 350 % ASX 100 ​ % Non-Market Net Fund Flows Condition ​ % Investment Performance Condition % Operating Margin Condition ​ % People Strategy Condition % 2015 and 2016 awards criteria (post-Merger) Weighting Market conditions ​ Relative TSR % Non-Market ​ Relative investment performance % Relative net income before tax growth ​ %
Schedule of assumptions used for fair value of stock options granted	At December 31, 2017, unrecognized and unearned compensation, based on vesting outcomes as of December 31, 2017 on the 2017 LTIP, and the weighted-average number of years over which the compensation cost will be recognized is summarized as follows (in millions): Unrecognized Weighted- DEP $ ​ LTIP RSP ​ ​ BAYE ExSOP ​ ​ CSOP SAYE ​ ​ RSA ​ ​ ​ ​ ​ ​ ​ ​ Stock-based payments expense ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ DEP Funds — Liability settled MFSA — liability settled ​ ​ Profits interests and other Social Security costs ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total remaining charge to the Consolidated Statements of Comprehensive Income $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Summary of outstanding options	Black-Scholes Options Pricing Model Year ended December 31, 2017 2016 CSOP U.S. CSOP ExSOP SAYE CSOP U.S. CSOP ExSOP SAYE U.S. SAYE Fair value of options granted (pence) ​ ​ ​ ​ ​ ​ ​ ​ ​ Assumptions: Dividend yield ​ % ​ % ​ % ​ % ​ % ​ % ​ % ​ % ​ % Expected volatility % % % % % % % % % Risk-free interest rate ​ % ​ % ​ % ​ % ​ % ​ % ​ % ​ % ​ % Expected life (years) Monte Carlo Model — LTIP 2015 Year ended December 31, 2017 % Allocation Tranche 1 Tranche 2 Fair Values: ​ Relative TSR % 118.96p 124.11p Relative investment performance ​ % 209.76p 206.59p Relative net income before tax growth % 209.76p 206.59p Assumptions: ​ Date of grant May 1, 2015 May 1, 2015 Start of performance period ​ ​ January 1, 2015 January 1, 2015 End of performance period December 31, 2017 December 31, 2018 Vesting date ​ ​ May 1, 2018 May 1, 2019 Date of modification ("DoM") May 1, 2017 May 1, 2017 Share price at DoM ​ ​ 233.7p 233.7p Risk free discount rate 0.1% pa 0.1%pa Dividend yield ​ ​ 4.5% pa 4.5% pa Share price volatility in GBP 30% pa 30% pa Holding period adjustment ​ ​ Percentage based on pre-modification performance conditions Monte Carlo Model — LTIP 2016 Year Ended December 31, 2017 % allocation Tranche 1 Tranche 2 Fair values: ​ Relative TSR % 120.98p 123.64p Relative investment performance ​ % 200.42p 197.39p Relative net income before tax growth % 200.42p 197.39p Assumptions: ​ Date of grant May 1, 2016 May 1, 2016 Start of performance period ​ ​ January 1, 2016 January 1, 2016 End of performance period December 31, 2018 December 31, 2019 Vesting date ​ ​ March 24, 2019 March 24, 2020 Date of modification ("DoM") May 30, 2017 May 30, 2017 Share price at DoM ​ ​ 233.7p 233.7p Risk free discount rate 0.1% pa 0.1%pa Dividend yield ​ ​ 4.5% pa 4.5% pa Share price volatility in GBP 30% pa 30% pa Holding period adjustment ​ ​ The table below summarizes the Group's outstanding options, exercisable options and options vested or expected to vest for the years ended December 31, 2017, 2016 and 2015: 2017 2016 2015 Shares Weighted- Shares Weighted- Shares Weighted- Outstanding at January 1 ​ $ ​ £ ​ £ Share consolidation ) $ — £ — — £ — Acquired from Merger ​ $ ​ — £ — ​ — £ — Granted $ £ £ Exercised ​ ) $ ​ ) £ ​ ) £ Forfeited ) $ ) £ ) £ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Outstanding at December 31 ​ $ ​ £ ​ £ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Exercisable (1) $ £ £ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Vested or expected to vest ​ $ ​ £ ​ £ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Included in the above table is the Group's nil cost LTIP options which constitute the majority of forfeitures. (1) The number of exercisable options represents instruments for which all vesting criteria have been satisfied and whose exercise price was below the closing price of the Group's common stock as of the end of the period.
Summary of intrinsic value of exercised, outstanding and exercisable options	The following table summarizes the intrinsic value of exercised, outstanding and exercisable options at December 31, 2017, 2016 and 2015 (in millions): December 31, 2017 2016 2015 Exercised $ £ £ Outstanding $ £ £ Exercisable $ £ £
LongTerm Incentive Plan
Components of long-term incentive compensation expense	The components of the Group's long-term incentive compensation expense for the years ended December 31, 2017, 2016 and 2015 are summarized as follows (in millions): Year ended December 31, 2017 2016 2015 DEP $ $ $ LTIP RSP ​ ​ ​ BAYE ExSOP ​ ​ ​ CSOP SAYE ​ ​ ​ RSA — — ESOP ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stock-based payments expense ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ DEP Funds — liability settled ​ ​ ​ MFSA — liability settled — — Profits interests and other ​ ​ — ​ — Social Security costs ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total charge to the Consolidated Statements of Comprehensive Income $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Deferred Equity Plan
Summary of unvested stock awards	2017 2016 2015 Shares Weighted- Shares Weighted- Shares Weighted- Outstanding at January 1 ​ $ ​ £ ​ £ Share consolidation ) $ — £ — — £ — Adjustment ​ $ ​ — £ — ​ £ Granted $ £ £ Exercised ​ ) $ ​ ) £ ​ ) £ Forfeited ) $ ) £ ) £ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unvested at December 31 ​ $ ​ £ ​ £ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Appreciation Rights October 2014
Summary of assumptions used for fair value of appreciation rights of INTECH long-term incentive awards	Assumptions October 2014 February 2015 March 2016 Dividend yield ​ % ​ % ​ % Expected volatility % % % Risk-free interest rate ​ % ​ % ​ % Expected life (in years) Grant date fair value (in millions) $ $ $ Merger date fair value (in millions) $ $ $
Restricted Stock Awards
Summary of unvested stock awards	2017 Shares Weighted- Outstanding at January 1 ​ — $ — Acquired from the Merger $ Granted ​ $ Exercised ) $ Forfeited ​ ) $ ​ ​ ​ ​ ​ ​ ​ ​ Unvested at December 31 $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Retirement Benefit Plans (Table

Retirement Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Retirement Benefit Plans
Schedule of plans assets and benefit obligations	The Group's plan assets, benefit obligations and funded status as at the December 31 measurement date are as follows (in millions): December 31, 2017 2016 Change in plan assets: ​ ​ Fair value of plan assets as of January 1 $ $ Return on plan assets ​ ​ Employer contributions Benefits paid ​ ) ​ ) Settlements ) — Foreign currency translation ​ ​ ) ​ ​ ​ ​ ​ ​ ​ ​ Fair value of plan assets as of December 31 ​ ​ ​ ​ ​ ​ ​ ​ Change in benefit obligation: ​ ​ Benefit obligation as of January 1 ) ) Service cost ​ ) ​ ) Interest cost ) ) Settlements ​ ​ — Benefits paid Actuarial loss ​ ) ​ ) Foreign currency translation ) ​ ​ ​ ​ ​ ​ ​ ​ Benefit obligation as of December 31 ​ ) ​ ) ​ ​ ​ ​ ​ ​ ​ ​ Funded status as at year end ​ ​ ​ ​ ​ ​ ​ ​ Tax at source ​ ) ​ ) ​ ​ ​ ​ ​ ​ ​ ​ Net retirement benefit asset recognized in the Consolidated Balance Sheets $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of retirement benefit asset recognized in the Consolidated Balance Sheets	Amounts recognized on the Consolidated Balance Sheet, net of tax at source as at December 31, 2017 and 2016, consist of the following (in millions): December 31, 2017 2016 Retirement benefit assets recognized in the Consolidated Balance Sheets: ​ ​ Janus Henderson Group UK Pension Scheme $ $ Retirement benefit obligations recognized in the Consolidated Balance Sheets: ​ ​ Janus Henderson Group unapproved pension scheme ) ) ​ ​​ ​ ​ ​​ ​ ​ ​ Net retirement benefit asset recognized in the Consolidated Balance Sheets: $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of key assumptions used in determining the defined benefit obligation	December 31, 2017 2016 Discount rate ​ % ​ % Inflation — salaries % % Inflation — RPI ​ % ​ % Inflation — CPI % % Pension increases (RPI capped at 5% p.a.) ​ % ​ % Pension increases (RPI capped at 2.5% p.a.) % % Life expectancy of male aged 60 at accounting date ​ ​ Life expectancy of male aged 60 in 15 years time
Schedule of fair values of the JHGPS plan assets	The fair values of the JHGPS plan assets as at December 31, 2017 and 2016, by major asset class, are as follows (in millions): December 31, 2017 2016 Cash and cash equivalents $ $ Money market instruments — Forward foreign exchange contracts ​ ​ ) Bond assets Equity investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets at fair value $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of reconciliation of the beginning and ending fair value measurement for Level 3 assets	The following table shows a reconciliation of the beginning and ending fair value measurement for Level 3 assets (in millions): December 31, 2017 2016 Fair value of Level 3 assets at beginning of year $ — $ Losses recognized in the period — ) Purchases, sales and settlements, net ​ — ​ ) ​ ​ ​ ​ ​ ​ ​ ​ Fair value of Level 3 assets at end of year $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of actuarial gains and losses	Cumulative amounts recognized in accumulated other comprehensive income and the actuarial gain, net of tax deducted at source, credited to other comprehensive income for the years ended December 31, 2017 and 2016 are shown below (in millions): December 31, 2017 2016 Opening accumulated unamortized actuarial gain $ $ Current year actuarial gain (loss) ) Tax at source on current year actuarial gain (loss) ​ ​ ) Release of actuarial gain due to settlement event ) — Release of tax at source due to settlement event ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ Closing accumulated unamortized actuarial gain $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of components of net periodic benefit credit	The components of net periodic benefit cost in respect of defined benefit plans for the years ended December 31, 2017, 2016 and 2015 include the following (in millions): December 31, 2017 2016 2015 Service cost $ ) $ ) $ ) Settlement gain — — Interest cost ​ ) ​ ) ​ ) Expected return on plan assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net periodic benefit credit ​ ​ ​ Contributions to money purchase section ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total cost $ ) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of key assumptions used in determining the net periodic benefit cost	The following key assumptions were used in determining the net periodic benefit cost for the years ended December 31, 2017, 2016 and 2015 (in millions): December 31, 2017 2016 2015 Discount rate ​ % ​ % ​ % Inflation — salaries % % % Inflation — RPI ​ % ​ % ​ % Inflation — CPI % % % Pension increases (RPI capped at 5% p.a.) ​ % ​ % ​ % Pension increases (RPI capped at 2.5% p.a.) % % % Expected return on plan assets ​ % ​ % ​ % Amortization period for net actuarial gains/losses at beginning of the year
Schedule of expected future cash flows	The expected future benefit payments for the Group's pension plan are as follows (in millions): 2018 $ 2019 $ 2020 $ 2021 $ 2022 $ 2023-2027 $

Accumulated Other Comprehensi43

Accumulated Other Comprehensive Loss (Tables)	12 Months Ended
	Dec. 31, 2017
Accumulated Other Comprehensive Loss
Schedule of the changes in accumulated other comprehensive loss, net of tax	Changes in accumulated other comprehensive loss, net of tax, for the years ended December 31, 2017 and 2016, are as follows (in millions): Year ended December 31, 2017 2016 Foreign Available- Retirement Total Foreign Available- Retirement Total Beginning balance $ ) $ $ $ ) $ ) $ $ $ ) Other comprehensive income (loss) before reclassifications ) ) ) Amounts reclassified from accumulated other comprehensive income (loss) ​ — ​ ) ​ ) ​ ) ​ — ​ ) ​ — ​ ) Total other comprehensive income (loss) ) ) ) ) ) Less: other comprehensive loss (income) attributable to noncontrolling interests ​ ​ ) ​ — ​ ​ ) ​ — ​ — ​ ) ​ ​ ​ ​ ​​ ​ ​ ​​ ​ ​ ​​ ​ ​ ​​ ​ ​ ​​ ​ ​ ​​ ​ ​ ​​ ​ ​ ​ Ending balance $ ) $ $ $ ) $ ) $ $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Components of other comprehensive income (loss), net of tax	The components of other comprehensive income (loss), net of tax for the years ended December 31, 2017, 2016 and 2015, are as follows (in millions): Year ended December 31, 2017 Pre-tax Tax Net Net unrealized losses on available-for-sale securities $ $ — $ Foreign currency translation adjustments — Retirement benefit asset, net ​ ) ​ ) ​ ) Reclassifications to net income ) — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total other comprehensive income $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, 2016 Pre-tax Tax Net Net unrealized gains on available-for-sale securities $ $ — $ Foreign currency translation adjustments ) ) Retirement benefit asset, net ​ ​ ​ Reclassifications to net income ) — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total other comprehensive income loss $ ) $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, 2015 Pre-tax Tax Net Net unrealized gains on available-for-sale securities $ $ — $ Foreign currency translation adjustments ) — ) Retirement benefit asset, net ​ ) ​ ) ​ ) Reclassifications to net income ) — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total other comprehensive income loss $ ) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Earnings and Dividends Per Sh44

Earnings and Dividends Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings and Dividends Per Share
Summary of earnings per share calculation	The following is a summary of the earnings per share calculation for the years ended December 31, 2017, 2016 and 2015 (in millions, except per share data): Year ended December 31, 2017 2016 2015 Net income attributable to JHG $ $ $ Less: Allocation of earnings to participating stock-based awards ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income attributable to JHG common shareholders $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average common shares outstanding — basic Dilutive effect of non-participating stock-based awards ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average diluted common shares outstanding — diluted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Earnings per share: ​ ​ ​ Basic $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted (two class) $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of anti-dilutive securities that have not been included in the calculation of weighted average diluted shares outstanding	The following instruments are anti-dilutive and have not been included in the weighted-average diluted shares outstanding calculation (in millions): Year ended 2017 2016 2015 Unvested nonparticipating stock awards ​ ​ ​ Dai-ichi options — —
Schedule of cash dividends declared and paid	Year ended December 31, 2017 2016 2015 Dividends paid per share — pre-Merger — in GBP £ £ £ Dividends paid per share — post-Merger — in USD $ $ — $ —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies
Future minimum rental commitments	As of December 31, 2017, future minimum rental commitments under non-cancelable operating and capital leases are as follows (in millions): Year ended December 31, Amount 2018 $ 2019 2020 ​ 2021 2022 ​ Thereafter ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2017
Related Party Transactions
Schedule of related party activity	The following table reflects amounts in the Consolidated Balance Sheets relating to fees receivable from managed funds which are deemed to be related parties (in millions): Year ended 2017 2016 12b-1 plan fees (1) $ $ — As of December 31 2017 2016 Accrued income $ $ Accounts receivable (1) The annual marketing or distribution fees on a mutual fund.

Geographic Information (Tables)

Geographic Information (Tables)	12 Months Ended
	Dec. 31, 2017
Geographic Information
Summary information of entity's geographic areas	The following summary provides information concerning the Group's principal geographic areas for the years ended and as of December 31, 2017, 2016 and 2015 (in millions): Year ended December 31, Operating revenues 2017 2016 2015 U.S. $ $ $ UK Luxembourg ​ ​ ​ International ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of Long-lived assets 2017 2016 UK $ $ U.S. Australia ​ ​ — Other ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Selected Quarterly Financial 48

Selected Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2017
Selected Quarterly Financial Data
Selected Quarterly Financial Data	2017 (in millions, except per share amounts) First Second Third Fourth Full Operating revenue $ $ $ $ $ Operating income Net income ​ ​ ​ ​ ​ Net income attributable to noncontrolling interests — ) ) ) Net income attributable to JHG ​ ​ ​ ​ ​ Basic earnings per share attributable to JHG common shareholders $ $ $ $ $ Diluted earnings per share attributable to JHG common shareholders $ $ $ $ $ 2016 (in millions, except per share amounts) First Second Third Fourth Full Operating revenue $ $ $ $ $ Operating income Net income ​ ​ ​ ​ ​ Net income attributable to noncontrolling interests ) ) Net income attributable to JHG ​ ​ ​ ​ ​ Basic earnings per share attributable to JHG common shareholders $ $ $ $ $ Diluted earnings per share attributable to JHG common shareholders $ $ $ $ $

Summary of Significant Accoun49

Summary of Significant Accounting Policies - Consolidation, Property, Equipment and Software, Deferred Commissions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Equipment and Software
Depreciation and amortization expense	$ 24.6	$ 8.2	$ 7.9
Property, equipment and software, gross	120	74.2
Accumulated depreciation	(49.4)	(33)
Property, equipment and software, net	70.6	41.2
Impairments of long-lived assets	$ 0	0	$ 0
Deferred Commissions
Amortization period of sales commission, maximum	4 years
Furniture, fixtures and computer equipment
Property, Equipment and Software
Property, equipment and software, gross	$ 31.9	17.5
Furniture, fixtures and computer equipment | Minimum
Property, Equipment and Software
Depreciation period	3 years
Furniture, fixtures and computer equipment | Maximum
Property, Equipment and Software
Depreciation period	10 years
Leasehold improvements
Property, Equipment and Software
Depreciation period, description	Over the shorter of 20 years or the period of the lease
Property, equipment and software, gross	$ 29.8	21.1
Computer software
Property, Equipment and Software
Property, equipment and software, gross	$ 58.3	$ 35.6
Computer software | Minimum
Property, Equipment and Software
Depreciation period	3 years
Computer software | Maximum
Property, Equipment and Software
Depreciation period	7 years

Summary of Significant Accoun50

Summary of Significant Accounting Policies - Financial Instruments (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)item$ / shares	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2017£ / shares	May 30, 2017$ / shares	May 03, 2017$ / shares	Apr. 26, 2017$ / shares	Apr. 26, 2017£ / shares	Dec. 31, 2016£ / shares
Financial Instruments
Percentage of ownership in new product	100.00%
Employer contributions to deferred compensation plan	$ 0	$ 0	$ 0
Impairment of investments	$ 0	$ 0	$ 0
Trade and other receivables, payment terms (in days)	30 days
Revenue Recognition
Performance fee adjustment, ultimate measurement period	36 months
Common Stock
Common stock, par (in dollars/pounds per share) | (per share)	$ 1.50			£ 1.50	$ 1.50	$ 0.15	$ 0.1547	£ 0.125	£ 0.125
Mutual funds
Revenue Recognition
Number of components involved in investment advisory fee payment | item	2
Performance fee adjustment, measurement period	36 months
Minimum | Mutual funds
Revenue Recognition
Performance fee adjustment, measurement period	12 months
Maximum | Mutual funds
Revenue Recognition
Performance fee adjustment, variable rate	0.15%
Performance fee adjustment, measurement period	18 months

Summary of Significant Accoun51

Summary of Significant Accounting Policies - Stock Based Compensation, Common Stock (Details) $ / shares in Units, $ in Millions	May 03, 2017USD ($)$ / shares	Apr. 26, 2017£ / shares	Dec. 31, 2017USD ($)item	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2017£ / shares	Dec. 31, 2017USD ($)$ / sharesshares	May 30, 2017$ / shares	Apr. 26, 2017USD ($)$ / sharesshares	Apr. 25, 2017USD ($)	Dec. 31, 2016£ / shares	Dec. 31, 2016USD ($)shares
Basis of Presentation
Stock-based compensation costs			$ 67.4	$ 37.3	$ 43.6
Proceeds from stock-based compensation plans			$ 6	11	15.6
Accumulated stock-based compensation costs							$ (105.4)					$ (92.9)
Goodwill and Intangible Assets, Net
Number of reporting unit for goodwill impairment testing purposes | item			1
Gain or loss recognized on purchase, issue, sale or cancellation of Henderson's own equity shares			$ 0
Common stock, par (in dollars/pounds per share) | (per share)	$ 0.15	£ 0.125				£ 1.50	$ 1.50	$ 1.50	$ 0.1547		£ 0.125
Common stock, shares issued | shares							200,406,138		1,131,842,110			1,131,842,109
Ordinary share capital amount	$ 169.8						$ 300.6		$ 175.1	$ 234.4		$ 234.4
Additional paid-in-capital	1,302.5						$ 3,842.9		$ 1,297.2	$ 1,237.9		$ 1,237.9
Reduction in ordinary share capital amount due change in par value	$ 5.3
Ordinary shares split conversion ratio		10
Retained earnings
Basis of Presentation
Stock-based compensation costs			9.9	37.3	$ 43.6
Proceeds from stock-based compensation plans			$ 0	$ 11
Client relationships
Goodwill and Intangible Assets, Net
Estimated useful life (in years)			13 years

Recent Accounting Pronounceme52

Recent Accounting Pronouncements (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Accounting Standards Update 2016-08
Recent Accounting Pronouncements
Increase in annual revenue due to change in presentation of distribution fees	$ 97
Accounting Standards Update 2017-07
Recent Accounting Pronouncements
Amount of other components of net periodic pension costs presented outside of operations	$ 2.7

Acquisitions - Merger with JCG

Acquisitions - Merger with JCG (Details) $ / shares in Units, $ in Millions	May 30, 2017USD ($)$ / sharesshares	Apr. 26, 2017$ / shares	Dec. 31, 2017USD ($)	Dec. 31, 2017£ / shares	Dec. 31, 2017USD ($)$ / shares	May 03, 2017$ / shares	Apr. 26, 2017£ / shares	Dec. 31, 2016£ / shares	Dec. 31, 2016USD ($)
Acquisitions
Par value ( in dollars per share) | (per share)	$ 1.50	$ 0.1547		£ 1.50	$ 1.50	$ 0.15	£ 0.125	£ 0.125
Ordinary shares split conversion ratio		10
Assets:
Intangible assets					$ 2,785
Goodwill					1,533.9				$ 741.5
Henderson Group plc
Acquisitions
Par value ( in dollars per share) | $ / shares	$ 1.50
Ordinary shares split conversion ratio	10
Janus Capital Group Inc
Acquisitions
Number of shares issued to common stock holders of Janus Capital Group | shares	87,200,000
Share price of common stock issued to stock holders of Janus Capital Group (in dollars per share) | $ / shares	$ 30.75
Preliminary allocation of the purchase price to the assets acquired and liabilities assumed
Goodwill	$ 697.9
Deferred tax liabilities	1,025.6
Other non-current liabilities	55.2
Noncontrolling interests	59.4
Net assets acquired	2,600.7
Adjustments
Goodwill			$ 28.6
Deferred tax liabilities			8.7
Other non-current liabilities			0.8
Noncontrolling interest			(10.4)
Net assets acquired			$ 29.5
Assets:
Cash and cash equivalents	417.2				417.2
Investment securities	270.4				270.4
Fees and other receivables	133.7				133.7
Other current assets, net	119.4				119.4
Property, equipment and software	32.3				32.3
Intangible assets	2,785				2,785
Goodwill					726.5
Other non-current assets, net	10.6				10.6
Liabilities:
Long-term debt	481.8				481.8
Deferred tax liabilities					1,034.3
Accounts payable and accrued liabilities	$ 243.8				243.8
Other non-current liabilities					56
Noncontrolling interests					49
Net assets acquired					$ 2,630.2
Janus Capital Group Inc | Henderson Group plc
Acquisitions
Number of shares received for each share of Janus common stock | shares	0.47190

Acquisitions - Merger with JC54

Acquisitions - Merger with JCG - Intangible Assets (Details) - USD ($) $ in Millions	May 30, 2017	Dec. 31, 2017
Investment management contracts:
Fair value		$ 2,785
Investment management agreements
Investment management contracts:
Fair value - Indefinite lived intangible assets		2,169
Trademarks
Investment management contracts:
Fair value - Indefinite lived intangible assets		381
Janus Capital Group Inc
Investment management contracts:
Fair value	$ 2,785	$ 2,785
Janus Capital Group Inc | Legacy-Janus | Separate accounts
Investment management contracts:
Fair value - Finite lived intangible assets	$ 202
Useful life (weighted-average in years)	15 years
Janus Capital Group Inc | Legacy-Janus | ETNs
Investment management contracts:
Fair value - Finite lived intangible assets	$ 33
Useful life (weighted-average in years)	15 years
Janus Capital Group Inc | Legacy-Janus | Mutual funds
Investment management contracts:
Fair value - Indefinite lived intangible assets	$ 2,155
Janus Capital Group Inc | Legacy-Janus | ETFs
Investment management contracts:
Fair value - Indefinite lived intangible assets	14
Janus Capital Group Inc | Legacy-Janus | Trademarks
Investment management contracts:
Fair value - Indefinite lived intangible assets	$ 381

Acquisitions - Merger with JC55

Acquisitions - Merger with JCG - Debt (Details) - USD ($) $ in Millions	Dec. 31, 2017	May 30, 2017	Dec. 31, 2016
0.750% Convertible Senior Notes due 2018
Business acquisition
Interest rate (as a percent)	0.75%		0.75%
4.875% Senior Notes due 2025
Business acquisition
Interest rate (as a percent)	4.875%		4.875%
Janus Capital Group Inc | 0.750% Convertible Senior Notes due 2018
Business acquisition
Interest rate (as a percent)		0.75%
Debt liability component		$ 115.2
Discounted cash flow rate (Percentage)		1.90%
Debt equity component		$ 42.9
Fair value of debt		158.1
Janus Capital Group Inc | 0.750% Convertible Senior Notes due 2018 | Maximum
Business acquisition
Debt liability component		$ 116.6
Janus Capital Group Inc | 4.875% Senior Notes due 2025
Business acquisition
Interest rate (as a percent)		4.875%
Fair value of debt		$ 323.7
Unamortized premium, net	$ 22

Acquisitions - Merger with JC56

Acquisitions - Merger with JCG - Pro Forma Results of Operations (Details) - USD ($) $ in Millions	7 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pro Forma Results of Operations
Revenue		$ 2,182.6	$ 2,010.6	$ 2,231.3
Net income attributable to JHG		$ 704.6	$ 336.2	$ 485.6
JCG's results of operations
Revenues included in JHG's Condensed Consolidated Statements of Comprehensive Income	$ 752.9
Net income attributable to JCG	$ 354

Acquisitions - Merger with JC57

Acquisitions - Merger with JCG - Options (Details) - Dai-ichi option £ / shares in Units, £ in Millions, $ in Millions	May 30, 2017GBP (£)tranche£ / sharesshares	May 30, 2017USD ($)trancheshares	Dec. 31, 2017USD ($)
Business Acquisition [Line Items]
Number of tranches | tranche	20	20
Allowed number of shares that may be purchased for each tranche of conditional shares | shares	500,000	500,000
Strike Price (in pounds per share) | £ / shares	£ 29.972
Cash consideration of the options	£ 19.8	$ 25.7
Fair value of the options | $			$ 26.1

Consolidation - VIEs (Details)

Consolidation - VIEs (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Other current assets	$ 75.9	$ 28.5
Accounts payable and accrued liabilities	(292.9)	(141.7)
Consolidated VIEs
Investment securities	419.7	313.7
Cash and cash equivalents	34.1	44.2
Other current assets	12.9	8.1
Accounts payable and accrued liabilities	(21.5)	(26.2)
Total	445.2	339.8
Redeemable noncontrolling interests in consolidated VIEs	(168.3)	(158)
Nonredeemable noncontrolling interests in consolidated VIEs	(24.9)	(44.8)
JHG's net interest in consolidated VIEs	252	137
Unconsolidated VIEs
Investment securities	$ 6.2	$ 0

Consolidation - VREs (Details)

Consolidation - VREs (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Other current assets	$ 75.9	$ 28.5
Accounts payable and accrued liabilities	(292.9)	(141.7)
Consolidated VREs
Investment securities	18.9	5.1
Cash and cash equivalents	5.9
Other current assets	0.6
Accounts payable and accrued liabilities	(2.2)
Total	23.2	5.1
Redeemable noncontrolling interests in consolidated VREs	6.6
JHG's net interest in consolidated VREs	16.6	5.1
Unconsolidated VREs
Investment securities	$ 50	$ 4.9

Investment Securities - General

Investment Securities - General Disclosure (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Short-term investments:
Estimated Fair Value	$ 700.1	$ 393.3
Assets
Gross amounts	0.9
Gross amounts offset by derivative instruments	(0.9)
Liabilities
Gross amounts, Liabilities	(10.1)	(5.1)
Gross amounts offset, Liabilities	0.9
Gross amounts offset by cash collateral pledge	4.9	1.6
Net amount, Liabilities	(4.3)	(3.5)
Net gains (losses) in net income related to:
Foreign currency translation	(3.2)	29.6	$ 3.5
Foreign currency forward contracts	3.2	(29.6)	(3.5)
Seeded investment products
Short-term investments:
Seeded investment products	575.9	297.6
Assets
Gross amounts	6.5	4.5
Gross amounts offset by derivative instruments	(2.6)	(1.5)
Gross amounts offset by cash collateral	2.3	(0.4)
Net amount, Assets	6.2	2.6
Liabilities
Gross amounts, Liabilities	(4.3)	(4)
Gross amounts offset, Liabilities	2.5	1.5
Gross amounts offset by cash collateral pledge	(0.1)	0.3
Net amount, Liabilities	(1.9)	(2.2)
Trading securities
Short-term investments:
Estimated Fair Value	678.1	367.2
Trading securities | Seeded investment products
Short-term investments:
Trading securities still held at period end	25.2	8.4	$ (5.6)
Trading securities | Separate accounts
Short-term investments:
Seeded investment products	75.6
Trading securities | Pooled investment funds
Short-term investments:
Seeded investment products	27.5
Trading securities | Investments related to deferred compensation plans
Short-term investments:
Estimated Fair Value	94	66.5
Trading securities | Other investments
Short-term investments:
Seeded investment products	8.2	3.1
Available-for-sale securities | Seeded investment products
Available-for-sale securities.
Available-for-sale Securities, Amortized Cost Basis, Total	18.5	15.1
Available-for-sale securities, Gross unrealized gains	2.7	3.4
Foreign currency translation	0.8	7.6
Available-for-sale securities, Fair value	22	26.1
Consolidated VIEs | Trading securities
Short-term investments:
Seeded investment products	402.8	288
Consolidated VIEs | Available-for-sale securities
Available-for-sale securities.
Available-for-sale securities, Fair value	16.9	25.7
Consolidated VREs | Trading securities
Short-term investments:
Seeded investment products	18.9	5.1
Unconsolidated VIEs and VREs | Trading securities
Short-term investments:
Seeded investment products	51.1	4.5
Unconsolidated VIEs and VREs | Available-for-sale securities
Available-for-sale securities.
Available-for-sale securities, Fair value	5.1	0.4
Consolidated | Credit default swap, selling protection contracts | Seeded investment products
Available-for-sale securities.
Notional value of derivative	4	0
Futures
Assets
Gross amounts	0.9
Gross amounts offset by derivative instruments	(0.9)
Liabilities
Gross amounts, Liabilities	(2.2)
Gross amounts offset, Liabilities	0.9
Net amount, Liabilities	(1.3)
Futures | Seeded investment products
Assets
Gross amounts	3.3	0.6
Gross amounts offset by derivative instruments	(1.7)	(0.1)
Net amount, Assets	1.6	0.5
Liabilities
Gross amounts, Liabilities	(1.7)	(0.1)
Gross amounts offset, Liabilities	(1.7)	0.1
Futures | Derivative Instruments | Not Designated as Hedging Instrument
Available-for-sale securities.
Notional value of derivative	190.6	14.7
Futures | Derivative Instruments | Seeded investment products
Available-for-sale securities.
Notional value of derivative	241.2	22.3
Credit default swaps
Liabilities
Gross amounts, Liabilities	(3)
Gross amounts offset by cash collateral pledge	0.9
Net amount, Liabilities	(2.1)
Credit default swaps | Seeded investment products
Assets
Gross amounts	0.1
Gross amounts offset by derivative instruments	(0.1)
Liabilities
Gross amounts, Liabilities	(1)	(0.1)
Gross amounts offset, Liabilities	0.1
Net amount, Liabilities	(0.9)	(0.1)
Credit default swaps | Derivative Instruments | Not Designated as Hedging Instrument
Available-for-sale securities.
Notional value of derivative	117.5
Credit default swaps | Derivative Instruments | Seeded investment products
Available-for-sale securities.
Notional value of derivative	15	1.8
Index swaps
Liabilities
Gross amounts, Liabilities	(2.1)	(0.8)
Gross amounts offset by cash collateral pledge	2.1	0.5
Net amount, Liabilities		(0.3)
Index swaps | Derivative Instruments | Not Designated as Hedging Instrument
Available-for-sale securities.
Notional value of derivative	76.7	34.2
Total return swaps
Liabilities
Gross amounts, Liabilities	(1)	(1.1)
Gross amounts offset by cash collateral pledge	1	1.1
Total return swaps | Seeded investment products
Assets
Gross amounts	0.1
Net amount, Assets	0.1
Total return swaps | Derivative Instruments | Not Designated as Hedging Instrument
Available-for-sale securities.
Notional value of derivative	70.3	59.5
Total return swaps | Derivative Instruments | Seeded investment products
Available-for-sale securities.
Notional value of derivative	36.7
Foreign currency forward contracts
Liabilities
Gross amounts, Liabilities	(1.8)	(3.2)
Gross amounts offset by cash collateral pledge	0.9
Net amount, Liabilities	(0.9)	(3.2)
Foreign currency forward contracts | Seeded investment products
Assets
Gross amounts	1.1	0.4
Gross amounts offset by derivative instruments	(0.4)
Gross amounts offset by cash collateral	2.3	(0.4)
Net amount, Assets	3
Liabilities
Gross amounts, Liabilities	(1.2)	(2.4)
Gross amounts offset, Liabilities	0.4
Gross amounts offset by cash collateral pledge	(0.1)	0.3
Net amount, Liabilities	(0.9)	(2.1)
Foreign currency forward contracts | Derivative Instruments | Not Designated as Hedging Instrument
Available-for-sale securities.
Notional value of derivative	118.8	170.1
Foreign currency forward contracts | Derivative Instruments | Seeded investment products
Available-for-sale securities.
Notional value of derivative	$ 135.9	$ 120

Investment Securities - Offsett

Investment Securities - Offsetting Derivatives (Details) - USD ($) $ in Millions	12 Months Ended			24 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Assets
Gross amounts	$ 0.9			$ 0.9
Gross amounts offset by derivative instruments	(0.9)			(0.9)
Liabilities
Gross amounts, Liabilities	(10.1)	$ (5.1)		(10.1)
Gross amounts offset, Liabilities	0.9			0.9
Gross amounts offset by cash collateral pledge	4.9	1.6		4.9
Net amount, Liabilities	(4.3)	(3.5)		(4.3)
Derivative Instrument Denominated in Foreign Currency
Investment gains (losses), net	18	(11.7)	$ 39.7
Cash flows related to investment securities
Purchases and settlements	(827.5)	(81.6)	(40.3)
Sales, settlements and maturities	976.4	36.6	45.9
Futures
Assets
Gross amounts	0.9			0.9
Gross amounts offset by derivative instruments	(0.9)			(0.9)
Liabilities
Gross amounts, Liabilities	(2.2)			(2.2)
Gross amounts offset, Liabilities	0.9			0.9
Net amount, Liabilities	(1.3)			(1.3)
Index swaps
Liabilities
Gross amounts, Liabilities	(2.1)	(0.8)		(2.1)
Gross amounts offset by cash collateral pledge	2.1	0.5		2.1
Net amount, Liabilities		(0.3)
Total return swaps
Liabilities
Gross amounts, Liabilities	(1)	(1.1)		(1)
Gross amounts offset by cash collateral pledge	1	1.1		1
Credit default swaps
Liabilities
Gross amounts, Liabilities	(3)			(3)
Gross amounts offset by cash collateral pledge	0.9			0.9
Net amount, Liabilities	(2.1)			(2.1)
Foreign currency forward contracts
Liabilities
Gross amounts, Liabilities	(1.8)	(3.2)		(1.8)
Gross amounts offset by cash collateral pledge	0.9			0.9
Net amount, Liabilities	(0.9)	(3.2)		(0.9)
Seeded investment products
Assets
Gross amounts	6.5	4.5		6.5
Gross amounts offset by derivative instruments	(2.6)	(1.5)		(2.6)
Gross amounts offset by cash collateral pledged	(2.3)	0.4		(2.3)
Net amount, Assets	6.2	2.6		6.2
Liabilities
Gross amounts, Liabilities	(4.3)	(4)		(4.3)
Gross amounts offset, Liabilities	2.5	1.5		2.5
Gross amounts offset by cash collateral pledge	(0.1)	0.3		(0.1)
Net amount, Liabilities	(1.9)	(2.2)		(1.9)
Derivative Instrument Denominated in Foreign Currency
Investment gains (losses), net	26	0.5	17.3
Seeded investment products | Futures
Assets
Gross amounts	3.3	0.6		3.3
Gross amounts offset by derivative instruments	(1.7)	(0.1)		(1.7)
Net amount, Assets	1.6	0.5		1.6
Liabilities
Gross amounts, Liabilities	(1.7)	(0.1)		(1.7)
Gross amounts offset, Liabilities	(1.7)	0.1		(1.7)
Seeded investment products | Contracts for differences
Assets
Gross amounts	0.1	0.3		0.1
Gross amounts offset by derivative instruments		(0.1)
Net amount, Assets	0.1	0.2		0.1
Liabilities
Gross amounts, Liabilities		(0.1)
Gross amounts offset, Liabilities		0.1
Seeded investment products | Interest rate swaps
Assets
Gross amounts	0.2	0.1		0.2
Gross amounts offset by derivative instruments	(0.1)	(0.1)		(0.1)
Net amount, Assets	0.1			0.1
Liabilities
Gross amounts, Liabilities	(0.2)	(0.1)		(0.2)
Gross amounts offset, Liabilities	0.1	0.1		0.1
Net amount, Liabilities	(0.1)			(0.1)
Seeded investment products | Total return swaps
Assets
Gross amounts	0.1			0.1
Net amount, Assets	0.1			0.1
Seeded investment products | Credit default swaps
Assets
Gross amounts	0.1			0.1
Gross amounts offset by derivative instruments	(0.1)			(0.1)
Liabilities
Gross amounts, Liabilities	(1)	(0.1)		(1)
Gross amounts offset, Liabilities	0.1			0.1
Net amount, Liabilities	(0.9)	(0.1)		(0.9)
Seeded investment products | Options
Assets
Gross amounts	1.5	3.1		1.5
Gross amounts offset by derivative instruments	(0.3)	(1.2)		(0.3)
Net amount, Assets	1.2	1.9		1.2
Liabilities
Gross amounts, Liabilities	(0.2)	(1.2)		(0.2)
Gross amounts offset, Liabilities	0.2	1.2		0.2
Seeded investment products | Swaptions
Assets
Gross amounts	0.1			0.1
Net amount, Assets	0.1			0.1
Seeded investment products | Foreign currency forward contracts
Assets
Gross amounts	1.1	0.4		1.1
Gross amounts offset by derivative instruments	(0.4)			(0.4)
Gross amounts offset by cash collateral pledged	(2.3)	0.4		(2.3)
Net amount, Assets	3			3
Liabilities
Gross amounts, Liabilities	(1.2)	(2.4)		(1.2)
Gross amounts offset, Liabilities	0.4			0.4
Gross amounts offset by cash collateral pledge	(0.1)	0.3		(0.1)
Net amount, Liabilities	(0.9)	(2.1)		(0.9)
Seeded investment products | Consolidated | Credit default swap, selling protection contracts
Seeded investment products, credit protection
Notional value of derivative	4	0		4
Fair value of credit default swap contracts	0.1	0		$ 0.1
Seeded investment products | Consolidated | Credit default swap, selling protection contracts | Minimum
Seeded investment products, credit protection
Term of credit default swap contracts (in years)				1 year
Seeded investment products | Consolidated | Credit default swap, selling protection contracts | Maximum
Seeded investment products, credit protection
Term of credit default swap contracts (in years)				5 years
Fair value movements on derivatives
Derivative Instrument Denominated in Foreign Currency
Investment gains (losses), net	(22)	(12.9)	1
Gain on sale of equity method investments
Derivative Instrument Denominated in Foreign Currency
Investment gains (losses), net			18.9
Gain on sale of Volantis
Derivative Instrument Denominated in Foreign Currency
Investment gains (losses), net	10.2
Other investments
Derivative Instrument Denominated in Foreign Currency
Investment gains (losses), net	3.8	0.7	2.5
Trading securities
Cash flows related to investment securities
Purchases and settlements	(792.3)	(81.6)	(40.3)
Sales, settlements and maturities	931	5	5.3
Available-for-sale securities
Cash flows related to investment securities
Purchases and settlements	(35.2)
Sales, settlements and maturities	45.4	31.6	$ 40.6
Derivative Instruments | Seeded investment products | Futures
Seeded investment products, credit protection
Notional value of derivative	241.2	22.3		$ 241.2
Derivative Instruments | Seeded investment products | Contracts for differences
Seeded investment products, credit protection
Notional value of derivative	10.2	9.2		10.2
Derivative Instruments | Seeded investment products | Interest rate swaps
Seeded investment products, credit protection
Notional value of derivative	58.3	8.3		58.3
Derivative Instruments | Seeded investment products | Total return swaps
Seeded investment products, credit protection
Notional value of derivative	36.7			36.7
Derivative Instruments | Seeded investment products | Credit default swaps
Seeded investment products, credit protection
Notional value of derivative	15	1.8		15
Derivative Instruments | Seeded investment products | Options
Seeded investment products, credit protection
Notional value of derivative	144.3	184.8		144.3
Derivative Instruments | Seeded investment products | Swaptions
Seeded investment products, credit protection
Notional value of derivative	2.7	1.7		2.7
Derivative Instruments | Seeded investment products | Foreign currency forward contracts
Seeded investment products, credit protection
Notional value of derivative	$ 135.9	$ 120		$ 135.9

Goodwill and Intangible Asset62

Goodwill and Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Indefinite-lived intangible assets:
Impairment		$ 4.9
Definite-lived intangible assets:
Accumulated amortization, balance at the end of the year	$ (60.4)
Amortization	(22.9)
Foreign currency translation	(6.4)
Accumulated amortization, balance at the end of the year	(89.7)	(60.4)
Net intangible assets
Net intangible assets, balance at the beginning of the year	401.3
Merger	2,785
Amortization	(22.9)
Foreign currency translation	41.4
Net intangible assets, balance at the end of the year	3,204.8	401.3
Goodwill
Goodwill, balance at the beginning of the year	741.5
Goodwill acquired	726.5
Foreign currency translation	65.9
Goodwill, balance at the end of the year	1,533.9	741.5
Impairment of goodwill			$ 0
Future Amortization expense:
2,018	29.7
2,019	29.7
2,020	29.7
2,021	26.8
2,022	18.3
Thereafter	145.5
Total	279.7
Client relationships
Definite-lived intangible assets:
Balance at the beginning of the year	126.9
Merger	235
Foreign currency translation	7.5
Balance at the end of the period	$ 369.4	126.9
Estimated life	13 years
Investment management agreements
Indefinite-lived intangible assets:
Balance at the beginning of the year	$ 334.8
Merger	2,169
Foreign currency translation	40.1
Balance at the end of the year	2,543.9	$ 334.8
Trademarks
Indefinite-lived intangible assets:
Merger	381
Foreign currency translation	0.2
Balance at the end of the year	$ 381.2

Equity Method Investments (Deta

Equity Method Investments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity Method Investments
Profit from equity method investments		$ 0.7
Net loss from equity method investments	$ 0.6	3.1	$ (17.9)
Equity method investment sold consideration			$ 122.7
Other non-current assets
Equity Method Investments
Equity method investments	$ 5.9	$ 0.2
Long Tail Alpha
Equity Method Investments
Percentage Owned	20.00%	20.00%
Optimum Investment Management Limited
Equity Method Investments
Percentage Owned	50.00%	50.00%
Northern Pines Groups
Equity Method Investments
Impairment loss related to shareholding		$ 3.8
Northern Pines Henderson Capital GP LLC
Equity Method Investments
Percentage Owned		50.00%
Northern Pines Henderson Capital LLC
Equity Method Investments
Percentage Owned		50.00%

Fair Value Measurements - Level

Fair Value Measurements - Level of Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Liabilities
Derivative liabilities	$ 4.3	$ 3.5
Total redeemable noncontrolling interests	190.3	158
Futures
Liabilities
Derivative liabilities	1.3
Index swaps
Liabilities
Derivative liabilities		0.3
Foreign currency forward contracts
Liabilities
Derivative liabilities	0.9	3.2
Credit default swaps
Liabilities
Derivative liabilities	2.1
Seeded investment products
Assets
Derivative assets	6.2	2.6
Liabilities
Derivative liabilities	1.9	2.2
Total redeemable noncontrolling interests	174.9	158	$ 82.9	$ 4.4
Seeded investment products | Futures
Assets
Derivative assets	1.6	0.5
Seeded investment products | Total return swaps
Assets
Derivative assets	0.1
Seeded investment products | Foreign currency forward contracts
Assets
Derivative assets	3
Liabilities
Derivative liabilities	0.9	2.1
Seeded investment products | Credit default swaps
Liabilities
Derivative liabilities	0.9	0.1
Consolidated VIEs
Assets
Total investment securities	419.7	313.7
Unconsolidated VIEs
Assets
Total investment securities	6.2	0
Consolidated VREs
Assets
Total investment securities	18.9	5.1
Unconsolidated VREs
Assets
Total investment securities	50	4.9
Intech Founders
Liabilities
Total redeemable noncontrolling interests	4.4
Consolidated | Seeded investment products
Liabilities
Total redeemable noncontrolling interests	174.9	158
Fair Value, Measurements, Recurring
Assets
Cash equivalents	422.5
Volantis contingent consideration	9
Total assets	1,139	397.3
Liabilities
Current portion of long-term debt	57.3
Long-term debt	323.4
Contingent consideration	76.6	25.5
Total liabilities	574.1	93.2
Total redeemable noncontrolling interests	190.3
Fair Value, Measurements, Recurring | Deferred bonuses
Liabilities
Derivative liabilities	64.7	42.9
Fair Value, Measurements, Recurring | Dai-ichi options
Liabilities
Derivative liabilities	26.1
Fair Value, Measurements, Recurring | Investment securities
Assets
Total investment securities	700.1	393.3
Fair Value, Measurements, Recurring | Seed hedge derivatives
Assets
Derivative assets	0.9
Liabilities
Derivative liabilities	10.1	5.1
Fair Value, Measurements, Recurring | Level 1
Assets
Cash equivalents	422.5
Total assets	743	218.4
Liabilities
Total liabilities	19.3	17.5
Fair Value, Measurements, Recurring | Level 1 | Investment securities
Assets
Total investment securities	316.7	215
Fair Value, Measurements, Recurring | Level 1 | Seed hedge derivatives
Assets
Derivative assets	0.9
Liabilities
Derivative liabilities	5.9
Fair Value, Measurements, Recurring | Level 2
Assets
Total assets	349.5	136.2
Liabilities
Current portion of long-term debt	57.3
Long-term debt	323.4
Total liabilities	387.4	7.3
Fair Value, Measurements, Recurring | Level 2 | Investment securities
Assets
Total investment securities	345.9	135.6
Fair Value, Measurements, Recurring | Level 2 | Seed hedge derivatives
Liabilities
Derivative liabilities	4.2	5.1
Fair Value, Measurements, Recurring | Level 3
Assets
Volantis contingent consideration	9
Total assets	46.5	42.7
Liabilities
Contingent consideration	76.6	25.5
Total liabilities	167.4	68.4
Total redeemable noncontrolling interests	190.3
Fair Value, Measurements, Recurring | Level 3 | Deferred bonuses
Liabilities
Derivative liabilities	64.7	42.9
Fair Value, Measurements, Recurring | Level 3 | Dai-ichi options
Liabilities
Derivative liabilities	26.1
Fair Value, Measurements, Recurring | Level 3 | Investment securities
Assets
Total investment securities	37.5	42.7
Fair Value, Measurements, Recurring | Consolidated VIEs | Trading securities | Investment securities
Assets
Total investment securities	402.8	288
Fair Value, Measurements, Recurring | Consolidated VIEs | Available-for-sale securities | Investment securities
Assets
Total investment securities	16.9	25.7
Fair Value, Measurements, Recurring | Consolidated VIEs | Level 1 | Trading securities | Investment securities
Assets
Total investment securities	114.1	128.2
Fair Value, Measurements, Recurring | Consolidated VIEs | Level 1 | Available-for-sale securities | Investment securities
Assets
Total investment securities	16.9	20.3
Fair Value, Measurements, Recurring | Consolidated VIEs | Level 2 | Trading securities | Investment securities
Assets
Total investment securities	251.4	117.1
Fair Value, Measurements, Recurring | Consolidated VIEs | Level 2 | Available-for-sale securities | Investment securities
Assets
Total investment securities		5.4
Fair Value, Measurements, Recurring | Consolidated VIEs | Level 3 | Trading securities
Assets
Total investment securities	37.3	42.7
Fair Value, Measurements, Recurring | Consolidated VIEs | Level 3 | Trading securities | Investment securities
Assets
Total investment securities	37.3	42.7
Fair Value, Measurements, Recurring | Unconsolidated VIEs | Trading securities | Investment securities
Assets
Total investment securities	275.3	79.2
Fair Value, Measurements, Recurring | Unconsolidated VIEs | Available-for-sale securities | Investment securities
Assets
Total investment securities	5.1	0.4
Fair Value, Measurements, Recurring | Unconsolidated VIEs | Level 1 | Trading securities | Investment securities
Assets
Total investment securities	180.6	66.1
Fair Value, Measurements, Recurring | Unconsolidated VIEs | Level 1 | Available-for-sale securities | Investment securities
Assets
Total investment securities	5.1	0.4
Fair Value, Measurements, Recurring | Unconsolidated VIEs | Level 2 | Trading securities | Investment securities
Assets
Total investment securities	94.5	13.1
Fair Value, Measurements, Recurring | Unconsolidated VIEs | Level 3 | Trading securities | Investment securities
Assets
Total investment securities	0.2
Fair Value, Measurements, Recurring | Intech Founders
Liabilities
Total redeemable noncontrolling interests	15.4
Fair Value, Measurements, Recurring | Intech Founders | Level 3
Liabilities
Total redeemable noncontrolling interests	15.4
Fair Value, Measurements, Recurring | Consolidated | Seeded investment products
Assets
Derivative assets	6.5	4
Liabilities
Derivative liabilities	4.3	3.5
Financial liabilities in consolidated seeded investment products	11.6	16.2
Total redeemable noncontrolling interests	174.9	158
Fair Value, Measurements, Recurring | Consolidated | Level 1 | Seeded investment products
Assets
Derivative assets	2.9	3.4
Liabilities
Derivative liabilities	1.8	1.3
Financial liabilities in consolidated seeded investment products	11.6	16.2
Fair Value, Measurements, Recurring | Consolidated | Level 2 | Seeded investment products
Assets
Derivative assets	3.6	0.6
Liabilities
Derivative liabilities	2.5	2.2
Fair Value, Measurements, Recurring | Consolidated | Level 3 | Seeded investment products
Liabilities
Total redeemable noncontrolling interests	$ 174.9	$ 158

Fair Value Measurements - Dispo

Fair Value Measurements - Disposal of Volantis (Details) - Volantis - USD ($) $ in Millions	Apr. 01, 2017	Dec. 31, 2017
Disposal of Volantis
Period of Performance of Investee for Recognizing consideration	3 years
Discontinued Operations, Disposed of by Sale
Disposal of Volantis
Percentage of share for consideration of sale	10.00%
Discount rate for forecasted contingent revenues (as a percent)	11.80%
Fair value of contingent consideration		$ 9

Fair Value Measurements - Acqui

Fair Value Measurements - Acquisition of Geneva (Details) - Geneva $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2014USD ($)tranche	Dec. 31, 2016USD ($)
Acquisitions
Number of contingent consideration payment tranches | tranche		2
Contingent consideration payable period		6 years
Fair value adjustment	$ 3
Fair value of contingent consideration asset	$ 19.3		$ 20.3
Maximum
Acquisitions
Contingent consideration payable in first tranche		$ 45.4
Contingent consideration payable in second tranche		$ 25

Fair Value Measurements - Acq67

Fair Value Measurements - Acquisition of Perennial (Details) - Perennial $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)tranche
Acquisitions
Maximum contingent consideration payable	$ 5.9
Additional maximum contingent consideration payable in 2019 & 2020	$ 41.2
Number of contingent consideration payment tranches | tranche	2
Changes in contingent consideration liability	$ 1.8
Other non-current liabilities
Acquisitions
Fair value of contingent consideration asset	$ 7

Fair Value Measurements - Acq68

Fair Value Measurements - Acquisition of Kapstream (Details) - Kapstream $ in Millions	1 Months Ended	12 Months Ended
	Jul. 31, 2015	Dec. 31, 2017USD ($)	Feb. 28, 2018USD ($)	Jan. 31, 2017USD ($)item
Business acquisition
Ownership interest acquired (as a percent)	51.00%			49.00%
Contingent consideration payable period, low	18 months
Contingent consideration payable period, high end	36 months
Fair value of contingent consideration asset		$ 44.2
Number of installments | item				3
Fair value adjustment		0
Contingent cash consideration if certain revenue targets are achieved		48.6	$ 15.3
Accounts payable and accrued liabilities
Business acquisition
Fair value of contingent consideration asset		18.8
Other non-current liabilities
Business acquisition
Fair value of contingent consideration asset		$ 25.4
Maximum
Business acquisition
Fair value of contingent consideration asset				$ 43.8

Fair Value Measurements - Acq69

Fair Value Measurements - Acquisition of VelocityShares (Details) - VelocityShares - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018	Dec. 31, 2014
Business acquisition
Contingent cash consideration if certain revenue targets are achieved	$ 8
Changes in contingent consideration liability	(0.8)
Fair value of contingent consideration asset	$ 6.1
Third Anniversary
Business acquisition
Contingent cash consideration if certain revenue targets are achieved		$ 3.6	$ 8
Fourth Anniversary
Business acquisition
Contingent cash consideration if certain revenue targets are achieved			$ 8

Fair Value Measurements - Dai-i

Fair Value Measurements - Dai-ichi Options (Details) $ in Millions	Dec. 31, 2017USD ($)
Dai-ichi option
Disposal of Dai-ichi Options
Fair value of the options	$ 26.1

Fair Value Measurements - Lev71

Fair Value Measurements - Level 3 Rollforward (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Changes in fair value
Foreign currency translation	$ (3.2)	$ 29.6	$ 3.5
Level 3 | Contingent consideration
Changes in fair value
Balance at the beginning of the year, Liability Value	25.5	19.5
Balances acquired from the Merger	45.4
Additions		10
Fair value adjustments	3
Foreign currency translation	2.7	(4)
Balance at the end of the year, Liability Value	76.6	25.5	19.5
Level 3 | Deferred bonuses
Changes in fair value
Balance at the beginning of the year, Liability Value	42.9	35.7
Net movement in bonus deferrals	19.4	14.2
Foreign currency translation	2.4	(7)
Balance at the end of the year, Liability Value	64.7	42.9	35.7
Level 3 | Dai-ichi options
Changes in fair value
Additions	25.7
Fair value adjustments	(0.6)
Foreign currency translation	1
Balance at the end of the year, Liability Value	26.1
Level 3 | Redeemable noncontrolling interests
Changes in fair value
Balance at the beginning of the year, Liability Value	158	82.9
Balances acquired from the Merger	35.8
Changes in ownership	3.7	61.7
Fair value adjustments	2
Unrealized gains (losses)	(11)	35.3
Amortization of Intech appreciation rights	2.3
Distributions	(0.3)
Foreign currency translation	(0.2)	(21.9)
Balance at the end of the year, Liability Value	190.3	158	82.9
Level 3 | Fair Value, Measurements, Recurring
Changes in fair value
Balance at the beginning of the year, Liability Value	42.7	58.2
Balances acquired from the Merger	3
Additions	10.9	0.4
Settlements	(11.5)
Transfers to Level 2	(1.1)
Movements recognized in net income	2.2	(17.5)
Movements recognized in other comprehensive income	0.2	10.4
Foreign currency translation	0.1	(8.8)
Balance at the end of the year, Liability Value	46.5	42.7	$ 58.2
Consolidated VIEs
Changes in fair value
Investment securities	$ 419.7	$ 313.7
Consolidated VIEs | Level 3 | Fair Value, Measurements, Recurring | Discounted cash flow | Minimum
Changes in fair value
Discount rate	12.00%	12.00%
EBITDA multiple	11.6	8.7
Price-earnings ratio	0.226	0.172
Consolidated VIEs | Level 3 | Fair Value, Measurements, Recurring | Discounted cash flow | Maximum
Changes in fair value
Discount rate	15.00%	30.00%
EBITDA multiple	0.151	0.110
Price-earnings ratio	0.613	0.240
Consolidated VIEs | Level 3 | Fair Value, Measurements, Recurring | Discounted cash flow | Weighted-average
Changes in fair value
Discount rate	14.30%	16.30%
EBITDA multiple	0.143	0.091
Price-earnings ratio	0.524	0.184
Trading securities | Consolidated VIEs | Level 3 | Fair Value, Measurements, Recurring
Changes in fair value
Investment securities	$ 37.3	$ 42.7

Fair Value Measurements - Trans

Fair Value Measurements - Transfers Between Levels (Details) $ in Millions	Dec. 31, 2017USD ($)
Fair Value Measurements
Transfers from Level 1 to Level 2	$ 0
Transfers from Level 2 to Level 1	$ 0

Debt (Details)

Debt (Details) $ / shares in Units, £ in Millions, $ in Millions	Jan. 01, 2018$ / shares	Mar. 11, 2011GBP (£)	Dec. 31, 2017USD ($)item	Dec. 31, 2016USD ($)	May 30, 2017USD ($)	Mar. 11, 2011USD ($)
Components of debt
Less: Current portion of long-term debt			$ 57.2
Total long-term debt			322
Other Disclosures
Face value of debt issued						$ 240.4
Settlement of debt in cash			92.5	$ 203.4
Carrying value
Components of debt
Total debt			379.2
Less: Current portion of long-term debt			57.2
Total long-term debt			322
Fair value
Components of debt
Total debt			380.7
Less: Current portion of long-term debt			57.3
Total long-term debt			$ 323.4
4.875% Senior Notes due 2025
Components of debt
Interest rate (as a percent)			4.875%	4.875%
Other Disclosures
Face value of debt issued					$ 300
4.875% Senior Notes due 2025 | Carrying value
Components of debt
Total debt			$ 322
4.875% Senior Notes due 2025 | Fair value
Components of debt
Total debt			$ 323.4
0.750% Convertible Senior Notes due 2018
Components of debt
Interest rate (as a percent)			0.75%	0.75%
Other Disclosures
Face value of debt issued			$ 57.5
Conversion rate, shares per $1,000 principal amount	45.1535
Adjusted conversion price per share of common stock (in dollars per share) | $ / shares	$ 22.15
Percentage of the conversion price that the last reported sales price of the entity's common stock must equal or exceed as per conversion eligibility terms			130.00%
Number of trading days within 30 consecutive trading days required per the conversion eligibility terms, minimum | item			20
Number of consecutive trading days required per the conversion eligibility terms | item			30
Redemption of debt instruments principal amount			$ 59.1
Settlement of debt in cash			92.5
Proceeds from convertible note hedge			59.3
Payments for settlement of warrants			47.8
0.750% Convertible Senior Notes due 2018 | Carrying value
Components of debt
Total debt			57.2
0.750% Convertible Senior Notes due 2018 | Fair value
Components of debt
Total debt			57.3
7.25% Senior Notes due 2016
Components of debt
Interest rate (as a percent)		7.25%				7.25%
Other Disclosures
Face value of debt issued | £		£ 150
Term of debt		5 years
Credit Facility
Other Disclosures
Credit facility, maximum borrowing capacity			$ 200
Credit facility covenant terms, financing leverage ratio, maximum			3
Borrowings under the Credit Facility			$ 0
Number of extension option available before maturity | item			2
Credit Facility | First Anniversary
Other Disclosures
Extended period of maturity on exercise of option			1 year
Janus Capital Group Inc | 4.875% Senior Notes due 2025
Components of debt
Interest rate (as a percent)					4.875%
Other Disclosures
Fair value of debt					$ 323.7
Unamortized premium, net			$ 22
Janus Capital Group Inc | 0.750% Convertible Senior Notes due 2018
Components of debt
Interest rate (as a percent)					0.75%
Other Disclosures
Face value of debt issued					$ 116.6
Fair value of debt					158.1
Debt liability component					$ 115.2
Discounted cash flow rate (Percentage)					1.90%
Debt equity component					$ 42.9
Janus Capital Group Inc | 0.750% Convertible Senior Notes due 2018 | Maximum
Other Disclosures
Debt liability component					$ 116.6

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	Jan. 01, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
U.S. including state and local					$ 83.1	$ 1.1	$ 4.3
Total Current income taxes					144.6	32.6	14.2
Deferred:
U.S. including state and local					(354.4)	3	(2.1)
Total deferred income taxes/(benefits)					(355.6)	2	(8.1)
Total income tax expense					(211)	34.6	6.1
Components of income before taxes
US					190.5	(0.1)	7.8
Income before taxes					$ 447.4	211.9	337.5
Reconciliation between statutory rate and effective tax rate:
statutory corporation tax rate (as a percentage)	21.00%		20.00%	19.00%	35.00%
Income tax benefit associated to Tax Cuts and Jobs Act		$ (340.7)
Estimated income tax benefit related to revaluation of deferred tax assets and liabilities		345.4
Tax expense related to one-time tax on deferred earnings		$ 4.7		$ 4.7	$ 4.7
Income Tax Expense (Benefit)					$ (211)	34.6	6.1
Non cash benefit from reduction of UK corporation tax rate						4	8.1
Statutory rate (as a percent)	21.00%		20.00%	19.00%	35.00%
Estimated statutory rate (as a percentage)					17.00%
UK
Current:
Non-US					$ 51.5	30.3	3.5
Deferred:
Non-US					0.3	(2.2)	(5.6)
Components of income before taxes
Non-US					$ 229	$ 180.9	$ 201
Reconciliation between statutory rate and effective tax rate:
statutory corporation tax rate (as a percentage)					19.30%	20.00%	20.30%
Effect of foreign tax rates (as a percentage)					7.40%	(1.10%)	(5.90%)
Impact of Property disposal (as a percentage)							(2.30%)
Equity-based compensation (as a percentage)					0.20%	(3.40%)	(3.70%)
Finalization of positions with HMRC (as a percentage)					0.30%	(0.80%)	(3.10%)
Tax adjustments (as a percentage)					0.70%	0.60%	0.30%
Non-deductible costs associated with the Merger (as a percentage)					1.20%	0.80%
Impact of changes in statutory tax rates on deferred taxes (as a percentage)					(77.40%)	(1.90%)	(2.40%)
Taxes applicable to prior years (as a percentage)					(0.40%)	0.90%	(1.00%)
Other, net (as a percentage)					1.70%	0.10%	(0.30%)
Effective income tax rate, controlling interest (as a percentage)					(47.00%)	15.20%	1.90%
Net income attributable to noncontrolling interests (as a percentage)					(0.10%)	1.10%	(0.10%)
Total effective income tax rate (as a percentage)					(47.10%)	16.30%	1.80%
Statutory rate (as a percent)					19.30%	20.00%	20.30%
International
Current:
Non-US					$ 10	$ 1.2	$ 6.4
Deferred:
Non-US					(1.5)	1.2	(0.4)
Components of income before taxes
Non-US					$ 27.9	$ 31.1	$ 128.7

Income Taxes - Deferred Taxes (

Income Taxes - Deferred Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Compensation and staff benefits	$ 55.2	$ 16.5
Loss carryforwards	59.4	18.8
Accrued liabilities	2.2	1.1
Debt premium	6.2
Other	7.9	1.2
Gross deferred tax assets	130.9	37.6
Valuation allowance	(57.2)	(18.8)
Deferred tax assets, net of valuation allowance	73.7	18.8
Deferred tax liabilities:
Retirement benefits	(24.4)	(19.2)
Goodwill and acquired intangible assets	(795.4)	(59.2)
Other	(6.5)	(2.8)
Gross deferred tax liabilities	(826.3)	(81.2)
Net deferred tax (liabilities)	(752.6)	(62.4)
Deferred tax assets and liabilities reflected on the balance sheet
Deferred tax liabilities, net	(752.6)	(70.7)
Net deferred tax (liabilities)	(752.6)	(62.4)
Increase in valuation allowance for deferred tax assets	38.4
Provision for income taxes on undistributed earnings	$ 0
Other non-current assets
Deferred tax assets and liabilities reflected on the balance sheet
Deferred tax assets, net (included in other non-current assets)		$ 8.3

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of beginning and ending liability:
Balance at the beginning of the year	$ 2.5	$ 18.4	$ 19.1
Balance acquired from the Merger	5
Additions for tax positions of current year	3.4		1
Additions/(reduction) for tax positions of prior years	0.8		(0.6)
Reduction due to settlement with taxing authorities	(0.9)	(13.1)
Reduction due to statute expirations	(0.9)
Foreign currency translation	0.3
Foreign currency translation		(2.8)	(1.1)
Balance at the end of the year	10.2	2.5	18.4
Accrued interest included in liability for income tax contingencies	$ 1.5	0.7	$ 1.2
Anticipated decrease in income tax contingency reserves in the next 12 months		$ 1.1

Other Financial Statement Cap77

Other Financial Statement Captions (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Other current assets
Prepaid expenses	$ 24.1	$ 10.8
Deferred acquisition costs	0.6	3.3
Current corporation tax	3.5	0.9
Other current assets	47.7	13.5
Total other current assets	75.9	28.5
Other non-current assets	21.5	8.5
Other accrued liabilities
Accrued commissions	44.4	41
Accrued rebates	24.4	23.4
Other accrued liabilities	48	41.9
Total other accrued liabilities	116.8	106.3
Accounts payable and accrued liabilities
Current corporation tax	33.7	17.6
Contingent consideration	24.9
Derivatives	10.5
Other current liabilities	80.9	17.8
Total accounts payable and accrued liabilities	292.9	141.7
Other non-current liabilities
Non-current tax liabilities	13.7	2.1
Other creditors	20.7
Deferred consideration	26.2	25.5
Other non-current accrued liabilities	39	11.4
Total other non-current liabilities	99.6	$ 39
Dai-ichi options
Accounts payable and accrued liabilities
Derivatives	$ 26.1

Other Financial Statement Cap78

Other Financial Statement Captions - Leases (Details)	12 Months Ended
	Dec. 31, 2017lease
Operating lease
Number of operating leases	3
Lancelot Place, London
Operating lease
Further term of operating lease	6 years
Rex House, Queen Street, London
Operating lease
Further term of operating lease	9 years

Noncontrolling Interests - Rede

Noncontrolling Interests - Redeemable (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Redeemable Noncontrolling Interests
Total redeemable noncontrolling interests	$ 158	$ 158		$ 190.3
Roll forward of redeemable noncontrolling interests in consolidated seed investment products
Opening balance	158
Closing balance	190.3	158
Seeded investment products
Redeemable Noncontrolling Interests
Total redeemable noncontrolling interests	158	82.9	$ 4.4	174.9
Roll forward of redeemable noncontrolling interests in consolidated seed investment products
Opening balance	158	82.9	4.4
Balance acquired from the Merger	23.2
Change in market value	(9.8)	35.3	(5.9)
Change in ownership	3.7	61.7	84.5
Foreign currency translation	(0.2)	(21.9)	(0.1)
Closing balance	174.9	158	$ 82.9
Subsidiaries
Redeemable Noncontrolling Interests
INTECH appreciation rights	11
Intech Founders
Redeemable Noncontrolling Interests
Total redeemable noncontrolling interests	4.4			$ 4.4
Roll forward of redeemable noncontrolling interests in consolidated seed investment products
Closing balance	4.4
Remaining interest (as a percent)				1.10%
Consolidated | Seeded investment products
Redeemable Noncontrolling Interests
Total redeemable noncontrolling interests	158	158		$ 174.9
Roll forward of redeemable noncontrolling interests in consolidated seed investment products
Opening balance	158
Closing balance	$ 174.9	$ 158

Noncontrolling Interests - Nonr

Noncontrolling Interests - Nonredeemable (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Nonredeemable noncontrolling interests
Total nonredeemable noncontrolling interests	$ 38.2	$ 44.8
Subsidiaries
Nonredeemable noncontrolling interests
Total nonredeemable noncontrolling interests	13.3
Seeded investment products
Nonredeemable noncontrolling interests
Total nonredeemable noncontrolling interests	$ 24.9	$ 44.8

Long-Term Incentive Compensat81

Long-Term Incentive Compensation - (Details) £ / shares in Units, $ / shares in Units, $ in Millions

Dec. 31, 2016shares

Dec. 31, 2014shares

Oct. 23, 2014

Nov. 18, 2013

Mar. 31, 2016USD ($)

Feb. 28, 2015USD ($)

Oct. 31, 2014USD ($)

Dec. 31, 2017GBP (£)shares

Dec. 31, 2017USD ($)$ / sharesshares

Dec. 31, 2016£ / shares

Dec. 31, 2016USD ($)shares

Dec. 31, 2015£ / shares

Dec. 31, 2015USD ($)shares

Dec. 31, 2014USD ($)

Deferred Equity Plan

Long-term incentive compensation expense

Number of years awards are deferred

3 years

3 years

Awards are vested in each year (as a percent)

0.33%

0.33%

Price-Vesting Units

Number of replacement awards shares granted to employees | shares

919,967

919,967

9,134,443

6,742,546

INTECH Long-Term Incentive Awards

Number of price-vesting units granted | shares

919,967

919,967

9,134,443

6,742,546

Weighted average price per share (in dollars per share) | (per share)

$ 31.40

£ 2.47

£ 2.82

Restricted Share Plan

Long-term incentive compensation expense

Consideration from employees | £

£ 0

Minimum amount of awards required for approval of remuneration committee | £

500,000

Minimum amount of vested awards required for approval of remuneration committee | £

£ 50,000

INTECH Long-Term Incentive Awards

Vesting period

3 years

3 years

Buy As You Earn Share Plan

Long-term incentive compensation expense

Maximum deduction from the gross salary (annually) | £

£ 1,800

Matching shares for each share awarded | shares

2

2

Additional payment for each share purchased | £

£ 0

Forfeiture period of matching shares if purchased shares are withdrawn

1 year

1 year

Restricted Stock Awards

Price-Vesting Units

Number of replacement awards shares granted to employees | shares

73,982

73,982

INTECH Long-Term Incentive Awards

Number of price-vesting units granted | shares

73,982

73,982

Weighted average price per share (in dollars per share) | $ / shares

$ 35.08

Restricted Stock Awards | Minimum

INTECH Long-Term Incentive Awards

Vesting period

3 years

3 years

Restricted Stock Awards | Maximum

INTECH Long-Term Incentive Awards

Vesting period

4 years

4 years

Mutual Fund Share Awards

Price-Vesting Units

Awards granted (in dollars)

$ 57.8

Mutual Fund Share Awards

Long-term incentive awards granted

57.8

Time-based mutual fund share awards

Price-Vesting Units

Awards granted (in dollars)

49.8

Mutual Fund Share Awards

Long-term incentive awards granted

$ 49.8

INTECH Long-Term Incentive Awards

Vesting period

4 years

4 years

Performance-based mutual fund share awards

Price-Vesting Units

Awards granted (in dollars)

$ 8

Mutual Fund Share Awards

Long-term incentive awards granted

$ 8

INTECH Long-Term Incentive Awards

Vesting period

5 years

5 years

Price-Vesting Units | Janus Capital Group Inc | Chief Executive Officer

Price-Vesting Units

Number of replacement awards shares granted to employees | shares

134,666

137,178

138,901

Awards granted (in dollars)

$ 1.8

$ 1.9

$ 2.2

Mutual Fund Share Awards

Long-term incentive awards granted

$ 1.8

$ 1.9

$ 2.2

INTECH Long-Term Incentive Awards

Vesting period

3 years

3 years

Number of price-vesting units granted | shares

134,666

137,178

138,901

Price-Vesting Units, Granted in 2014 | Chief Executive Officer

Price-Vesting Units

Awards granted (in dollars)

$ 2.3

Number of price-vesting units vested | shares

75,634

75,634

Mutual Fund Share Awards

Long-term incentive awards granted

$ 2.3

Price Vesting Units, Granted in 2015 | Chief Executive Officer

Price-Vesting Units

Number of replacement awards shares granted to employees | shares

65,548

65,548

Awards granted (in dollars)

$ 2

Mutual Fund Share Awards

Long-term incentive awards granted

$ 2

INTECH Long-Term Incentive Awards

Number of price-vesting units granted | shares

65,548

65,548

Price Vesting Units, Granted in 2016 | Chief Executive Officer

Price-Vesting Units

Number of replacement awards shares granted to employees | shares

63,549

Awards granted (in dollars)

$ 2

Mutual Fund Share Awards

Long-term incentive awards granted

$ 2

INTECH Long-Term Incentive Awards

Number of price-vesting units granted | shares

63,549

Senior profits interests awards | Perkins Investment Management LLC | Senior profits interests awards granted on November 18, 2013

Perkins Senior Profits Interests Awards

Liability associated with senior profits interests awards

$ 0

Appreciation Rights | Intech Investment Management LLC

INTECH Long-Term Incentive Awards

Dividend yield (as a percent)

2.89%

2.56%

1.98%

Expected volatility (as a percent)

28.00%

30.00%

34.00%

Risk-free interest rate (as a percent)

1.93%

1.81%

2.53%

Expected life (in years)

6 years

6 years

12 years

Grant date fair value (in millions)

$ 2.6

$ 2

$ 23.2

Merger date fair value (in millions)

$ 1.8

$ 0.9

$ 13.3

Vesting period

10 years

Number of years the rights are expected to be exercised

4 years

4 years

2014 Stock Appreciation Rights SARS | Intech Investment Management LLC

INTECH Long-Term Incentive Awards

Expected life (in years)

10 years

10 years

2015 Stock Appreciation Rights SARS | Intech Investment Management LLC

INTECH Long-Term Incentive Awards

Expected life (in years)

5 years

5 years

Merger date fair value (in millions)

$ 0.9

2016 Stock Appreciation Rights SARS | Intech Investment Management LLC

INTECH Long-Term Incentive Awards

Expected life (in years)

7 years

7 years

Merger date fair value (in millions)

$ 1.8

Profits Interests | Perkins Investment Management LLC | Senior profits interests awards granted on November 18, 2013

Perkins Senior Profits Interests Awards

Percentage of Annual Taxable Income to which Senior Profit Interest Awards are Entitled

10.00%

Percentage of annual taxable income to which senior profit interest awards are entitled in 2015 (as a percent)

2.00%

Percentage of increase in annual taxable income to which senior profit interest awards are entitled thereafter until reaching the maximum of 10% (as a percent)

2.00%

Formula driven value

$ 0

Profits Interests | Intech Investment Management LLC

INTECH Long-Term Incentive Awards

Vesting period

10 years

Maximum period for which distribution are made under profits interests post employment

10 years

Phantom Interests | Intech Investment Management LLC

INTECH Long-Term Incentive Awards

Vesting period

5 years

Profits Interest and Phantom Interests | Intech Investment Management LLC

INTECH Long-Term Incentive Awards

Percentage of equity-like stake in pre-incentive profits

9.20%

Discount rate

2.00%

Undiscounted estimated post-employment payments

$ 49.8

Profits Interest and Phantom Interests | Intech Investment Management LLC | Other non-current assets

INTECH Long-Term Incentive Awards

Profits and Phantom Interests

$ 13.6

Profits Interest and Phantom Interests | Intech Investment Management LLC | Minimum

INTECH Long-Term Incentive Awards

Expected life (in years)

10 years

10 years

Profits Interest and Phantom Interests | Intech Investment Management LLC | Maximum

INTECH Long-Term Incentive Awards

Expected life (in years)

20 years

20 years

Long-Term Incentive Compensat82

Long-Term Incentive Compensation - Compensation Plans (Details)	1 Months Ended	12 Months Ended
	Apr. 30, 2017£ / shares	Dec. 31, 2017GBP (£)£ / shares	Dec. 31, 2017USD ($)	Dec. 31, 2016$ / shares£ / shares	Dec. 31, 2016USD ($)$ / shares	Dec. 31, 2015$ / shares£ / shares	Dec. 31, 2015USD ($)$ / shares	Dec. 31, 2017USD ($)shares	Dec. 31, 2016£ / shares	Dec. 31, 2015£ / shares
Share Plan
Performance hurdle related to Group TSR (as a percent)		95.00%	95.00%
Performance hurdle related to risk and sustainability metrics (as a percent)		5.00%	5.00%
Stock-based compensation plan expense			$ 67,400,000		$ 37,300,000		$ 43,600,000
DEP Funds - Liability settled			41,400,000		35,000,000		24,600,000
MFSA - liability settled			20,700,000
Profits interests and other			12,300,000
Social Security costs			10,300,000		13,200,000		16,500,000
Total charge to the Consolidated Statements of Comprehensive Income			$ 151,500,000		85,500,000		84,700,000
Stock-based payments expense unrecognized								$ 90,300,000
Stock-based payments expense, weighted average years		2 years 2 months 12 days	2 years 2 months 12 days
DEP Funds - Liability settled, Unrecognised compensation			$ 29,700,000
MFSA - liability settled, Unrecognized compensation			21,500,000
Profits interests, Unrecognized compensation			37,900,000
Social security costs, Unrecognised compensation			19,200,000
Total remaining charge to the Consolidated Statements of Comprehensive Income			$ 198,600,000
DEP Funds - Liability settled		1 year 4 months 24 days	1 year 4 months 24 days
MFSA - Liability settled		2 years 4 months 24 days	2 years 4 months 24 days
Profits interests and other		6 years 2 months 12 days	6 years 2 months 12 days
Social Security costs, weighted average years		1 year	1 year
Weighted average years, remaining charge to comprehensive income		2 years 8 months 12 days	2 years 8 months 12 days
Tranche 1
Share Plan
Additional holding period		2 years	2 years
Tranche 2
Share Plan
Additional holding period		1 year	1 year
Employee Share Ownership Plan
Share Plan
Stock-based compensation plan expense					200,000		600,000
Deferred Equity Plan
Share Plan
Stock-based compensation plan expense			$ 17,600,000		17,500,000		18,600,000
Stock-based payments expense unrecognized								11,800,000
Stock-based payments expense, weighted average years		1 year 4 months 24 days	1 year 4 months 24 days
Restricted Share Plan
Share Plan
Vesting period		3 years	3 years
Stock-based compensation plan expense			$ 3,400,000		5,100,000		8,300,000
Stock-based payments expense unrecognized								8,400,000
Stock-based payments expense, weighted average years		1 year 10 months 24 days	1 year 10 months 24 days
Buy As You Earn Share Plan
Share Plan
Maximum deduction from the gross salary (monthly) | £		£ 150
Stock-based compensation plan expense			$ 3,200,000		3,000,000		2,900,000
Stock-based payments expense unrecognized								1,000,000
Stock-based payments expense, weighted average years		7 months 6 days	7 months 6 days
Sharesave Plan
Share Plan
Vesting period		2 years	2 years
Maximum deduction from the gross salary (monthly)			$ 312.50		$ 312.50		$ 312.50
Option exercise price | $ / shares				$ 31.20	$ 31.20	$ 35.50	$ 35.50
Discount to the average share price		15.00%	15.00%
Market price at grant date | £ / shares		£ 75.28		$ 58.49
Stock-based compensation plan expense			$ 800,000		$ 700,000		$ 800,000
Stock-based payments expense unrecognized								3,400,000
Stock-based payments expense, weighted average years		2 years 2 months 12 days	2 years 2 months 12 days
Black Scholes options pricing model
Fair value of options granted (pence) | £ / shares		£ 75.28		58.49
Dividend yield (as a percent)		3.99%	3.99%		3.98%
Expected volatility (as a percent)		32.13%	32.13%		29.72%
Risk-free interest rate (as a percent)		0.19%	0.19%		0.53%
Expected life (in years)		3 years	3 years		3 years
US SAYE
Share Plan
Market price at grant date | £ / shares				64.71
Black Scholes options pricing model
Fair value of options granted (pence) | £ / shares				64.71
Dividend yield (as a percent)					3.98%
Expected volatility (as a percent)					29.35%
Risk-free interest rate (as a percent)					0.40%
Expected life (in years)					2 years
RSA
Share Plan
Stock-based compensation plan expense			$ 32,800,000
Stock-based payments expense unrecognized								49,000,000
Stock-based payments expense, weighted average years		2 years 8 months 12 days	2 years 8 months 12 days
Company Share Option Plan
Share Plan
Option exercise price | £ / shares		£ 22.80							£ 26.10	£ 28.48
Exercisable period after vesting		3 months	3 months
Market price at grant date | £ / shares		£ 33.43		33.51
Stock-based compensation plan expense			$ 1,100,000		$ 1,400,000		1,700,000
Stock-based payments expense unrecognized								2,900,000
Stock-based payments expense, weighted average years		1 year 9 months 18 days	1 year 9 months 18 days
Black Scholes options pricing model
Fair value of options granted (pence) | £ / shares		£ 33.43		33.51
Dividend yield (as a percent)		4.64%	4.64%		4.12%
Expected volatility (as a percent)		32.41%	32.41%		30.26%
Risk-free interest rate (as a percent)		0.27%	0.27%		0.58%
Expected life (in years)		3 years	3 years		3 years
US CSOP
Share Plan
Exercisable period after vesting	2 years
Market price at grant date | £ / shares		£ 32.81		27.01
Black Scholes options pricing model
Fair value of options granted (pence) | £ / shares		£ 32.81		27.01
Dividend yield (as a percent)		4.64%	4.64%		4.12%
Expected volatility (as a percent)		35.19%	35.19%		29.67%
Risk-free interest rate (as a percent)		0.16%	0.16%		0.45%
Expected life (in years)		2 years	2 years		2 years
Executive Shared Ownership Plan
Share Plan
Market price at grant date | £ / shares		£ 27.78		27.40
Stock-based compensation plan expense			$ 1,500,000		$ 1,900,000		2,000,000
Stock-based payments expense unrecognized								1,900,000
Stock-based payments expense, weighted average years		1 year 8 months 12 days	1 year 8 months 12 days
Black Scholes options pricing model
Fair value of options granted (pence) | £ / shares		£ 27.78		27.40
Dividend yield (as a percent)		4.64%	4.64%		4.12%
Expected volatility (as a percent)		32.41%	32.41%		30.26%
Risk-free interest rate (as a percent)		0.27%	0.27%		0.58%
Expected life (in years)		3 years	3 years		3 years
2017 ExSOP
Share Plan
Vesting period		3 years	3 years
Exercisable period after vesting		2 years	2 years
Market price at grant date | £ / shares		£ 22.62		25		$ 28.21
Hurdle price | £ / shares		24.90		28.45		31.05
Black Scholes options pricing model
Fair value of options granted (pence) | £ / shares		22.62		$ 25		$ 28.21
2014 ExSOP
Share Plan
Market price at grant date | £ / shares	£ 26.81
Hurdle price | £ / shares	29.22
Black Scholes options pricing model
Fair value of options granted (pence) | £ / shares	26.81
LongTerm Incentive Plan
Share Plan
Option exercise price | £ / shares		£ 0
Stock-based compensation plan expense			$ 6,400,000		$ 7,500,000		$ 8,700,000
Stock-based payments expense unrecognized								$ 11,900,000
Stock-based payments expense, weighted average years		1 year 4 months 24 days	1 year 4 months 24 days
2013 LTIP
Share Plan
Vesting period		3 years	3 years
Options exercise period		5 years	5 years
2014 LTIP
Share Plan
Vesting period		3 years	3 years
Options exercise period		5 years	5 years
Awards to be vested (in percentage)					3.00%
2014 LTIP | Tranche 2
Share Plan
Awards to be vested (in percentage)		3.00%	3.00%
2015 LTIP
Share Plan
Vesting period		4 years	4 years
Options exercise period		4 years	4 years
Award exercisable percentage from end of year four		33.00%	33.00%
2015 LTIP | Tranche 1
Share Plan
Awards to be vested pre-Merger (in percentage)		25.00%	25.00%
Awards to be vested post-Merger (in percentage)		74.60%	74.60%
Monte Carlo Model
Share price at DoM		233.70%	233.70%
Risk free discount rate		0.10%	0.10%
Dividend yield		4.50%	4.50%
Share price volatility		30.00%	30.00%
Holding period adjustment		9	9
Percentage based on pre-modification performance conditions		80.00%	80.00%
2015 LTIP | Tranche 2
Monte Carlo Model
Share price at DoM		233.70%	233.70%
Risk free discount rate		0.10%	0.10%
Dividend yield		4.50%	4.50%
Share price volatility		30.00%	30.00%
Holding period adjustment		6.2	6.2
Percentage based on pre-modification performance conditions		60.00%	60.00%
2016 LTIP
Share Plan
Award exercisable percentage from end of year three		67.00%	67.00%
Award exercisable percentage from end of year four		33.00%	33.00%
2016 LTIP | Tranche 1
Monte Carlo Model
Share price at DoM		233.70%	233.70%
Risk free discount rate		0.10%	0.10%
Dividend yield		4.50%	4.50%
Share price volatility		30.00%	30.00%
Holding period adjustment		9	9
2016 LTIP | Tranche 2
Monte Carlo Model
Share price at DoM		233.70%	233.70%
Risk free discount rate		0.10%	0.10%
Dividend yield		4.50%	4.50%
Share price volatility		30.00%	30.00%
Holding period adjustment		6.2	6.2
Relative TSR
Share Plan
Weight of awards criteria in performance conditions		50.00%	50.00%
Relative TSR | 2015 LTIP
Monte Carlo Model
Allocation of award (as a percent)		50.00%	50.00%
Relative TSR | 2015 LTIP | Tranche 1
Monte Carlo Model
Allocation of award (as a percent)		118.96%	118.96%
Relative TSR | 2015 LTIP | Tranche 2
Monte Carlo Model
Allocation of award (as a percent)		124.11%	124.11%
Relative TSR | 2016 LTIP
Monte Carlo Model
Allocation of award (as a percent)		50.00%	50.00%
Relative TSR | 2016 LTIP | Tranche 1
Monte Carlo Model
Allocation of award (as a percent)		120.98%	120.98%
Relative TSR | 2016 LTIP | Tranche 2
Monte Carlo Model
Allocation of award (as a percent)		123.64%	123.64%
Relative investment performance
Share Plan
Weight of awards criteria in performance conditions		25.00%	25.00%
Relative investment performance | 2015 LTIP
Monte Carlo Model
Allocation of award (as a percent)		25.00%	25.00%
Relative investment performance | 2015 LTIP | Tranche 1
Monte Carlo Model
Allocation of award (as a percent)		209.76%	209.76%
Relative investment performance | 2015 LTIP | Tranche 2
Monte Carlo Model
Allocation of award (as a percent)		206.59%	206.59%
Relative investment performance | 2016 LTIP
Monte Carlo Model
Allocation of award (as a percent)		25.00%	25.00%
Relative investment performance | 2016 LTIP | Tranche 1
Monte Carlo Model
Allocation of award (as a percent)		200.42%	200.42%
Relative investment performance | 2016 LTIP | Tranche 2
Monte Carlo Model
Allocation of award (as a percent)		197.39%	197.39%
Relative net income before tax growth
Share Plan
Weight of awards criteria in performance conditions		25.00%	25.00%
Relative net income before tax growth | 2015 LTIP
Monte Carlo Model
Allocation of award (as a percent)		25.00%	25.00%
Relative net income before tax growth | 2015 LTIP | Tranche 1
Monte Carlo Model
Allocation of award (as a percent)		209.76%	209.76%
Relative net income before tax growth | 2015 LTIP | Tranche 2
Monte Carlo Model
Allocation of award (as a percent)		206.59%	206.59%
Relative net income before tax growth | 2016 LTIP
Monte Carlo Model
Allocation of award (as a percent)		25.00%	25.00%
Relative net income before tax growth | 2016 LTIP | Tranche 1
Monte Carlo Model
Allocation of award (as a percent)		200.42%	200.42%
Relative net income before tax growth | 2016 LTIP | Tranche 2
Monte Carlo Model
Allocation of award (as a percent)		197.39%	197.39%
FTSE 350
Share Plan
Weight of awards criteria in performance conditions		25.00%	25.00%
ASX 100
Share Plan
Weight of awards criteria in performance conditions		25.00%	25.00%
Net Fund Flows Condition
Share Plan
Weight of awards criteria in performance conditions		15.00%	15.00%
Investment Performance Condition
Share Plan
Weight of awards criteria in performance conditions		15.00%	15.00%
Operating Margin Condition
Share Plan
Weight of awards criteria in performance conditions		10.00%	10.00%
People Strategy Condition
Share Plan
Weight of awards criteria in performance conditions		10.00%	10.00%
UK employees | Sharesave Plan
Share Plan
Vesting period		3 years	3 years
Maximum deduction from the gross salary (monthly) | £		£ 500
Option exercise price | £ / shares		£ 18.40							£ 20.60	£ 22.70
Discount to the average share price		20.00%	20.00%
Exercisable period after vesting		6 months	6 months
UK employees | Company Share Option Plan
Share Plan
Vesting period		3 years	3 years
Option exercise price | £ / shares	£ 26.71
Exercisable period after vesting		2 years	2 years
Maximum value of unvested options approved | shares								30,000

Long-Term Incentive Compensat83

Long-Term Incentive Compensation - ESOP and RSA (Details) £ / shares in Units, £ in Millions	Dec. 31, 2016GBP (£)$ / shares£ / sharesshares	Dec. 31, 2017$ / shares	Dec. 31, 2017GBP (£)£ / sharesshares	Dec. 31, 2016GBP (£)£ / sharesshares	Dec. 31, 2015GBP (£)£ / sharesshares	Dec. 31, 2017GBP (£)shares
Deferred Equity Plan
Summary of unvested restricted stock awards
Unvested at the beginning of the year (in shares)			16,466,630	26,653,694	39,546,315
Share consolidation (in shares)			(14,825,509)
Adjustment (in shares)			1,275		8,210
Granted (in shares)			919,967	9,134,443	6,742,546
Exercised (in shares)			(873,810)	(16,862,324)	(18,464,223)
Forfeited (in shares)			(246,462)	(2,459,183)	(1,179,154)
Unvested at the end of the year (in shares)	16,466,630		1,442,091	16,466,630	26,653,694
Weighted-average grant date fair value
Balance at the beginning of the year (in dollars per share) | (per share)		$ 3.17	£ 2.46	£ 1.79	£ 1.44
Share consolidation (in dollars per share) | $ / shares		31.64
Adjustment (in dollars per share) | (per share)		15.43			2.18
Granted (in dollars per share) | (per share)		31.40		2.47	2.82
Exercised (in dollars per share) | (per share)		31.33		1.63	1.40
Forfeited (in dollars per share) | (per share)		28.06		1.59	2.05
Balance at the end of the year (in dollars per share) | (per share)	$ 3.17	32.36		£ 2.46	£ 1.79
Stock Options
Shares
Outstanding at the beginning of the year (in shares)			45,560,242	43,890,407	50,187,980
Share consolidation (in shares)			(41,004,619)
Acquired from Merger (in shares)			92,949
Granted (in shares)			2,042,321	16,251,758	15,375,429
Exercised (in shares)			(404,735)	(11,039,274)	(12,818,494)
Forfeited (in shares)			(1,966,452)	(3,542,649)	(8,854,508)
Outstanding at the end of the year (in shares)	45,560,242		4,319,706	45,560,242	43,890,407
Exercisable (in shares)	5,014,642			5,014,642	2,419,325	663,342
Vested or expected to vest (in shares)	24,849,673			24,849,673	39,184,673	2,999,811
Weighted-average price
Outstanding at the beginning of the year (in dollars per share) | (per share)		1.97	£ 1.53	£ 1.34	£ 0.93
Share consolidation (in dollars per share) | $ / shares		19.82
Acquired from Merger (in dollars per share) | $ / shares		18.76
Granted (in dollars per share) | (per share)		13.66		1.53	1.70
Exercised (in dollars per share) | (per share)		20.32		0.73	0.79
Forfeited (in dollars per share) | (per share)		7.41		1.81	0.45
Outstanding at the end of the year (in dollars per share) | (per share)	$ 1.97	22.55		1.53	1.34
Exercisable (in dollars per share) | (per share)	$ 0.87	34.67		0.87	0.66
Vested or expected to vest (in dollars per share) | (per share)	$ 0.44	$ 15.57		£ 0.44	£ 1.13
Intrinsic value of options
Exercised | £			£ 2.8	£ 18.9	£ 26.7
Outstanding | £	$ 47.7			47.7	77	£ 15.9
Exercisable | £	$ 7.5			£ 7.5	£ 5.9	£ 3.9
Restricted Stock Awards
Summary of unvested restricted stock awards
Acquired from the Merger (in shares)			4,068,619
Granted (in shares)			73,982
Exercised (in shares)			(444,884)
Forfeited (in shares)			(160,496)
Unvested at the end of the year (in shares)			3,537,221
Weighted-average grant date fair value
Acquired from the Merger (in dollars per share) | $ / shares		30.72
Granted (in dollars per share) | $ / shares		$ 35.08
Exercised (in dollars per share) | $ / shares		30.73
Forfeited (in dollars per share) | $ / shares		30.72
Balance at the end of the year (in dollars per share) | $ / shares		$ 30.81

Retirement benefit plans (Detai

Retirement benefit plans (Details) £ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017GBP (£)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Net periodic benefit credit
Expenses related to 401(k) plan		$ 8.6
Defined Benefit Plans
Number of years of contributions	4 years	4 years
Defined benefit pension Plan
Defined Benefit Plans
Deficit on technical provisions basis	£ 29	$ 39.2
Contributions to the plan starting from 2017 to recover the deficit	£ 8.4	11.4
Non-US
Defined Contribution Plan
Amounts charged to consolidated statements of comprehensive income		$ 11.8	$ 11.6	$ 11.7
Maximum | U.S.
Net periodic benefit credit
Employer matching contribution per calendar year (as a percent of compensation)	5.00%	5.00%

Retirement benefit plans - Chan

Retirement benefit plans - Change in plan assets and benefit obligations, net retirement benefit recognized in balance sheet, assumptions (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Key assumptions used in determining the defined benefit obligation
Number of years in time	15 years
Defined benefit pension Plan
Change in plan assets:
Fair value of plan assets at the beginning of the year	$ 877.3	$ 877.2
Return on plan assets	34.8	183.3
Employer contributions	20.5	3
Benefits paid	(13.8)	(30.8)
Settlements	(58.6)
Foreign currency translation	81.6	(155.4)
Fair value of plan assets at the end of the year	941.8	877.3	$ 877.2
Change in benefit obligation:
Benefit obligations at the beginning of the year	(679.2)	(674.5)
Service cost	(1.2)	(1.2)	(1.5)
Interest cost	(19.2)	(22.6)	(25.8)
Settlements	58.6
Benefits paid	13.8	30.8
Actuarial loss	(29.8)	(131.6)
Foreign currency translation	(62.1)	119.9
Benefit obligations at the end of the year	(719.1)	(679.2)	$ (674.5)
Funded status as at year end	222.7	198.1
Tax at source	(28)	(29.8)
Net retirement benefit asset recognized in the Consolidated Balance Sheets	194.7	168.3
Retirement benefit assets recognized in the Consolidated Balance Sheets:
Janus Henderson Group UK Pension Scheme	199.3	180.2
Retirement benefit obligations recognized in the Consolidated Balance Sheets:
Janus Henderson Group unapproved pension scheme	(4.6)	(11.9)
Net retirement benefit asset recognized in the Consolidated Balance Sheets	$ 194.7	$ 168.3
Key assumptions used in determining the defined benefit obligation
Discount rate	2.60%	2.90%
Inflation - salaries	2.5	2.5
Inflation - RPI	3.1	3.2
Inflation - CPI	2	2.1
Pension increases (RPI capped at 5% p.a.)	3	3
Pension increases (RPI capped at 2.5% p.a.)	2.1	2.1
Life expectancy of male aged 60 at accounting date	28 years 3 months 18 days	28 years 7 months 6 days
Life expectancy of male aged 60 in 15 years time	29 years 4 months 24 days	29 years 10 months 24 days

Retirement benefit plans - Plan

Retirement benefit plans - Plan assets (Details) - Defined benefit pension Plan $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Fair value of plan assets
Total assets at fair value	$ 877.3	$ 877.2	$ 941.8	$ 877.3
Assets held in JHG managed funds			231.1
Change in fair value of plan assets level 3 reconciliation
Fair value of plan assets at the beginning of the year	877.3	877.2
Losses recognized in the period	34.8	183.3
Fair value of plan assets at the end of the year	$ 941.8	$ 877.3
Expected rate of return on plan assets (as a percent)	2.6	3.4
Cash and cash equivalents
Fair value of plan assets
Total assets at fair value	$ 3.9	$ 3.9	10.8	3.9
Change in fair value of plan assets level 3 reconciliation
Fair value of plan assets at the beginning of the year	3.9
Fair value of plan assets at the end of the year	10.8	3.9
Money market instruments
Fair value of plan assets
Total assets at fair value	1.7		1.7
Change in fair value of plan assets level 3 reconciliation
Fair value of plan assets at the end of the year	1.7
Forward foreign exchange contracts
Fair value of plan assets
Total assets at fair value	(0.8)	(0.8)	0.4	(0.8)
Change in fair value of plan assets level 3 reconciliation
Fair value of plan assets at the beginning of the year	(0.8)
Fair value of plan assets at the end of the year	0.4	(0.8)
Bond assets
Fair value of plan assets
Total assets at fair value	694	694	745.2	$ 694
Strategic allocation of plan assets				75.00%
Change in fair value of plan assets level 3 reconciliation
Fair value of plan assets at the beginning of the year	694
Fair value of plan assets at the end of the year	745.2	694
Equity investments
Fair value of plan assets
Total assets at fair value	180.2	180.2	$ 183.7	$ 180.2
Change in fair value of plan assets level 3 reconciliation
Fair value of plan assets at the beginning of the year	180.2
Fair value of plan assets at the end of the year	183.7	180.2
Growth portfolio
Fair value of plan assets
Strategic allocation of plan assets			25.00%
Level 2
Fair value of plan assets
Total assets at fair value	232.8		$ 232.8
Change in fair value of plan assets level 3 reconciliation
Fair value of plan assets at the end of the year	$ 232.8
Level 3
Fair value of plan assets
Total assets at fair value		0.4
Change in fair value of plan assets level 3 reconciliation
Fair value of plan assets at the beginning of the year		0.4
Losses recognized in the period		(0.3)
Purchases, sales and settlements, net		$ (0.1)

Retirement benefit plans - Actu

Retirement benefit plans - Actuarial gains(losses), benefit cost, cash flows (Details) - Defined benefit pension Plan $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Actuarial gains and losses
Opening accumulated unamortized actuarial gain	$ 32.1	$ 17.1
Current year actuarial gain (loss)	(15.3)	26.1
Tax at source on current year actuarial gain (loss)	4.7	(11.1)
Release of actuarial gain due to settlement event	(1.6)
Release of tax at source due to settlement event	1.1
Closing accumulated unamortized actuarial gain	21	32.1
Actuarial gains amortized from AOCI	0	0
Actuarial gains expected to be amortized during 2018	0
Components of net periodic benefit cost
Service cost	(1.2)	(1.2)	$ (1.5)
Settlement gain	1.6
Interest cost	(19.2)	(22.6)	(25.8)
Expected return on plan assets	20.3	25.6	27.8
Net periodic benefit credit	1.5	1.8	0.5
Contributions to money purchase section	(7.4)	(7.5)	(8.1)
Net periodic benefit credit	$ (5.9)	$ (5.7)	$ (7.6)
Key assumptions used in determining the net periodic benefit cost
Discount rate	2.90%	3.80%	3.60%
Inflation - salaries	2.5	2.5	2.5
Inflation - RPI	3.2	3	3.1
Inflation - CPI	2.1	2	2.1
Pension increases (RPI capped at 5% p.a.)	3	2.9	3
Pension increases (RPI capped at 2.5% p.a.)	2.1	2	2.1
Expected return on plan assets	2.60%	3.40%	3.20%
Amortization period for net actuarial gains/losses at beginning of the year	11 years	11 years	11 years
Employer contributions to the plan excluding credits to member's Money Purchase Accounts	$ 20.5
Expected contributions to the scheme during 2018	12.9
Expected future benefit payments
2,018	17.6
2,019	19.3
2,020	19.9
2,021	21.6
2,022	23.3
2023-2027	$ 134.5

Accumulated Other Comprehensi88

Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in accumulated other comprehensive loss, net of tax
Beginning balance	$ 1,647.5
Total other comprehensive income (loss)	132.7	$ (244.9)	$ (108.1)
Less: other comprehensive income (loss) attributable to noncontrolling interests	(20.8)	12.4	(0.4)
Ending balance	4,837.3	1,647.5
Accumulated other comprehensive loss
Changes in accumulated other comprehensive loss, net of tax
Beginning balance	(434.5)	(189.6)
Other comprehensive income (loss) before reclassifications	116.3	(231.3)
Amounts reclassified from accumulated other comprehensive income (loss)	(4.4)	(1.2)
Total other comprehensive income (loss)	111.9	(232.5)
Less: other comprehensive income (loss) attributable to noncontrolling interests	20.8	(12.4)
Ending balance	(301.8)	(434.5)	(189.6)
Foreign currency translation adjustments
Changes in accumulated other comprehensive loss, net of tax
Beginning balance	(471.3)	(211.8)
Other comprehensive income (loss) before reclassifications	125	(247.1)
Total other comprehensive income (loss)	125	(247.1)
Less: other comprehensive income (loss) attributable to noncontrolling interests	21	(12.4)
Ending balance	(325.3)	(471.3)	(211.8)
Available-for-sale securities
Changes in accumulated other comprehensive loss, net of tax
Beginning balance	4.7	5.1
Other comprehensive income (loss) before reclassifications	1.9	0.8
Amounts reclassified from accumulated other comprehensive income (loss)	(3.9)	(1.2)
Total other comprehensive income (loss)	(2)	(0.4)
Less: other comprehensive income (loss) attributable to noncontrolling interests	(0.2)
Ending balance	2.5	4.7	5.1
Retirement benefit asset, net
Changes in accumulated other comprehensive loss, net of tax
Beginning balance	32.1	17.1
Other comprehensive income (loss) before reclassifications	(10.6)	15
Amounts reclassified from accumulated other comprehensive income (loss)	(0.5)
Total other comprehensive income (loss)	(11.1)	15
Ending balance	$ 21	$ 32.1	$ 17.1

Accumulated Other Comprehensi89

Accumulated Other Comprehensive Loss - OCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other comprehensive income, net of tax
Pre-tax amount	$ 112.3	$ (233.1)	$ (108.3)
Tax (expense) benefit	(0.4)	0.6	(0.2)
Other comprehensive income (loss ), net of tax	111.9	(232.5)	(108.5)
Available-for-sale securities
Other comprehensive income, net of tax
Pre-tax amount	1.9	0.8	1.4
Other comprehensive income (loss ), net of tax	1.9	0.8	1.4
Foreign currency translation adjustments
Other comprehensive income, net of tax
Pre-tax amount	125	(247.4)	(94.5)
Tax (expense) benefit		0.3
Other comprehensive income (loss ), net of tax	125	(247.1)	(94.5)
Retirement benefit asset, net
Other comprehensive income, net of tax
Pre-tax amount	(10.2)	14.7	(0.5)
Tax (expense) benefit	(0.4)	0.3	(0.2)
Other comprehensive income (loss ), net of tax	(10.6)	15	(0.7)
Reclassifications to net income
Other comprehensive income, net of tax
Pre-tax amount	(4.4)	(1.2)	(14.7)
Other comprehensive income (loss ), net of tax	$ (4.4)	$ (1.2)	$ (14.7)

Earnings and Dividends Per Sh90

Earnings and Dividends Per Share (Details) $ / shares in Units, shares in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017USD ($)$ / shares	Sep. 30, 2017USD ($)$ / shares	Jun. 30, 2017USD ($)$ / shares	Mar. 31, 2017USD ($)$ / shares	Dec. 31, 2016USD ($)$ / shares	Sep. 30, 2016USD ($)$ / shares	Jun. 30, 2016USD ($)$ / shares	Mar. 31, 2016USD ($)$ / shares	Dec. 31, 2017£ / shares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016£ / shares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015£ / shares	Dec. 31, 2015USD ($)$ / sharesshares
Earnings per share
Net income attributable to JHG | $	$ 471,700,000	$ 99,500,000	$ 41,700,000	$ 42,600,000	$ 37,800,000	$ 53,400,000	$ 46,300,000	$ 51,500,000		$ 655,500,000		$ 189,000,000		$ 329,800,000
Less: Allocation of earnings to participating stock-based awards | $										(17,300,000)		(4,500,000)		(9,000,000)
Net income attributable to JHG common shareholders | $										$ 638,200,000		$ 184,500,000		$ 320,800,000
Weighted-average common shares outstanding - basic										160.7		109.1		109.3
Dilutive effect of non-participating stock-based awards										1.6		2		6.1
Weighted-average diluted common shares outstanding - diluted										162.3		111.1		115.4
Earnings per share:
Basic (in dollars per share) | $ / shares	$ 2.34	$ 0.49	$ 0.29	$ 0.38	$ 0.34	$ 0.48	$ 0.42	$ 0.46		$ 3.97		$ 1.69		$ 2.93
Diluted (two class) (in dollars per share) | $ / shares	$ 2.32	$ 0.49	$ 0.28	$ 0.38	$ 0.33	$ 0.46	$ 0.40	$ 0.44		$ 3.93		$ 1.66		$ 2.78
Dividends paid per share - pre Merger | £ / shares									£ 0.0915		£ 0.1040		£ 0.0950
Dividends paid per share - post Merger | $										$ 0.6400
Unvested nonparticipating stock awards
Anti-dilutive securities that have not been included in the calculation of weighted average diluted shares outstanding
Number of anti-dilutive securities that have not been included in the calculation of weighted average diluted shares outstanding										0.8		7.8		1.9
Dai-ichi options
Anti-dilutive securities that have not been included in the calculation of weighted average diluted shares outstanding
Number of anti-dilutive securities that have not been included in the calculation of weighted average diluted shares outstanding										10

Commitments and Contingencies91

Commitments and Contingencies (Details) $ in Millions	Dec. 31, 2017USD ($)
Future minimum rental commitments under non-cancelable operating and capital leases
2,018	$ 35.8
2,019	31.9
2,020	29
2,021	26.4
2,022	24.4
Thereafter	84.5
Total	$ 232

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related party transaction
Revenue recognized from managed funds	$ 1,473.5	$ 885	$ 1,082.8
12b-1 plan fees	12.1
Accrued income	261.6	130.8
Accounts receivable	39.8	3.1
Dai-ichi option
Related party transaction
Investment management fees	$ 11	$ 0

Geographic Information (Details

Geographic Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Revenues	$ 592	$ 537.4	$ 384.8	$ 229.5	$ 243.4	$ 245	$ 257.1	$ 254.4	$ 1,743.7	$ 999.9	$ 1,155.1
Long-lived assets:
Long-lived assets	3,175.4				401.3				3,175.4	401.3
UK
Revenue:
Revenues									653.2	518.4	699.7
Long-lived assets:
Long-lived assets	397				321.9				397	321.9
Luxembourg
Revenue:
Revenues									280.9	282.7	273.5
U.S.
Revenue:
Revenues									703.8	172.1	172
Long-lived assets:
Long-lived assets	2,629.8				54				2,629.8	54
Australia
Long-lived assets:
Long-lived assets	245.1								245.1
International
Revenue:
Revenues									105.8	26.7	$ 9.9
Other
Long-lived assets:
Long-lived assets	$ 3.5				$ 25.4				$ 3.5	$ 25.4

Selected Quarterly Financial 94

Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Selected Quarterly Financial Data
Operating revenue	$ 592	$ 537.4	$ 384.8	$ 229.5	$ 243.4	$ 245	$ 257.1	$ 254.4	$ 1,743.7	$ 999.9	$ 1,155.1
Operating income	196.6	138.2	56.7	50.8	46	64.1	56.4	65.6	442.3	232.1	317.3
Net income	472.1	102.2	41.5	42.6	28.9	53.6	40.2	54.6	658.4	177.3	331.4
Net income attributable to noncontrolling interests	0.4	2.7	(0.2)		(8.9)	0.2	(6.1)	3.1	2.9	(11.7)	1.6
Net income attributable to JHG	$ 471.7	$ 99.5	$ 41.7	$ 42.6	$ 37.8	$ 53.4	$ 46.3	$ 51.5	$ 655.5	$ 189	$ 329.8
Basic earnings per share attributable to JHG common shareholders (in dollars per share)	$ 2.34	$ 0.49	$ 0.29	$ 0.38	$ 0.34	$ 0.48	$ 0.42	$ 0.46	$ 3.97	$ 1.69	$ 2.93
Diluted earnings per share attributable to JHG common shareholders (in dollars per share)	$ 2.32	$ 0.49	$ 0.28	$ 0.38	$ 0.33	$ 0.46	$ 0.40	$ 0.44	$ 3.93	$ 1.66	$ 2.78

Subsequent Events (Details)

Subsequent Events (Details) $ / shares in Units, $ in Millions	Feb. 05, 2018$ / shares	Jan. 01, 2018$ / shares	Feb. 22, 2018USD ($)	Jan. 31, 2018$ / shares	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Mar. 31, 2018USD ($)
Subsequent Events
Settlement of debt in cash					$ 92.5	$ 203.4
0.750% Convertible Senior Notes due 2018
Subsequent Events
Conversion rate, shares per $1,000 principal amount		45.1535
Redemption of debt instruments principal amount					59.1
Settlement of debt in cash					$ 92.5
Adjusted conversion price per share of common stock (in dollars per share) | $ / shares		$ 22.15
Subsequent Events
Subsequent Events
Cash dividend declared (in dollars per share) | $ / shares	$ 0.32
Subsequent Events | Discontinued Operations, Disposed of by Sale | JHG's back office
Subsequent Events
Consideration for discontinuous operations							$ 36
Subsequent Events | 0.750% Convertible Senior Notes due 2018
Subsequent Events
Conversion rate, shares per $1,000 principal amount				45.1535
Redemption of debt instruments principal amount			$ 22.5
Settlement of debt in cash			39.1
Adjusted conversion price per share of common stock (in dollars per share) | $ / shares				$ 22.15
Additional conversion notices amount			$ 25.4