Morningstar (MORN) 10-K 1 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information Document - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 16, 2018	Jun. 30, 2017
Document and Entity Information Abstract
Entity Registrant Name	MORNINGSTAR, INC.
Entity Central Index Key	1,289,419
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		42,498,136
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 1,415,121,617

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue	$ 911.7	$ 798.6	$ 788.8
Operating expense:
Cost of revenue	386.6	344.3	330.1
Sales and marketing	134.3	97.6	96.6
General and administrative	129.8	105.2	107.1
Depreciation and amortization	91.2	70.7	64.4
Total operating expense	741.9	617.8	598.2
Operating income	169.8	180.8	190.6
Non-operating income:
Interest income (expense), net	(3.6)	0.3	1.3
Gain on sale of investments, reclassified from other comprehensive income	3.2	0.6	0.6
Total gain on sale of business	16.7	0	0
Holding gain upon acquisition of additional ownership of equity-method investments	0	37.1	0
Other income (expense), net	(5)	6.1	1.2
Non-operating income, net	11.3	44.1	3.1
Income before income taxes and equity in net income (loss) of unconsolidated entities	181.1	224.9	193.7
Equity in net income (loss) of unconsolidated entities	(1.3)	(0.2)	1.8
Income tax expense	42.9	63.7	62.7
Consolidated net income	136.9	161	132.8
Net income attributable to the noncontrolling interest	0	0	(0.2)
Net income attributable to Morningstar, Inc.	$ 136.9	$ 161	$ 132.6
Net income per share attributable to Morningstar, Inc.:
Basic net income per share attributable to Morningstar, Inc. (in dollars per share)	$ 3.21	$ 3.74	$ 3
Diluted net income per share attributable to Morningstar, Inc. (in dollars per share)	3.18	3.72	3
Dividends per common share:
Dividends declared per common share	0.94	0.89	0.79
Dividends paid per common share	$ 0.92	$ 0.88	$ 0.76
Weighted average shares outstanding:
Basic (in shares)	42.7	43	44.2
Diluted (in shares)	43	43.3	44.3

Consolidated Consolidated State

Consolidated Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated net income	$ 136.9	$ 161	$ 132.8
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustment	33.4	(27.8)	(28.2)
Unrealized gains (losses) on securities:
Unrealized holding gains (losses) arising during period	3.4	3.3	(1)
Reclassification of gains included in net income	(1.9)	(2.4)	(0.4)
Other comprehensive income (loss)	34.9	(26.9)	(29.6)
Comprehensive income	171.8	134.1	103.2
Comprehensive (income) loss attributable to noncontrolling interest	0	0	(0.4)
Comprehensive income attributable to Morningstar, Inc.	$ 171.8	$ 134.1	$ 102.8

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 308.2	$ 259.1
Investments	45.1	44.9
Accounts receivable, less allowance of $3.2 and $2.1, respectively	148.2	145.8
Other	28.3	22.2
Total current assets	529.8	472
Property, equipment, and capitalized software, net	147.4	152.1
Investments in unconsolidated entities	62	40.3
Goodwill	564.9	556.8
Intangible assets, net	95.4	120.9
Other assets	6.2	8.8
Total assets	1,405.7	1,350.9
Current liabilities:
Accounts payable and accrued liabilities	49.2	44.6
Accrued compensation	92	71.7
Deferred revenue	171.3	165.4
Other current liabilities	10.7	13.2
Total current liabilities	323.2	294.9
Accrued compensation	11.7	10.3
Deferred tax liability, net	23.6	38.2
Long-term debt	180	250
Deferred rent	26.9	24.8
Other long-term liabilities	35.4	35.9
Total liabilities	600.8	654.1
Morningstar, Inc. shareholders’ equity:
Common stock, no par value, 200,000,000 shares authorized, of which 42,547,707 and 42,932,994 shares were outstanding as of December 31, 2017 and December 31, 2016, respectively	0	0
Treasury stock at cost, 10,633,637 and 10,106,249 shares as of December 31, 2017 and December 31, 2016, respectively	(708.2)	(667.9)
Additional paid-in capital	601	584
Retained earnings	958.7	861.9
Accumulated other comprehensive loss:
Currency translation adjustment	(47.9)	(81.3)
Unrealized gain (loss) on available-for-sale investments	1.3	(0.2)
Total accumulated other comprehensive loss	(46.6)	(81.5)
Total Morningstar, Inc. shareholders’ equity	804.9	696.5
Noncontrolling interest	0	0.3
Total equity	804.9	696.8
Total liabilities and equity	$ 1,405.7	$ 1,350.9

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 3.2	$ 2.1
Common stock, no par value	$ 0	$ 0
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares outstanding	42,547,707	42,932,994
Treasury stock, shares	10,633,637	10,106,249

Condensed Consolidated Stateme6

Condensed Consolidated Statement of Equity - USD ($) $ in Millions	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Non Controlling Interests
Balance at Dec. 31, 2014	$ 654.4		$ (524.3)	$ 561.1	$ 641.5	$ (24.8)	$ 0.9
Balance (in shares) at Dec. 31, 2014		44,345,763
Increase (Decrease) in Stockholders' Equity
Net income	132.8				132.6		0.2
Other Comprehensive Income (loss)
Unrealized gain on available-for-sale investments, net of income tax	(1)					(1)
Reclassification of adjustments for gains included in net income, net of income tax	(0.4)					(0.4)
Foreign currency translation adjustment, net	(28.2)					(28.4)	0.2
Other comprehensive income (loss)	(29.6)					(29.8)	0.2
Issuance of common stock related to stock-option exercises and vesting of restricted stock units, net	(1.7)		1.5	(3.2)
Issuance of common stock related to stock-option exercises and vesting of restricted stock units, net (in shares)		298,435
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition [Abstract]
Stock-based compensation — restricted stock units	16.1			16.1
Stock-based compensation — restricted stock	0.1			0.1
Stock-based compensation — performance share awards	1			1
Stock-based compensation — stock options	0.2			0.2
Excess tax benefit derived from stock-option exercises and vesting of restricted stock units	2.6			2.6
Dividends declared — common shares outstanding	(34.8)				(34.8)
Dividends declared — restricted stock units	(0.1)			0	(0.1)
Purchase of additional interest in majority-owned investment	(3.4)			(2.4)			(1)
Common share repurchased	(97)		(97)
Common share repurchased (in shares)		(1,241,122)
Balance at Dec. 31, 2015	640.6		(619.8)	575.5	739.2	(54.6)	0.3
Balance (in shares) at Dec. 31, 2015		43,403,076
Increase (Decrease) in Stockholders' Equity
Net income	161				161		0
Other Comprehensive Income (loss)
Unrealized gain on available-for-sale investments, net of income tax	3.3					3.3
Reclassification of adjustments for gains included in net income, net of income tax	(2.4)					(2.4)
Foreign currency translation adjustment, net	(27.8)					(27.8)	0
Other comprehensive income (loss)	(26.9)					(26.9)	0
Issuance of common stock related to stock-option exercises and vesting of restricted stock units, net	(4.6)		1.4	(6)
Issuance of common stock related to stock-option exercises and vesting of restricted stock units, net (in shares)		174,911
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition [Abstract]
Stock-based compensation — restricted stock units	14.6			14.6
Stock-based compensation — performance share awards	(0.1)			(0.1)
Dividends declared — common shares outstanding	(38.3)				(38.3)
Dividends declared — restricted stock units	0			0	0
Common share repurchased	(49.5)		(49.5)
Common share repurchased (in shares)		(644,993)
Balance at Dec. 31, 2016	$ 696.8	$ 0	(667.9)	584	861.9	(81.5)	0.3
Balance (in shares) at Dec. 31, 2016	42,932,994	42,932,994
Increase (Decrease) in Stockholders' Equity
Net income	$ 136.9				136.9		0
Other Comprehensive Income (loss)
Unrealized gain on available-for-sale investments, net of income tax	3.4					3.4
Reclassification of adjustments for gains included in net income, net of income tax	(1.9)					(1.9)
Foreign currency translation adjustment, net	33.4					33.4	0
Other comprehensive income (loss)	34.9					34.9	0
Issuance of common stock related to stock-option exercises and vesting of restricted stock units, net	(4.6)		1.6	(6.2)
Issuance of common stock related to stock-option exercises and vesting of restricted stock units, net (in shares)		161,445
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition [Abstract]
Stock-based compensation — restricted stock units	16.5			16.5
Stock-based compensation — performance share awards	7.1			7.1
Stock-based compensation — market stock units	0.5			0.5
Dividends declared — common shares outstanding	(40.1)				(40.1)
Purchase of additional interest in majority-owned investment	(1.2)			(0.9)			(0.3)
Common share repurchased	(41.9)		(41.9)
Common share repurchased (in shares)		(546,732)
Balance at Dec. 31, 2017	$ 804.9	$ 0	$ (708.2)	$ 601	$ 958.7	$ (46.6)	$ 0
Balance (in shares) at Dec. 31, 2017	42,547,707	42,547,707

Condensed Consolidated Stateme7

Condensed Consolidated Statement of Equity (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	$ 1.8	$ 1.3	$ 0.4
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Tax	$ 1.2	$ 1.8	$ 0.1

Condensed Consolidated Stateme8

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Consolidated net income	$ 136.9	$ 161	$ 132.8
Adjustments to reconcile consolidated net income to net cash flows from operating activities:
Depreciation and amortization	91.2	70.7	64.4
Deferred income taxes	(14.1)	4.7	2.9
Stock-based compensation expense	24.1	14.5	17.4
Provision for bad debt	2.3	1.3	0.5
Equity in net (income) loss of unconsolidated entities	1.3	0.2	(1.8)
Gain on sale of business	(16.7)	0	0
Holding gain upon acquisition of additional ownership of equity-method investments	0	(37.1)	0
Other, net	1.8	(6.8)	(1.1)
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(1.2)	(0.1)	(6.9)
Other assets	(7.8)	1.1	0.7
Accounts payable and accrued liabilities	0.7	3.4	4.7
Accrued compensation	20.2	(8.8)	7
Income taxes—current	9.7	1	10.1
Deferred revenue	2.5	6.7	10.6
Deferred rent	2.6	(2.9)	(0.3)
Other liabilities	(3.4)	4.8	0.5
Cash provided by operating activities	250.1	213.7	241.5
Investing activities
Purchases of investments	(34.9)	(32)	(34.7)
Proceeds from maturities and sales of investments	42.2	28.6	30
Capital expenditures	(66.6)	(62.8)	(57.3)
Acquisitions, net of cash acquired	(1)	(191.6)	(11.1)
Proceeds from sale of a business, net	23.7	0	0
Purchases of equity- and cost-method investments	(24.8)	(16.5)	(6.2)
Other, net	0.6	0.1	(0.2)
Cash used for investing activities	(60.8)	(274.2)	(79.5)
Financing activities
Common shares repurchased	(42.3)	(48.8)	(97)
Dividends paid	(39.3)	(37.9)	(33.7)
Proceeds from short-term debt	0	40	50
Repayment of short-term debt	0	(15)	(45)
Proceeds from long-term debt	0	190	0
Repayment of long-term debt	(70)	0	0
Proceeds from stock-option exercises	0.2	0.4	3.9
Employee taxes withheld for restricted stock units	(4.8)	(5)	(5.6)
Other, net	(1.3)	0	(0.1)
Cash provided by (used for) financing activities	(157.5)	123.7	(127.5)
Effect of exchange rate changes on cash and cash equivalents	17.3	(11.2)	(12.6)
Net increase in cash and cash equivalents	49.1	52	21.9
Cash and cash equivalents—beginning of period	259.1	207.1	185.2
Cash and cash equivalents—end of period	308.2	259.1	207.1
Supplemental disclosure of cash flow information:
Cash paid for income taxes	47.1	58	50.1
Cash paid for interest	5.4	1.2	0.4
Supplemental information of non-cash investing and financing activities:
Unrealized gain (loss) on available-for-sale investments	2	1.2	(2)
Software and equipment obtained under long-term financing arrangement	$ 0.6	$ 9	$ 5.3

Description of Business

Description of Business	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business Morningstar, Inc. and its subsidiaries (Morningstar, we, our, the company), provides independent investment research for investors around the world. We offer an extensive line of products and services for individual investors, financial advisors, asset managers, retirement plan providers and sponsors, and institutional investors in the private capital markets. We have operations in 27 countries.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies The acronyms that appear in these Notes to our Consolidated Financial Statements refer to the following: ASC Accounting Standards Codification ASU Accounting Standards Update EITF Emerging Issues Task Force FASB Financial Accounting Standards Board SEC Securities and Exchange Commission Principles of Consolidation. We conduct our business operations through wholly owned or majority-owned operating subsidiaries. The accompanying consolidated financial statements include the accounts of Morningstar, Inc. and our subsidiaries. We consolidate assets, liabilities, and results of operations of subsidiaries in which we have a controlling interest and eliminate all significant intercompany accounts and transactions. We account and report the noncontrolling (minority) interest in our Consolidated Financial Statements in accordance with FASB ASC 810, Consolidation . A noncontrolling interest is the portion of equity (net assets) in a subsidiary not attributable, directly or indirectly, to the parent company. We report the noncontrolling interest in our Consolidated Balance Sheet within equity separate from the shareholders' equity attributable to Morningstar, Inc. In addition, we present the net income (loss) and comprehensive income (loss) attributable to Morningstar, Inc.'s shareholders and the noncontrolling interest in our Consolidated Statements of Income, Consolidated Statements of Comprehensive Income, and Consolidated Statements of Equity. We account for investments in entities in which we exercise significant influence, but do not control, using the equity method. As part of our investment management operations, we manage certain funds outside of the United States that are considered variable interest entities. For the majority of these variable interest entities, we do not have a variable interest in them. In cases where we do have a variable interest, we are not the primary beneficiary. Accordingly, we do not consolidate any of these variable interest entities. Use of Estimates. The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires us to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, and expenses during the reporting period. Actual results may differ from these estimates. Cash and Cash Equivalents. Cash and cash equivalents consists of cash and investments with original maturities of three months or less. We state them at cost, which approximates fair value. We state the portion of our cash equivalents that are invested in money market funds at fair value, as these funds are actively traded and have quoted market prices. Investments. We account for our investments in accordance with FASB ASC 320, Investments—Debt and Equity Securities. We classify our investments into three categories: held-to-maturity, trading, and available-for-sale. • Held-to-maturity: We classify certain investments, primarily certificates of deposit, as held-to-maturity securities, based on our intent and ability to hold these securities to maturity. We record held-to-maturity investments at amortized cost in our Consolidated Balance Sheets. • Trading: We classify certain other investments, primarily equity securities, as trading securities as these relate mainly to investments tracking the strategies of our newsletter portfolios. We include realized and unrealized gains and losses associated with these investments as a component of our operating income in our Consolidated Statements of Income. We record these securities at their fair value in our Consolidated Balance Sheets. • Available-for-sale: Investments not considered held-to-maturity or trading securities are classified as available-for-sale securities. Available-for-sale securities primarily consist of equity securities, exchange-traded funds, and mutual funds. We report unrealized gains and losses for available-for-sale securities as other comprehensive income (loss), net of related income taxes. We record these securities at their fair value in our Consolidated Balance Sheets. Fair Value Measurements. We follow FASB ASC 820, Fair Value Measurements . FASB ASC 820 defines fair value, establishes a framework for measuring fair value, and expands disclosures about fair value measurements. Under FASB ASC 820, fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants as of the measurement date. The standard applies whenever other standards require (or permit) assets or liabilities to be measured at fair value. The standard does not expand the use of fair value in any new circumstances and does not require any new fair value measurements. FASB ASC 820 uses a fair value hierarchy based on three broad levels of valuation inputs: • Level 1: Valuations based on quoted prices in active markets for identical assets or liabilities that the company has the ability to access. • Level 2: Valuations based on quoted prices in markets that are not active or for which all significant inputs are observable, either directly or indirectly. • Level 3: Valuations based on inputs that are unobservable and significant to the overall fair value measurement. We provide additional information about our cash equivalents and investments that are subject to valuation under FASB ASC 820 in Note 6 . Concentration of Credit Risk. No single customer is large enough to pose a significant credit risk to our operations or financial condition. For the years ended December 31, 2017 , 2016 , and 2015 , no single customer represented 5% or more of our consolidated revenue. If receivables from our customers become delinquent, we begin a collections process. We maintain an allowance for doubtful accounts based on our estimate of the probable losses of accounts receivable. Property, Equipment, and Depreciation. We state property and equipment at historical cost, net of accumulated depreciation. We depreciate property and equipment primarily using the straight-line method based on the useful life of the asset, which generally is three years. We amortize leasehold improvements over the lease term or their useful lives, whichever is shorter. Computer Software and Internal Product Development Costs. We capitalize certain costs in accordance with FASB ASC 350-40, Internal-Use Software , FASB ASC 350-50, Website Development Costs, and FASB ASC 985, Software . Internal product development costs mainly consist of employee costs for developing new web-based products and certain major enhancements of existing products. We amortize these costs on a straight-line basis over the estimated economic life, which is generally three to five years. We include capitalized software development costs related to projects that have not been placed into service in our construction in progress balance. The table below summarizes our depreciation expense related to internally developed software for the past three years: (in millions) 2017 2016 2015 Internally developed software depreciation expense $ 30.6 $ 20.0 $ 13.0 The table below summarizes our capitalized software development costs for the past three years: (in millions) 2017 2016 2015 Capitalized software development costs $ 46.3 $ 28.2 $ 21.8 Business Combinations . When we make acquisitions, we allocate the purchase price to the assets acquired, liabilities assumed, and goodwill. We follow FASB ASC 805, Business Combinations . We recognize and measure the fair value of the acquired operation as a whole, as well as the assets acquired and liabilities assumed, at their full fair values as of the date we obtain control, regardless of the percentage ownership in the acquired operation or how the acquisition was achieved. We expense direct costs related to the business combination, such as advisory, accounting, legal, valuation, and other professional fees, as incurred. We recognize restructuring costs, including severance and relocation for employees of the acquired entity, as post-combination expenses unless the target entity meets the criteria of FASB ASC 420, Exit or Disposal Cost Obligations , on the acquisition date. As part of the purchase price allocation, we follow the requirements of FASB ASC 740, Income Taxes. This includes establishing deferred tax assets or liabilities reflecting the difference between the values assigned for financial statement purposes and income tax purposes. In certain acquisitions, the goodwill resulting from the purchase price allocation may not be deductible for income tax purposes. FASB ASC 740 prohibits recognition of a deferred tax asset or liability for temporary differences in goodwill if goodwill is not amortizable and deductible for tax purposes. Goodwill . Changes in the carrying amount of our recorded goodwill are mainly the result of business acquisitions, divestitures, and the effect of foreign currency translations. In accordance with FASB ASC 350, Intangibles—Goodwill and Other , we do not amortize goodwill; instead, goodwill is subject to an impairment test annually, or whenever indicators of impairment exist. An impairment would occur if the carrying amount of a reporting unit exceeded the fair value of that reporting unit. We performed annual impairment reviews in the fourth quarter of 2017 and 2016 . We did not record any impairment losses in 2017 and 2016 . Intangible Assets. We amortize intangible assets using the straight-line method over their estimated useful lives, which range from one to 25 years. We have no intangible assets with indefinite useful lives. In accordance with FASB ASC 360-10-35, Subsequent Measurement—Impairment or Disposal of Long-Lived Assets , we review intangible assets for impairment whenever events or changes in circumstances indicate that the carrying value may not be recoverable. If the value of future undiscounted cash flows is less than the carrying amount of an asset group, we record an impairment loss based on the excess of the carrying amount over the fair value of the asset group. We did not record any impairment losses in 2017 and 2016 . Revenue Recognition. We recognize revenue in accordance with SEC SAB Topic 13, Revenue Recognition , ASC 605-25, Revenue Recognition: Multiple Element Arrangements , and ASC 985-605, Software: Revenue Recognition . We recognize revenue when all of the following conditions are met: • There is persuasive evidence of an arrangement, as evidenced by a signed contract; • Delivery of our products and services has taken place. If arrangements include an acceptance provision, we generally begin recognizing revenue when we receive customer acceptance; • The amount of fees to be paid by the customer is fixed or determinable; and • The collectibility of the fees is reasonably assured. We generate revenue through sales of Morningstar Data, Morningstar Advisor Workstation (including Morningstar Office), Morningstar Direct, Morningstar Research, Premium Membership subscriptions for Morningstar.com, our structured credit ratings offerings, and a variety of other investment-related products and services. We generally structure the revenue agreements for these offerings as licenses or subscriptions. We recognize revenue from licenses and subscription sales ratably as we deliver the product or service and over the service obligation period defined by the terms of the customer contract. For new-issue ratings and analysis for commercial mortgage-backed securities (CMBS), residential mortgage-backed securities (RMBS), other asset-backed securities (ABS), and corporate and financial institutions, we charge asset-based fees that are paid by the issuer on the rated balance of the transaction and recognize the revenue immediately upon issuance. We also generate revenue from Internet advertising, primarily from “impression-based” contracts. For advertisers who use our cost-per-impression pricing, we charge fees each time we display their ads on our site. Our Investment Management business includes a broad range of services. Pricing for consulting services is based on the scope of work and the level of service provided and includes asset-based fees for work we perform that involves investment management or acting as a subadvisor to investment portfolios. In arrangements that involve asset-based fees, we generally invoice clients quarterly in arrears based on average assets for the quarter. We recognize asset-based fees once the fees are fixed or determinable assuming all other revenue recognition criteria are met. Our Workplace Solutions offerings help retirement plan participants plan and invest for retirement. We offer these services both through retirement plan providers (typically third-party asset management companies that provide administrative and record-keeping services) and directly to plan sponsors (employers that offer retirement plans to their employees). For our Workplace Solutions offerings, we provide both a hosted solution as well as proprietary installed software advice solution. Clients can integrate the installed customized software into their existing systems to help investors accumulate wealth, transition into retirement, and manage income during retirement. The revenue arrangements for Workplace Solutions generally extend over multiple years. Our contracts may include one-time setup fees, implementation fees, technology licensing and maintenance fees, asset-based fees for managed retirement accounts, fixed and variable fees for advice and guidance, or a combination of these fee structures. Upon customer acceptance, we recognize revenue ratably over the term of the agreement. We recognize asset-based fees and variable fees in excess of any minimum once the value is fixed or determinable. Some of our revenue arrangements combine multiple products and services. These products and services may be provided at different points in time or over different time periods within the same arrangement. We allocate fees to the separate deliverables based on the deliverables’ relative selling price, which is generally based on the price we charge when the same deliverable is sold separately. We record taxes imposed on revenue-producing transactions (such as sales, use, value-added, and some excise taxes) on a net basis; therefore, we exclude such taxes from revenue in our Consolidated Statements of Income. Deferred revenue represents the portion of licenses or subscriptions billed or collected in advance of the service being provided which we expect to recognize as revenue in future periods. Certain arrangements may have cancellation or refund provisions. If we make a refund, it typically reflects the amount collected from a customer for which we have not yet provided services. The refund therefore results in a reduction of deferred revenue. Sales Commissions. Through December 31, 2013, we paid sales commissions based on a formula driven by the total contract value of sales opportunities closed, with any subsequent adjustments (such as clawbacks for contract cancellations) reflected in future commission payouts. We considered the corresponding commission expense an incremental direct acquisition cost and treated it as a deferred charge, which we expensed over the term of the underlying sales contracts. In the first quarter of 2014, we modified our sales incentive plan. The revised plan is based on a combination of net new sales and specific business objectives not solely tied to revenue growth. Because of this new structure and the discretion involved in determining the related incentives, we started expensing sales commissions as incurred instead of amortizing them over the contract terms. However, we continued to amortize the deferred charge capitalized in connection with sales commissions paid in 2013 and previous periods as part of the previous incentive plan. This amortization added $0.2 million , $0.6 million , and $3.5 million of sales commission cost in 2017, 2016, and 2015, respectively. Advertising Costs. Advertising costs include expenses incurred for various print and Internet ads, search engine fees, and direct mail campaigns. We expense advertising costs as incurred. The table below summarizes our advertising expense for the past three years: (in millions) 2017 2016 2015 Advertising expense $ 7.0 $ 7.6 $ 8.3 Stock-Based Compensation Expense. We account for our stock-based compensation expense in accordance with FASB ASC 718, Compensation—Stock Compensation . Our stock-based compensation expense reflects grants of restricted stock units, restricted stock, performance share awards, market stock units, and stock options. We measure the fair value of our restricted stock units, restricted stock, and performance share awards on the date of grant based on the closing market price of Morningstar's common stock on the day prior to grant. For market stock units, we estimate the fair value of the awards using a Monte Carlo valuation model. For stock options, we estimate the fair value of our stock options on the date of grant using a Black-Scholes option-pricing model. We amortize the fair values to stock-based compensation expense, net of estimated forfeitures, ratably over the vesting period. We estimate expected forfeitures of all employee stock-based awards and recognize compensation cost only for those awards expected to vest. We determine forfeiture rates based on historical experience and adjust the estimated forfeitures to actual forfeiture experience as needed. Liability for Sabbatical Leave. In some of our operations, we offer employees a sabbatical leave. Although the sabbatical policy varies by region, Morningstar's full-time employees are generally eligible for six weeks of paid time off after four years of continuous service. We account for our sabbatical liability in accordance with FASB ASC 710-10-25 , Compensated Absences . We record a liability for employees' sabbatical benefits over the period employees earn the right for sabbatical leave and include this liability in Accrued Compensation in our Consolidated Balance Sheet. Income Taxes. We record deferred income taxes for the temporary differences between the carrying amount of assets and liabilities for financial statement purposes and tax purposes in accordance with FASB ASC 740, Income Taxes . FASB ASC 740 prescribes the minimum recognition threshold a tax position is required to meet before being recognized in the financial statements. It also provides guidance on derecognition, measurement, classification, interest and penalties, accounting in interim periods, and disclosure for uncertain tax positions. We recognize interest and penalties related to unrecognized tax benefits as part of income tax expense in our Consolidated Statements of Income. We classify liabilities related to unrecognized tax benefits as either current or long-term liabilities in our Consolidated Balance Sheet, depending on when we expect to make payment.

Credit Arrangements

Credit Arrangements	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Credit Arrangements	Credit Arrangements In November 2016, we amended our credit agreement to provide us with a three -year credit facility with a borrowing capacity of up to $300.0 million . The credit agreement also provides for issuance of up to $25.0 million of letters of credit under the revolving credit facility. The interest rate applicable to any loan under the credit agreement is, at our option, either: (i) the applicable London interbank offered rate (LIBOR) plus an applicable margin for such loans, which ranges between 1.00% and 1.75% , based on our consolidated leverage ratio or (ii) the lender's base rate plus the applicable margin for such loans, which ranges between 2.00% and 2.75% , based on our consolidated leverage ratio. The credit agreement also contains financial covenants under which we: (i) may not exceed a maximum consolidated leverage ratio of 3.00 to 1.00 and (ii) are required to maintain a minimum consolidated interest coverage ratio of not less than 3.00 to 1.00. We were in compliance with the financial covenants as of December 31, 2017 . We had an outstanding principal balance of $180.0 million at a one-month LIBOR interest rate plus 100 basis points as of December 31, 2017 , leaving borrowing availability of $120.0 million .

Income Per Share

Income Per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Income Per Share	Income Per Share The following table shows how we reconcile our net income and the number of shares used in computing basic and diluted income per share: (in millions, except per share amounts) 2017 2016 2015 Basic net income per share attributable to Morningstar, Inc.: Net income attributable to Morningstar, Inc. $ 136.9 $ 161.0 $ 132.6 Weighted average common shares outstanding 42.7 43.0 44.2 Basic net income per share attributable to Morningstar, Inc. $ 3.21 $ 3.74 $ 3.00 Diluted net income per share attributable to Morningstar, Inc.: Net income attributable to Morningstar, Inc. $ 136.9 $ 161.0 $ 132.6 Weighted average common shares outstanding 42.7 43.0 44.2 Net effect of dilutive stock options and restricted stock units 0.3 0.3 0.1 Weighted average common shares outstanding for computing diluted income per share 43.0 43.3 44.3 Diluted net income per share attributable to Morningstar, Inc. $ 3.18 $ 3.72 $ 3.00 The number of weighted average restricted stock units, performance share awards, and market stock units excluded from our calculation of diluted earnings per share because their inclusion would have been anti-dilutive was immaterial during the periods presented.

Segment and Geographical Area I

Segment and Geographical Area Information	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment and Geographical Area Information	Segment and Geographical Area Information Segment Information We report our results in a single reportable segment, which reflects how our chief operating decision maker allocates resources and evaluates our financial results. Because we have a single reportable segment, all required financial segment information can be found directly in the Consolidated Financial Statements. The accounting policies for our reportable segment are the same as those described in Note 2 . We evaluate the performance of our reporting segment based on revenue and operating income. Geographical Area Information The tables below summarize our revenue and long-lived assets by geographical area: External revenue by geographical area Year ended December 31 (in millions) 2017 2016 2015 United States $ 687.0 $ 590.5 $ 585.1 United Kingdom 64.7 61.1 64.2 Continental Europe 69.9 62.6 58.8 Australia 34.6 32.2 30.5 Canada 29.4 28.2 27.9 Asia 21.2 20.0 18.5 Other 4.9 4.0 3.8 Total International 224.7 208.1 203.7 Consolidated revenue $ 911.7 $ 798.6 $ 788.8 Long-lived assets by geographical area As of December 31 (in millions) 2017 2016 United States $ 131.9 $ 139.1 United Kingdom 6.0 6.6 Continental Europe 1.7 1.9 Australia 2.3 0.6 Canada 0.2 0.4 Asia 5.2 3.4 Other 0.1 0.1 Total International 15.5 13.0 Consolidated property, equipment, and capitalized software, net $ 147.4 $ 152.1

Investments and Fair Value Meas

Investments and Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Investments and Fair Value Measurements	Investments and Fair Value Measurements We classify our investments into three categories: available-for-sale, held-to-maturity, and trading. Our investment portfolio consists of stocks, bonds, options, mutual funds, money market funds, or exchange-traded products that replicate the model portfolios and strategies created by Morningstar. These investment accounts may also include exchange-traded products where Morningstar is an index provider. We classify our investment portfolio as shown below: As of December 31 (in millions) 2017 2016 Available-for-sale $ 21.5 $ 27.7 Held-to-maturity 21.9 15.7 Trading securities 1.7 1.5 Total $ 45.1 $ 44.9 The following table shows the cost, unrealized gains (losses), and fair values related to investments classified as available-for-sale and held-to-maturity: As of December 31, 2017 As of December 31, 2016 (in millions) Cost Unrealized Gain Unrealized Loss Fair Value Cost Unrealized Gain Unrealized Loss Fair Value Available-for-sale: Equity securities and exchange-traded funds $ 17.1 $ 2.4 $ (0.6 ) $ 18.9 $ 25.6 $ 1.3 $ (1.5 ) $ 25.4 Mutual funds 2.4 0.2 — 2.6 2.2 0.1 — 2.3 Total $ 19.5 $ 2.6 $ (0.6 ) $ 21.5 $ 27.8 $ 1.4 $ (1.5 ) $ 27.7 Held-to-maturity: Certificates of deposit $ 19.9 $ — $ — $ 19.9 $ 13.8 $ — $ — $ 13.8 Convertible note 2.0 — — 2.0 1.9 — — 1.9 Total $ 21.9 $ — $ — $ 21.9 $ 15.7 $ — $ — $ 15.7 As of December 31, 2017 and December 31, 2016 , investments with unrealized losses for greater than a 12-month period were not material to the Consolidated Balance Sheets and were not deemed to have other than temporary declines in value. The table below shows the cost and fair value of investments classified as available-for-sale and held-to-maturity based on their contractual maturities as of December 31, 2017 and December 31, 2016 . As of December 31, 2017 As of December 31, 2016 (in millions) Cost Fair Value Cost Fair Value Available-for-sale: Equity securities, exchange-traded funds, and mutual funds $ 19.5 $ 21.5 $ 27.8 $ 27.7 Total $ 19.5 $ 21.5 $ 27.8 $ 27.7 Held-to-maturity: Due in one year or less $ 19.7 $ 19.7 $ 13.8 $ 13.8 Due in one to three years 2.2 2.2 1.9 1.9 Total $ 21.9 $ 21.9 $ 15.7 $ 15.7 The following table shows the realized gains and losses arising from sales of our investments classified as available-for-sale recorded in our Consolidated Statements of Income: (in millions) 2017 2016 2015 Realized gains $ 3.4 $ 1.6 $ 1.3 Realized losses (0.2 ) (1.0 ) (0.7 ) Realized gains, net $ 3.2 $ 0.6 $ 0.6 We determine realized gains and losses using the specific identification method. The following table shows the net unrealized gains (losses) on trading securities as recorded in our Consolidated Statements of Income: (in millions) 2017 2016 2015 Unrealized gains (losses), net $ 0.1 $ — $ (0.8 ) The table below shows the fair value of our assets subject to fair value measurements that are measured at fair value on a recurring basis using a fair value hierarchy: Level 1: Valuations based on quoted prices in active markets for identical assets or liabilities that we have the ability to access. Level 2: Valuations based on quoted prices in markets that are not active or for which all significant inputs are observable, either directly or indirectly. Level 3: Valuations based on inputs that are unobservable and significant to the overall fair value measurement. Fair Value Fair Value Measurements as of December 31, 2017 as of Using Fair Value Hierarchy (in millions) December 31, 2017 Level 1 Level 2 Level 3 Available-for-sale investments Equity securities and exchange-traded funds $ 18.9 $ 18.9 $ — $ — Mutual funds 2.6 2.6 — — Trading securities 1.7 1.7 — — Cash equivalents 0.5 0.5 — — Total $ 23.7 $ 23.7 $ — $ — Fair Value Fair Value Measurements as of December 31, 2016 as of Using Fair Value Hierarchy (in millions) December 31, 2016 Level 1 Level 2 Level 3 Available-for-sale investments Equity securities and exchange-traded funds $ 25.4 $ 25.4 $ — $ — Mutual funds 2.3 2.3 — — Trading securities 1.5 1.5 — — Cash equivalents 0.2 0.2 — — Total $ 29.4 $ 29.4 $ — $ — Based on our analysis of the nature and risks of our investments in equity securities and mutual funds, we have determined that presenting each of these investment categories in the aggregate is appropriate. We measure the fair value of money market funds, mutual funds, equity securities, and exchange-traded funds based on quoted prices in active markets for identical assets or liabilities. We did not hold any securities categorized as Level 2 or Level 3 as of December 31, 2017 and December 31, 2016 .

Acquisitions, Goodwill, and Oth

Acquisitions, Goodwill, and Other Intangible Assets	12 Months Ended
	Dec. 31, 2017
Acquisitions, Goodwill, and Other Intangible Assets [Abstract]
Acquisitions, Goodwill, and Other Intangible Assets	Acquisitions, Goodwill, and Other Intangible Assets 2017 Acquisitions We did not complete any acquisitions in 2017. 2016 Acquisitions Increased Ownership Interest in PitchBook Data, Inc. (PitchBook) In December 2016, we acquired an additional 78% interest in PitchBook Data, Inc. (PitchBook), increasing our ownership to 100% from 22% . PitchBook delivers data, research, and technology covering the private capital markets, including venture capital, private equity, and mergers and acquisitions. We began consolidating the financial results of this acquisition in our Consolidated Financial Statements on December 1, 2016. PitchBook contributed $4.1 million of revenue and $7.5 million of operating expense during the one-month period that PitchBook was included in our consolidated results for 2016. PitchBook's total estimated fair value of $235.1 million includes $188.2 million in cash paid to acquire the remaining 78% interest in PitchBook as well as a $46.9 million fair value related to our previous 22% ownership interest. The book value of this ownership immediately prior to the acquisition date was $9.8 million , and we recorded a non-cash holding gain of $37.1 million for the difference between the fair value and the book value of our previously held investment. We used the income approach and a discounted cash flow analysis of PitchBook’s projected revenue, operating expense, and other amounts to arrive at the estimated fair value. The gain is classified as "Holding gain upon acquisition of additional ownership of equity-method investments" in our Consolidated Statement of Income for the year ended December 31, 2016. The transaction has been accounted for using the acquisition method of accounting, which requires that assets acquired and liabilities assumed be recognized at their fair values as of the acquisition date. Adjustments recorded in the measurement period to the purchase price allocation were not significant. The following table summarizes our allocation of the estimated fair values of the assets acquired and liabilities assumed at the date of acquisition: (in millions) Cash and cash equivalents $ 12.4 Accounts receivable 10.8 Other current and non-current assets 3.2 Intangible assets 60.7 Goodwill 192.0 Deferred revenue (22.0 ) Deferred tax liability, net (12.3 ) Other current and non-current liabilities (9.7 ) Total fair value of PitchBook $ 235.1 Accounts receivable acquired were recorded at gross contractual amounts receivable, which approximates fair value. The allocation includes $60.7 million of acquired intangible assets, as follows: (in millions) Weighted Average Useful Life (years) Customer-related assets $ 17.1 10 Technology-based assets 40.8 5 Intellectual property (trademarks and trade names) 2.8 4 Total intangible assets $ 60.7 6 We recognized a net deferred tax liability of $12.3 million mainly because the amortization expense related to certain intangible assets is not deductible for income tax purposes. Goodwill of $192.0 million represents the excess over the fair value of the net tangible and intangible assets acquired with this acquisition. We paid this premium for a number of reasons, including the opportunity to offer comprehensive data coverage across the full life cycle of private market transactions. The goodwill is not deductible for income tax purposes. Unaudited Pro Forma Information for PitchBook Acquisition The following unaudited pro forma information presents a summary of our Consolidated Statements of Income for the years ended December 31, 2016 and 2015 as if we had completed the PitchBook acquisition as of January 1, 2015. This unaudited pro forma information is presented for illustrative purposes and is not intended to represent or be indicative of the actual results of operations of the combined company that would have been achieved had the acquisition occurred at the beginning of the earliest period presented, nor is it intended to represent or be indicative of future results of operations. In calculating the pro forma information below, we included an estimate of amortization expense related to the intangible assets acquired, stock-based compensation expense related to the PitchBook bonus plan (see Note 12 for additional information), and interest expense incurred on the long-term debt. The 2016 pro forma net income excludes the $37.1 million non-cash holding gain generated in connection with the transaction. Unaudited Pro Forma Financial Information (in millions) 2016 2015 Revenue $ 834.1 $ 813.3 Operating income $ 157.7 $ 170.0 Net income $ 105.5 $ 117.1 Basic net income per share attributable to Morningstar, Inc. $ 2.45 $ 2.65 Diluted net income per share attributable to Morningstar, Inc. $ 2.44 $ 2.65 RequiSight, LLC (RightPond) On March 31, 2016, we acquired RequiSight, LLC, which does business as RightPond, a provider of business intelligence data and analytics on defined contribution and defined benefit plans for financial services firms. We began consolidating the financial results of RightPond in our Consolidated Financial Statements on March 31, 2016. InvestSoft Technology, Inc. (InvestSoft) On May 31, 2016, we acquired InvestSoft Technology, Inc. (InvestSoft), a provider of fixed-income analytics. We began consolidating the financial results of InvestSoft in our Consolidated Financial Statements on May 31, 2016. 2015 Acquisitions Increased Ownership Interest in Ibbotson Associates Japan K.K. (IAJ) In July 2015, we acquired an additional 28.9% interest in Ibbotson Associates Japan K.K. (IAJ), increasing our ownership to 100% from 71.1% . Because we previously owned more than 50% of the company, IAJ's financial results were consolidated in our Consolidated Financial Statements prior to acquiring the remaining interest. Total Rebalance Expert (tRx) In November 2015, we acquired Total Rebalance Expert (tRx), an automated, tax-efficient investment portfolio rebalancing platform for financial advisors. tRx streamlines the rebalancing process for advisors and automates the complexities involved in rebalancing and managing portfolios. We began consolidating the financial results of tRx in our Consolidated Financial Statements on November 2, 2015. Goodwill The following table shows the changes in our goodwill balances from January 1, 2016 to December 31, 2017 : (in millions) Balance as of January 1, 2016 $ 364.2 Acquisition of PitchBook 193.6 Other acquisitions and foreign currency translation (1.0 ) Balance as of December 31, 2016 $ 556.8 Divestiture of HelloWallet (See Note 8) (2.4 ) Foreign currency translation and adjustments to purchase price allocation 10.5 Balance as of December 31, 2017 $ 564.9 We did not record any impairment losses in 2017 and 2016 as the estimated fair values of our reporting unit exceeded its carrying value. We perform our annual impairment testing during the fourth quarter of each year. Intangible Assets The following table summarizes our intangible assets: As of December 31, 2017 As of December 31, 2016 (in millions) Gross Accumulated Amortization Net Weighted Average Useful Life (years) Gross Accumulated Amortization Net Weighted Average Useful Life (years) Intellectual property $ 31.5 $ (28.9 ) $ 2.6 9 $ 30.9 $ (27.4 ) $ 3.5 9 Customer-related assets 156.6 (108.1 ) 48.5 12 152.0 (97.7 ) 54.3 12 Supplier relationships 0.2 (0.1 ) 0.1 20 0.2 (0.1 ) 0.1 20 Technology-based assets 127.9 (84.2 ) 43.7 7 133.2 (72.1 ) 61.1 7 Non-competition agreements 2.5 (2.0 ) 0.5 5 5.0 (3.1 ) 1.9 5 Total intangible assets $ 318.7 $ (223.3 ) $ 95.4 10 $ 321.3 $ (200.4 ) $ 120.9 10 The following table summarizes our amortization expense related to intangible assets: (in millions) 2017 2016 2015 Amortization expense $ 23.6 $ 19.4 $ 22.0 We did not record any impairment losses involving intangible assets in 2017 and 2016 . We amortize intangible assets using the straight-line method over their expected economic useful lives. Based on acquisitions and divestitures completed through December 31, 2017 , we expect intangible amortization expense for 2018 and subsequent years to be as follows: (in millions) 2018 $ 20.7 2019 19.3 2020 16.3 2021 13.0 2022 5.2 Thereafter 20.9 Our estimates of future amortization expense for intangible assets may be affected by additional acquisitions, divestitures, changes in the estimated average useful life, and foreign currency translation.

Divestitures

Divestitures	12 Months Ended
	Dec. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Divestitures	Divestiture In June 2014, we acquired the remaining 81.3% interest in HelloWallet Holdings, Inc. (HelloWallet), increasing our ownership to 100% . This valued HelloWallet at $54.0 million , an amount that included $39.2 million of goodwill and $9.5 million of intangible assets. On June 30, 2017, we sold HelloWallet to KeyBank National Association, a bank-based financial services company. We recorded a noncash gain on the sale of $16.7 million . This gain mainly represents the sale proceeds of $23.7 million less $2.4 million of goodwill and the write-off of the remaining net book value on the acquired intangible assets. As some aspects of HelloWallet had been integrated into Morningstar's single reporting unit, the goodwill attributable to this transaction was calculated using a relative fair value allocation method. The sale of HelloWallet did not meet the criteria to be classified as a discontinued operation because the divestiture did not represent a strategic shift that has, or will have, a major effect on our operations and financial results. The following table summarizes the amounts included in the gain on sale of business for the year ended December 31, 2017: Year ended December 31 (in millions) 2017 Proceeds received $ 23.7 Intangibles and internally developed software (4.5 ) Goodwill (2.4 ) Other assets and liabilities (0.1 ) Total gain on sale of business $ 16.7

Investments in Unconsolidated E

Investments in Unconsolidated Entities	12 Months Ended
	Dec. 31, 2017
Investments in Unconsolidated Entities [Abstract]
Investments in Unconsolidated Entities	Investments in Unconsolidated Entities Our investments in unconsolidated entities consist primarily of the following: As of December 31 (in millions) 2017 2016 Investment in MJKK $ 26.4 $ 25.1 Investment in Sustainalytics 20.7 — Other-equity method investments 12.6 13.5 Investments accounted for using the cost method 2.3 1.7 Total investments in unconsolidated entities $ 62.0 $ 40.3 Morningstar Japan K.K. Morningstar Japan K.K. (MJKK) develops and markets products and services customized for the Japanese market. MJKK’s shares are traded on the Tokyo Stock Exchange under the ticker 47650. We account for our investment in MJKK using the equity method. The following table summarizes our ownership percentage in MJKK and the market value of this investment based on MJKK’s publicly quoted share price: As of December 31 2017 2016 Morningstar’s approximate ownership of MJKK 34 % 34 % Approximate market value of Morningstar’s ownership in MJKK: Japanese yen (¥ in millions) ¥ 10,649.6 ¥ 8,558.2 Equivalent U.S. dollars ($ in millions) $ 94.6 $ 73.2 Sustainalytics Holding B.V. In July 2017, we acquired a minority stake in Sustainalytics Holding B.V. (Sustainalytics), which is an independent ESG and corporate governance research, ratings, and analysis firm supporting investors around the world with the development and implementation of responsible investment strategies. Our ownership in Sustainalytics as of December 31, 2017 was 40% . Other Equity Method Investments . As of December 31, 2017 and December 31, 2016, other equity method investments consist of our investment in Ellevate Financial, Inc. (Ellevest), United Income, Inc. (United Income), and YCharts, Inc. (YCharts). Ellevest provides an engaging investing experience to help women meet their financial goals. Our ownership interest in Ellevest was approximately 17% as of December 31, 2017 and 22% as of December 31, 2016. United Income helps investors transition to retirement and manage their retirement income. Our ownership interest in United Income was approximately 35% as of December 31, 2017 and 38% as of December 31, 2016. YCharts is a technology company that provides stock research and analysis. Our ownership interest in YCharts was approximately 22% as of December 31, 2017 and 2016 . As of December 31, 2016, other equity method investments also includes our investment in Inquiry Financial Europe AB (Inquiry Financial). Inquiry Financial is a provider of sell-side consensus estimate data. Our ownership interest in Inquiry Financial was approximately 34% as of December 31, 2016. During 2017, we sold our stake in Inquiry Financial. In December 2016, we purchased the remaining ownership interest in PitchBook. See Note 7 for additional information concerning our acquisition of PitchBook.

Property, Equipment, and Capita

Property, Equipment, and Capitalized Software	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property, Equipment, and Capitalized Software	Property, Equipment, and Capitalized Software The following table shows our property, equipment, and capitalized software summarized by major category: As of December 31 (in millions) 2017 2016 Computer equipment $ 81.6 $ 70.1 Capitalized software 239.2 189.8 Furniture and fixtures 27.6 26.0 Leasehold improvements 72.5 69.0 Telephone equipment 2.3 2.1 Construction in progress 8.9 9.9 Property, equipment, and capitalized software, at cost 432.1 366.9 Less accumulated depreciation (284.7 ) (214.8 ) Property, equipment, and capitalized software, net $ 147.4 $ 152.1 The following table summarizes our depreciation expense: (in millions) 2017 2016 2015 Depreciation expense $ 67.6 $ 51.3 $ 42.4 Depreciation expense in 2017 includes a $4.1 million impairment charge for certain software licenses due to a shift toward a cloud-based strategy.

Operating Leases

Operating Leases	12 Months Ended
	Dec. 31, 2017
Leases, Operating [Abstract]
Operating Leases	Operating Leases The following table shows our minimum future rental commitments due in each of the next five years and thereafter for all non-cancelable operating leases, consisting primarily of commitments for office space: Minimum Future Rental Commitments (in millions) 2018 $ 26.8 2019 30.4 2020 32.5 2021 29.8 2022 19.1 Thereafter 54.9 Total $ 193.5 The following table summarizes our rent expense, including taxes, insurance, and related operating costs: (in millions) 2017 2016 2015 Rent expense $ 30.3 $ 26.3 $ 27.1 Deferred rent includes build-out and rent abatement allowances received, which are amortized over the remaining portion of the original term of the lease as a reduction in office lease expense. We include deferred rent, as appropriate, in “Accounts payable and accrued liabilities” and “Deferred rent, noncurrent” on our Consolidated Balance Sheets. As of December 31 (in millions) 2017 2016 Deferred rent $ 31.2 $ 28.4

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation Stock-Based Compensation Plans Our shareholders approved the Morningstar 2011 Stock Incentive Plan (the 2011 Plan) on May 17, 2011. As of that date, we stopped granting awards under the Morningstar 2004 Stock Incentive Plan (the 2004 Plan). The 2004 Plan amended and restated the Morningstar 1993 Stock Option Plan, the Morningstar 2000 Stock Option Plan, and the Morningstar 2001 Stock Option Plan. The 2011 Plan provides for a variety of stock-based awards, including, among other things, restricted stock units, restricted stock, performance share awards, market stock units, and stock options. We granted restricted stock units, restricted stock, and stock options under the 2004 Plan. All of our employees and our non-employee directors are eligible for awards under the 2011 Plan. Grants awarded under the 2011 Plan or the 2004 Plan that are forfeited, canceled, settled, or otherwise terminated without a distribution of shares, or shares withheld by us in connection with the exercise of options, will be available for awards under the 2011 Plan. For any shares subject to awards that are withheld by us in connection with the payment of any required income tax withholding, the 2011 Plan provides for the ability to have these shares become available for new awards, but this feature of the 2011 plan has not been implemented. The following table summarizes the number of shares available for future grants under our 2011 Plan: As of December 31 (in millions) 2017 Shares available for future grants 3.4 Accounting for Stock-Based Compensation Awards The following table summarizes our stock-based compensation expense and the related income tax benefit we recorded in the past three years: Year ended December 31 (in millions) 2017 2016 2015 Restricted stock units $ 16.5 $ 14.6 $ 16.1 Restricted stock — — 0.1 Performance share awards 7.1 (0.1 ) 1.0 Market stock units 0.5 — — Stock options — — 0.2 Total stock-based compensation expense $ 24.1 $ 14.5 $ 17.4 Income tax benefit related to the stock-based compensation expense $ 7.8 $ 4.3 $ 5.0 The following table summarizes the stock-based compensation expense included in each of our operating expense categories for the past three years: Year ended December 31 (in millions) 2017 2016 2015 Cost of revenue $ 9.6 $ 7.5 $ 8.1 Sales and marketing 3.0 1.9 2.2 General and administrative 11.5 5.1 7.1 Total stock-based compensation expense $ 24.1 $ 14.5 $ 17.4 The following table summarizes the amount of unrecognized stock-based compensation expense as of December 31, 2017 and the expected number of months over which the expense will be recognized: Unrecognized stock-based compensation expense (in millions) Weighted average expected amortization period (months) Restricted stock units $ 36.5 35 Performance share awards — 12 Market stock units 2.8 32 Total unrecognized stock-based compensation expense $ 39.3 35 In accordance with FASB ASC 718, Compensation—Stock Compensation , we estimate forfeitures of employee stock-based awards and recognize compensation cost only for those awards expected to vest. Most of our larger annual equity grants typically have vesting dates in the second quarter. We adjust the stock-based compensation expense annually in the third quarter to reflect those awards that ultimately vested and update our estimate of the forfeiture rate that will be applied to awards not yet vested. Restricted Stock Units Restricted stock units represent the right to receive a share of Morningstar common stock when that unit vests. Restricted stock units granted to employees vest ratably over a four -year period. Restricted stock units granted to non-employee directors vest ratably over a three -year period. We measure the fair value of our restricted stock units on the date of grant based on the closing market price of the underlying common stock on the day prior to grant. We amortize that value to stock-based compensation expense, net of estimated forfeitures, ratably over the vesting period. The following table summarizes restricted stock unit activity during the past three years: Restricted Stock Units (RSUs) Unvested Vested but Deferred Total Weighted Average Grant Date Value per RSU RSUs Outstanding - December 31, 2014 655,934 14,778 670,712 $ 67.51 Granted 235,213 — 235,213 77.17 Dividend equivalents 1,409 146 1,555 56.42 Vested (253,038 ) — (253,038 ) 64.65 Forfeited (66,992 ) — (66,992 ) 53.61 RSUs Outstanding - December 31, 2015 572,526 14,924 587,450 $ 72.14 Granted 241,609 — 241,609 77.82 Dividend equivalents 370 136 506 56.52 Vested (225,590 ) — (225,590 ) 69.39 Issued — (5,312 ) (5,312 ) 44.47 Forfeited (47,670 ) — (47,670 ) 74.45 RSUs Outstanding - December 31, 2016 541,245 9,748 550,993 $ 75.77 Granted 331,470 — 331,470 78.33 Dividend equivalents — 78 78 60.99 Vested (212,005 ) — (212,005 ) 75.38 Issued — (6,547 ) (6,547 ) 49.40 Forfeited (55,831 ) — (55,831 ) 76.49 RSUs Outstanding - December 31, 2017 604,879 3,279 608,158 $ 77.52 Performance Share Awards In March 2015 and 2016, executive officers, other than Joe Mansueto, and certain other employees, were granted performance share awards. These awards entitle the holder to a number of shares of Morningstar common stock equal to the number of notional performance shares that become vested. Each award specifies a number of performance shares that will vest if pre-established target performance goals are attained. The number of performance shares that actually vest may be more or less than the specified number of performance shares to the extent Morningstar exceeds or fails to achieve, respectively, the target performance goals over a three -year performance period. We base the grant date fair value for these awards on the closing market price of the underlying common stock on the day prior to the grant date. We amortize that value to stock-based compensation expense ratably over the vesting period based on the satisfaction of the performance condition that is most likely to be satisfied over the three -year performance period. The table below shows target performance share awards granted and shares that would be issued at current performance levels for performance share awards granted as of December 31, 2017 : As of December 31, 2017 Target performance share awards granted 93,701 Weighted average fair value per award $ 77.55 Number of shares that would be issued based on current performance levels — Unamortized expense, based on current performance levels (in millions) $ — Market Stock Units In May and November 2017, executive officers, other than Joe Mansueto, and certain other employees, were granted market stock units. These market stock units represent the right to receive a target number of shares that will vest at the end of a three-year performance period depending on the company’s total shareholder return over that three-year period. We measure the fair value of our market stock units on the date of grant using a Monte Carlo valuation model. We amortize that value to stock-based compensation expense ratably over the vesting period. We used the following assumptions to estimate the fair value of our market stock units during 2017: Assumptions for Monte Carlo Valuation Model Grant Date Expected volatility Dividend yield Risk-free interest rate May 15, 2017 17.4 % 1.20 % 1.49 % November 15, 2017 17.7 % 1.04 % 1.79 % The table below shows market stock units granted and target market stock units outstanding as of December 31, 2017 : As of December 31, 2017 Market stock units granted 45,663 Weighted average fair value per award $ 72.29 Number of target market stock units outstanding 44,606 Unamortized expense, based on current performance levels (in millions) $ 2.8 PitchBook Bonus Plan In connection with our acquisition of PitchBook, we adopted a management bonus sub-plan under the 2011 Plan for certain employees of PitchBook (the PitchBook Plan). Pursuant to the terms of the PitchBook Plan, awards having an aggregate target value equal to $30.0 million will be available for issuance with annual grants of $7.5 million for 2017, $7.5 million in 2018, and $15.0 million in 2019. Each grant will consist of performance-based share unit awards which will vest over a one -year period and will be measured primarily based on the achievement of certain annual revenue targets specifically related to PitchBook’s business. Upon achievement of these targets, earned performance units will be settled in shares of our common stock on a one -for-one basis. If PitchBook exceeds certain performance conditions, the PitchBook Plan participants may receive payment for performance units in excess of the aggregate target values described above. If PitchBook fails to meet threshold performance conditions, the PitchBook Plan participants will not be entitled to receive payment for any performance units. In certain circumstances, the PitchBook Plan participants may be able to receive a catch-up award with respect to 2017 or 2018 if certain additional performance conditions are met in a subsequent year. The table below shows target performance share awards granted and shares that will be issued based on final performance levels for performance share awards granted as of December 31, 2017 : As of December 31, 2017 Target performance share awards granted 100,924 Weighted average fair value per award $ 74.31 Number of shares that will be issued based on final 2017 performance levels 113,941 Unamortized expense, based on current performance levels (in millions) $ — Stock Options Stock options granted to employees vest ratably over a four -year period. Grants to our non-employee directors vest ratably over a three -year period. All grants expire 10 years after the date of grant. In May 2011, we granted 86,106 stock options under the 2004 Stock Incentive Plan. In November 2011, we granted 6,095 stock options under the 2011 Plan. All options granted in 2011 have an exercise price equal to the fair market value on the grant date. We estimated the fair value of the options on the grant date using a Black-Scholes option-pricing model. The weighted average fair value of options granted during 2011 was $23.81 per share, based on the following assumptions: Assumptions for Black-Scholes Option Pricing Model Expected life (years): 7.4 Volatility factor: 35.1 % Dividend yield: 0.35 % Interest rate: 2.87 % The following table summarizes stock option activity in the past three years for our various stock option grants: 2017 2016 2015 All Other Option Grants, Excluding Activity Shown Above Underlying Shares Weighted Average Exercise Price Underlying Shares Weighted Average Exercise Price Underlying Shares Weighted Average Exercise Price Options outstanding—beginning of year 46,001 $ 57.28 52,096 $ 57.52 169,810 $ 40.20 Granted — — — — — — Canceled — — — — — — Exercised (4,316 ) 57.28 (6,095 ) 59.35 (117,714 ) 32.91 Options outstanding—end of year 41,685 $ 57.28 46,001 $ 57.28 52,096 $ 57.52 Options exercisable—end of year 41,685 $ 57.28 46,001 $ 57.28 52,096 $ 57.52 The following table summarizes the total intrinsic value (difference between the market value of our stock on the date of exercise and the exercise price of the option) of options exercised: (in millions) 2017 2016 2015 Intrinsic value of options exercised $ 0.1 $ 0.1 $ 5.1 The table below shows additional information for options outstanding and exercisable as of December 31, 2017 : Options Outstanding Options Exercisable Range of Exercise Prices Number of Options Weighted Average Remaining Contractual Life (years) Weighted Average Exercise Price Aggregate Intrinsic Value (in millions) Exercisable Shares Weighted Average Remaining Contractual Life (years) Weighted Average Exercise Price Aggregate Intrinsic Value (in millions) $57.28 41,685 3.37 $ 57.28 $ 1.7 41,685 3.37 $ 57.28 $ 1.7 Vested or Expected to Vest $57.28 41,685 3.37 $ 57.28 $ 1.7 The aggregate intrinsic value in the table above represents the total pretax intrinsic value all option holders would have received if they had exercised all outstanding options on December 31, 2017 . The intrinsic value is based on our closing stock price of $96.97 on December 29, 2017.

Defined Contribution Plan

Defined Contribution Plan	12 Months Ended
	Dec. 31, 2017
Defined Contribution Plan [Abstract]
Defined Contribution Plan	Defined Contribution Plan We sponsor a defined contribution 401(k) plan, which allows our U.S.-based employees to voluntarily contribute pre-tax dollars up to a maximum amount allowable by the U.S. Internal Revenue Service. In 2017 , 2016 , and 2015 , we made matching contributions to our 401(k) plan in the United States in an amount equal to 75 cents for every dollar of an employee's contribution, up to a maximum of 7% of the employee's compensation in the pay period. The following table summarizes our matching contributions: (in millions) 2017 2016 2015 401(k) matching contributions $ 10.4 $ 9.0 $ 8.3

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income Tax Expense and Effective Tax Rate The following table shows our income tax expense and our effective tax rate for the years ended December 31, 2017 , 2016 , and 2015 : (in millions) 2017 2016 2015 Income before income taxes and equity in net income (loss) of unconsolidated entities $ 181.1 $ 224.9 $ 193.7 Equity in net income (loss) of unconsolidated entities (1.3 ) (0.2 ) 1.8 Net income attributable to the noncontrolling interest — — (0.2 ) Total $ 179.8 $ 224.7 $ 195.3 Income tax expense $ 42.9 $ 63.7 $ 62.7 Effective tax rate 23.9 % 28.3 % 32.1 % On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act ("Tax Reform Act"). The legislation significantly changes U.S. tax law by, among other things, lowering corporate income tax rates, changing to a territorial tax system and imposing a transitional tax on deemed repatriated earnings of foreign subsidiaries. The Tax Reform Act permanently reduces the U.S. corporate income tax rate from a maximum of 35% to a flat 21% rate, effective January 1, 2018. On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 ("SAB 118") to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Reform Act. We have recognized the provisional tax impacts related to the changes under the Tax Reform Act and have included these amounts in our consolidated financial statements for the year ended December 31, 2017. The ultimate impact may differ from these provisional amounts, possibly materially, due to, among other things, additional analysis, changes in interpretations and assumptions that we have made, additional regulatory guidance that may be issued, and actions that we may take as a result of the Tax Reform Act. The accounting is expected to be complete when our 2017 U.S. corporate income tax return is filed in 2018. We use the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to reverse. As a result of the reduction in the U.S. corporate income tax rate from 35% to 21% under the Tax Reform Act, we revalued our ending net deferred tax liabilities at December 31, 2017 and recognized a provisional $14.7 million tax benefit in our Consolidated Statement of Income for the year ended December 31, 2017. With respect to the transitional tax related to the change to a territorial system, the Tax Reform Act provided for a one-time deemed mandatory repatriation of post-1986 undistributed foreign subsidiary earnings and profits ("E&P") through the year ended December 31, 2017. We had an estimated $183.7 million of undistributed foreign E&P subject to the deemed mandatory repatriation. After the utilization of corresponding tax credits, we have recorded a provisional tax charge of $7.5 million on the deemed mandatory repatriation of earnings of our foreign subsidiaries payable over 8 years. We have also recorded a provisional reduction of a deferred tax liability of $6.4 million previously recorded for our foreign equity method investments. The transitional tax charge of $7.5 million offset by the reduction of the $6.4 million deferred tax liability results in a net tax expense of $1.1 million on the deemed mandatory repatriation of earnings of our foreign affiliates. We are continuing to assess our indefinite reinvestment assertion as a result of the Tax Reform Act. We have recorded a provisional estimate of deferred taxes in the amount of $3.0 million for foreign withholding taxes that would be due upon remittance of dividends from certain of our foreign affiliates. We are still evaluating whether to change our overall indefinite reinvestment assertion in light of the Tax Reform Act and consider our conclusion to be incomplete under SAB 118. Accordingly, we consider that most of our remaining foreign outside basis differences to be indefinitely reinvested. Accordingly, we have not recorded deferred taxes on those outside basis differences. As part of our continuing evaluation, we will need to gather additional information to compute outside basis differences for our foreign affiliates in order to assess whether any new deferred taxes should be recorded. We will also need to account for any prospective interpretive guidance issued on the Tax Reform Act as part of our evaluation. If we subsequently change our assertion during the measurement period allowed under SAB 118, we will account for a change in assertion as part of our accounting for the Tax Reform Act. The Tax Reform Act also establishes other provisions that may affect our 2018 results, including but not limited to, the creation of a new minimum tax called the base erosion anti-abuse tax (BEAT); a new provision that taxes U.S. allocated expenses (e.g. interest and general administrative expenses) as well as currently taxes certain income from foreign operations (Global Intangible Low-Tax Income, or "GILTI"); a new limitation on deductible interest expense; the repeal of the domestic manufacturing deduction; and limitations on the deductibility of certain employee compensation. The BEAT provisions in the Tax Reform Act eliminate the deduction of certain base-erosion payments made to related foreign corporations and impose a minimum tax if greater than regular tax. We are still evaluating the BEAT provisions which are applicable after December 31, 2017. While the Tax Reform Act generally eliminates U.S. federal income tax on dividends from foreign subsidiaries going forward, certain income earned by certain subsidiaries may be included in our U.S. taxable income under the new GILTI inclusion rules (as a result of U.S. expense allocation rules). Because of the complexity of the new GILTI tax rules, we are continuing to evaluate this provision of the Tax Reform Act and the application of U.S. GAAP. Under U.S. GAAP, we are allowed to make an accounting policy election and either treat taxes due from GILTI as a current-period expense when they are incurred or factor such amounts into our measurement of deferred taxes. Our selection of an accounting policy with respect to the new GILTI rules will depend in part on analyzing our global income to determine whether we expect to have future U.S. inclusions in taxable income related to GILTI, and if so, what the impact is expected to be. We have not yet computed a reasonable estimate of the effect of this provision, and therefore, we have not made a policy decision regarding whether to record deferred taxes related to GILTI nor have we made any adjustments related to GILTI tax in our year-end financial statements. The following table reconciles our income tax expense at the U.S. federal income tax rate of 35% to income tax expense as recorded: 2017 2016 2015 (in millions, except percentages) Amount % Amount % Amount % Income tax expense at U.S. federal rate $ 63.0 35.0 % $ 78.6 35.0 % $ 68.4 35.0 % State income taxes, net of federal income tax benefit 3.0 1.7 4.5 2.0 6.6 3.4 Change in U.S. tax rate (14.7 ) (8.2 ) — — — — Deemed mandatory repatriation 7.5 4.2 — — — — Reduction of deferred tax liabilities for foreign equity method investments (6.4 ) (3.6 ) — — — — Withholding tax - repatriation 3.0 1.7 — — — — Stock-based compensation activity 0.3 0.2 (0.6 ) (0.3 ) 0.4 0.2 Equity in net income of unconsolidated subsidiaries (including holding gains upon acquisition) 1.2 0.7 (12.1 ) (5.4 ) — — Book gain over tax gain on sale of HelloWallet (6.8 ) (3.8 ) — — — — Net change in valuation allowance related to non-U.S. deferred tax assets, primarily net operating losses 0.1 0.1 (0.1 ) — (2.0 ) (1.0 ) Difference between U.S. federal statutory and foreign tax rates (5.2 ) (2.9 ) (5.3 ) (2.4 ) (4.4 ) (2.3 ) Change in unrecognized tax benefits 1.2 0.7 2.6 1.2 (1.4 ) (0.7 ) Credits and incentives (3.7 ) (2.1 ) (3.7 ) (1.6 ) (5.1 ) (2.6 ) Other - net 0.4 0.2 (0.2 ) (0.1 ) 0.2 0.1 Total income tax expense $ 42.9 23.9 % $ 63.7 28.3 % $ 62.7 32.1 % Income tax expense consists of the following: Year ended December 31 (in millions) 2017 2016 2015 Current tax expense: U.S. Federal $ 40.3 $ 42.8 $ 42.8 State 6.6 6.5 8.3 Non-U.S. 9.9 9.7 8.7 Current tax expense 56.8 59.0 59.8 Deferred tax expense (benefit): U.S. Federal (10.9 ) 5.1 4.3 State (1.9 ) 0.4 1.8 Non-U.S. (1.1 ) (0.8 ) (3.2 ) Deferred tax expense, net (13.9 ) 4.7 2.9 Income tax expense $ 42.9 $ 63.7 $ 62.7 The following table provides our income before income taxes and equity in net income (loss) of unconsolidated entities, generated by our U.S. and non-U.S. operations: Year ended December 31 (in millions) 2017 2016 2015 U.S. $ 143.5 $ 186.5 $ 160.6 Non-U.S. 37.6 38.4 33.1 Income before income taxes and equity in net income (loss) of unconsolidated entities $ 181.1 $ 224.9 $ 193.7 Deferred Tax Assets and Liabilities We recognize deferred income taxes for the temporary differences between the carrying amount of assets and liabilities for financial statement purposes and their tax basis. The tax effects of the temporary differences that give rise to the deferred income tax assets and liabilities are as follows: As of December 31 (in millions) 2017 2016 Deferred tax assets: Stock-based compensation expense $ 3.7 $ 2.6 Accrued liabilities 14.2 19.0 Deferred revenue 3.5 5.1 Net operating loss carryforwards - U.S. federal and state 1.9 12.9 Net operating loss carryforwards - Non-U.S. 3.1 3.0 Credits and incentive carryforwards 0.3 0.6 Deferred royalty revenue 0.2 0.3 Allowance for doubtful accounts 1.1 1.2 Deferred rent 6.2 10.3 Other 0.3 — Total deferred tax assets 34.5 55.0 Deferred tax liabilities: Acquired intangible assets (18.6 ) (34.3 ) Property, equipment, and capitalized software (24.6 ) (37.6 ) Unrealized exchange gains, net (0.6 ) (0.1 ) Prepaid expenses (3.9 ) (5.3 ) Investments in unconsolidated entities (5.4 ) (14.0 ) Withholding tax - foreign dividends (3.0 ) — Other — (0.3 ) Total deferred tax liabilities (56.1 ) (91.6 ) Net deferred tax liability before valuation allowance (21.6 ) (36.6 ) Valuation allowance (2.0 ) (1.6 ) Deferred tax liability, net $ (23.6 ) $ (38.2 ) The deferred tax assets and liabilities are presented in our Consolidated Balance Sheets as follows: As of December 31 (in millions) 2017 2016 Deferred tax liability, net $ (23.6 ) $ (38.2 ) The following table summarizes our U.S. net operating loss (NOL) carryforwards: As of December 31 (in millions) 2017 2016 Expiration Dates Expiration Dates U.S. federal NOLs subject to expiration dates $ 9.1 2023-2036 $ 36.9 2023-2036 The net decrease in the U.S. federal NOL carryforwards as of December 31, 2017 compared with 2016 primarily reflects the utilization of U.S. federal NOLs. We have not recorded a valuation allowance against the U.S. federal NOLs of $9.1 million because we expect the benefit of the U.S. federal NOLs to be fully utilized before expiration. The following table summarizes our NOL carryforwards for our non-U.S. operations: As of December 31 (in millions) 2017 2016 Non-U.S. NOLs subject to expiration dates from 2019 through 2037 $ 5.7 $ 3.8 Non-U.S. NOLs with no expiration date 9.1 10.8 Total $ 14.8 $ 14.6 Non-U.S. NOLs not subject to valuation allowances $ 5.4 $ 6.8 The change in non-U.S. NOL carryforwards as of December 31, 2017 compared with 2016 primarily reflects the use of NOL carryforwards offset by NOLs generated. In assessing the realizability of our deferred tax assets, we consider whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. We have recorded a valuation allowance against all but approximately $5.4 million of the non-U.S. NOLs, reflecting the likelihood that the benefit of these NOLs will not be realized. Uncertain Tax Positions We conduct business globally and as a result, we file income tax returns in U.S. federal, state, local, and foreign jurisdictions. In the normal course of business, we are subject to examination by tax authorities throughout the world. The open tax years for our U.S. Federal tax returns and most state tax returns include the years 2008 to the present. We are currently under audit by federal, state and local tax authorities in the United States as well as tax authorities in certain non-U.S. jurisdictions. It is likely that the examination phase of some of these U.S. federal, state, local, and non-U.S. audits will conclude in 2018 . It is not possible to estimate the effect of current audits on previously recorded unrecognized tax benefits. As of December 31, 2017 , our Consolidated Balance Sheet included a current liability of $8.7 million and a non-current liability of $7.0 million for unrecognized tax benefits. As of December 31, 2016 , our Consolidated Balance Sheet included a current liability of $8.9 million and a non-current liability of $5.4 million for unrecognized tax benefits. These amounts include interest and penalties, less any associated tax benefits. The table below reconciles the beginning and ending amount of the gross unrecognized tax benefits as follows: (in millions) 2017 2016 Gross unrecognized tax benefits - beginning of the year $ 18.4 $ 14.5 Increases as a result of tax positions taken during a prior-year period 1.4 2.2 Decreases as a result of tax positions taken during a prior-year period (0.4 ) (0.1 ) Increases as a result of tax positions taken during the current period 1.9 2.4 Decreases relating to settlements with tax authorities — — Reductions as a result of lapse of the applicable statute of limitations (2.6 ) (0.6 ) Gross unrecognized tax benefits - end of the year $ 18.7 $ 18.4 In 2017 , we recorded a net increase of $2.9 million of gross unrecognized tax benefits before settlements and lapses of statutes of limitations, of which $2.9 million increased our income tax expense by $3.1 million . In addition, we reduced our unrecognized tax benefits by $2.6 million for settlements and lapses of statutes of limitations, of which $2.6 million decreased our income tax expense by $2.2 million . As of December 31, 2017 , we had $18.7 million of gross unrecognized tax benefits, of which $15.0 million , if recognized, would reduce our effective income tax rate and decrease our income tax expense by $14.4 million . We record interest and penalties related to uncertain tax positions as part of our income tax expense. The following table summarizes our gross liability for interest and penalties: As of December 31 (in millions) 2017 2016 Liabilities for interest and penalties $ 1.7 $ 1.6 We recorded the increase in the liabilities for penalties and interest, net of any tax benefits, to income tax expense in our Consolidated Statement of Income in 2017 .

Contingencies

Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Contingencies Michael D. Green In August 2017, Michael D. Green, individually and purportedly on behalf of all others similarly situated, filed a complaint in the United States District Court for the Northern District of Illinois. The complaint names as defendants Morningstar, Inc., Prudential Investment Management Services LLC, and Prudential Retirement Insurance and Annuity Co., and contains one count alleging violation of the Racketeer Influenced and Corrupt Organizations Act (RICO). Plaintiff, a participant in a pension plan, alleges that the defendants engaged in concerted racketeering actions to steer plan participants into high-cost investments that pay unwarranted fees to the defendants. The complaint seeks unspecified compensatory damages for plaintiff and the members of the putative class, treble damages, injunctive relief, costs, and attorneys’ fees. Morningstar has filed a motion to dismiss the complaint, which is fully briefed and under advisement by the court. Although Morningstar is vigorously contesting the claim asserted, we cannot predict the outcome of the proceeding. Other Matters We are involved from time to time in legal proceedings and litigation that arise in the normal course of our business. While it is difficult to predict the outcome of any particular proceeding, we do not believe the result of any of these matters will have a material adverse effect on our business, operating results, or financial position.

Share Repurchase Program

Share Repurchase Program	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Quarterly Dividend and Share Repurchase Programs	Share Repurchase Program We had an ongoing authorization, originally approved by our board of directors in September 2010 and subsequently amended, to repurchase up to $1.0 billion in shares of our outstanding common stock. The authorization expired on December 31, 2017. As of December 31, 2017 , we had repurchased a total of 10,574,857 shares for $714.8 million under this authorization, leaving no shares available for future repurchases as the plan expired on December 31, 2017. On December 8, 2017, the board of directors approved a new share repurchase program that authorizes the company to repurchase up to $500.0 million in shares of the company's outstanding common stock, effective January 1, 2018. The authorization expires on December 31, 2020. We may repurchase shares from time to time at prevailing market prices on the open market or in private transactions in amounts that we deem appropriate.

Recently Issued Accounting Pron

Recently Issued Accounting Pronouncements	12 Months Ended
	Dec. 31, 2017
Accounting Changes and Error Corrections [Abstract]
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements On May 28, 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers , which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The ASU will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective. The original effective date for ASU No. 2014-09 would have required us to adopt it beginning on January 1, 2017. In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers — Deferral of the Effective Date , which defers the effective date of ASU No. 2014-09 for one year and permits early adoption as early as the original effective date of ASU No. 2014-09. We elected the deferral, and the new standard is effective for us on January 1, 2018. We have obtained an understanding of ASU No. 2014-09 and have substantially completed our analysis of the impact of the new standard on our financial results. We have completed a high-level assessment of the attributes within our contracts for our major products and services, and we have assessed the impacts to our internal processes, control environment, and disclosures. We have determined that the adoption of ASU No. 2014-09 will not result in a material change to the timing of when revenue is recognized and we intend to retain similar accounting treatment used to recognize revenue under current practices. We have identified that there will be certain changes in accounting treatment related to delivery of third-party content (principal vs. agent) and costs to obtain contracts (e.g., sales commissions). The change related to delivery of third-party content (principal vs. agent) is expected to result in no impact on our consolidated operating income; however it will result in a increase in both revenue and cost of revenue versus prior periods of approximately $6 million to $7 million as revenue will be recognized on a gross rather than net basis for certain arrangements. The change related to the capitalization of cost to obtain contracts is expected to result in an increase to retained earnings of approximately $25 million to $30 million for commission expenses which were previously expensed. We expected to amortize this adjustment over a period not to exceed three years and expect 2018 commission expense resulting from this change will range between $14 million and $16 million . Additionally, in 2018 we will expense any discretionary payments made under our commission plans as well as pro-rata portions of any new commission amounts paid in 2018. The standard allows for both retrospective and modified retrospective methods of adoption. We plan to adopt using the modified retrospective transition method applied to those contracts which were not completed as of January 1, 2018. Upon adoption, we will recognize the cumulative effect of adopting this guidance as an adjustment to our opening balance of retained earnings as noted above. Prior periods will not be retrospectively adjusted and we will discuss the comparability of these adjustments within our 2018 results against the prior periods. We are continuing to evaluate the effect that ASU No. 2014-09 will have on our consolidated financial statement presentation and related disclosures. We expect expanded disclosures related to the revenue recognized in the reporting period that was included in the contract liability (i.e., deferred revenue) balance at the beginning of the period. We also plan to provide additional disclosures on our unsatisfied performance obligations at the end of the period and expected timing of when that contract liability will be recognized into revenue. On March 17, 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers: Principal versus Agent Considerations (Reporting Revenue Gross versus Net) , which provides guidance on assessing whether an entity is a principal or an agent in a revenue transaction and whether an entity reports revenue on a gross or net basis. On April 14, 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing , which provides guidance on identifying performance obligations and accounting for licenses of intellectual property. On May 6, 2016, the FASB issued ASU No. 2016-11, Revenue Recognition and Derivatives and Hedging: Rescission of SEC guidance because of ASU No. 2014-09 and ASU No. 2014-16 pursuant to staff announcements at the March 3, 2016 EITF Meeting , which rescinds the following SEC Staff Observer comments from ASC 605, Revenue Recognition , upon an entity's early adoption of ASC 606, Revenue from Contracts with Customers : Revenue and expense recognition for freight services in process, accounting for shipping and handling fees and costs, and accounting for consideration given by a vendor to a customer (including a reseller of the vendor's products). On May 9, 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients , which makes narrow-scope amendments to ASU No. 2014-09 and provides practical expedients to simplify the transition to the new standard and clarify certain aspects of the standard. On December 21, 2016, the FASB issued ASU No. 2016-20, Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers , which makes narrow-scope amendments to ASU No. 2014-09. The effective date and transition requirements for ASU No. 2016-08, ASU No. 2016-10, ASU No. 2016-11, ASU No. 2016-12, and ASU No. 2016-20 are the same as the effective date and transition requirements of ASU No. 2014-09. We are evaluating the effect that ASU No. 2016-08, ASU No. 2016-10, ASU No. 2016-11, ASU No. 2016-12, and ASU No. 2016-20 will have on our consolidated financial statements and related disclosures. On February 25, 2016, the FASB issued ASU No. 2016-02, Leases , which will require lessees to recognize almost all leases on their balance sheet as a right-of-use asset and a lease liability. The new standard is effective for us on January 1, 2019. The new standard must be adopted using a modified retrospective transition and provides for certain practical expedients. Transition will require application of the new guidance at the beginning of the earliest comparative period presented. We are evaluating the effect that ASU No. 2016-02 will have on our consolidated financial statements and related disclosures. On August 26, 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments , which reduces diversity in practice of how certain transactions are classified in the statement of cash flows. The new guidance clarifies the classification of cash activities related to debt prepayment or debt extinguishment costs, settlement of zero-coupon debt instruments, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate and bank-owned life insurance policies, distributions received from equity-method investments, and beneficial interests in securitization transactions. The guidance also describes a predominance principle in which cash flows with aspects of more than one class that cannot be separated should be classified based on the activity that is likely to be the predominant source or use of cash flow. The new standard is effective for us on January 1, 2018. Early adoption is permitted, including adoption in an interim period, but requires all elements of the amendments to be adopted at once rather than individually. The new standard must be adopted using a retrospective transition method. We are evaluating the effect that ASU No. 2016-15 will have on our consolidated financial statements and related disclosures. On January 5, 2017, the FASB issued ASU No. 2017-01, Business Combinations: Clarifying the Definition of a Business, which revises the definition of a business. When substantially all of the fair value of gross assets acquired is concentrated in a single asset (or a group of similar assets), the assets acquired would not represent a business. To be considered a business, an acquisition would have to include an input and a substantive process that together significantly contribute to the ability to create outputs. The new guidance provides a framework to evaluate when an input and substantive process are present (including for early-stage companies that have not generated outputs). To be a business without outputs, there will now need to be an organized workforce. The new guidance also narrows the definition of the term outputs to be consistent with how it is described in Topic 606 , Revenue from Contracts with Customers . The new standard is effective for us on January 1, 2018. Early adoption is permitted. We are evaluating the effect that ASU No. 2017-01 will have on our consolidated financial statements and related disclosures. On January 26, 2017, the FASB issued ASU No. 2017-04, Intangibles — Goodwill and Other , which simplifies the accounting for goodwill impairment. The guidance removes Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. A goodwill impairment will now be the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. All other goodwill impairment guidance will remain largely unchanged. Entities will continue to have the option to perform a qualitative assessment to determine if a quantitative impairment test is necessary. The same one-step impairment test will be applied to goodwill at all reporting units, even those with zero or negative carrying amounts. Entities will be required to disclose the amount of goodwill at reporting units with zero or negative carrying amounts. The new standard is effective for us on January 1, 2020. The new standard should be applied prospectively. Early adoption is permitted for any impairment tests performed after January 1, 2017. We are evaluating the effect that ASU No. 2017-04 will have on our consolidated financial statements and related disclosures. On May 10, 2017, the FASB issued ASU No. 2017-09, Compensation—Stock Compensation: Scope of Modification Accounting , which clarifies when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new guidance, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. The new standard is effective for us on January 1, 2018. The new standard should be applied prospectively. Early adoption is permitted. We are evaluating the effect that ASU No. 2017-09 will have on our consolidated financial statements and related disclosures.

Selected Quarterly Financial Da

Selected Quarterly Financial Data	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data	Selected Quarterly Financial Data (unaudited) 2016 2017 (in millions except per share amounts) Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Revenue $ 192.1 $ 198.2 $ 196.1 $ 212.2 $ 209.5 $ 229.2 $ 229.9 $ 243.1 Total operating expense 149.8 153.8 151.9 162.3 181.1 183.2 177.1 200.5 Operating income 42.3 44.4 44.2 49.9 28.4 46.0 52.8 42.6 Non-operating income (expense), net 0.5 3.0 2.1 38.5 (1) (1.3 ) 15.3 (2) (2.0 ) (0.7 ) Income before income taxes and equity in net income (loss) of unconsolidated entities 42.8 47.4 46.3 88.4 27.1 61.3 50.8 41.9 Equity in net income (loss) of unconsolidated entities 0.5 (0.2 ) 0.4 (0.9 ) (0.8 ) (0.2 ) — (0.3 ) Income tax expense 14.6 15.4 16.5 17.2 8.3 15.0 16.9 2.7 (3) Consolidated net income $ 28.7 $ 31.8 $ 30.2 $ 70.3 $ 18.0 $ 46.1 $ 33.9 $ 38.9 Net income per share: Basic $ 0.67 $ 0.74 $ 0.70 $ 1.63 $ 0.42 $ 1.07 $ 0.80 $ 0.91 Diluted $ 0.67 $ 0.73 $ 0.70 $ 1.63 $ 0.42 $ 1.07 $ 0.79 $ 0.91 Dividends per common share: Dividends declared per common share $ 0.22 $ 0.22 $ 0.22 $ 0.23 $ 0.23 $ 0.23 $ — $ 0.48 Dividends paid per common share $ 0.22 $ 0.22 $ 0.22 $ 0.22 $ 0.23 $ 0.23 $ 0.23 $ 0.23 Weighted average shares outstanding: Basic 43.0 43.0 43.1 43.0 42.9 42.9 42.5 42.5 Diluted 43.1 43.3 43.3 43.2 43.2 43.1 42.8 42.9 (1) Non-operating income in the fourth quarter of 2016 included a $37.1 million holding gain related to the purchase of the remaining ownership interest in PitchBook, which was previously a minority investment. (2) Non-operating income in the second quarter of 2017 included a $17.5 million gain on the sale of HelloWallet. We recorded an immaterial adjustment to this gain in the fourth quarter of 2017. (3) Tax expense in the fourth quarter of 2017 includes a net benefit of $10.6 million related to the impact of the Tax Reform Act.

Summary of Significant Accoun27

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation. We conduct our business operations through wholly owned or majority-owned operating subsidiaries. The accompanying consolidated financial statements include the accounts of Morningstar, Inc. and our subsidiaries. We consolidate assets, liabilities, and results of operations of subsidiaries in which we have a controlling interest and eliminate all significant intercompany accounts and transactions. We account and report the noncontrolling (minority) interest in our Consolidated Financial Statements in accordance with FASB ASC 810, Consolidation . A noncontrolling interest is the portion of equity (net assets) in a subsidiary not attributable, directly or indirectly, to the parent company. We report the noncontrolling interest in our Consolidated Balance Sheet within equity separate from the shareholders' equity attributable to Morningstar, Inc. In addition, we present the net income (loss) and comprehensive income (loss) attributable to Morningstar, Inc.'s shareholders and the noncontrolling interest in our Consolidated Statements of Income, Consolidated Statements of Comprehensive Income, and Consolidated Statements of Equity. We account for investments in entities in which we exercise significant influence, but do not control, using the equity method. As part of our investment management operations, we manage certain funds outside of the United States that are considered variable interest entities. For the majority of these variable interest entities, we do not have a variable interest in them. In cases where we do have a variable interest, we are not the primary beneficiary. Accordingly, we do not consolidate any of these variable interest entities.
Use of Estimates	Use of Estimates. The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires us to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, and expenses during the reporting period. Actual results may differ from these estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents. Cash and cash equivalents consists of cash and investments with original maturities of three months or less. We state them at cost, which approximates fair value. We state the portion of our cash equivalents that are invested in money market funds at fair value, as these funds are actively traded and have quoted market prices.
Investments	Investments. We account for our investments in accordance with FASB ASC 320, Investments—Debt and Equity Securities. We classify our investments into three categories: held-to-maturity, trading, and available-for-sale. • Held-to-maturity: We classify certain investments, primarily certificates of deposit, as held-to-maturity securities, based on our intent and ability to hold these securities to maturity. We record held-to-maturity investments at amortized cost in our Consolidated Balance Sheets. • Trading: We classify certain other investments, primarily equity securities, as trading securities as these relate mainly to investments tracking the strategies of our newsletter portfolios. We include realized and unrealized gains and losses associated with these investments as a component of our operating income in our Consolidated Statements of Income. We record these securities at their fair value in our Consolidated Balance Sheets. • Available-for-sale: Investments not considered held-to-maturity or trading securities are classified as available-for-sale securities. Available-for-sale securities primarily consist of equity securities, exchange-traded funds, and mutual funds. We report unrealized gains and losses for available-for-sale securities as other comprehensive income (loss), net of related income taxes. We record these securities at their fair value in our Consolidated Balance Sheets.
Concentration of Credit Risk	Concentration of Credit Risk. No single customer is large enough to pose a significant credit risk to our operations or financial condition. For the years ended December 31, 2017 , 2016 , and 2015 , no single customer represented 5% or more of our consolidated revenue. If receivables from our customers become delinquent, we begin a collections process. We maintain an allowance for doubtful accounts based on our estimate of the probable losses of accounts receivable.
Property, Equipment, and Depreciation	Property, Equipment, and Depreciation. We state property and equipment at historical cost, net of accumulated depreciation. We depreciate property and equipment primarily using the straight-line method based on the useful life of the asset, which generally is three years. We amortize leasehold improvements over the lease term or their useful lives, whichever is shorter.
Computer Software and Internal Product Development Costs	Computer Software and Internal Product Development Costs. We capitalize certain costs in accordance with FASB ASC 350-40, Internal-Use Software , FASB ASC 350-50, Website Development Costs, and FASB ASC 985, Software . Internal product development costs mainly consist of employee costs for developing new web-based products and certain major enhancements of existing products. We amortize these costs on a straight-line basis over the estimated economic life, which is generally three to five years. We include capitalized software development costs related to projects that have not been placed into service in our construction in progress balance.
Business Combinations	Business Combinations . When we make acquisitions, we allocate the purchase price to the assets acquired, liabilities assumed, and goodwill. We follow FASB ASC 805, Business Combinations . We recognize and measure the fair value of the acquired operation as a whole, as well as the assets acquired and liabilities assumed, at their full fair values as of the date we obtain control, regardless of the percentage ownership in the acquired operation or how the acquisition was achieved. We expense direct costs related to the business combination, such as advisory, accounting, legal, valuation, and other professional fees, as incurred. We recognize restructuring costs, including severance and relocation for employees of the acquired entity, as post-combination expenses unless the target entity meets the criteria of FASB ASC 420, Exit or Disposal Cost Obligations , on the acquisition date. As part of the purchase price allocation, we follow the requirements of FASB ASC 740, Income Taxes. This includes establishing deferred tax assets or liabilities reflecting the difference between the values assigned for financial statement purposes and income tax purposes. In certain acquisitions, the goodwill resulting from the purchase price allocation may not be deductible for income tax purposes. FASB ASC 740 prohibits recognition of a deferred tax asset or liability for temporary differences in goodwill if goodwill is not amortizable and deductible for tax purposes.
Goodwill	Goodwill . Changes in the carrying amount of our recorded goodwill are mainly the result of business acquisitions, divestitures, and the effect of foreign currency translations. In accordance with FASB ASC 350, Intangibles—Goodwill and Other , we do not amortize goodwill; instead, goodwill is subject to an impairment test annually, or whenever indicators of impairment exist. An impairment would occur if the carrying amount of a reporting unit exceeded the fair value of that reporting unit. We performed annual impairment reviews in the fourth quarter of 2017 and 2016 . We did not record any impairment losses in 2017 and 2016 .
Intangible Assets	Intangible Assets. We amortize intangible assets using the straight-line method over their estimated useful lives, which range from one to 25 years. We have no intangible assets with indefinite useful lives. In accordance with FASB ASC 360-10-35, Subsequent Measurement—Impairment or Disposal of Long-Lived Assets , we review intangible assets for impairment whenever events or changes in circumstances indicate that the carrying value may not be recoverable. If the value of future undiscounted cash flows is less than the carrying amount of an asset group, we record an impairment loss based on the excess of the carrying amount over the fair value of the asset group. We did not record any impairment losses in 2017 and 2016 .
Revenue Recognition	Revenue Recognition. We recognize revenue in accordance with SEC SAB Topic 13, Revenue Recognition , ASC 605-25, Revenue Recognition: Multiple Element Arrangements , and ASC 985-605, Software: Revenue Recognition . We recognize revenue when all of the following conditions are met: • There is persuasive evidence of an arrangement, as evidenced by a signed contract; • Delivery of our products and services has taken place. If arrangements include an acceptance provision, we generally begin recognizing revenue when we receive customer acceptance; • The amount of fees to be paid by the customer is fixed or determinable; and • The collectibility of the fees is reasonably assured. We generate revenue through sales of Morningstar Data, Morningstar Advisor Workstation (including Morningstar Office), Morningstar Direct, Morningstar Research, Premium Membership subscriptions for Morningstar.com, our structured credit ratings offerings, and a variety of other investment-related products and services. We generally structure the revenue agreements for these offerings as licenses or subscriptions. We recognize revenue from licenses and subscription sales ratably as we deliver the product or service and over the service obligation period defined by the terms of the customer contract. For new-issue ratings and analysis for commercial mortgage-backed securities (CMBS), residential mortgage-backed securities (RMBS), other asset-backed securities (ABS), and corporate and financial institutions, we charge asset-based fees that are paid by the issuer on the rated balance of the transaction and recognize the revenue immediately upon issuance. We also generate revenue from Internet advertising, primarily from “impression-based” contracts. For advertisers who use our cost-per-impression pricing, we charge fees each time we display their ads on our site. Our Investment Management business includes a broad range of services. Pricing for consulting services is based on the scope of work and the level of service provided and includes asset-based fees for work we perform that involves investment management or acting as a subadvisor to investment portfolios. In arrangements that involve asset-based fees, we generally invoice clients quarterly in arrears based on average assets for the quarter. We recognize asset-based fees once the fees are fixed or determinable assuming all other revenue recognition criteria are met. Our Workplace Solutions offerings help retirement plan participants plan and invest for retirement. We offer these services both through retirement plan providers (typically third-party asset management companies that provide administrative and record-keeping services) and directly to plan sponsors (employers that offer retirement plans to their employees). For our Workplace Solutions offerings, we provide both a hosted solution as well as proprietary installed software advice solution. Clients can integrate the installed customized software into their existing systems to help investors accumulate wealth, transition into retirement, and manage income during retirement. The revenue arrangements for Workplace Solutions generally extend over multiple years. Our contracts may include one-time setup fees, implementation fees, technology licensing and maintenance fees, asset-based fees for managed retirement accounts, fixed and variable fees for advice and guidance, or a combination of these fee structures. Upon customer acceptance, we recognize revenue ratably over the term of the agreement. We recognize asset-based fees and variable fees in excess of any minimum once the value is fixed or determinable. Some of our revenue arrangements combine multiple products and services. These products and services may be provided at different points in time or over different time periods within the same arrangement. We allocate fees to the separate deliverables based on the deliverables’ relative selling price, which is generally based on the price we charge when the same deliverable is sold separately. We record taxes imposed on revenue-producing transactions (such as sales, use, value-added, and some excise taxes) on a net basis; therefore, we exclude such taxes from revenue in our Consolidated Statements of Income. Deferred revenue represents the portion of licenses or subscriptions billed or collected in advance of the service being provided which we expect to recognize as revenue in future periods. Certain arrangements may have cancellation or refund provisions. If we make a refund, it typically reflects the amount collected from a customer for which we have not yet provided services. The refund therefore results in a reduction of deferred revenue.
Sales Commissions	Sales Commissions. Through December 31, 2013, we paid sales commissions based on a formula driven by the total contract value of sales opportunities closed, with any subsequent adjustments (such as clawbacks for contract cancellations) reflected in future commission payouts. We considered the corresponding commission expense an incremental direct acquisition cost and treated it as a deferred charge, which we expensed over the term of the underlying sales contracts. In the first quarter of 2014, we modified our sales incentive plan. The revised plan is based on a combination of net new sales and specific business objectives not solely tied to revenue growth. Because of this new structure and the discretion involved in determining the related incentives, we started expensing sales commissions as incurred instead of amortizing them over the contract terms. However, we continued to amortize the deferred charge capitalized in connection with sales commissions paid in 2013 and previous periods as part of the previous incentive plan. This amortization added $0.2 million , $0.6 million , and $3.5 million of sales commission cost in 2017, 2016, and 2015, respectively.
Advertising Costs	Advertising Costs. Advertising costs include expenses incurred for various print and Internet ads, search engine fees, and direct mail campaigns. We expense advertising costs as incurred.
Stock-Based Compensation Expense	Stock-Based Compensation Expense. We account for our stock-based compensation expense in accordance with FASB ASC 718, Compensation—Stock Compensation . Our stock-based compensation expense reflects grants of restricted stock units, restricted stock, performance share awards, market stock units, and stock options. We measure the fair value of our restricted stock units, restricted stock, and performance share awards on the date of grant based on the closing market price of Morningstar's common stock on the day prior to grant. For market stock units, we estimate the fair value of the awards using a Monte Carlo valuation model. For stock options, we estimate the fair value of our stock options on the date of grant using a Black-Scholes option-pricing model. We amortize the fair values to stock-based compensation expense, net of estimated forfeitures, ratably over the vesting period. We estimate expected forfeitures of all employee stock-based awards and recognize compensation cost only for those awards expected to vest. We determine forfeiture rates based on historical experience and adjust the estimated forfeitures to actual forfeiture experience as needed.
Liability for Sabbatical Leave	Liability for Sabbatical Leave. In some of our operations, we offer employees a sabbatical leave. Although the sabbatical policy varies by region, Morningstar's full-time employees are generally eligible for six weeks of paid time off after four years of continuous service. We account for our sabbatical liability in accordance with FASB ASC 710-10-25 , Compensated Absences . We record a liability for employees' sabbatical benefits over the period employees earn the right for sabbatical leave and include this liability in Accrued Compensation in our Consolidated Balance Sheet.
Income Taxes	Income Taxes. We record deferred income taxes for the temporary differences between the carrying amount of assets and liabilities for financial statement purposes and tax purposes in accordance with FASB ASC 740, Income Taxes . FASB ASC 740 prescribes the minimum recognition threshold a tax position is required to meet before being recognized in the financial statements. It also provides guidance on derecognition, measurement, classification, interest and penalties, accounting in interim periods, and disclosure for uncertain tax positions. We recognize interest and penalties related to unrecognized tax benefits as part of income tax expense in our Consolidated Statements of Income. We classify liabilities related to unrecognized tax benefits as either current or long-term liabilities in our Consolidated Balance Sheet, depending on when we expect to make payment.
Fair Value Measurements	Fair Value Measurements. We follow FASB ASC 820, Fair Value Measurements . FASB ASC 820 defines fair value, establishes a framework for measuring fair value, and expands disclosures about fair value measurements. Under FASB ASC 820, fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants as of the measurement date. The standard applies whenever other standards require (or permit) assets or liabilities to be measured at fair value. The standard does not expand the use of fair value in any new circumstances and does not require any new fair value measurements. FASB ASC 820 uses a fair value hierarchy based on three broad levels of valuation inputs: • Level 1: Valuations based on quoted prices in active markets for identical assets or liabilities that the company has the ability to access. • Level 2: Valuations based on quoted prices in markets that are not active or for which all significant inputs are observable, either directly or indirectly. • Level 3: Valuations based on inputs that are unobservable and significant to the overall fair value measurement. We provide additional information about our cash equivalents and investments that are subject to valuation under FASB ASC 820 in Note 6 . We classify our investments into three categories: available-for-sale, held-to-maturity, and trading. Our investment portfolio consists of stocks, bonds, options, mutual funds, money market funds, or exchange-traded products that replicate the model portfolios and strategies created by Morningstar. These investment accounts may also include exchange-traded products where Morningstar is an index provider.
Segment Information	Segment Information We report our results in a single reportable segment, which reflects how our chief operating decision maker allocates resources and evaluates our financial results. Because we have a single reportable segment, all required financial segment information can be found directly in the Consolidated Financial Statements. The accounting policies for our reportable segment are the same as those described in Note 2 . We evaluate the performance of our reporting segment based on revenue and operating income.

Summary of Significant Accoun28

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Acronyms Used	The acronyms that appear in these Notes to our Consolidated Financial Statements refer to the following: ASC Accounting Standards Codification ASU Accounting Standards Update EITF Emerging Issues Task Force FASB Financial Accounting Standards Board SEC Securities and Exchange Commission
Summary of Depreciation for Internally Developed Software	The table below summarizes our depreciation expense related to internally developed software for the past three years: (in millions) 2017 2016 2015 Internally developed software depreciation expense $ 30.6 $ 20.0 $ 13.0
Summary of Capitalized Software Development Costs	The table below summarizes our capitalized software development costs for the past three years: (in millions) 2017 2016 2015 Capitalized software development costs $ 46.3 $ 28.2 $ 21.8
Summary of Advertising Expense	The table below summarizes our advertising expense for the past three years: (in millions) 2017 2016 2015 Advertising expense $ 7.0 $ 7.6 $ 8.3

Income Per Share (Tables)

Income Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table shows how we reconcile our net income and the number of shares used in computing basic and diluted income per share: (in millions, except per share amounts) 2017 2016 2015 Basic net income per share attributable to Morningstar, Inc.: Net income attributable to Morningstar, Inc. $ 136.9 $ 161.0 $ 132.6 Weighted average common shares outstanding 42.7 43.0 44.2 Basic net income per share attributable to Morningstar, Inc. $ 3.21 $ 3.74 $ 3.00 Diluted net income per share attributable to Morningstar, Inc.: Net income attributable to Morningstar, Inc. $ 136.9 $ 161.0 $ 132.6 Weighted average common shares outstanding 42.7 43.0 44.2 Net effect of dilutive stock options and restricted stock units 0.3 0.3 0.1 Weighted average common shares outstanding for computing diluted income per share 43.0 43.3 44.3 Diluted net income per share attributable to Morningstar, Inc. $ 3.18 $ 3.72 $ 3.00

Segment and Geographical Area30

Segment and Geographical Area Information (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas	The tables below summarize our revenue and long-lived assets by geographical area: External revenue by geographical area Year ended December 31 (in millions) 2017 2016 2015 United States $ 687.0 $ 590.5 $ 585.1 United Kingdom 64.7 61.1 64.2 Continental Europe 69.9 62.6 58.8 Australia 34.6 32.2 30.5 Canada 29.4 28.2 27.9 Asia 21.2 20.0 18.5 Other 4.9 4.0 3.8 Total International 224.7 208.1 203.7 Consolidated revenue $ 911.7 $ 798.6 $ 788.8 Long-lived assets by geographical area As of December 31 (in millions) 2017 2016 United States $ 131.9 $ 139.1 United Kingdom 6.0 6.6 Continental Europe 1.7 1.9 Australia 2.3 0.6 Canada 0.2 0.4 Asia 5.2 3.4 Other 0.1 0.1 Total International 15.5 13.0 Consolidated property, equipment, and capitalized software, net $ 147.4 $ 152.1

Investments and Fair Value Me31

Investments and Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Schedule of Investments	We classify our investment portfolio as shown below: As of December 31 (in millions) 2017 2016 Available-for-sale $ 21.5 $ 27.7 Held-to-maturity 21.9 15.7 Trading securities 1.7 1.5 Total $ 45.1 $ 44.9
Unrealized Gain (Loss) on Investments	The following table shows the cost, unrealized gains (losses), and fair values related to investments classified as available-for-sale and held-to-maturity: As of December 31, 2017 As of December 31, 2016 (in millions) Cost Unrealized Gain Unrealized Loss Fair Value Cost Unrealized Gain Unrealized Loss Fair Value Available-for-sale: Equity securities and exchange-traded funds $ 17.1 $ 2.4 $ (0.6 ) $ 18.9 $ 25.6 $ 1.3 $ (1.5 ) $ 25.4 Mutual funds 2.4 0.2 — 2.6 2.2 0.1 — 2.3 Total $ 19.5 $ 2.6 $ (0.6 ) $ 21.5 $ 27.8 $ 1.4 $ (1.5 ) $ 27.7 Held-to-maturity: Certificates of deposit $ 19.9 $ — $ — $ 19.9 $ 13.8 $ — $ — $ 13.8 Convertible note 2.0 — — 2.0 1.9 — — 1.9 Total $ 21.9 $ — $ — $ 21.9 $ 15.7 $ — $ — $ 15.7
Investments Classified by Contractual Maturity Date	The table below shows the cost and fair value of investments classified as available-for-sale and held-to-maturity based on their contractual maturities as of December 31, 2017 and December 31, 2016 . As of December 31, 2017 As of December 31, 2016 (in millions) Cost Fair Value Cost Fair Value Available-for-sale: Equity securities, exchange-traded funds, and mutual funds $ 19.5 $ 21.5 $ 27.8 $ 27.7 Total $ 19.5 $ 21.5 $ 27.8 $ 27.7 Held-to-maturity: Due in one year or less $ 19.7 $ 19.7 $ 13.8 $ 13.8 Due in one to three years 2.2 2.2 1.9 1.9 Total $ 21.9 $ 21.9 $ 15.7 $ 15.7
Schedule of Realized Gain (Loss)	The following table shows the realized gains and losses arising from sales of our investments classified as available-for-sale recorded in our Consolidated Statements of Income: (in millions) 2017 2016 2015 Realized gains $ 3.4 $ 1.6 $ 1.3 Realized losses (0.2 ) (1.0 ) (0.7 ) Realized gains, net $ 3.2 $ 0.6 $ 0.6
Unrealized Gain Loss On Trading Securities	The following table shows the net unrealized gains (losses) on trading securities as recorded in our Consolidated Statements of Income: (in millions) 2017 2016 2015 Unrealized gains (losses), net $ 0.1 $ — $ (0.8 )
Fair Value, Assets Measured on Recurring Basis	The table below shows the fair value of our assets subject to fair value measurements that are measured at fair value on a recurring basis using a fair value hierarchy: Level 1: Valuations based on quoted prices in active markets for identical assets or liabilities that we have the ability to access. Level 2: Valuations based on quoted prices in markets that are not active or for which all significant inputs are observable, either directly or indirectly. Level 3: Valuations based on inputs that are unobservable and significant to the overall fair value measurement. Fair Value Fair Value Measurements as of December 31, 2017 as of Using Fair Value Hierarchy (in millions) December 31, 2017 Level 1 Level 2 Level 3 Available-for-sale investments Equity securities and exchange-traded funds $ 18.9 $ 18.9 $ — $ — Mutual funds 2.6 2.6 — — Trading securities 1.7 1.7 — — Cash equivalents 0.5 0.5 — — Total $ 23.7 $ 23.7 $ — $ — Fair Value Fair Value Measurements as of December 31, 2016 as of Using Fair Value Hierarchy (in millions) December 31, 2016 Level 1 Level 2 Level 3 Available-for-sale investments Equity securities and exchange-traded funds $ 25.4 $ 25.4 $ — $ — Mutual funds 2.3 2.3 — — Trading securities 1.5 1.5 — — Cash equivalents 0.2 0.2 — — Total $ 29.4 $ 29.4 $ — $ —

Acquisitions, Goodwill, and O32

Acquisitions, Goodwill, and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Acquisitions, Goodwill, and Other Intangible Assets [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The following table summarizes our allocation of the estimated fair values of the assets acquired and liabilities assumed at the date of acquisition: (in millions) Cash and cash equivalents $ 12.4 Accounts receivable 10.8 Other current and non-current assets 3.2 Intangible assets 60.7 Goodwill 192.0 Deferred revenue (22.0 ) Deferred tax liability, net (12.3 ) Other current and non-current liabilities (9.7 ) Total fair value of PitchBook $ 235.1
Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination	The allocation includes $60.7 million of acquired intangible assets, as follows: (in millions) Weighted Average Useful Life (years) Customer-related assets $ 17.1 10 Technology-based assets 40.8 5 Intellectual property (trademarks and trade names) 2.8 4 Total intangible assets $ 60.7 6
Pro Forma Information	Unaudited Pro Forma Financial Information (in millions) 2016 2015 Revenue $ 834.1 $ 813.3 Operating income $ 157.7 $ 170.0 Net income $ 105.5 $ 117.1 Basic net income per share attributable to Morningstar, Inc. $ 2.45 $ 2.65 Diluted net income per share attributable to Morningstar, Inc. $ 2.44 $ 2.65
Schedule of Goodwill	The following table shows the changes in our goodwill balances from January 1, 2016 to December 31, 2017 : (in millions) Balance as of January 1, 2016 $ 364.2 Acquisition of PitchBook 193.6 Other acquisitions and foreign currency translation (1.0 ) Balance as of December 31, 2016 $ 556.8 Divestiture of HelloWallet (See Note 8) (2.4 ) Foreign currency translation and adjustments to purchase price allocation 10.5 Balance as of December 31, 2017 $ 564.9
Schedule of Intangible Assets	The following table summarizes our intangible assets: As of December 31, 2017 As of December 31, 2016 (in millions) Gross Accumulated Amortization Net Weighted Average Useful Life (years) Gross Accumulated Amortization Net Weighted Average Useful Life (years) Intellectual property $ 31.5 $ (28.9 ) $ 2.6 9 $ 30.9 $ (27.4 ) $ 3.5 9 Customer-related assets 156.6 (108.1 ) 48.5 12 152.0 (97.7 ) 54.3 12 Supplier relationships 0.2 (0.1 ) 0.1 20 0.2 (0.1 ) 0.1 20 Technology-based assets 127.9 (84.2 ) 43.7 7 133.2 (72.1 ) 61.1 7 Non-competition agreements 2.5 (2.0 ) 0.5 5 5.0 (3.1 ) 1.9 5 Total intangible assets $ 318.7 $ (223.3 ) $ 95.4 10 $ 321.3 $ (200.4 ) $ 120.9 10
Schedule of Intangible Asset, Amortization Expense	The following table summarizes our amortization expense related to intangible assets: (in millions) 2017 2016 2015 Amortization expense $ 23.6 $ 19.4 $ 22.0
Schedule of Expected Amortization Expense	Based on acquisitions and divestitures completed through December 31, 2017 , we expect intangible amortization expense for 2018 and subsequent years to be as follows: (in millions) 2018 $ 20.7 2019 19.3 2020 16.3 2021 13.0 2022 5.2 Thereafter 20.9

Divestitures (Tables)

Divestitures (Tables)	12 Months Ended
	Dec. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Disposal Groups, Including Discontinued Operations	The following table summarizes the amounts included in the gain on sale of business for the year ended December 31, 2017: Year ended December 31 (in millions) 2017 Proceeds received $ 23.7 Intangibles and internally developed software (4.5 ) Goodwill (2.4 ) Other assets and liabilities (0.1 ) Total gain on sale of business $ 16.7

Investments in Unconsolidated34

Investments in Unconsolidated Entities (Tables)	12 Months Ended
	Dec. 31, 2017
Investments in Unconsolidated Entities [Abstract]
Schedule of Equity Method And Cost Method Investments	Our investments in unconsolidated entities consist primarily of the following: As of December 31 (in millions) 2017 2016 Investment in MJKK $ 26.4 $ 25.1 Investment in Sustainalytics 20.7 — Other-equity method investments 12.6 13.5 Investments accounted for using the cost method 2.3 1.7 Total investments in unconsolidated entities $ 62.0 $ 40.3
Schedule of Equity Method Investments	The following table summarizes our ownership percentage in MJKK and the market value of this investment based on MJKK’s publicly quoted share price: As of December 31 2017 2016 Morningstar’s approximate ownership of MJKK 34 % 34 % Approximate market value of Morningstar’s ownership in MJKK: Japanese yen (¥ in millions) ¥ 10,649.6 ¥ 8,558.2 Equivalent U.S. dollars ($ in millions) $ 94.6 $ 73.2

Property, Equipment, and Capi35

Property, Equipment, and Capitalized Software (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Schedule of Property, Equipment, and Capitalized Software by Major Category	The following table shows our property, equipment, and capitalized software summarized by major category: As of December 31 (in millions) 2017 2016 Computer equipment $ 81.6 $ 70.1 Capitalized software 239.2 189.8 Furniture and fixtures 27.6 26.0 Leasehold improvements 72.5 69.0 Telephone equipment 2.3 2.1 Construction in progress 8.9 9.9 Property, equipment, and capitalized software, at cost 432.1 366.9 Less accumulated depreciation (284.7 ) (214.8 ) Property, equipment, and capitalized software, net $ 147.4 $ 152.1
Summary of Depreciation Expense	The following table summarizes our depreciation expense: (in millions) 2017 2016 2015 Depreciation expense $ 67.6 $ 51.3 $ 42.4

Operating Leases Operating Leas

Operating Leases Operating Leases (Tables)	12 Months Ended
	Dec. 31, 2017
Leases, Operating [Abstract]
Schedule of Minimum Future Rental Commitments	The following table shows our minimum future rental commitments due in each of the next five years and thereafter for all non-cancelable operating leases, consisting primarily of commitments for office space: Minimum Future Rental Commitments (in millions) 2018 $ 26.8 2019 30.4 2020 32.5 2021 29.8 2022 19.1 Thereafter 54.9 Total $ 193.5
Schedule of Rent Expense	The following table summarizes our rent expense, including taxes, insurance, and related operating costs: (in millions) 2017 2016 2015 Rent expense $ 30.3 $ 26.3 $ 27.1
Schedule of Deferred Rent	Deferred rent includes build-out and rent abatement allowances received, which are amortized over the remaining portion of the original term of the lease as a reduction in office lease expense. We include deferred rent, as appropriate, in “Accounts payable and accrued liabilities” and “Deferred rent, noncurrent” on our Consolidated Balance Sheets. As of December 31 (in millions) 2017 2016 Deferred rent $ 31.2 $ 28.4

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Shares Available for Future Grants	The following table summarizes the number of shares available for future grants under our 2011 Plan: As of December 31 (in millions) 2017 Shares available for future grants 3.4
Schedule of Stock-Based Compensation Expense	The following table summarizes our stock-based compensation expense and the related income tax benefit we recorded in the past three years: Year ended December 31 (in millions) 2017 2016 2015 Restricted stock units $ 16.5 $ 14.6 $ 16.1 Restricted stock — — 0.1 Performance share awards 7.1 (0.1 ) 1.0 Market stock units 0.5 — — Stock options — — 0.2 Total stock-based compensation expense $ 24.1 $ 14.5 $ 17.4 Income tax benefit related to the stock-based compensation expense $ 7.8 $ 4.3 $ 5.0
Allocation of Stock-based Compensation Expense	The following table summarizes the stock-based compensation expense included in each of our operating expense categories for the past three years: Year ended December 31 (in millions) 2017 2016 2015 Cost of revenue $ 9.6 $ 7.5 $ 8.1 Sales and marketing 3.0 1.9 2.2 General and administrative 11.5 5.1 7.1 Total stock-based compensation expense $ 24.1 $ 14.5 $ 17.4
Schedule of Uncategorized Stock-Based Compensation Expense	The following table summarizes the amount of unrecognized stock-based compensation expense as of December 31, 2017 and the expected number of months over which the expense will be recognized: Unrecognized stock-based compensation expense (in millions) Weighted average expected amortization period (months) Restricted stock units $ 36.5 35 Performance share awards — 12 Market stock units 2.8 32 Total unrecognized stock-based compensation expense $ 39.3 35
Schedule of Restricted Stock Units Award Activity	The following table summarizes restricted stock unit activity during the past three years: Restricted Stock Units (RSUs) Unvested Vested but Deferred Total Weighted Average Grant Date Value per RSU RSUs Outstanding - December 31, 2014 655,934 14,778 670,712 $ 67.51 Granted 235,213 — 235,213 77.17 Dividend equivalents 1,409 146 1,555 56.42 Vested (253,038 ) — (253,038 ) 64.65 Forfeited (66,992 ) — (66,992 ) 53.61 RSUs Outstanding - December 31, 2015 572,526 14,924 587,450 $ 72.14 Granted 241,609 — 241,609 77.82 Dividend equivalents 370 136 506 56.52 Vested (225,590 ) — (225,590 ) 69.39 Issued — (5,312 ) (5,312 ) 44.47 Forfeited (47,670 ) — (47,670 ) 74.45 RSUs Outstanding - December 31, 2016 541,245 9,748 550,993 $ 75.77 Granted 331,470 — 331,470 78.33 Dividend equivalents — 78 78 60.99 Vested (212,005 ) — (212,005 ) 75.38 Issued — (6,547 ) (6,547 ) 49.40 Forfeited (55,831 ) — (55,831 ) 76.49 RSUs Outstanding - December 31, 2017 604,879 3,279 608,158 $ 77.52
Schedule of Share-based Compensation Arrangement by Share-based Payment Award, Performance-Based Units, Vested and Expected to Vest [Table Text Block]	The table below shows target performance share awards granted and shares that would be issued at current performance levels for performance share awards granted as of December 31, 2017 : As of December 31, 2017 Target performance share awards granted 93,701 Weighted average fair value per award $ 77.55 Number of shares that would be issued based on current performance levels — Unamortized expense, based on current performance levels (in millions) $ — The table below shows target performance share awards granted and shares that will be issued based on final performance levels for performance share awards granted as of December 31, 2017 : As of December 31, 2017 Target performance share awards granted 100,924 Weighted average fair value per award $ 74.31 Number of shares that will be issued based on final 2017 performance levels 113,941 Unamortized expense, based on current performance levels (in millions) $ —
Market Units, Valuation Assumptions	We used the following assumptions to estimate the fair value of our market stock units during 2017: Assumptions for Monte Carlo Valuation Model Grant Date Expected volatility Dividend yield Risk-free interest rate May 15, 2017 17.4 % 1.20 % 1.49 % November 15, 2017 17.7 % 1.04 % 1.79 %
Schedule of Market Stocks Units	The table below shows market stock units granted and target market stock units outstanding as of December 31, 2017 : As of December 31, 2017 Market stock units granted 45,663 Weighted average fair value per award $ 72.29 Number of target market stock units outstanding 44,606 Unamortized expense, based on current performance levels (in millions) $ 2.8
Schedule of Stock Options, Valuation Assumptions	The weighted average fair value of options granted during 2011 was $23.81 per share, based on the following assumptions: Assumptions for Black-Scholes Option Pricing Model Expected life (years): 7.4 Volatility factor: 35.1 % Dividend yield: 0.35 % Interest rate: 2.87 %
Schedule of All Other Option Granted	The following table summarizes stock option activity in the past three years for our various stock option grants: 2017 2016 2015 All Other Option Grants, Excluding Activity Shown Above Underlying Shares Weighted Average Exercise Price Underlying Shares Weighted Average Exercise Price Underlying Shares Weighted Average Exercise Price Options outstanding—beginning of year 46,001 $ 57.28 52,096 $ 57.52 169,810 $ 40.20 Granted — — — — — — Canceled — — — — — — Exercised (4,316 ) 57.28 (6,095 ) 59.35 (117,714 ) 32.91 Options outstanding—end of year 41,685 $ 57.28 46,001 $ 57.28 52,096 $ 57.52 Options exercisable—end of year 41,685 $ 57.28 46,001 $ 57.28 52,096 $ 57.52
Schedule of Intrinsic Value of Stock Options Exercised During Period	The following table summarizes the total intrinsic value (difference between the market value of our stock on the date of exercise and the exercise price of the option) of options exercised: (in millions) 2017 2016 2015 Intrinsic value of options exercised $ 0.1 $ 0.1 $ 5.1
Schedule of Options, Vested and Expected to Vest, Outstanding and Exercisable	The table below shows additional information for options outstanding and exercisable as of December 31, 2017 : Options Outstanding Options Exercisable Range of Exercise Prices Number of Options Weighted Average Remaining Contractual Life (years) Weighted Average Exercise Price Aggregate Intrinsic Value (in millions) Exercisable Shares Weighted Average Remaining Contractual Life (years) Weighted Average Exercise Price Aggregate Intrinsic Value (in millions) $57.28 41,685 3.37 $ 57.28 $ 1.7 41,685 3.37 $ 57.28 $ 1.7 Vested or Expected to Vest $57.28 41,685 3.37 $ 57.28 $ 1.7

Defined Contribution Plan (Tabl

Defined Contribution Plan (Tables)	12 Months Ended
	Dec. 31, 2017
Defined Contribution Plan [Abstract]
Schedule of Defined Contribution Plan, Employer Matching Contributions	The following table summarizes our matching contributions: (in millions) 2017 2016 2015 401(k) matching contributions $ 10.4 $ 9.0 $ 8.3

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Schedule of Income Tax Expense and Effective Tax Rate	The following table shows our income tax expense and our effective tax rate for the years ended December 31, 2017 , 2016 , and 2015 : (in millions) 2017 2016 2015 Income before income taxes and equity in net income (loss) of unconsolidated entities $ 181.1 $ 224.9 $ 193.7 Equity in net income (loss) of unconsolidated entities (1.3 ) (0.2 ) 1.8 Net income attributable to the noncontrolling interest — — (0.2 ) Total $ 179.8 $ 224.7 $ 195.3 Income tax expense $ 42.9 $ 63.7 $ 62.7 Effective tax rate 23.9 % 28.3 % 32.1 %
Schedule of Effective Income Tax Rate Reconciliation	The following table reconciles our income tax expense at the U.S. federal income tax rate of 35% to income tax expense as recorded: 2017 2016 2015 (in millions, except percentages) Amount % Amount % Amount % Income tax expense at U.S. federal rate $ 63.0 35.0 % $ 78.6 35.0 % $ 68.4 35.0 % State income taxes, net of federal income tax benefit 3.0 1.7 4.5 2.0 6.6 3.4 Change in U.S. tax rate (14.7 ) (8.2 ) — — — — Deemed mandatory repatriation 7.5 4.2 — — — — Reduction of deferred tax liabilities for foreign equity method investments (6.4 ) (3.6 ) — — — — Withholding tax - repatriation 3.0 1.7 — — — — Stock-based compensation activity 0.3 0.2 (0.6 ) (0.3 ) 0.4 0.2 Equity in net income of unconsolidated subsidiaries (including holding gains upon acquisition) 1.2 0.7 (12.1 ) (5.4 ) — — Book gain over tax gain on sale of HelloWallet (6.8 ) (3.8 ) — — — — Net change in valuation allowance related to non-U.S. deferred tax assets, primarily net operating losses 0.1 0.1 (0.1 ) — (2.0 ) (1.0 ) Difference between U.S. federal statutory and foreign tax rates (5.2 ) (2.9 ) (5.3 ) (2.4 ) (4.4 ) (2.3 ) Change in unrecognized tax benefits 1.2 0.7 2.6 1.2 (1.4 ) (0.7 ) Credits and incentives (3.7 ) (2.1 ) (3.7 ) (1.6 ) (5.1 ) (2.6 ) Other - net 0.4 0.2 (0.2 ) (0.1 ) 0.2 0.1 Total income tax expense $ 42.9 23.9 % $ 63.7 28.3 % $ 62.7 32.1 %
Schedule of Components of Income Tax Expense	Income tax expense consists of the following: Year ended December 31 (in millions) 2017 2016 2015 Current tax expense: U.S. Federal $ 40.3 $ 42.8 $ 42.8 State 6.6 6.5 8.3 Non-U.S. 9.9 9.7 8.7 Current tax expense 56.8 59.0 59.8 Deferred tax expense (benefit): U.S. Federal (10.9 ) 5.1 4.3 State (1.9 ) 0.4 1.8 Non-U.S. (1.1 ) (0.8 ) (3.2 ) Deferred tax expense, net (13.9 ) 4.7 2.9 Income tax expense $ 42.9 $ 63.7 $ 62.7
Schedule of Income before Income Tax	The following table provides our income before income taxes and equity in net income (loss) of unconsolidated entities, generated by our U.S. and non-U.S. operations: Year ended December 31 (in millions) 2017 2016 2015 U.S. $ 143.5 $ 186.5 $ 160.6 Non-U.S. 37.6 38.4 33.1 Income before income taxes and equity in net income (loss) of unconsolidated entities $ 181.1 $ 224.9 $ 193.7
Schedule of Deferred Tax Assets and Liabilities	The tax effects of the temporary differences that give rise to the deferred income tax assets and liabilities are as follows: As of December 31 (in millions) 2017 2016 Deferred tax assets: Stock-based compensation expense $ 3.7 $ 2.6 Accrued liabilities 14.2 19.0 Deferred revenue 3.5 5.1 Net operating loss carryforwards - U.S. federal and state 1.9 12.9 Net operating loss carryforwards - Non-U.S. 3.1 3.0 Credits and incentive carryforwards 0.3 0.6 Deferred royalty revenue 0.2 0.3 Allowance for doubtful accounts 1.1 1.2 Deferred rent 6.2 10.3 Other 0.3 — Total deferred tax assets 34.5 55.0 Deferred tax liabilities: Acquired intangible assets (18.6 ) (34.3 ) Property, equipment, and capitalized software (24.6 ) (37.6 ) Unrealized exchange gains, net (0.6 ) (0.1 ) Prepaid expenses (3.9 ) (5.3 ) Investments in unconsolidated entities (5.4 ) (14.0 ) Withholding tax - foreign dividends (3.0 ) — Other — (0.3 ) Total deferred tax liabilities (56.1 ) (91.6 ) Net deferred tax liability before valuation allowance (21.6 ) (36.6 ) Valuation allowance (2.0 ) (1.6 ) Deferred tax liability, net $ (23.6 ) $ (38.2 )
Schedule of Deferred Tax Assets and Liabilities Included in Consolidated Balance Sheets	The deferred tax assets and liabilities are presented in our Consolidated Balance Sheets as follows: As of December 31 (in millions) 2017 2016 Deferred tax liability, net $ (23.6 ) $ (38.2 )
Schedule of Gross Unrecognized Tax Benefits	The table below reconciles the beginning and ending amount of the gross unrecognized tax benefits as follows: (in millions) 2017 2016 Gross unrecognized tax benefits - beginning of the year $ 18.4 $ 14.5 Increases as a result of tax positions taken during a prior-year period 1.4 2.2 Decreases as a result of tax positions taken during a prior-year period (0.4 ) (0.1 ) Increases as a result of tax positions taken during the current period 1.9 2.4 Decreases relating to settlements with tax authorities — — Reductions as a result of lapse of the applicable statute of limitations (2.6 ) (0.6 ) Gross unrecognized tax benefits - end of the year $ 18.7 $ 18.4
Summary of Income Tax Examinations	The following table summarizes our gross liability for interest and penalties: As of December 31 (in millions) 2017 2016 Liabilities for interest and penalties $ 1.7 $ 1.6
U.S [Member]
Operating Loss Carryforwards [Line Items]
Summary of Operating Loss Carryforwards	The following table summarizes our U.S. net operating loss (NOL) carryforwards: As of December 31 (in millions) 2017 2016 Expiration Dates Expiration Dates U.S. federal NOLs subject to expiration dates $ 9.1 2023-2036 $ 36.9 2023-2036
Non-U.S. [Member]
Operating Loss Carryforwards [Line Items]
Summary of Operating Loss Carryforwards	The following table summarizes our NOL carryforwards for our non-U.S. operations: As of December 31 (in millions) 2017 2016 Non-U.S. NOLs subject to expiration dates from 2019 through 2037 $ 5.7 $ 3.8 Non-U.S. NOLs with no expiration date 9.1 10.8 Total $ 14.8 $ 14.6 Non-U.S. NOLs not subject to valuation allowances $ 5.4 $ 6.8

Selected Quarterly Financial 40

Selected Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Data	2016 2017 (in millions except per share amounts) Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Revenue $ 192.1 $ 198.2 $ 196.1 $ 212.2 $ 209.5 $ 229.2 $ 229.9 $ 243.1 Total operating expense 149.8 153.8 151.9 162.3 181.1 183.2 177.1 200.5 Operating income 42.3 44.4 44.2 49.9 28.4 46.0 52.8 42.6 Non-operating income (expense), net 0.5 3.0 2.1 38.5 (1) (1.3 ) 15.3 (2) (2.0 ) (0.7 ) Income before income taxes and equity in net income (loss) of unconsolidated entities 42.8 47.4 46.3 88.4 27.1 61.3 50.8 41.9 Equity in net income (loss) of unconsolidated entities 0.5 (0.2 ) 0.4 (0.9 ) (0.8 ) (0.2 ) — (0.3 ) Income tax expense 14.6 15.4 16.5 17.2 8.3 15.0 16.9 2.7 (3) Consolidated net income $ 28.7 $ 31.8 $ 30.2 $ 70.3 $ 18.0 $ 46.1 $ 33.9 $ 38.9 Net income per share: Basic $ 0.67 $ 0.74 $ 0.70 $ 1.63 $ 0.42 $ 1.07 $ 0.80 $ 0.91 Diluted $ 0.67 $ 0.73 $ 0.70 $ 1.63 $ 0.42 $ 1.07 $ 0.79 $ 0.91 Dividends per common share: Dividends declared per common share $ 0.22 $ 0.22 $ 0.22 $ 0.23 $ 0.23 $ 0.23 $ — $ 0.48 Dividends paid per common share $ 0.22 $ 0.22 $ 0.22 $ 0.22 $ 0.23 $ 0.23 $ 0.23 $ 0.23 Weighted average shares outstanding: Basic 43.0 43.0 43.1 43.0 42.9 42.9 42.5 42.5 Diluted 43.1 43.3 43.3 43.2 43.2 43.1 42.8 42.9 (1) Non-operating income in the fourth quarter of 2016 included a $37.1 million holding gain related to the purchase of the remaining ownership interest in PitchBook, which was previously a minority investment. (2) Non-operating income in the second quarter of 2017 included a $17.5 million gain on the sale of HelloWallet. We recorded an immaterial adjustment to this gain in the fourth quarter of 2017. (3) Tax expense in the fourth quarter of 2017 includes a net benefit of $10.6 million related to the impact of the Tax Reform Act.

Description of Business (Detail

Description of Business (Details)	Dec. 31, 2017Countries
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of countries in which entity operates	27

Summary of Significant Accoun42

Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Depreciation expense	$ 67.6	$ 51.3	$ 42.4
Capitalized software development costs	46.3	28.2	21.8
Amortization of sales commission cost	0.2	0.6	3.5
Advertising expense	7	7.6	8.3
Internally developed software expense [Member]
Business Acquisition [Line Items]
Depreciation expense	$ 30.6	$ 20	$ 13
Property and equipment [Member]
Business Acquisition [Line Items]
Asset useful life	3 years
Capitalized software [Member] | Minimum [Member]
Business Acquisition [Line Items]
Asset useful life	3 years
Capitalized software [Member] | Maximum [Member]
Business Acquisition [Line Items]
Asset useful life	5 years

Credit Arrangements (Details)

Credit Arrangements (Details)	Dec. 31, 2017USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Line of Credit Facility [Line Items]
Long-term debt	$ 180,000,000	$ 180,000,000	$ 250,000,000
Credit agreement [Member]
Line of Credit Facility [Line Items]
Credit agreement term		3 years
Maximum borrowing capacity	300,000,000	$ 300,000,000
Long-term debt	180,000,000	180,000,000
Remaining borrowing capacity	120,000,000	120,000,000
Letters of credit [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 25,000,000	$ 25,000,000
London Interbank Offered Rate (LIBOR) [Member] | Credit agreement [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate debt	1.00%
Maximum [Member]
Line of Credit Facility [Line Items]
Debt covenant, consolidated leverage ratio		3
Maximum [Member] | London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate debt		1.75%
Maximum [Member] | Lender's base rate [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate debt		2.75%
Minimum [Member]
Line of Credit Facility [Line Items]
Debt covenant, consolidated interest coverage ratio		3
Minimum [Member] | London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate debt		1.00%
Minimum [Member] | Lender's base rate [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate debt		2.00%

Income Per Share (Details)

Income Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ 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
Basic net income per share attributable to Morningstar, Inc.:
Net income attributable to Morningstar, Inc.									$ 136.9	$ 161	$ 132.6
Weighted average common shares outstanding (in shares)	42.5	42.5	42.9	42.9	43	43.1	43	43	42.7	43	44.2
Basic net income per share attributable to Morningstar, Inc. (in dollars per share)									$ 3.21	$ 3.74	$ 3
Diluted net income per share attributable to Morningstar, Inc.:
Net income attributable to Morningstar, Inc.									$ 136.9	$ 161	$ 132.6
Weighted average common shares outstanding (in shares)	42.5	42.5	42.9	42.9	43	43.1	43	43	42.7	43	44.2
Net effect of dilutive stock options and restricted stock units (in shares)									0.3	0.3	0.1
Weighted average common shares outstanding for computing diluted income per share (in shares)	42.9	42.8	43.1	43.2	43.2	43.3	43.3	43.1	43	43.3	44.3
Diluted net income per share attributable to Morningstar, Inc. (in dollars per share)									$ 3.18	$ 3.72	$ 3

Segment and Geographical Area45

Segment and Geographical Area Information (Operating Segments) (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
Segment Reporting Information, Operating Income (Loss) [Abstract]
External revenue	$ 243.1	$ 229.9	$ 229.2	$ 209.5	$ 212.2	$ 196.1	$ 198.2	$ 192.1	$ 911.7	$ 798.6	$ 788.8
Stock-based compensation expense									24.1	14.5	17.4
Depreciation and amortization									91.2	70.7	64.4
Operating income	42.6	$ 52.8	$ 46	$ 28.4	49.9	$ 44.2	$ 44.4	$ 42.3	169.8	180.8	190.6
Segment Reporting Information, Additional Information [Abstract]
Goodwill	$ 564.9				$ 556.8				564.9	556.8	364.2
United States [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
External revenue									$ 687	$ 590.5	$ 585.1

Segment and Geographical Area46

Segment and Geographical Area Information (External Revenue and Long-Lived Assets) (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
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 243.1	$ 229.9	$ 229.2	$ 209.5	$ 212.2	$ 196.1	$ 198.2	$ 192.1	$ 911.7	$ 798.6	$ 788.8
Long-lived assets	147.4				152.1				147.4	152.1
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									687	590.5	585.1
Long-lived assets	131.9				139.1				131.9	139.1
United Kingdom [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									64.7	61.1	64.2
Long-lived assets	6				6.6				6	6.6
Europe excluding the United Kingdom [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									69.9	62.6	58.8
Long-lived assets	1.7				1.9				1.7	1.9
Australia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									34.6	32.2	30.5
Long-lived assets	2.3				0.6				2.3	0.6
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									29.4	28.2	27.9
Long-lived assets	0.2				0.4				0.2	0.4
Asia, Excluding Japan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									21.2	20	18.5
Long-lived assets	5.2				3.4				5.2	3.4
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									4.9	4	3.8
Long-lived assets	0.1				0.1				0.1	0.1
Non United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									224.7	208.1	$ 203.7
Long-lived assets	$ 15.5				$ 13				$ 15.5	$ 13

Investments and Fair Value Me47

Investments and Fair Value Measurements (Classification of Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Available-for-sale	$ 21.5	$ 27.7
Held-to-maturity	21.9	15.7
Trading securities, fair value disclosure	1.7	1.5
Total	$ 45.1	$ 44.9

Investments and Fair Value Me48

Investments and Fair Value Measurements (Gains (Losses) on Investments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Available-for-sale:
Available-for-sale securities, amortized cost basis	$ 19.5	$ 27.8
Available-for-sale securities, unrealized gain	2.6	1.4
Available-for-sale securities, unrealized loss	(0.6)	(1.5)
Available-for-sale securities, current	21.5	27.7
Held-to-maturity:
Held-to-maturity securities, total amortized cost	21.9	15.7
Held-to-maturity securities, unrealized gain	0	0
Held-to-maturity securities, unrealized loss	0	0
Held-to-maturity securities, current	21.9	15.7
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Available-for-sale securities, realized gains	3.4	1.6	$ 1.3
Available-for-sale securities, realized losses	(0.2)	(1)	(0.7)
Available-for-sale securities, realized gains, net	3.2	0.6	$ 0.6
Equity securities and exchange-traded funds [Member]
Available-for-sale:
Available-for-sale securities, amortized cost basis	17.1	25.6
Available-for-sale securities, unrealized gain	2.4	1.3
Available-for-sale securities, unrealized loss	(0.6)	(1.5)
Available-for-sale securities, fair value disclosure	18.9	25.4
Mutual funds [Member]
Available-for-sale:
Available-for-sale securities, amortized cost basis	2.4	2.2
Available-for-sale securities, unrealized gain	0.2	0.1
Available-for-sale securities, unrealized loss	0	0
Available-for-sale securities, fair value disclosure	2.6	2.3
Certificates of deposit [Member]
Held-to-maturity:
Held-to-maturity securities, total amortized cost	19.9	13.8
Held-to-maturity securities, unrealized gain	0	0
Held-to-maturity securities, unrealized loss	0	0
Held-to-maturity securities, current	19.9	13.8
Convertible note [Member]
Held-to-maturity:
Held-to-maturity securities, total amortized cost	2	1.9
Held-to-maturity securities, unrealized gain	0	0
Held-to-maturity securities, unrealized loss	0	0
Held-to-maturity securities, current	$ 2	$ 1.9

Investments and Fair Value Me49

Investments and Fair Value Measurements (Cost and Fair Value of Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities, Debt Maturities [Abstract]
Available-for-sale securities, equity securities and mutual funds, amortized cost basis	$ 19.5	$ 27.8
Available-for-sale securities, equity securities and mutual funds, fair value	21.5	27.7
Available-for-sale securities, amortized cost basis	19.5	27.8
Available-for-sale securities, current	21.5	27.7
Held-to-maturity Securities, Debt Maturities [Abstract]
Held-to-maturity securities, due within one year, net carrying amount	19.7	13.8
Held-to-maturity securities, due within one year, fair value	19.7	13.8
Held-to-maturity securities, due within one year, carrying amount	2.2	1.9
Held-to-maturity securities, due within one year, fair value	2.2	1.9
Held-to-maturity securities, total amortized cost	21.9	15.7
Held-to-maturity securities, current	$ 21.9	$ 15.7

Investments and Fair Value Me50

Investments and Fair Value Measurements (Unrealized Gains on Trading Securities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Unrealized gains (losses), net	$ 0.1	$ 0	$ (0.8)

Investments and Fair Value Me51

Investments and Fair Value Measurements (Fair Value of Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities, fair value disclosure	$ 1.7	$ 1.5
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities, fair value disclosure	1.7	1.5
Cash equivalents, fair value disclosure	0.5	0.2
Investments, fair value disclosure	23.7	29.4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Equity securities and exchange-traded funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	18.9	25.4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	2.6	2.3
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities, fair value disclosure	0	0
Cash equivalents, fair value disclosure	0	0
Investments, fair value disclosure	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Equity securities and exchange-traded funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities, fair value disclosure	0	0
Cash equivalents, fair value disclosure	0	0
Investments, fair value disclosure	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Equity securities and exchange-traded funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities, fair value disclosure	1.7	1.5
Cash equivalents, fair value disclosure	0.5	0.2
Investments, fair value disclosure	23.7	29.4
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Equity securities and exchange-traded funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	18.9	25.4
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	$ 2.6	$ 2.3

Acquisitions, Goodwill, and O52

Acquisitions, Goodwill, and Other Intangible Assets (Narrative) (Details) - USD ($)	Dec. 01, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2017	Nov. 30, 2016	Jun. 30, 2016	Jul. 31, 2015	Jun. 30, 2014
Business Acquisition [Line Items]
Percentage of voting interest after subsequent acquisition (percent)											100.00%
Holding gain upon acquisition of additional ownership of equity-method investments			$ 37,100,000	$ 0	$ 37,100,000	$ 0
Impairment of intangible assets				0	0	0
Goodwill		$ 556,800,000	$ 556,800,000	564,900,000	556,800,000	364,200,000
Goodwill impairment loss				$ 0	$ 0	$ 0
PitchBook [Member]
Business Acquisition [Line Items]
Percentage of voting interests acquired	78.20%
Percentage of voting interest after subsequent acquisition (percent)	100.00%
Percentage of voting interest before subsequent acquisition (percent)								22.00%
Pro Forma, revenue, actual		4,100,000
Pro Forma, income (expense), actual		$ 7,500,000
Acquisition estimated fair value	$ 235,100,000
Cash paid to acquire the entity	188,200,000
Equity method investments, fair value	46,900,000
Book value prior to business acquisition								$ 9,800,000
Holding gain upon acquisition of additional ownership of equity-method investments	37,100,000
Intangible assets	60,700,000
Deferred tax liability	(12,300,000)
Goodwill	$ 192,000,000
Ibbotson Associates Japan K.K. (IAJ) [Member]
Business Acquisition [Line Items]
Ownership percentage of subsidiary by noncontrolling owners							28.90%
Ownership percentage of subsidiary by parent									71.10%	100.00%
HelloWallet [Member]
Business Acquisition [Line Items]
Percentage of voting interests acquired											81.30%
Acquisition estimated fair value											$ 54,000,000
Intangible assets											9,500,000
Goodwill											$ 39,200,000

Acquisitions, Goodwill, and O53

Acquisitions, Goodwill, and Other Intangible Assets (Purchase Price Allocation) (Details) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 01, 2016	Dec. 31, 2015	Jun. 30, 2014
Business Acquisition, Purchase Price Allocation [Abstract]
Goodwill	$ 564.9	$ 556.8		$ 364.2
PitchBook [Member]
Business Acquisition, Purchase Price Allocation [Abstract]
Cash and cash equivalents			$ 12.4
Accounts receivable and other current assets			10.8
Other non-current assets			3.2
Intangible assets			60.7
Goodwill			192
Deferred revenue			(22)
Deferred tax liability			(12.3)
Other current and non-current liabilities			(9.7)
Acquisition estimated fair value			$ 235.1
HelloWallet [Member]
Business Acquisition, Purchase Price Allocation [Abstract]
Intangible assets					$ 9.5
Goodwill					39.2
Acquisition estimated fair value					$ 54

Acquisitions, Goodwill, and O54

Acquisitions, Goodwill, and Other Intangible Assets (Allocation of Acquired Intangible Assets) (Details) - USD ($) $ in Millions	Dec. 01, 2016	Jun. 30, 2014
HelloWallet [Member]
Business Acquisition [Line Items]
Intangible assets		$ 9.5
PitchBook [Member]
Business Acquisition [Line Items]
Intangible assets	$ 60.7
Weighted Average Useful Life (years)	6 years
PitchBook [Member] | Customer-related intangible assets [Member]
Business Acquisition [Line Items]
Intangible assets	$ 17.1
Weighted Average Useful Life (years)	10 years
PitchBook [Member] | Technology-based assets [Member]
Business Acquisition [Line Items]
Intangible assets	$ 40.8
Weighted Average Useful Life (years)	5 years
PitchBook [Member] | Intellectual property (trademarks and trade names) [Member]
Business Acquisition [Line Items]
Intangible assets	$ 2.8
Weighted Average Useful Life (years)	4 years

Acquisitions, Goodwill, and O55

Acquisitions, Goodwill, and Other Intangible Assets (Schedule of Goodwill) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Goodwill, Beginning Balance	$ 556.8	$ 364.2
Other acquisitions and foreign currency translation		(1)
Foreign currency translation and adjustments to purchase price allocation	10.5
Goodwill, Ending Balance	564.9	556.8
PitchBook [Member]
Goodwill [Roll Forward]
Acquisition of PitchBook		$ 193.6
HelloWallet [Member]
Goodwill [Roll Forward]
Divestiture of HelloWallet	$ (2.4)

Acquisitions, Goodwill, and O56

Acquisitions, Goodwill, and Other Intangible Assets (Schedule of Intangible Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross	$ 318.7	$ 321.3
Accumulated Amortization	(223.3)	(200.4)
Net	$ 95.4	$ 120.9
Weighted Average Useful Life (years)	10 years	10 years
Intellectual property [Member]
Finite-Lived Intangible Assets [Line Items]
Gross	$ 31.5	$ 30.9
Accumulated Amortization	(28.9)	(27.4)
Net	$ 2.6	$ 3.5
Weighted Average Useful Life (years)	9 years	9 years
Customer-related assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross	$ 156.6	$ 152
Accumulated Amortization	(108.1)	(97.7)
Net	$ 48.5	$ 54.3
Weighted Average Useful Life (years)	12 years	12 years
Supplier relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross	$ 0.2	$ 0.2
Accumulated Amortization	(0.1)	(0.1)
Net	$ 0.1	$ 0.1
Weighted Average Useful Life (years)	20 years	20 years
Technology-based assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross	$ 127.9	$ 133.2
Accumulated Amortization	(84.2)	(72.1)
Net	$ 43.7	$ 61.1
Weighted Average Useful Life (years)	7 years	7 years
Non-competition agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross	$ 2.5	$ 5
Accumulated Amortization	(2)	(3.1)
Net	$ 0.5	$ 1.9
Weighted Average Useful Life (years)	5 years	5 years

Acquisitions, Goodwill, and O57

Acquisitions, Goodwill, and Other Intangible Assets (Amortization Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Acquisitions, Goodwill, and Other Intangible Assets [Abstract]
Amortization expense	$ 23.6	$ 19.4	$ 22
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2,017	20.7
2,018	19.3
2,019	16.3
2,020	13
2,021	5.2
Thereafter	$ 20.9

Acquisitions, Goodwill, and O58

Acquisitions, Goodwill, and Other Intangible Assets Acquisition, Goodwill, and Other Intangible Assets - Pro Forma (Details) - PitchBook [Member] - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Revenue	$ 834.1	$ 813.3
Operating income	157.7	170
Net income	$ 105.5	$ 117.1
Basic net income per share attributable to Morningstar, Inc. (in dollars per share)	$ 2.45	$ 2.65
Diluted net income per share attributable to Morningstar, Inc. (in dollars per share)	$ 2.44	$ 2.65

Divestitures (Narrative) (Detai

Divestitures (Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of voting interest after subsequent acquisition (percent)						100.00%
Goodwill			$ 564.9	$ 556.8	$ 364.2
Gain on sale of business		$ 17.5	16.7	$ 0	$ 0
HelloWallet [Member] | Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of business	$ 16.7		16.7
Proceeds from sale	23.7
Disposal group, goodwill	$ 2.4	$ 2.4	$ 2.4
HelloWallet [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of voting interests acquired						81.30%
Acquisition estimated fair value						$ 54
Goodwill						39.2
Intangible assets						$ 9.5

Divestitures (Amounts Included

Divestitures (Amounts Included in the Gain on Sale of Business (Details) - USD ($) $ in Millions	Jun. 30, 2017	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total gain on sale of business		$ 17.5	$ 16.7	$ 0	$ 0
HelloWallet [Member] | Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds received			23.7
Intangibles and internally developed software			(4.5)
Goodwill	$ (2.4)	$ (2.4)	(2.4)
Other assets and liabilities			(0.1)
Total gain on sale of business	$ 16.7		$ 16.7

Investments in Unconsolidated61

Investments in Unconsolidated Entities (Details) ¥ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2017JPY (¥)	Dec. 31, 2016JPY (¥)
Schedule of Equity Method Investments [Line Items]
Cost method investments	$ 2.3	$ 1.7
Total investments in unconsolidated entities	62	40.3
Cost-method investments, other than temporary impairment	0	0
Equity method investment, other than temporary impairment	0	0
Other Equity Method Investments [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 12.6	$ 13.5
YCharts [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	22.00%	22.00%	22.00%	22.00%
Morningstar Japan KK [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 26.4	$ 25.1
Equity method investment, ownership percentage	34.00%	34.00%	34.00%	34.00%
Equity method investment, approximate market value	$ 94.6	$ 73.2	¥ 10,649.6	¥ 8,558.2
Sustainalytics [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 20.7	$ 0
Equity method investment, ownership percentage	40.00%		40.00%
Inquiry Financial Europe AB [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		34.00%		34.00%
Ellevest [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	17.00%	22.00%	17.00%	22.00%
United Income [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	35.00%	38.00%	35.00%	38.00%

Property, Equipment, and Capi62

Property, Equipment, and Capitalized Software (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment, Net [Abstract]
Property, equipment, and capitalized software, at cost	$ 432.1	$ 366.9
Less accumulated depreciation	(284.7)	(214.8)
Property, equipment, and capitalized software, net	147.4	152.1
Depreciation expense	67.6	51.3	$ 42.4
Computer equipment [Member]
Property, Plant and Equipment, Net [Abstract]
Property, equipment, and capitalized software, at cost	81.6	70.1
Capitalized software [Member]
Property, Plant and Equipment, Net [Abstract]
Property, equipment, and capitalized software, at cost	239.2	189.8
Tangible Asset Impairment Charges	4.1
Furniture and fixtures [Member]
Property, Plant and Equipment, Net [Abstract]
Property, equipment, and capitalized software, at cost	27.6	26
Leasehold improvements [Member]
Property, Plant and Equipment, Net [Abstract]
Property, equipment, and capitalized software, at cost	72.5	69
Telephone equipment [Member]
Property, Plant and Equipment, Net [Abstract]
Property, equipment, and capitalized software, at cost	2.3	2.1
Construction in progress [Member]
Property, Plant and Equipment, Net [Abstract]
Property, equipment, and capitalized software, at cost	$ 8.9	$ 9.9

Operating Leases Operating Le63

Operating Leases Operating Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2,012	$ 26.8
2,013	30.4
2,014	32.5
2,015	29.8
2,016	19.1
Thereafter	54.9
Total	193.5
Rent expense	30.3	$ 26.3	$ 27.1
Deferred rent	$ 31.2	$ 28.4

Stock-Based Compensation (Narra

Stock-Based Compensation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended		12 Months Ended
	Nov. 30, 2011	May 31, 2011	Dec. 31, 2017	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense			$ 39.3
Expected amortization period (months)			35 years
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period			10 years
Restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			4 years
Unrecognized stock-based compensation expense			$ 36.5
Expected amortization period (months)			35 years
Performance share awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years
Unrecognized stock-based compensation expense			$ 0
Expected amortization period (months)			12 years
2004 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option granted		86,106
Fair value per share (in dollars per share)				$ 23.81
2011 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option granted	6,095
Non-employee director [Member] | Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years
Non-employee director [Member] | Restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years
Employee [Member] | Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			4 years

Stock-Based Compensation (Share

Stock-Based Compensation (Shares Available for Future Grants) (Details) shares in Millions	Dec. 31, 2017shares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Shares available for future grants	0

Stock-Based Compensation (Alloc

Stock-Based Compensation (Allocation of Stock-Based Compensation Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 24.1	$ 14.5	$ 17.4
Income tax benefit related to the stock-based compensation expense	7.8	4.3	5
Restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	16.5	14.6	16.1
Restricted stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	0	0	0.1
Performance share awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	7.1	(0.1)	1
Market Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	0.5	0	0
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 0	$ 0	$ 0.2

Stock-Based Compensation (Unrec

Stock-Based Compensation (Unrecognized Stock-Based Compensation Expense) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Income tax benefit related to the stock-based compensation expense	$ 39.3
Expected amortization period (months)	35 years
Restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Income tax benefit related to the stock-based compensation expense	$ 36.5
Expected amortization period (months)	35 years
Performance share awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Income tax benefit related to the stock-based compensation expense	$ 0
Expected amortization period (months)	12 years
Market Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Income tax benefit related to the stock-based compensation expense	$ 2.8
Expected amortization period (months)	32 years

Stock-Based Compensation (Restr

Stock-Based Compensation (Restricted Stock Units Activity) (Details) - Restricted stock units [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
RSUs Outstanding, Beginning Balance, Unvested	541,245	572,526	655,934
RSUs Outstanding, Beginning Balance, Vested but Deferred	9,748	14,924	14,778
RSUs Outstanding, Beginning Balance	550,993	587,450	670,712
RSUs Outstanding, Beginning Balance, Weighted Average Grant Date Value per RSU	$ 75.77	$ 72.14	$ 67.51
Target performance share awards granted	331,470	241,609	235,213
Granted, Vested but Deferred	0	0	0
Granted	331,470	241,609	235,213
Granted, Weighted Average Grant Date Value per RSU	$ 78.33	$ 77.82	$ 77.17
Dividend equivalents, Unvested	0	370	1,409
Dividends equivalents, Vested but Deferred	78	136	146
Dividends equivalents	78	506	1,555
Dividends equivalents, Weighted Average Grant Date Value per RSU	$ 60.99	$ 56.52	$ 56.42
Vested, Unvested	(212,005)	(225,590)	(253,038)
Vested, Vested but Deferred	0	0	0
Vested	(212,005)	(225,590)	(253,038)
Vested, Weighted Average Grant Date Value per RSU	$ 75.38	$ 69.39	$ 64.65
Issued, Unvested	0	0
Issued, Vested but Deferred	(6,547)	(5,312)
Issued	(6,547)	(5,312)
Issued, Weighted Average Grant Date Value per RSU	$ 49.40	$ 44.47
Forfeited, Unvested	(55,831)	(47,670)	(66,992)
Forfeited, Vested but Deferred	0	0	0
Forfeited	(55,831)	(47,670)	(66,992)
Forfeited, Weighted Average Grant Date Value per RSU	$ 76.49	$ 74.45	$ 53.61
RSUs Outstanding, Ending Balance, Unvested	604,879	541,245	572,526
RSUs Outstanding, Ending Balance, Vested but Deferred	3,279	9,748	14,924
RSUs Outstanding, Ending Balance	608,158	550,993	587,450
RSUs Outstanding, Ending Balance, Weighted Average Grant Date Value per RSU	$ 77.52	$ 75.77	$ 72.14

Stock-Based Compensation (Perfo

Stock-Based Compensation (Performance Shares) (Details) - Performance share awards [Member] - USD ($) $ / shares in Units, $ in Millions	12 Months Ended	36 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target performance share awards granted		93,701
Granted, Weighted Average Grant Date Value per RSU	$ 77.55
Number of shares that will be issued based on final 2017 performance levels	0
Unamortized expense, based on current performance levels (in millions)	$ 0

Stock-Based Compensation Stock-

Stock-Based Compensation Stock-Based Compensation (Assumptions Used to Estimate Fair Value of Market Units (Details) - Market Stock Units [Member]	Nov. 15, 2017	May 15, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	17.70%	17.40%
Dividend yield	1.00%	1.20%
Risk-free interest rate	1.80%	1.50%

Stock-Based Compensation (Marke

Stock-Based Compensation (Market Units) (Details) - Market Stock Units [Member] $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Market stock units granted (in shares)	45,663
Weighted average fair value per award (in dollars per share) | $ / shares	$ 72.29
Number of target market stock units outstanding (in shares)	44,606
Unamortized expense, based on current performance levels (in millions) | $	$ 2.8

Stock-Based Compensation (Assum

Stock-Based Compensation (Assumptions for Black-Scholes Option Pricing Model) (Details) - Stock options [Member]	12 Months Ended
	Dec. 31, 2014
Assumptions for Black-Scholes Option Pricing Model [Line Items]
Expected life (years):	7 years 4 months 24 days
Expected volatility	35.10%
Dividend yield	0.35%
Risk-free interest rate	2.87%

Stock-Based Compensation (Stock

Stock-Based Compensation (Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Option exercise price grouping [Member]
Intrinsic Value of Options Exercised [Abstract]
Intrinsic value of options exercised	$ 0.1	$ 0.1	$ 5.1
Option grants excluding options granted at discount [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning Balance, Options, Outstanding, Underlying Shares	46,001	52,096	169,810
Granted, Underlying Shares	0	0	0
Canceled, Underlying Shares	0	0	0
Exercised, Underlying Shares	(4,316)	(6,095)	(117,714)
Ending Balance, Options, Outstanding, Underlying Shares	41,685	46,001	52,096
Options, Weighted Average Exercise Price [Abstract]
Beginning Balance, Options, Outstanding, Weighted Average Exercise Price	$ 57.28	$ 57.52	$ 40.20
Granted, Weighted Average Exercise Price	0	0	0
Canceled, Weighted Average Exercise Price	0	0	0
Exercised, Weighted Average Exercise Price	57.28	59.35	32.91
Ending Balance, Options, Outstanding, Weighted Average Exercise Price	$ 57.28	$ 57.28	$ 57.52
Options, Exercisable, Number of Shares and Weighted Average Exercise Price [Abstract]
Options exercisable - end of year, Underlying Shares	41,685	46,001	52,096
Options exercisable - end of year, Weighted Average Exercise Price	$ 57.28	$ 57.28	$ 57.52

Stock-Based Compensation (Addit

Stock-Based Compensation (Additional Information on Options) (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)$ / sharesshares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Closing Stock Price Used to Calculate Intrinsic Value	$ 96.97
Range One [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices	57.28
Exercise price range, lower range limit	$ 57.28
Exercise price range, upper range limit	$ 59.35
Options Outstanding, Number of Options | shares	41,685
Options Outstanding, Weighted Average Remaining Contractual Life (years)	3 years 4 months 13 days
Options Outstanding, Weighted Average Exercise Price	$ 57.28
Options Outstanding, Aggregate Intrinsic Value | $	$ 1.7
Options Exercisable, Exercisable Shares | shares	41,685
Options Exercisable, Weighted Average Remaining Contractual Life (years)	3 years 4 months 13 days
Options Exercisable, Weighted Average Exercise Price	$ 57.28
Options Exercisable, Aggregate Intrinsic Value | $	$ 1.7
Share Based Compensation, Arrangement By Share Based Payments, Vested or Expected to Vest, Range of Exercise Prices	57.28
Option Outstanding, Number of Options, Vested or Expected to Vest | shares	41,685
Options Outstanding, Weighted Average Remaining Contractual Life (years), Vested or Expected to vest	3 years 4 months 13 days
Options Outstanding, Weighted Average Exercise Price, Vested or Expected to Vest	$ 57.28
Options Outstanding, Average Intrinsic Value, Vested or Expected to Vest | $	$ 1.7

Stock-Based Compensation (Total

Stock-Based Compensation (Total Stock-Based Compensation Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 24.1	$ 14.5	$ 17.4
Cost of revenue [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	9.6	7.5	8.1
Selling and marketing expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	3	1.9	2.2
General and administrative expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 11.5	$ 5.1	$ 7.1

Stock-based Compensation (Pitch

Stock-based Compensation (PitchBook Bonus Plan) (Details) - Performance share awards [Member] - USD ($) $ / shares in Units, $ in Millions	12 Months Ended	36 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Target performance share awards granted			93,701
Number of shares that will be issued based on final 2017 performance levels	0
Unamortized expense, based on current performance levels (in millions)	$ 0
PitchBook Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance, aggregate target value	30
Target value of shares expected to be granted in 2017	7.5
Target value of shares expected to be granted in 2018	7.5
Target value of shares expected to be granted in 2019	$ 15
Award vesting period	1 year
Shares of common stock to be issued for each equity instrument	1
Weighted average fair value per award	$ 74.31
Unamortized expense, based on current performance levels (in millions)	$ 0
Forecast [Member] | PitchBook Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target performance share awards granted		100,924
Number of shares that will be issued based on final 2017 performance levels		113,941

Defined Contribution Plan (Deta

Defined Contribution Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan [Abstract]
401(k) matching contributions	$ 10,400,000	$ 9,000,000	$ 8,300,000
Matching contribution to 401(k) for every dollar	$ 0.75	$ 0.75	$ 0.75
Matching contribution percent to employee's contribution in pay period	7.00%	7.00%	7.00%

Income Taxes (Schedule of Incom

Income Taxes (Schedule of Income Tax Expense and Effective Tax Rate) (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
Income Tax Disclosure [Abstract]
Income before income taxes and equity in net income (loss) of unconsolidated entities	$ 41.9	$ 50.8	$ 61.3	$ 27.1	$ 88.4	$ 46.3	$ 47.4	$ 42.8	$ 181.1	$ 224.9	$ 193.7
Equity in net income (loss) of unconsolidated entities	(0.3)	0	(0.2)	(0.8)	(0.9)	0.4	(0.2)	0.5	(1.3)	(0.2)	1.8
Net income attributable to the noncontrolling interest									0	0	(0.2)
Income loss from continuing operations before income taxes domestic and foreign									179.8	224.7	195.3
Income tax expense	2.7	$ 16.9	$ 15	$ 8.3	17.2	$ 16.5	$ 15.4	$ 14.6	$ 42.9	$ 63.7	$ 62.7
Effective income tax rate									23.90%	28.30%	32.10%
Provisional tax benefit, Tax Reform Act									$ 14.7
Undistributed foreign E&P subject to the deemed mandatory repatriation, Tax Reform Act	183.7								183.7
Provisional tax charge on deemed mandatory repatriation of foreign earnings, Tax Reform Act	7.5								7.5
Reduction of deferred tax liabilities for foreign equity method investments, Tax Reform Act									6.4
Net transition tax for accumulated foreign earnings, provisional income tax expense, Tax Reform Act									1.1
Provisional estimate of deferred taxes for foreign withholding taxes, Tax Reform Act	$ 3				$ 0				$ 3	$ 0

Income Taxes (Schedule of Effec

Income Taxes (Schedule of Effective Income Tax Rate Reconciliation) (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
Income Tax Examination [Line Items]
Income tax expense at U.S. federal rate									$ 63	$ 78.6	$ 68.4
Income tax expense at U.S. federal rate, percent									35.00%	35.00%	35.00%
State income taxes, net of federal income tax benefit									$ 3	$ 4.5	$ 6.6
State income taxes, net of federal income tax benefit, percent									1.70%	2.00%	3.40%
Change in U.S. tax rate									$ (14.7)	$ 0	$ 0
Change in U.S. tax rate, percent									(8.20%)	0.00%	0.00%
Deemed mandatory repatriation									$ 7.5	$ 0	$ 0
Deemed mandatory repatriation, percent									4.20%	0.00%	0.00%
Reduction of deferred tax liabilities for foreign equity method investments									$ (6.4)	$ 0	$ 0
Reduction of deferred tax liabilities for foreign equity method investments, percent									(3.60%)	(0.00%)	(0.00%)
Withholding tax - repatriation									$ 3	$ 0	$ 0
Withholding tax - repatriation, percent									1.70%	0.00%	0.00%
Stock-based compensation activity									$ 0.3	$ (0.6)	$ 0.4
Stock-based compensation activity, percent									0.20%	(0.30%)	0.20%
Equity in net income of unconsolidated subsidiaries (including holding gains upon acquisition)									$ 1.2	$ (12.1)	$ 0
Holding gain upon acquisition of additional ownership of equity method investments, percent									0.70%	(5.40%)	(0.00%)
Book gain over tax gain on sale of HelloWallet									$ (6.8)	$ 0	$ 0
Book gain over tax gain on sale of HelloWallet, percent									(3.80%)	0.00%	0.00%
Net change in valuation allowance related to non-U.S. deffered tax assets, primarily net operating losses									$ 0.1	$ (0.1)	$ (2)
Net change in valuation allowance related to non-U.S. deffered tax assets, primarily net operating losses, percent									0.10%	0.00%	(1.00%)
Difference between U.S. federal statutory and foreign tax rates									$ (5.2)	$ (5.3)	$ (4.4)
Difference between U.S. federal statutory and foreign tax rates, percent									(2.90%)	(2.40%)	(2.30%)
Change in unrecognized tax benefits									$ 1.2	$ 2.6	$ (1.4)
Changes in unrecognized tax benefits, percent									0.70%	1.20%	(0.70%)
Other tax credits									$ (3.7)	$ (3.7)	$ (5.1)
Other tax credits, percent									(2.10%)	(1.60%)	(2.60%)
Other - net									$ 0.4	$ (0.2)	$ 0.2
Other - net, percent									0.20%	(0.10%)	0.10%
Income tax expense	$ 2.7	$ 16.9	$ 15	$ 8.3	$ 17.2	$ 16.5	$ 15.4	$ 14.6	$ 42.9	$ 63.7	$ 62.7
Income tax expense, percent									23.90%	28.30%	32.10%

Income Taxes (Schedule of Compo

Income Taxes (Schedule of Components of Income Tax Expense) (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
Income Tax Disclosure [Abstract]
Federal									$ 40.3	$ 42.8	$ 42.8
State									6.6	6.5	8.3
Non-U.S.									9.9	9.7	8.7
Current tax expense									56.8	59	59.8
Federal									(10.9)	5.1	4.3
State									(1.9)	0.4	1.8
Non-U.S.									(1.1)	(0.8)	(3.2)
Deferred tax expense (benefit)									(13.9)	4.7	2.9
Income tax expense	$ 2.7	$ 16.9	$ 15	$ 8.3	$ 17.2	$ 16.5	$ 15.4	$ 14.6	$ 42.9	$ 63.7	$ 62.7

Income Taxes (Schedule of Inc81

Income Taxes (Schedule of Income before Income Taxes and Equity in Net Income of Unconsolidated Entities) (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
Income Tax Disclosure [Abstract]
U.S.									$ 143.5	$ 186.5	$ 160.6
Non-U.S.									37.6	38.4	33.1
Income before income taxes and equity in net income (loss) of unconsolidated entities	$ 41.9	$ 50.8	$ 61.3	$ 27.1	$ 88.4	$ 46.3	$ 47.4	$ 42.8	$ 181.1	$ 224.9	$ 193.7

Income Taxes (Schedule of Defer

Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Stock-based compensation expense	$ 3.7	$ 2.6
Accrued liabilities	14.2	19
Deferred revenue	3.5	5.1
Net operating loss carryforwards - U.S.	1.9	12.9
Net operating loss carryforwards - Non-U.S.	3.1	3
Credits and incentive carryforwards	0.3	0.6
Deferred royalty revenue	0.2	0.3
Allowance for doubtful accounts	1.1	1.2
Deferred rent	6.2	10.3
Other	0.3	0
Total deferred tax assets	34.5	55
Deferred tax liabilities:
Acquired intangible assets	(18.6)	(34.3)
Property, equipment and capitalized software	(24.6)	(37.6)
Unrealized exchange gains, net	(0.6)	(0.1)
Prepaid expenses	(3.9)	(5.3)
Investments in unconsolidated entities	(5.4)	(14)
Withholding tax - foreign dividends	(3)	0
Other	0	(0.3)
Total deferred tax liabilities	56.1	91.6
Net deferred tax liability before valuation allowance	21.6	36.6
Valuation allowance	(2)	(1.6)
Total deferred tax liabilities	$ (23.6)	$ (38.2)

Income Taxes (Schedule of Def83

Income Taxes (Schedule of Deferred Tax Assets and Liabilities Included in Consolidated Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Deferred tax liability, net	$ (23.6)	$ (38.2)

Income Taxes (Summary of Operat

Income Taxes (Summary of Operating Loss Carryforwards - U.S and Non-U.S) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Non-U.S. [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 14.8	$ 14.6
Operating loss carryforwards, not subject to valuation allowances	5.4	6.8
Non-U.S. [Member] | Subject to Expiration Date [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	5.7	3.8
Non-U.S. [Member] | No Expiration Date [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	9.1	10.8
U.S [Member] | Subject to Expiration Date [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 9.1	$ 36.9

Income Taxes (Accounting for Un

Income Taxes (Accounting for Uncertainty in Tax Positions) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Gross unrecognized tax benefits - beginning of the year	$ 18.4	$ 14.5
Increases as a resulting of tax positions taken during a prior-year period	1.4	2.2
Decreases as a result of tax positions taken during a prior-year period	(0.4)	(0.1)
Increases as a result of tax positions taken during the current period	1.9	2.4
Decreases relating to settlements with tax authorities	0	0
Reductions as a result of lapse of the applicable statute of limitations	(2.6)	(0.6)
Gross unrecognized tax benefits - end of the year	18.7	18.4
Decrease of unrecognized tax benefits relating to settlements with tax authorities	2.6
Unrecognized tax benefits included in current liabilities	8.7	8.9
Unrecognized tax benefits included in non-current liabilities	7	$ 5.4
Result of tax position taken during period	2.9
Increase in income tax expense	3.1
Reductions resulting from settlements and lapse of statute of limitations	2.6
Unrecognized tax benefits that would impact effective tax rate	15
Unrecognized tax benefits, period increase (decrease)	2.9
Reductions resulting from settlements and lapse statute of limitations, tax effect	2.2
Decrease in income tax expense upon recognition of gross unrecognized tax benefits	$ 14.4

Income Taxes (Summary of Income

Income Taxes (Summary of Income Tax Examinations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Liabilities for interest and penalties	$ 1.7	$ 1.6

Share Repurchase Program (Detai

Share Repurchase Program (Details) - USD ($)	Dec. 31, 2017	Dec. 08, 2017
Equity [Abstract]
Shares repurchased, program life to date, shares	10,574,857
Shares repurchased, program life to date, value	$ 714,800,000
Stock repurchase program, authorized amount	$ 1,000,000,000	$ 500,000,000

Recently Issued Accounting Pr88

Recently Issued Accounting Pronouncements (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, 2018

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Revenue

$ 243.1

$ 229.9

$ 229.2

$ 209.5

$ 212.2

$ 196.1

$ 198.2

$ 192.1

$ 911.7

$ 798.6

$ 788.8

Cost of revenue

$ 386.6

$ 344.3

$ 330.1

Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Forecast [Member] | Minimum [Member] | Accounting Standards Update 2014-09

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Revenue

$ 6

Cost of revenue

6

Commission expense

14

Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Forecast [Member] | Minimum [Member] | Retained Earnings | Accounting Standards Update 2014-09

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Cumulative effect of new accounting principle in period of adoption

25

Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Forecast [Member] | Maximum [Member] | Accounting Standards Update 2014-09

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Revenue

7

Cost of revenue

7

Commission expense

16

Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Forecast [Member] | Maximum [Member] | Retained Earnings | Accounting Standards Update 2014-09

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Cumulative effect of new accounting principle in period of adoption

$ 30

Selected Quarterly Financial 89

Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, shares in Millions, $ 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
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 243.1	$ 229.9	$ 229.2	$ 209.5	$ 212.2	$ 196.1	$ 198.2	$ 192.1	$ 911.7	$ 798.6	$ 788.8
Total operating expense	200.5	177.1	183.2	181.1	162.3	151.9	153.8	149.8	741.9	617.8	598.2
Operating income	42.6	52.8	46	28.4	49.9	44.2	44.4	42.3	169.8	180.8	190.6
Non-operating income (expense), net	(0.7)	(2)	15.3	(1.3)	38.5	2.1	3	0.5	11.3	44.1	3.1
Income before income taxes and equity in net income (loss) of unconsolidated entities	41.9	50.8	61.3	27.1	88.4	46.3	47.4	42.8	181.1	224.9	193.7
Equity in net income (loss) of unconsolidated entities	(0.3)	0	(0.2)	(0.8)	(0.9)	0.4	(0.2)	0.5	(1.3)	(0.2)	1.8
Income tax expense	2.7	16.9	15	8.3	17.2	16.5	15.4	14.6	42.9	63.7	62.7
Consolidated net income	$ 38.9	$ 33.9	$ 46.1	$ 18	$ 70.3	$ 30.2	$ 31.8	$ 28.7	$ 136.9	$ 161	$ 132.8
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.91	$ 0.80	$ 1.07	$ 0.42	$ 1.63	$ 0.70	$ 0.74	$ 0.67
Earnings Per Share, Basic [Abstract]
Basic net income per share attributable to Morningstar, Inc. (in dollars per share)									$ 3.21	$ 3.74	$ 3
Weighted average common shares outstanding - basic (in shares)	42.5	42.5	42.9	42.9	43	43.1	43	43	42.7	43	44.2
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.91	$ 0.79	$ 1.07	$ 0.42	$ 1.63	$ 0.70	$ 0.73	$ 0.67
Earnings Per Share, Diluted [Abstract]
Diluted net income per share attributable to Morningstar, Inc. (in dollars per share)									$ 3.18	$ 3.72	$ 3
Weighted average common shares outstanding - diluted (in shares)	42.9	42.8	43.1	43.2	43.2	43.3	43.3	43.1	43	43.3	44.3
Dividends Per Common Share: [Abstract]
Common stock, dividends, per share, declared	$ 0.48	$ 0	$ 0.23	$ 0.23	$ 0.23	$ 0.22	$ 0.22	$ 0.22	$ 0.94	$ 0.89	$ 0.79
Dividends paid per common share	$ 0.23	$ 0.23	$ 0.23	$ 0.23	$ 0.22	$ 0.22	$ 0.22	$ 0.22	$ 0.92	$ 0.88	$ 0.76
Holding gain upon acquisition of additional ownership of equity-method investments					$ 37.1				$ 0	$ 37.1	$ 0
Gain on sale of business			$ 17.5						$ 16.7	$ 0	$ 0
Income tax benefit related to the impact of the Tax Reform Act	$ 10.6