Northern Trust (NTRS) 10-Q 2 May 17 2017 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information	3 Months Ended
	Mar. 31, 2017shares
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q1
Trading Symbol	NTRS
Entity Registrant Name	NORTHERN TRUST CORP
Entity Central Index Key	73,124
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding	229,585,949

Consolidated Balance Sheet

Consolidated Balance Sheet - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Assets
Cash and Due from Banks	$ 4,649.2	$ 5,332
Federal Reserve and Other Central Bank Deposits	25,959.5	26,674.2
Interest-Bearing Deposits with Banks	5,247.8	4,800.6
Federal Funds Sold and Securities Purchased under Agreements to Resell	1,933.8	1,974.3
Securities
Available for Sale	34,997.6	35,579.8
Held to Maturity (Fair value of $8,933.4 and $8,905.1)	8,938.4	8,921.1
Trading Account	1.4	0.3
Total Securities	43,937.4	44,501.2
Loans and Leases
Total Loans and Leases (Net of unearned income of $39.1 and $41.2)	33,471.8	33,822.1
Allowance for Credit Losses Assigned to Loans and Leases	(162)	(161)
Buildings and Equipment	459.9	466.6
Client Security Settlement Receivables	1,559.9	1,043.7
Goodwill	519.3	519.4
Other Assets	3,912.1	4,953.8
Total Assets	121,488.7	123,926.9
Deposits
Demand and Other Noninterest-Bearing	20,698.6	22,190.4
Savings and Money Market	15,878.8	16,509
Savings Certificates and Other Time	1,346.8	1,331.7
Non U.S. Offices — Noninterest-Bearing	9,848	7,972.5
Non U.S. Offices - Interest-Bearing	52,757.3	53,648.1
Total Deposits	100,529.5	101,651.7
Federal Funds Purchased	369.5	204.8
Securities Sold Under Agreements to Repurchase	433.2	473.7
Other Borrowings	4,077.1	5,109.5
Senior Notes	1,496.8	1,496.6
Long-Term Debt	1,321.8	1,330.9
Floating Rate Capital Debt	277.4	277.4
Other Liabilities	3,005.7	3,611.9
Total Liabilities	111,511	114,156.5
Stockholders' Equity
Common Stock, $1.66 2/3 Par Value; Authorized 560,000,000 shares; Outstanding shares of 229,585,949 and 228,605,485	408.6	408.6
Additional Paid-In Capital	1,010.2	1,035.8
Retained Earnings	9,074.4	8,908.4
Accumulated Other Comprehensive Loss	(352)	(370)
Treasury Stock (15,585,575 and 16,566,039 shares, at cost)	(1,045.5)	(1,094.4)
Total Stockholders’ Equity	9,977.7	9,770.4
Total Liabilities and Stockholders’ Equity	121,488.7	123,926.9
Commercial
Loans and Leases
Total Loans and Leases (Net of unearned income of $39.1 and $41.2)	15,527.4	15,902.3
Personal
Loans and Leases
Total Loans and Leases (Net of unearned income of $39.1 and $41.2)	17,944.4	17,919.8
Series C Preferred Stock
Stockholders' Equity
Preferred Stock, No Par Value; Authorized 10,000,000 shares: Series C, outstanding shares of 16,000, Series D, outstanding shares of 5,000	388.5	$ 388.5
Series D Preferred Stock
Stockholders' Equity
Preferred Stock, No Par Value; Authorized 10,000,000 shares: Series C, outstanding shares of 16,000, Series D, outstanding shares of 5,000	$ 493.5

Consolidated Balance Sheet (Par

Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Held to maturity, fair value	$ 8,933.4	$ 8,905.1
Total loans and leases, unearned income	$ 39.1	$ 41.2
Preferred stock, par value (in dollars per share)	$ 0	$ 0
Preferred stock, authorized (in shares)	10,000,000	10,000,000
Common stock, par value (in dollars per share)	$ 1.6667	$ 1.6667
Common stock, authorized (in shares)	560,000,000	560,000,000
Common stock, outstanding (in shares)	229,585,949	228,605,485
Treasury stock, (in shares)	15,585,575	16,566,039
Series C Preferred Stock
Preferred stock, outstanding (in shares)	16,000	16,000
Series D Preferred Stock
Preferred stock, outstanding (in shares)	5,000	5,000

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Noninterest Income
Trust, Investment and Other Servicing Fees	$ 808.2	$ 748.2
Foreign Exchange Trading Income	48.1	60.5
Treasury Management Fees	14.7	16.2
Security Commissions and Trading Income	20.5	18.9
Other Operating Income	39.7	38.1
Investment Security Gains (Losses), net (Note)	(0.3)	0.3
Total Noninterest Income	930.9	882.2
Net Interest Income
Interest Income	410.3	352
Interest Expense	56.8	44.2
Net Interest Income	353.5	307.8
Provision for Credit Losses	(1)	2
Net Interest Income after Provision for Credit Losses	354.5	305.8
Noninterest Expense
Compensation	425.8	378.8
Employee Benefits	77.8	70.6
Outside Services	153.1	149.9
Equipment and Software	127.3	114.2
Occupancy	45.4	40.9
Other Operating Expense	65.1	74.4
Total Noninterest Expense	894.5	828.8
Income before Income Taxes	390.9	359.2
Provision for Income Taxes	114.8	113.8
Net Income	276.1	245.4
Preferred Stock Dividends	20.7	5.9
Net Income Applicable to Common Stock	$ 255.4	$ 239.5
Per Common Share
Net Income — Basic (in dollars per share)	$ 1.10	$ 1.03
Net Income - Diluted (in dollars per share)	$ 1.09	$ 1.03
Average number of common shares outstanding
Basic (in shares)	229,059,540	228,619,089
Diluted (in shares)	230,630,876	229,797,945
Changes in Other-Than-Temporary-Impairment (OTTI) Losses	$ (0.1)	$ 0
Other Security Gains (Losses), net	(0.2)	0.3
Investment Security Gains (Losses), net	$ (0.3)	$ 0.3

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net Income	$ 276.1	$ 245.4
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)
Net Unrealized Gains on Securities Available for Sale	19.3	74.7
Net Unrealized Gains (Losses) on Cash Flow Hedges	(5.3)	6.1
Foreign Currency Translation Adjustments	2	3.9
Pension and Other Postretirement Benefit Adjustments	2	4.1
Other Comprehensive Income (Loss)	18	88.8
Comprehensive Income	$ 294.1	$ 334.2

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Millions	Total	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning balance at Dec. 31, 2015		$ 388.5		$ 1,072.3	$ 8,242.8	$ (372.7)	$ (1,033.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Preferred Stock, Series D		0
Treasury Stock Transactions — Stock Options and Awards				(71.2)			76.6
Stock Options and Awards — Amortization				26.4
Stock Options and Awards — Tax Benefit				(9)
Net Income	$ 245.4				245.4
Dividends Declared — Common Stock					(83.9)
Dividends Declared — Preferred Stock					(5.9)
Net Unrealized Gains on Securities Available for Sale	74.7					74.7
Net Unrealized Gains (Losses) on Cash Flow Hedges	6.1					6.1
Foreign Currency Translation Adjustments	3.9					3.9
Pension and Other Postretirement Benefit Adjustments	4.1					4.1
Stock Purchased							(140.3)
Ending balance at Mar. 31, 2016	8,832.8	388.5	$ 408.6	1,018.5	8,398.4	(283.9)	(1,097.3)
Beginning balance at Dec. 31, 2016	9,770.4	882	408.6	1,035.8	8,908.4	(370)	(1,094.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Preferred Stock, Series D		0
Treasury Stock Transactions — Stock Options and Awards				(81.8)			119
Stock Options and Awards — Amortization				56.2
Stock Options and Awards — Tax Benefit				0
Net Income	276.1				276.1
Dividends Declared — Common Stock					(89.4)
Dividends Declared — Preferred Stock					(20.7)
Net Unrealized Gains on Securities Available for Sale	19.3					19.3
Net Unrealized Gains (Losses) on Cash Flow Hedges	(5.3)					(5.3)
Foreign Currency Translation Adjustments	2					2
Pension and Other Postretirement Benefit Adjustments	2					2
Stock Purchased	(70.1)						(70.1)
Ending balance at Mar. 31, 2017	$ 9,977.7	$ 882	$ 408.6	$ 1,010.2	$ 9,074.4	$ (352)	$ (1,045.5)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash Flows from Operating Activities:
Net Income	$ 276.1	$ 245.4
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Investment Security Losses (Gains), net	0.3	(0.3)
Amortization and Accretion of Securities and Unearned Income, net	18.9	12.5
Provision for Credit Losses	(1)	2
Depreciation on Buildings and Equipment	23.3	22.4
Pension Plan Contributions	(11.5)	(9.1)
Change in Receivables	(5.6)	(95.4)
Change in Interest Payable	5.9	2.3
Change in Collateral With Derivative Counterparties, net	572.5	(200.1)
Other Operating Activities, net	(172.2)	(343.1)
Net Cash Provided by (Used in) Operating Activities	784.7	(295.5)
Cash Flows from Investing Activities:
Net Change in Federal Funds Sold and Securities Purchased under Agreements to Resell	52.7	(143.9)
Change in Interest-Bearing Deposits with Banks	(327.8)	721.9
Net Change in Federal Reserve and Other Central Bank Deposits	767.1	1,987.3
Purchases of Securities — Held to Maturity	(2,284.1)	(1,287.7)
Proceeds from Maturity and Redemption of Securities — Held to Maturity	2,450.9	726.3
Purchases of Securities — Available for Sale	(2,633.6)	(3,285.2)
Proceeds from Sale, Maturity and Redemption of Securities — Available for Sale	3,235.9	2,416.6
Change in Loans and Leases	153	(950.6)
Purchases of Buildings and Equipment	(14.3)	(12)
Purchases and Development of Computer Software	(79.9)	(65)
Change in Client Security Settlement Receivables	(519.8)	261
Other Investing Activities, net	226.4	293.8
Net Cash Provided by Investing Activities	1,026.5	662.5
Cash Flows from Financing Activities:
Change in Deposits	(1,671.8)	388.6
Change in Federal Funds Purchased	164.7	(88.2)
Change in Securities Sold under Agreements to Repurchase	(40.4)	(39.5)
Change in Short-Term Other Borrowings	(1,030.6)	(27.1)
Repayments of Senior Notes and Long-Term Debt	(3.8)	(1.4)
Treasury Stock Purchased	(70.1)	(140.3)
Net Proceeds from Stock Options	37.2	5.3
Cash Dividends Paid on Common Stock	(86.9)	(82.8)
Cash Dividends Paid on Preferred Stock	(5.9)	(5.9)
Other Financing Activities, net	0	(8.9)
Net Cash Used in Financing Activities	(2,707.6)	(0.2)
Effect of Foreign Currency Exchange Rates on Cash	213.6	203.1
(Decrease) Increase in Cash and Due from Banks	(682.8)	569.9
Cash and Due from Banks at Beginning of Year	5,332	6,418.5
Cash and Due from Banks at End of Period	4,649.2	6,988.4
Supplemental Disclosures of Cash Flow Information:
Interest Paid	50.8	41.8
Income Taxes Paid	43.5	215
Transfers from Loans to OREO	2.3	4.6
Computer Software
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Amortization of Intangibles	75.6	65.8
Other Intangible Assets
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Amortization of Intangibles	$ 2.4	$ 2.1

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The consolidated financial statements include the accounts of Northern Trust Corporation (the Corporation) and its wholly-owned subsidiary, The Northern Trust Company (the Bank), and various other wholly-owned subsidiaries of the Corporation and the Bank. Throughout the notes, the term “Northern Trust” refers to the Corporation and its subsidiaries. Intercompany balances and transactions have been eliminated in consolidation. The consolidated financial statements, as of and for the periods ended March 31, 2017 and 2016 , have not been audited by the Corporation’s independent registered public accounting firm. In the opinion of management, all accounting entries and adjustments, including normal recurring accruals, necessary for a fair presentation of the financial position and the results of operations for the interim periods have been made. The accounting and financial reporting policies of Northern Trust conform to U.S. generally accepted accounting principles (GAAP) and reporting practices prescribed by the banking industry. The consolidated statements of income include results of acquired subsidiaries from the dates of acquisition. Certain amounts in prior periods have been reclassified to conform with the current year’s presentation. For a description of Northern Trust’s significant accounting policies, refer to Note 1 of the Notes to Consolidated Financial Statements in the Annual Report on Form 10-K for the year ended December 31, 2016 . Change in Presentation. Based on the increase in trade clearing activity taking place outside of the United States, during the year ended December 31, 2016, Northern Trust became a participant in the Clearing House Automated Payment System (CHAPS) in the United Kingdom. In addition, Northern Trust anticipates becoming a participant in the European solution for securities settlements, the Target 2 Securities (T2S) platform, in 2017. As a part of the implementation of these programs, management assessed the nature of Northern Trust’s deposits with non-U.S. central banks and determined that they were similar to the deposits Northern Trust has with the U.S. Federal Reserve System (Federal Reserve). As such, during the year ended December 31, 2016, the presentation of non-U.S. central bank deposits was combined with the presentation of Federal Reserve deposits on a single financial statement line, Federal Reserve and Other Central Bank Deposits, on the face of the consolidated balance sheets. Northern Trust determined that this change in presentation was material to the financial statements and has revised the prior-period presentation of the consolidated balance sheets, statements of cash flows and applicable notes to the financial statements. This change in presentation has no impact on the consolidated statements of income, comprehensive income or changes in stockholders’ equity. The table below shows the effect of the change in presentation on the Corporation’s consolidated statements of cash flows and related footnotes for the three months ended March 31, 2016 . Table 30: Change in Presentation Consolidated Statements of Cash Flows Three Months Ended March 31, 2016 (In Millions) Previously Reported Adjustment Revised Change in Interest-Bearing Deposits with Banks $ 716.7 $ 5.2 $ 721.9 Net Change in Federal Reserve Deposits 1,983.2 (1,983.2 ) — Net Change in Federal Reserve and Other Central Bank Deposits — 1,987.3 1,987.3 Net Cash Provided by Investing Activities 653.2 9.3 662.5 Effect of Foreign Currency Exchange Rates on Cash 202.9 0.2 203.1 Increase in Cash and Due from Banks 560.4 9.5 569.9 Cash and Due from Banks at Beginning of Year 6,444.6 (26.1 ) 6,418.5 Cash and Due from Banks at End of Period 7,005.0 (16.6 ) 6,988.4 Footnote 14 Net Interest Income Three Months Ended March 31, 2016 (In Millions) Previously Reported Adjustment Revised Interest-Bearing Due from and Deposits with Banks $ 23.7 $ (6.2 ) $ 17.5 Federal Reserve Deposits and Other 23.0 (23.0 ) — Federal Reserve and Other Central Bank Deposits $ — $ 29.2 $ 29.2 Adoption of ASU No. 2016-09. The Corporation adopted ASU No. 2016-09 on July 1, 2016 with an effective date of January 1, 2016, which resulted in a reclassification $3.6 million from additional paid-in capital to provision for income taxes, representing excess tax benefits previously recognized in additional paid-in-capital during the three months ended March 31, 2016 . Adoption of the standard impacted the Corporation’s previously reported quarterly results as follows: Three Months Ended March 31, 2016 ($ In Millions except per share data) As Reported As Adjusted Provision for Income Taxes $ 117.4 $ 113.8 Net Income 241.8 245.4 Earnings Allocated to Participating Securities 4.1 4.1 Net Income Applicable to Common Stock 235.9 239.5 Effective Tax Rate 32.7 % 31.7 % Basic Earnings per Share 1.01 1.03 Diluted Earnings per Share 1.01 1.03 Diluted Weighted Average Shares Outstanding (000s) 229,980 229,798 Additional Paid-In Capital 1,022.1 1,018.5 Retained Earnings 8,394.8 8,398.4

Recent Accounting Pronouncement

Recent Accounting Pronouncements	3 Months Ended
	Mar. 31, 2017
Accounting Changes and Error Corrections [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements On January 1, 2017, the Corporation adopted ASU 2016-05, “Derivatives and Hedging (Topics 815): Effects of Derivative Contract Novations on Existing Hedge Accounting Relationships (a consensus of the Emerging Issues Task Force)” (ASU 2016-05). ASU 2016-05 clarifies that a change in the counterparty to a derivative instrument that has been designated as the hedging instrument under Topic 815, does not, in and of itself, require dedesignation of that hedging relationship provided all other hedge accounting criteria continue to be met. Upon adoption of ASU 2016-05, the Corporation did not dedesignate any hedging relationships due to change in counterparty and therefore there was no impact to its consolidated financial condition or results of operations. On January 1, 2017, the Corporation adopted ASU 2016-06, “Derivatives and Hedging (Topic 815): Contingent Put and Call Options in Debt Instruments (a consensus of the Emerging Issues Task Force)” (ASU 2016-06). The amendments in ASU 2016-06 clarify what steps are required when assessing whether the economic characteristics and risks of call (put) options are clearly and closely related to the economic characteristics and risks of their debt hosts, which is one of the criteria for bifurcating an embedded derivative. The Corporation currently applies the approach for analyzing potential embedded derivative instruments in debt instruments detailed in ASU 2016-06 and therefore upon adoption there was no impact to its consolidated financial condition or results of operations. On January 1, 2017, the Corporation adopted ASU 2016-07, “Investments - Equity Method and Joint Ventures (Topic 323), Simplifying the Transition to the Equity Method of Accounting” (ASU 2016-07), which requires that when an investment qualifies for use of the equity method as a result of an increase in the level of ownership interest or degree of influence, the equity method investor add the cost of acquiring the additional interest in the investee to the current basis of the investor’s previously held interest and adopt the equity method of accounting as of the date the investment becomes qualified for equity method accounting. Upon adoption of ASU 2016-07, the Corporation did not hold an interest in an investee that subsequently qualified for the use of the equity method and therefore there was no impact to the Corporation’s consolidated financial condition or results of operations. On January 1, 2017, the Corporation adopted ASU 2016-17, “Consolidation (Topic 810): Interests Held through Related Parties That Are under Common Control” (ASU 2016-17). Under ASU 2016-17, a single decision maker evaluating whether it is the primary beneficiary of a variable interest entity will consider its indirect interests held by related parties that are under common control on a proportionate basis. Upon adoption of ASU 2016-17, there was no impact to the Corporation’s consolidated financial condition or results of operations.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Fair Value Hierarchy. The following describes the hierarchy of valuation inputs (Levels 1, 2, and 3) used to measure fair value and the primary valuation methodologies used by Northern Trust for financial instruments measured at fair value on a recurring basis. Observable inputs reflect market data obtained from sources independent of the reporting entity; unobservable inputs reflect the entity’s own assumptions about how market participants would value an asset or liability based on the best information available. GAAP requires an entity measuring fair value to maximize the use of observable inputs and minimize the use of unobservable inputs and establishes a fair value hierarchy of inputs. Financial instruments are categorized within the hierarchy based on the lowest level input that is significant to their valuation. Northern Trust’s policy is to recognize transfers into and transfers out of fair value levels as of the end of the reporting period in which the transfer occurred. No transfers between fair value levels occurred during the three months ended March 31, 2017 or the year ended December 31, 2016 . Level 1 — Quoted, active market prices for identical assets or liabilities. Northern Trust’s Level 1 assets are comprised of available for sale investments in U.S. treasury securities. Level 2 — Observable inputs other than Level 1 prices, such as quoted active market prices for similar assets or liabilities, quoted prices for identical or similar assets in inactive markets, and model-derived valuations in which all significant inputs are observable in active markets. Northern Trust’s Level 2 assets include available for sale and trading account securities, the fair values of which are determined predominantly by external pricing vendors. Prices received from vendors are compared to other vendor and third-party prices. If a security price obtained from a pricing vendor is determined to exceed pre-determined tolerance levels that are assigned based on an asset type’s characteristics, the exception is researched and, if the price is not able to be validated, an alternate pricing vendor is utilized, consistent with Northern Trust’s pricing source hierarchy. As of March 31, 2017 , Northern Trust’s available for sale securities portfolio included 1,434 Level 2 securities with an aggregate market value of $28.2 billion . All 1,434 securities were valued by external pricing vendors. As of December 31, 2016 , Northern Trust’s available for sale securities portfolio included 1,409 Level 2 securities with an aggregate market value of $28.1 billion . All 1,409 securities were valued by external pricing vendors. Trading account securities, which totaled $1.4 million and $0.3 million as of March 31, 2017 and December 31, 2016 , respectively, were all valued using external pricing vendors. Level 2 assets and liabilities also include derivative contracts which are valued internally using widely accepted income-based models that incorporate inputs readily observable in actively quoted markets and reflect the contractual terms of the contracts. Observable inputs include foreign exchange rates and interest rates for foreign exchange contracts; interest rates for interest rate swap contracts and forward contracts; and interest rates and volatility inputs for interest rate option contracts. Northern Trust evaluates the impact of counterparty credit risk and its own credit risk on the valuation of its derivative instruments. Factors considered include the likelihood of default by Northern Trust and its counterparties, the remaining maturities of the instruments, net exposures after giving effect to master netting arrangements or similar agreements, available collateral, and other credit enhancements in determining the appropriate fair value of derivative instruments. The resulting valuation adjustments have not been considered material. Level 3 — Valuation techniques in which one or more significant inputs are unobservable in the marketplace. Northern Trust’s Level 3 assets consist of auction rate securities purchased in 2008 from Northern Trust clients. To estimate the fair value of auction rate securities, Northern Trust uses external pricing vendors that incorporate transaction details and market based inputs such as past auction results, trades and bids. The significant unobservable inputs used in the fair value measurement are the prices of the securities supported by little market activity and for which trading is limited. Northern Trust’s Level 3 liabilities consist of swaps that Northern Trust entered into with the purchaser of 1.1 million and 1.0 million shares of Visa Inc. Class B common stock (Visa Class B common shares) previously held by Northern Trust and sold in June 2016 and 2015, respectively. Pursuant to the swaps, Northern Trust retains the risks associated with the ultimate conversion of the Visa Class B common shares into shares of Visa Inc. Class A common stock (Visa Class A common shares), such that the counterparty will be compensated for any dilutive adjustments to the conversion ratio and Northern Trust will be compensated for any anti-dilutive adjustments to the ratio. The swaps also require periodic payments from Northern Trust to the counterparty calculated by reference to the market price of Visa Class A common shares and a fixed rate of interest. The fair value of the swaps is determined using a discounted cash flow methodology. The significant unobservable inputs used in the fair value measurement are Northern Trust’s own assumptions about estimated changes in the conversion rate of the Visa Class B common shares into Visa Class A common shares, the date on which such conversion is expected to occur and the estimated growth rate of the Visa Class A common share price. See “Visa Class B Common Shares” under Note 19 — “Contingent Liabilities” for further information. Northern Trust believes its valuation methods for its assets and liabilities carried at fair value are appropriate; however, the use of different methodologies or assumptions, particularly as applied to Level 3 assets and liabilities, could have a material effect on the computation of their estimated fair values. The following presents the fair values of, and the valuation techniques, significant unobservable inputs, and quantitative information used to develop significant unobservable inputs for, Northern Trust’s Level 3 assets and liabilities as of March 31, 2017 and December 31, 2016 . Table 31: Level 3 Significant Unobservable Inputs March 31, 2017 Financial Instrument Fair Value Valuation Technique Unobservable Inputs Range of Inputs Auction Rate Securities $ 4.3 million Comparables Price $84 — 99 Swaps Related to Sale of Certain Visa Class B Common Shares $ 26.4 million Discounted Cash Flow Visa Class A Appreciation 7.0 % — 11.0% Conversion Rate 1.63x — 1.65x Expected Duration 1.25 — 4.25 years December 31, 2016 Financial Instrument Fair Value Valuation Technique Unobservable Inputs Range of Inputs Auction Rate Securities $ 4.7 million Comparables Price $84 — 99 Swap Related to Sale of Certain Visa Class B Common Shares $ 25.2 million Discounted Cash Flow Visa Class A Appreciation 7.0 % — 11.0% Conversion Rate 1.63x — 1.65x Expected Duration 1.50 — 4.50 years The following tables present assets and liabilities measured at fair value on a recurring basis as of March 31, 2017 and December 31, 2016 , segregated by fair value hierarchy level. Table 32: Recurring Basis Hierarchy Leveling (In Millions) Level 1 Level 2 Level 3 Netting Assets/Liabilities at Fair Value March 31, 2017 Securities Available for Sale U.S. Government $ 6,830.2 $ — $ — $ — $ 6,830.2 Obligations of States and Political Subdivisions — 951.5 — — 951.5 Government Sponsored Agency — 17,936.4 — — 17,936.4 Non-U.S. Government — 218.1 — — 218.1 Corporate Debt — 3,559.0 — — 3,559.0 Covered Bonds — 884.9 — — 884.9 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds — 1,761.3 — — 1,761.3 Other Asset-Backed — 2,351.9 — — 2,351.9 Auction Rate — — 4.3 — 4.3 Commercial Mortgage-Backed — 456.2 — — 456.2 Other — 43.8 — — 43.8 Total Available for Sale 6,830.2 28,163.1 4.3 — 34,997.6 Trading Account — 1.4 — — 1.4 Total Available for Sale and Trading Securities 6,830.2 28,164.5 4.3 — 34,999.0 Other Assets Derivative Assets Foreign Exchange Contracts — 1,882.3 — — 1,882.3 Interest Rate Contracts — 116.2 — — 116.2 Total Derivative Assets — 1,998.5 — (1,352.5 ) 646.0 Other Liabilities Derivative Liabilities Foreign Exchange Contracts — 1,874.7 — — 1,874.7 Interest Rate Contracts — 84.8 — — 84.8 Other Financial Derivatives (1) — — 26.4 — 26.4 Total Derivative Liabilities $ — $ 1,959.5 $ 26.4 $ (1,148.7 ) $ 837.2 Note: Northern Trust has elected to net derivative assets and liabilities when legally enforceable master netting arrangements or similar agreements exist between Northern Trust and the counterparty. As of March 31, 2017 , derivative assets and liabilities shown above also include reductions of $411.0 million and $207.2 million , respectively, as a result of cash collateral received from and deposited with derivative counterparties. (1) This line consists of swaps related to the sale of certain Visa Class B common shares. (In Millions) Level 1 Level 2 Level 3 Netting Assets/Liabilities at Fair Value December 31, 2016 Securities Available for Sale U.S. Government $ 7,522.6 $ — $ — $ — $ 7,522.6 Obligations of States and Political Subdivisions — 885.2 — — 885.2 Government Sponsored Agency — 17,892.8 — — 17,892.8 Non-U.S. Government — 417.9 — — 417.9 Corporate Debt — 3,765.2 — — 3,765.2 Covered Bonds — 1,143.9 — — 1,143.9 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds — 1,340.7 — — 1,340.7 Other Asset-Backed — 2,085.1 — — 2,085.1 Auction Rate — — 4.7 — 4.7 Commercial Mortgage-Backed — 471.6 — — 471.6 Other — 50.1 — — 50.1 Total Available for Sale 7,522.6 28,052.5 4.7 — 35,579.8 Trading Account — 0.3 — — 0.3 Total Available for Sale and Trading Securities 7,522.6 28,052.8 4.7 — 35,580.1 Other Assets Derivative Assets Foreign Exchange Contracts — 3,609.6 — — 3,609.6 Interest Rate Contracts — 247.2 — — 247.2 Total Derivative Assets — 3,856.8 — (2,170.4 ) 1,686.4 Other Liabilities Derivative Liabilities Foreign Exchange Contracts — 3,242.9 — — 3,242.9 Interest Rate Contracts — 108.0 — — 108.0 Other Financial Derivatives (1) — — 25.2 — 25.2 Total Derivative Liabilities $ — $ 3,350.9 $ 25.2 $ (2,431.2 ) $ 944.9 Note: Northern Trust has elected to net derivative assets and liabilities when legally enforceable master netting arrangements or similar agreements exist between Northern Trust and the counterparty. As of December 31, 2016 , derivative assets and liabilities shown above also include reductions of $461.3 million and $722.1 million , respectively, as a result of cash collateral received from and deposited with derivative counterparties. (1) This line consists of swaps related to the sale of certain Visa Class B common shares. The following tables present the changes in Level 3 assets and liabilities for the three months ended March 31, 2017 and 2016 . Table 33: Changes in Level 3 Assets Level 3 Assets (In Millions) Auction Rate Securities Three Months Ended March 31, 2017 2016 Fair Value at January 1 $ 4.7 $ 17.1 Total Gains (Losses): Included in Earnings — — Included in Other Comprehensive Income (1) — (0.4 ) Purchases, Issues, Sales, and Settlements Sales — (0.1 ) Settlements (0.4 ) — Fair Value at March 31 $ 4.3 $ 16.6 (1) Unrealized gains (losses) are included in net unrealized gains (losses) on securities available for sale in the consolidated statements of comprehensive income. Table 34: Changes in Level 3 Liabilities Level 3 Liabilities (In Millions) Swaps Related to Sale of Certain Visa Class B Common Shares Three Months Ended March 31, 2017 2016 Fair Value at January 1 $ 25.2 $ 10.8 Total (Gains) Losses: Included in Earnings (1) 2.9 (0.3 ) Included in Other Comprehensive Income — — Purchases, Issues, Sales, and Settlements Purchases — — Settlements (1.7 ) (0.8 ) Fair Value at March 31 $ 26.4 $ 9.7 (1) (Gains) losses are recorded in other operating income in the consolidated statements of income. During the three months ended March 31, 2017 and 2016 , there were no transfers into or out of Level 3 assets or liabilities. Carrying values of assets and liabilities that are not measured at fair value on a recurring basis may be adjusted to fair value in periods subsequent to their initial recognition, for example, to record an impairment of an asset. GAAP requires entities to disclose separately these subsequent fair value measurements and to classify them under the fair value hierarchy. Assets measured at fair value on a nonrecurring basis at March 31, 2017 and 2016 , all of which were categorized as Level 3 under the fair value hierarchy, were comprised of impaired loans whose values were based on real estate and other available collateral, and of other real estate owned (OREO) properties. Fair values of real-estate loan collateral were estimated using a market approach typically supported by third-party valuations and property-specific fees and taxes, and were subject to adjustments to reflect management’s judgment as to realizable value. Other loan collateral, which typically consists of accounts receivable, inventory and equipment, is valued using a market approach adjusted for asset-specific characteristics and in limited instances third-party valuations are used. OREO assets are carried at the lower of cost or fair value less estimated costs to sell, with fair value typically based on third-party appraisals. Collateral-based impaired loans and OREO assets that have been adjusted to fair value totaled $28.7 million and $0.6 million , respectively, at March 31, 2017 , and $10.1 million and $2.5 million , respectively, at March 31, 2016 . Assets measured at fair value on a nonrecurring basis reflect management’s judgment as to realizable value. The following table provides the fair value of, and the valuation technique, significant unobservable inputs and quantitative information used to develop the significant unobservable inputs for, Northern Trust’s Level 3 assets that were measured at fair value on a nonrecurring basis as of March 31, 2017 and December 31, 2016 . Table 35: Level 3 Nonrecurring Basis Significant Unobservable Inputs March 31, 2017 Financial Instrument Fair Value Valuation Technique Unobservable Input Range of Discounts Applied Loans $28.7 million Market Approach Discount to reflect realizable value 15.0 % - 25.0% OREO $0.6 million Market Approach Discount to reflect realizable value 15.0 % - 20.0% December 31, 2016 Financial Instrument Fair Value Valuation Technique Unobservable Input Range of Discounts Applied Loans $6.7 million Market Approach Discount to reflect realizable value 15.0 % - 25.0% OREO $0.7 million Market Approach Discount to reflect realizable value 15.0 % - 20.0% Fair Value of Financial Instruments. GAAP requires disclosure of the estimated fair value of certain financial instruments and the methods and significant assumptions used to estimate fair value. It excludes from this requirement nonfinancial assets and liabilities, as well as a wide range of franchise, relationship and intangible values that add value to Northern Trust. Accordingly, the required fair value disclosures provide only a partial estimate of the fair value of Northern Trust. Financial instruments recorded at fair value in Northern Trust’s consolidated balance sheets are discussed above. The following methods and assumptions were used in estimating the fair values of financial instruments that are not carried at fair value. Held to Maturity Securities. The fair values of held to maturity securities, excluding U.S. treasury securities, were obtained from external pricing vendors, or in limited cases internally, using widely accepted models which are based on an income approach (discounted cash flow) that incorporates current market yield curves. The fair values of U.S. treasury securities were determined using quoted, active market prices for identical securities. Loans (excluding lease receivables). The fair value of the loan portfolio was estimated using an income approach (discounted cash flow) that incorporates current market rates offered by Northern Trust as of the date of the consolidated financial statements. The fair values of all loans were adjusted to reflect current assessments of loan collectability. Loans held for sale are recorded at the lower of cost or fair value. Federal Reserve and Federal Home Loan Bank Stock. The fair values of Federal Reserve and Federal Home Loan Bank stock are equal to their carrying values which represent redemption value. Community Development Investments. The fair values of these instruments were estimated using an income approach (discounted cash flow) that incorporates current market rates. Employee Benefit and Deferred Compensation. These assets include U.S. Treasury securities and investments in mutual and collective trust funds held to fund certain supplemental employee benefit obligations and deferred compensation plans. Fair values of U.S. Treasury securities were determined using quoted, active market prices for identical securities. The fair values of investments in mutual and collective trust funds were valued at the funds’ net asset values based on a market approach. Savings Certificates and Other Time Deposits. The fair values of these instruments were estimated using an income approach (discounted cash flow) that incorporates market interest rates currently offered by Northern Trust for deposits with similar maturities. Senior Notes, Subordinated Debt, and Floating Rate Capital Debt. Fair values were determined using a market approach based on quoted market prices, when available. If quoted market prices were not available, fair values were based on quoted market prices for comparable instruments. Federal Home Loan Bank Borrowings. The fair values of these instruments were estimated using an income approach (discounted cash flow) that incorporates market interest rates available to Northern Trust. Loan Commitments. The fair values of loan commitments represent the estimated costs to terminate or otherwise settle the obligations with a third party adjusted for any related allowance for credit losses. Standby Letters of Credit. The fair values of standby letters of credit are measured as the amount of unamortized fees on these instruments, inclusive of the related allowance for credit losses. Fees are determined by applying basis points to the principal amounts of the letters of credit. Financial Instruments Valued at Carrying Value. Due to their short maturity, the carrying values of certain financial instruments approximated their fair values. These financial instruments include: cash and due from banks; federal funds sold and securities purchased under agreements to resell; interest-bearing deposits with banks; Federal Reserve and other central bank deposits; client security settlement receivables; non-U.S. offices interest-bearing deposits; federal funds purchased; securities sold under agreements to repurchase; and other borrowings (includes term federal funds purchased and other short-term borrowings). The fair values of demand, noninterest-bearing, savings, and money market deposits represent the amounts payable on demand as of the reporting date, although such deposits are typically priced at a premium in banking industry consolidations. The following tables summarize the fair values of all financial instruments. Table 36: Fair Value of Financial Instruments (In Millions) March 31, 2017 Book Value Total Fair Value Fair Value Level 1 Level 2 Level 3 Assets Cash and Due from Banks $ 4,649.2 $ 4,649.2 $ 4,649.2 $ — $ — Federal Reserve and Other Central Bank Deposits 25,959.5 25,959.5 — 25,959.5 — Interest-Bearing Deposits with Banks 5,247.8 5,247.8 — 5,247.8 — Federal Funds Sold and Resell Agreements 1,933.8 1,933.8 — 1,933.8 — Securities Available for Sale (Note) 34,997.6 34,997.6 6,830.2 28,163.1 4.3 Held to Maturity 8,938.4 8,933.4 6.0 8,927.4 — Trading Account 1.4 1.4 — 1.4 — Loans (excluding Leases) Held for Investment 33,056.5 33,151.9 — — 33,151.9 Held for Sale — — — — — Client Security Settlement Receivables 1,559.9 1,559.9 — 1,559.9 — Other Assets Federal Reserve and Federal Home Loan Bank Stock 158.1 158.1 — 158.1 — Community Development Investments 209.8 209.8 — 209.8 — Employee Benefit and Deferred Compensation 185.2 182.3 118.3 64.0 — Liabilities Deposits Demand, Noninterest-Bearing, Savings and Money Market $ 46,425.4 $ 46,425.4 $ 46,425.4 $ — $ — Savings Certificates and Other Time 1,346.8 1,351.4 — 1,351.4 — Non U.S. Offices Interest-Bearing 52,757.3 52,757.3 — 52,757.3 — Federal Funds Purchased 369.5 369.5 — 369.5 — Securities Sold under Agreements to Repurchase 433.2 433.2 — 433.2 — Other Borrowings 4,077.1 4,079.7 — 4,079.7 — Senior Notes 1,496.8 1,537.3 — 1,537.3 — Long Term Debt (excluding Leases) Subordinated Debt 1,302.5 1,315.5 — 1,315.5 — Floating Rate Capital Debt 277.4 252.6 — 252.6 — Other Liabilities Standby Letters of Credit 36.8 36.8 — — 36.8 Loan Commitments 37.5 37.5 — — 37.5 Derivative Instruments Asset/Liability Management Foreign Exchange Contracts Assets $ 30.5 $ 30.5 $ — $ 30.5 $ — Liabilities 42.1 42.1 — 42.1 — Interest Rate Contracts Assets 39.4 39.4 — 39.4 — Liabilities 17.5 17.5 — 17.5 — Other Financial Derivatives Liabilities (1) 26.4 26.4 — — 26.4 Client-Related and Trading Foreign Exchange Contracts Assets 1,851.8 1,851.8 — 1,851.8 — Liabilities 1,832.6 1,832.6 — 1,832.6 — Interest Rate Contracts Assets 76.8 76.8 — 76.8 — Liabilities 67.3 67.3 — 67.3 — Note: Refer to the table located on page 32 for the disaggregation of available for sale securities. (1) This line consists of swaps related to the sale of certain Visa Class B common shares. (In Millions) December 31, 2016 Book Value Total Fair Value Fair Value Level 1 Level 2 Level 3 Assets Cash and Due from Banks $ 5,332.0 $ 5,332.0 $ 5,332.0 $ — $ — Federal Reserve and Other Central Bank Deposits 26,674.2 26,674.2 — 26,674.2 — Interest-Bearing Deposits with Banks 4,800.6 4,800.6 — 4,800.6 — Federal Funds Sold and Resell Agreements 1,974.3 1,974.3 — 1,974.3 — Securities Available for Sale (Note) 35,579.8 35,579.8 7,522.6 28,052.5 4.7 Held to Maturity 8,921.1 8,905.1 15.0 8,890.1 — Trading Account 0.3 0.3 — 0.3 — Loans (excluding Leases) Held for Investment 33,354.1 33,471.3 — — 33,471.3 Held for Sale 13.4 13.4 — — 13.4 Client Security Settlement Receivables 1,043.7 1,043.7 — 1,043.7 — Other Assets Federal Reserve and Federal Home Loan Bank Stock 203.1 203.1 — 203.1 — Community Development Investments 218.9 215.5 — 215.5 — Employee Benefit and Deferred Compensation 166.2 162.5 107.2 55.3 — Liabilities Deposits Demand, Noninterest-Bearing, Savings and Money Market $ 46,671.9 $ 46,671.9 $ 46,671.9 $ — $ — Savings Certificates and Other Time 1,331.7 1,337.5 — 1,337.5 — Non U.S. Offices Interest-Bearing 53,648.1 53,648.1 — 53,648.1 — Federal Funds Purchased 204.8 204.8 — 204.8 — Securities Sold under Agreements to Repurchase 473.7 473.7 — 473.7 — Other Borrowings 5,109.5 5,113.4 — 5,113.4 — Senior Notes 1,496.6 1,535.5 — 1,535.5 — Long Term Debt (excluding Leases) Subordinated Debt 1,307.9 1,316.0 — 1,316.0 — Floating Rate Capital Debt 277.4 251.0 — 251.0 — Other Liabilities Standby Letters of Credit 37.2 37.2 — — 37.2 Loan Commitments 41.2 41.2 — — 41.2 Derivative Instruments Asset/Liability Management Foreign Exchange Contracts Assets $ 335.4 $ 335.4 $ — $ 335.4 $ — Liabilities 21.2 21.2 — 21.2 — Interest Rate Contracts Assets 160.2 160.2 — 160.2 — Liabilities 22.8 22.8 — 22.8 — Other Financial Derivatives Liabilities (1) 25.2 25.2 — — 25.2 Client-Related and Trading Foreign Exchange Contracts Assets 3,274.2 3,274.2 — 3,274.2 — Liabilities 3,221.7 3,221.7 — 3,221.7 — Interest Rate Contracts Assets 87.0 87.0 — 87.0 — Liabilities 85.2 85.2 — 85.2 — Note: Refer to the table located on page 33 for the disaggregation of available for sale securities. (1) This line consists of swaps related to the sale of certain Visa Class B common shares.

Securities

Securities	3 Months Ended
	Mar. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Securities	Securities The following tables provide the amortized cost and fair values of securities at March 31, 2017 and December 31, 2016 . Table 37: Reconciliation of Amortized Cost to Fair Value of Securities Available for Sale Securities Available for Sale March 31, 2017 Amortized Cost Gross Unrealized Fair Value (In Millions) Gains Losses U.S. Government $ 6,815.5 $ 27.9 $ 13.2 $ 6,830.2 Obligations of States and Political Subdivisions 953.2 0.2 1.9 951.5 Government Sponsored Agency 17,947.4 52.6 63.6 17,936.4 Non-U.S. Government 219.8 — 1.7 218.1 Corporate Debt 3,578.0 3.6 22.6 3,559.0 Covered Bonds 887.3 1.1 3.5 884.9 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 1,761.0 3.1 2.8 1,761.3 Other Asset-Backed 2,349.0 4.4 1.5 2,351.9 Auction Rate 4.6 — 0.3 4.3 Commercial Mortgage-Backed 459.1 — 2.9 456.2 Other 43.8 — — 43.8 Total $ 35,018.7 $ 92.9 $ 114.0 $ 34,997.6 Securities Available for Sale December 31, 2016 Amortized Cost Gross Unrealized Fair Value (In Millions) Gains Losses U.S. Government $ 7,514.5 $ 22.4 $ 14.3 $ 7,522.6 Obligations of States and Political Subdivisions 890.8 — 5.6 885.2 Government Sponsored Agency 17,914.1 49.3 70.6 17,892.8 Non-U.S. Government 420.0 — 2.1 417.9 Corporate Debt 3,787.4 2.6 24.8 3,765.2 Covered Bonds 1,148.6 0.8 5.5 1,143.9 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 1,343.6 0.9 3.8 1,340.7 Other Asset-Backed 2,083.7 2.7 1.3 2,085.1 Auction Rate 5.0 — 0.3 4.7 Commercial Mortgage-Backed 474.1 — 2.5 471.6 Other 50.1 — — 50.1 Total $ 35,631.9 $ 78.7 $ 130.8 $ 35,579.8 Table 38: Reconciliation of Amortized Cost to Fair Value of Securities Held to Maturity Securities Held to Maturity March 31, 2017 Amortized Cost Gross Unrealized Fair Value (In Millions) Gains Losses U.S Government $ 6.0 $ — $ — $ 6.0 Obligations of States and Political Subdivisions 49.0 2.6 — 51.6 Government Sponsored Agency 6.8 0.5 — 7.3 Corporate Debt 252.6 0.1 0.4 252.3 Covered Bonds 2,295.6 11.6 2.7 2,304.5 Non-U.S. Government 3,282.6 6.6 0.4 3,288.8 Certificates of Deposit 306.5 — — 306.5 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 2,422.3 10.8 1.3 2,431.8 Other Asset-Backed 186.4 1.6 — 188.0 Other 130.6 — 34.0 96.6 Total $ 8,938.4 $ 33.8 $ 38.8 $ 8,933.4 Securities Held to Maturity December 31, 2016 Amortized Cost Gross Unrealized Fair Value (In Millions) Gains Losses U.S Government $ 15.0 $ — $ — $ 15.0 Obligations of States and Political Subdivisions 63.6 2.7 — 66.3 Government Sponsored Agency 7.4 0.5 — 7.9 Corporate Debt 231.2 0.2 0.4 231.0 Covered Bonds 2,051.6 10.1 3.7 2,058.0 Non-U.S. Government 3,517.5 4.9 2.3 3,520.1 Certificates of Deposit 606.0 0.2 0.1 606.1 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 2,154.7 10.5 2.8 2,162.4 Other Asset-Backed 143.4 0.1 — 143.5 Other 130.7 — 35.9 94.8 Total $ 8,921.1 $ 29.2 $ 45.2 $ 8,905.1 Securities held to maturity consist of debt securities that management intends to, and Northern Trust has the ability to, hold until maturity. The following table provides the remaining maturity of securities as of March 31, 2017 . Table 39: Remaining Maturity of Securities Available for Sale and Held to Maturity March 31, 2017 (In Millions) Amortized Cost Fair Value Available for Sale Due in One Year or Less $ 6,665.1 $ 6,660.1 Due After One Year Through Five Years 21,136.2 21,124.3 Due After Five Years Through Ten Years 6,015.5 6,017.7 Due After Ten Years 1,201.9 1,195.5 Total 35,018.7 34,997.6 Held to Maturity Due in One Year or Less 2,914.6 2,916.9 Due After One Year Through Five Years 5,764.1 5,783.4 Due After Five Years Through Ten Years 201.2 200.2 Due After Ten Years 58.5 32.9 Total $ 8,938.4 $ 8,933.4 Note: Mortgage-backed and asset-backed securities are included in the above table taking into account anticipated future prepayments. Investment Security Gains / Losses. Net investment security losses of $0.3 million were recognized in the three months ended March 31, 2017 , which include $0.1 million of charges related to the other-than-temporary impairment (OTTI) of certain Community Reinvestment ACT (CRA) eligible held to maturity securities. Net investment security gains of $0.3 million were recognized in the three months ended March 31, 2016 . For three months ended March 31, 2017 , proceeds of $541.3 million were received from the sale of securities resulting in gross realized losses of $0.2 million . For the three months ended March 31, 2016, proceeds of $513.6 million were received from the sale of securities, resulting in realized gross gains of $0.3 million . Securities with Unrealized Losses. The following tables provide information regarding securities that had been in a continuous unrealized loss position for less than twelve months and for twelve months or longer as of March 31, 2017 and December 31, 2016 . Table 40: Securities with Unrealized Losses Securities with Unrealized Losses as of March 31, 2017 Less than 12 Months 12 Months or Longer Total (In Millions) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. Government $ 1,701.3 $ 13.2 $ — $ — $ 1,701.3 $ 13.2 Obligations of States and Political Subdivisions 750.1 1.9 — — 750.1 1.9 Government Sponsored Agency 7,455.5 51.5 2,433.8 12.1 9,889.3 63.6 Non-U.S. Government 1,729.3 2.1 — — 1,729.3 2.1 Corporate Debt 1,555.2 9.6 807.3 13.4 2,362.5 23.0 Covered Bonds 829.3 6.0 139.2 0.2 968.5 6.2 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 1,089.2 3.4 249.3 0.7 1,338.5 4.1 Other Asset-Backed 714.5 1.5 — — 714.5 1.5 Auction Rate 0.4 0.1 3.8 0.2 4.2 0.3 Commercial Mortgage-Backed 439.3 2.9 — — 439.3 2.9 Other 48.4 14.1 51.6 19.9 100.0 34.0 Total $ 16,312.5 $ 106.3 $ 3,685.0 $ 46.5 $ 19,997.5 $ 152.8 Securities with Unrealized Losses as of December 31, 2016 Less than 12 Months 12 Months or Longer Total (In Millions) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. Government $ 1,603.0 $ 14.3 $ — $ — $ 1,603.0 $ 14.3 Obligations of States and Political Subdivisions 865.3 5.6 — — 865.3 5.6 Government Sponsored Agency 8,252.5 58.5 2,121.0 12.1 10,373.5 70.6 Non-U.S. Government 2,957.1 4.4 — — 2,957.1 4.4 Corporate Debt 1,601.7 11.2 1,054.4 14.0 2,656.1 25.2 Covered Bonds 809.0 8.6 138.9 0.6 947.9 9.2 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 1,136.1 5.7 249.1 0.9 1,385.2 6.6 Other Asset-Backed 584.3 1.3 — — 584.3 1.3 Certificates of Deposit 81.4 0.1 — — 81.4 0.1 Auction Rate 0.4 0.1 4.3 0.2 4.7 0.3 Commercial Mortgage-Backed 471.5 2.5 — — 471.5 2.5 Other 50.5 17.9 59.7 18.0 110.2 35.9 Total $ 18,412.8 $ 130.2 $ 3,627.4 $ 45.8 $ 22,040.2 $ 176.0 As of March 31, 2017 , 1,074 securities with a combined fair value of $20.0 billion were in an unrealized loss position, with their unrealized losses totaling $152.8 million . Unrealized losses of $63.6 million related to government sponsored agency securities are primarily attributable to changes in market interest rates since their purchase. Unrealized losses of $23.0 million within corporate debt securities primarily reflect widened credit spreads and higher market rates since purchase; 35% of the corporate debt portfolio is backed by guarantees provided by U.S. and non-U.S. governmental entities. The majority of the $34.0 million of unrealized losses in securities classified as “other” at March 31, 2017 , related to securities primarily purchased at a premium or par by Northern Trust for compliance with the CRA. Unrealized losses on these CRA-related securities were attributable to yields that were below market rates for the purpose of supporting institutions and programs that benefit low- to moderate- income communities within Northern Trust’s market area. Unrealized losses of $0.3 million related to auction rate securities primarily reflected reduced market liquidity as a majority of auctions continued to fail, preventing holders from liquidating their investments at par. The remaining unrealized losses on Northern Trust’s securities portfolio as of March 31, 2017 , were attributable to changes in overall market interest rates, increased credit spreads or reduced market liquidity. As of March 31, 2017 , Northern Trust did not intend to sell any investment in an unrealized loss position and it was more likely than not that Northern Trust would not be required to sell any such investment before the recovery of its amortized cost basis, which may be maturity. Security impairment reviews are conducted quarterly to identify and evaluate securities that have indications of possible OTTI. A determination as to whether a security’s decline in market value is other-than-temporary takes into consideration numerous factors and the relative significance of any single factor can vary by security. Factors Northern Trust considers in determining whether impairment is other-than-temporary include, but are not limited to: the length of time the security has been impaired; the severity of the impairment; the cause of the impairment and the financial condition and near-term prospects of the issuer; activity in the market of the issuer, which may indicate adverse credit conditions; Northern Trust’s intent regarding the sale of the security as of the balance sheet date; and the likelihood that it will not be required to sell the security for a period of time sufficient to allow for the recovery of the security’s amortized cost basis. For each security meeting the requirements of Northern Trust’s internal screening process, an extensive review is conducted to determine if OTTI has occurred. While all securities are considered, the process for identifying credit impairment within CRA-eligible mortgage-backed securities incorporates an expected loss approach using discounted cash flows on the underlying collateral pools. To evaluate whether an unrealized loss on CRA-eligible mortgage-backed securities is other-than-temporary, a calculation of the security’s present value is made using current pool data, the current delinquency pipeline, default rates and loan loss severities based on the historical performance of the mortgage pools, and Northern Trust’s outlook for the housing market and the overall economy. If the present value of the collateral pools was found to be less than the current amortized cost of the security, a credit-related OTTI loss would be recorded in earnings equal to the difference between the two amounts. Impairments of CRA-eligible mortgage-backed securities are influenced by a number of factors, including but not limited to, U.S. economic and housing market performance, pool credit enhancement level, year of origination and estimated credit quality of the collateral. The factors used in estimating losses related to CRA-eligible mortgage-backed securities vary by vintage of loan origination and collateral quality. There were $0.1 million of OTTI losses recognized in the three months ended March 31, 2017 related to CRA-eligible mortgage-backed securities. There were no OTTI losses recognized during the three months ended March 31, 2016 . Credit Losses on Debt Securities. The table below provides the cumulative credit-related losses recognized in earnings on debt securities other-than-temporarily impaired. Table 41: Cumulative Credit-Related Losses on Securities Three Months Ended March 31, (In Millions) 2017 2016 Cumulative Credit-Related Losses on Securities Held — Beginning of Period $ 3.4 $ 5.2 Plus: Losses on Newly Identified Impairments — — Additional Losses on Previously Identified Impairments 0.1 — Less: Current and Prior Period Losses on Securities Sold During the Period — — Cumulative Credit-Related Losses on Securities Held — End of Period $ 3.5 $ 5.2

Securities Sold Under Agreement

Securities Sold Under Agreements to Repurchase	3 Months Ended
	Mar. 31, 2017
Banking and Thrift [Abstract]
Securities Sold Under Agreements to Repurchase	Securities Sold Under Agreements to Repurchase Securities sold under agreements to repurchase are accounted for as collateralized financings and recorded at the amounts at which the securities were sold plus accrued interest. To minimize any potential credit risk associated with these transactions, the fair value of the securities sold is monitored, limits are set on exposure with counterparties, and the financial condition of counterparties is regularly assessed. Securities sold under agreements to repurchase are held by the counterparty until the repurchase. The following table provides information regarding repurchase agreements that are accounted for as secured borrowings as of March 31, 2017 . Table 42: Repurchase Agreements Accounted for as Secured Borrowings March 31, 2017 (In Millions) Remaining Contractual Maturity of the Agreements Repurchase Agreements Overnight and Continuous U.S. Treasury and Agency Securities $ 433.2 Total Borrowings $ 433.2 Gross Amount of Recognized Liabilities for Repurchase Agreements in Note 21 $ 433.2 Amounts related to agreements not included in Note 21 $ —

Loans and Leases

Loans and Leases	3 Months Ended
	Mar. 31, 2017
Receivables [Abstract]
Loans and Leases	Loans and Leases Amounts outstanding for loans and leases, by segment and class, are shown below. Table 43: Loans and Leases (In Millions) March 31, December 31, Commercial Commercial and Institutional $ 9,487.3 $ 9,523.0 Commercial Real Estate 3,922.8 4,002.5 Non-U.S. 1,654.0 1,877.8 Lease Financing, net 253.6 293.9 Other 209.7 205.1 Total Commercial 15,527.4 15,902.3 Personal Private Client 10,375.8 10,052.0 Residential Real Estate 7,542.1 7,841.9 Other 26.5 25.9 Total Personal 17,944.4 17,919.8 Total Loans and Leases 33,471.8 33,822.1 Allowance for Credit Losses Assigned to Loans and Leases (162.0 ) (161.0 ) Net Loans and Leases $ 33,309.8 $ 33,661.1 Residential real estate loans consist of traditional first lien mortgages and equity credit lines that generally require a loan-to-collateral value of no more than 65% to 80% at inception. Northern Trust’s equity credit line products generally have draw periods of up to 10 years and a balloon payment of any outstanding balance is due at maturity. Payments are interest only with variable interest rates. Northern Trust does not offer equity credit lines that include an option to convert the outstanding balance to an amortizing payment loan. As of March 31, 2017 and December 31, 2016 , equity credit lines totaled $1.1 billion and $1.2 billion , respectively, and equity credit lines for which first liens were held by Northern Trust represented 92% and 91% of the total equity credit lines as of March 31, 2017 and December 31, 2016 , respectively. Included within the non-U.S., commercial-other and personal-other classes are short-duration advances primarily related to the processing of custodied client investments that totaled $920.1 million at March 31, 2017 , and $1.4 billion at December 31, 2016 . Demand deposits reclassified as loan balances totaled $74.8 million and $88.1 million at March 31, 2017 and December 31, 2016 , respectively. There were no loans classified as held for sale as of March 31, 2017 . Loans classified as held for sale totaled $13.4 million as of December 31, 2016 . Leases classified as held for sale totaled $32.3 million as of March 31, 2017 and $43.0 million as of December 31, 2016 , respectively, related to the decision to exit a non-strategic loan and lease portfolio. Credit Quality Indicators. Credit quality indicators are statistics, measurements or other metrics that provide information regarding the relative credit risk of loans and leases. Northern Trust utilizes a variety of credit quality indicators to assess the credit risk of loans and leases at the segment, class and individual credit exposure levels. As part of its credit process, Northern Trust utilizes an internal borrower risk rating system to support identification, approval and monitoring of credit risk. Borrower risk ratings are used in credit underwriting, management reporting and the calculation of credit loss allowances and economic capital. Risk ratings are used for ranking the credit risk of borrowers and the probability of their default. Each borrower is rated using one of a number of ratings models or other subjective assessment methodologies, which consider both quantitative and qualitative factors. The ratings models vary among classes of loans and leases in order to capture the unique risk characteristics inherent within each particular type of credit exposure. Provided below are the more significant performance indicator attributes considered within Northern Trust’s borrower rating models, by loan and lease class. • Commercial and Institutional: leverage, profit margin, liquidity, asset size and capital levels; • Commercial Real Estate: debt service coverage, loan-to-value ratio, leasing status and guarantor support; • Lease Financing and Commercial-Other: leverage, profit margin, liquidity, asset size and capital levels; • Non-U.S.: leverage, profit margin, liquidity, return on assets and capital levels; • Residential Real Estate: payment history, credit bureau scores and loan-to-value ratio; • Private Client: cash-flow-to-debt and net worth ratios, leverage and liquidity; and • Personal-Other: cash-flow-to-debt and net worth ratios. While the criteria vary by model, the objective is for the borrower ratings to be consistent in both the measurement and ranking of risk. Each model is calibrated to a master rating scale to support this consistency. Ratings for borrowers not in default range from “1” for the strongest credits to “7” for the weakest non-defaulted credits. Ratings of “8” or “9” are used for defaulted borrowers. Borrower risk ratings are monitored and are revised when events or circumstances indicate a change is required. Risk ratings are validated at least annually. Loan and lease segment and class balances as of March 31, 2017 and December 31, 2016 are provided below, segregated by borrower ratings into “1 to 3,” “4 to 5” and “6 to 9” (watch list), categories. Table 44: Borrower Ratings March 31, 2017 December 31, 2016 (In Millions) 1 to 3 Category 4 to 5 Category 6 to 9 Category (Watch List) Total 1 to 3 Category 4 to 5 Category 6 to 9 Category (Watch List) Total Commercial Commercial and Institutional $ 6,278.1 $ 3,080.6 $ 128.6 $ 9,487.3 $ 6,293.2 $ 3,108.5 $ 121.3 $ 9,523.0 Commercial Real Estate 1,742.3 2,157.6 22.9 3,922.8 1,825.7 2,134.8 42.0 4,002.5 Non-U.S. 379.9 1,272.8 1.3 1,654.0 602.8 1,273.5 1.5 1,877.8 Lease Financing, net 200.8 52.8 — 253.6 214.3 79.6 — 293.9 Other 113.4 95.5 0.8 209.7 135.5 67.9 1.7 205.1 Total Commercial 8,714.5 6,659.3 153.6 15,527.4 9,071.5 6,664.3 166.5 15,902.3 Personal Private Client 6,526.9 3,839.4 9.5 10,375.8 6,373.2 3,668.4 10.4 10,052.0 Residential Real Estate 2,564.4 4,664.3 313.4 7,542.1 2,617.8 4,913.9 310.2 7,841.9 Other 14.4 12.0 0.1 26.5 17.1 8.5 0.3 25.9 Total Personal 9,105.7 8,515.7 323.0 17,944.4 9,008.1 8,590.8 320.9 17,919.8 Total Loans and Leases $ 17,820.2 $ 15,175.0 $ 476.6 $ 33,471.8 $ 18,079.6 $ 15,255.1 $ 487.4 $ 33,822.1 Loans and leases in the “1 to 3” category are expected to exhibit minimal to modest probabilities of default and are characterized by borrowers having the strongest financial qualities, including above average financial flexibility, cash flows and capital levels. Borrowers assigned these ratings are anticipated to experience very little to moderate financial pressure in adverse down cycle scenarios. As a result of these characteristics, borrowers within this category exhibit a minimal to modest likelihood of loss. Loans and leases in the “4 to 5” category are expected to exhibit moderate to acceptable probabilities of default and are characterized by borrowers with less financial flexibility than those in the “1 to 3” category. Cash flows and capital levels are generally sufficient to allow for borrowers to meet current requirements, but have reduced cushion in adverse down cycle scenarios. As a result of these characteristics, borrowers within this category exhibit a moderate likelihood of loss. Loans and leases in the watch list category have elevated credit risk profiles that are monitored through internal watch lists, and consist of credits with borrower ratings of “6 to 9.” These credits, which include all nonperforming credits, are expected to exhibit minimally acceptable probabilities of default, elevated risk of default, or are currently in default. Borrowers associated with these risk profiles that are not currently in default have limited financial flexibility. Cash flows and capital levels range from acceptable to potentially insufficient to meet current requirements, particularly in adverse down cycle scenarios. As a result of these characteristics, borrowers in this category exhibit an elevated likelihood of loss. Recognition of Income. Interest income on loans is recorded on an accrual basis unless, in the opinion of management, there is a question as to the ability of the debtor to meet the terms of the loan agreement, or interest or principal is more than 90 days contractually past due and the loan is not well-secured and in the process of collection. Loans meeting such criteria are classified as nonperforming and interest income is recorded on a cash basis. At the time a loan is determined to be nonperforming, interest accrued but not collected is reversed against interest income in the current period. Interest collected on nonperforming loans is applied to principal unless, in the opinion of management, collectability of principal is not in doubt. Management’s assessment of the indicators of loan and lease collectability, and its policies relative to the recognition of interest income, including the suspension and subsequent resumption of income recognition, do not meaningfully vary between loan and lease classes. Nonperforming loans are returned to performing status when factors indicating doubtful collectability no longer exist. Factors considered in returning a loan to performing status are consistent across all classes of loans and leases and, in accordance with regulatory guidance, relate primarily to expected payment performance. Loans are eligible to be returned to performing status when: (i) no principal or interest that is due is unpaid and repayment of the remaining contractual principal and interest is expected or (ii) the loan has otherwise become well-secured (possessing realizable value sufficient to discharge the debt, including accrued interest, in full) and is in the process of collection (through action reasonably expected to result in debt repayment or restoration to a current status in the near future). A loan that has not been brought fully current may be restored to performing status provided there has been a sustained period of repayment performance (generally a minimum of six months) by the borrower in accordance with the contractual terms, and Northern Trust is reasonably assured of repayment within a reasonable period of time. Additionally, a loan that has been formally restructured so as to be reasonably assured of repayment and performance according to its modified terms may be returned to accrual status, provided there was a well-documented credit evaluation of the borrower’s financial condition and prospects of repayment under the revised terms and there has been a sustained period of repayment performance (generally a minimum of six months) under the revised terms. Past due status is based on how long since the contractual due date a principal or interest payment has been past due. For disclosure purposes, loans that are 29 days past due or less are reported as current. The following tables provide balances and delinquency status of performing and nonperforming loans and leases by segment and class, as well as the total OREO and nonperforming asset balances, as of March 31, 2017 and December 31, 2016 . Table 45: Delinquency Status March 31, 2017 (In Millions) Current 30-59 Days Past Due 60-89 Days Past Due 90 Days or More Past Due Total Performing Nonperforming Total Loans and Leases Commercial Commercial and Institutional $ 9,398.5 $ 21.8 $ 2.4 $ 4.0 $ 9,426.7 $ 60.6 $ 9,487.3 Commercial Real Estate 3,887.8 15.8 3.0 4.1 3,910.7 12.1 3,922.8 Non-U.S. 1,654.0 — — — 1,654.0 — 1,654.0 Lease Financing, net 253.6 — — — 253.6 — 253.6 Other 209.7 — — — 209.7 — 209.7 Total Commercial 15,403.6 37.6 5.4 8.1 15,454.7 72.7 15,527.4 Personal Residential Real Estate 7,389.4 40.0 5.6 0.1 7,435.1 107.0 7,542.1 Private Client 10,216.4 155.0 2.5 1.7 10,375.6 0.2 10,375.8 Other 26.5 — — — 26.5 — 26.5 Total Personal 17,632.3 195.0 8.1 1.8 17,837.2 107.2 17,944.4 Total Loans and Leases $ 33,035.9 $ 232.6 $ 13.5 $ 9.9 $ 33,291.9 $ 179.9 $ 33,471.8 Other Real Estate Owned $ 6.9 Total Nonperforming Assets $ 186.8 December 31, 2016 (In Millions) Current 30-59 Days Past Due 60-89 Days Past Due 90 Days or More Past Due Total Performing Nonperforming Total Loans and Leases Commercial Commercial and Institutional $ 9,470.0 $ 5.3 $ 2.3 $ 11.7 $ 9,489.3 $ 33.7 $ 9,523.0 Commercial Real Estate 3,974.4 10.9 1.0 4.6 3,990.9 11.6 4,002.5 Non-U.S. 1,877.7 0.1 — — 1,877.8 — 1,877.8 Lease Financing, net 293.9 — — — 293.9 — 293.9 Other 205.1 — — — 205.1 — 205.1 Total Commercial 15,821.1 16.3 3.3 16.3 15,857.0 45.3 15,902.3 Personal Private Client 9,988.7 40.8 8.5 13.7 10,051.7 0.3 10,052.0 Residential Real Estate 7,675.7 44.5 6.1 1.0 7,727.3 114.6 7,841.9 Other 25.9 — — — 25.9 — 25.9 Total Personal 17,690.3 85.3 14.6 14.7 17,804.9 114.9 17,919.8 Total Loans and Leases $ 33,511.4 $ 101.6 $ 17.9 $ 31.0 $ 33,661.9 $ 160.2 $ 33,822.1 Other Real Estate Owned $ 5.2 Total Nonperforming Assets $ 165.4 Impaired Loans. A loan is considered to be impaired when, based on current information and events, management determines that it is probable that Northern Trust will be unable to collect all amounts due according to the contractual terms of the loan agreement. Impaired loans are identified through ongoing credit management and risk rating processes, including the formal review of past due and watch list credits. Payment performance and delinquency status are critical factors in identifying impairment for all loans and leases, particularly those within the residential real estate, private client and personal-other classes. Other key factors considered in identifying impairment of loans and leases within the commercial and institutional, non-U.S., lease financing, and commercial-other classes relate to the borrower’s ability to perform under the terms of the obligation as measured through the assessment of future cash flows, including consideration of collateral value, market value, and other factors. A loan is also considered to be impaired if its terms have been modified as a concession by Northern Trust or a bankruptcy court resulting from the debtor’s financial difficulties, referred to as a troubled debt restructuring (TDR). All TDRs are reported as impaired loans in the calendar year of their restructuring. In subsequent years, a TDR may cease being reported as impaired if the loan was modified at a market rate and has performed according to the modified terms for at least six payment periods. A loan that has been modified at a below market rate will return to performing status if it satisfies the six payment periods performance requirement; however, it will remain reported as impaired. Impairment is measured based upon the present value of expected future cash flows, discounted at the loan's original effective interest rate, the fair value of the collateral if the loan is collateral dependent, or the loan's observable market value. If the loan valuation is less than the recorded value of the loan, based on the certainty of loss, either a specific allowance is established, or a charge-off is recorded, for the difference. Smaller balance (individually less than $1 million ) homogeneous loans are collectively evaluated for impairment and excluded from impaired loan disclosures as allowed under applicable accounting standards. Northern Trust’s accounting policies for material impaired loans is consistent across all classes of loans and leases. The following tables provide information related to impaired loans by segment and class. Table 46: Information about Impaired Loans as of the Period End As of March 31, 2017 As of December 31, 2016 (In Millions) Recorded Investment Unpaid Principal Balance Specific Allowance Recorded Investment Unpaid Principal Balance Specific Allowance With No Related Specific Allowance Commercial and Institutional $ 31.9 $ 34.5 $ — $ 32.2 $ 34.6 $ — Commercial Real Estate 11.6 14.1 — 14.7 18.6 — Lease Financing, net — — — — — — Private Client 0.1 0.1 — 0.3 0.3 — Residential Real Estate 91.8 127.5 — 101.2 138.4 — With a Related Specific Allowance Commercial and Institutional 27.3 27.6 7.2 — — — Commercial Real Estate 2.8 2.8 0.7 — — — Lease Financing, net — — — — — — Private Client — — — — — — Residential Real Estate 7.3 7.4 0.8 7.7 7.9 2.1 Total Commercial 73.6 79.0 7.9 46.9 53.2 — Personal 99.2 135.0 0.8 109.2 146.6 2.1 Total $ 172.8 $ 214.0 $ 8.7 $ 156.1 $ 199.8 $ 2.1 Three Months Ended March 31, 2017 2016 (In Millions) Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized With No Related Specific Allowance Commercial and Institutional $ 39.0 $ — $ 28.3 $ — Commercial Real Estate 14.9 0.1 17.7 0.1 Lease Financing, net — — 0.4 0.1 Private Client 0.2 — 0.3 — Residential Real Estate 101.7 0.5 99.6 0.4 With a Related Specific Allowance Commercial and Institutional 9.1 — 8.4 — Commercial Real Estate 0.9 — — — Lease Financing, net — — 2.1 — Private Client — — — — Residential Real Estate 2.4 — 1.5 — Total Commercial 63.9 0.1 56.9 0.2 Personal 104.3 0.5 101.4 0.4 Total $ 168.2 $ 0.6 $ 158.3 $ 0.6 Note: Average recorded investment in impaired loans is calculated as the average of the month-end impaired loan balances for the period. Interest income that would have been recorded for nonperforming loans in accordance with their original terms was $2.3 million and $2.1 million , respectively, for the three months ended March 31, 2017 and 2016 . There were $5.0 million and $2.3 million of aggregate undrawn loan commitments and standby letters of credit at March 31, 2017 and December 31, 2016 , respectively, issued to borrowers whose loans were classified as nonperforming or impaired. Troubled Debt Restructurings (TDRs). Included within impaired loans were $79.9 million and $85.2 million of nonperforming TDRs, and $37.9 million and $42.4 million of performing TDRs as of March 31, 2017 and December 31, 2016 , respectively. All TDRs are reported as impaired loans in the calendar year of their restructuring. In subsequent years, a TDR may cease being reported as impaired if the loan was modified at a market rate and has performed according to the modified terms for at least six months. A loan that has been modified at a below market rate will return to performing status if it satisfies the six-month performance requirement; however, it will remain reported as impaired. The following tables provide, by segment and class, the number of loans and leases modified in TDRs during the three - month periods ended March 31, 2017 and 2016 , and the recorded investments and unpaid principal balances as of March 31, 2017 and 2016 . Table 47: Modified Troubled Debt Restructurings ($ In Millions) Three Months Ended March 31, 2017 Number of Loans and Leases Recorded Investment Unpaid Principal Balance Commercial Commercial and Institutional — $ — $ — Commercial Real Estate 1 1.4 1.4 Total Commercial 1 1.4 1.4 Personal Private Client 1 — 0.1 Residential Real Estate 19 3.9 3.9 Total Personal 20 3.9 4.0 Total Loans and Leases 21 $ 5.3 $ 5.4 Note: Period end balances reflect all paydowns and charge-offs during the period. ($ In Millions) Three Months Ended March 31, 2016 Number of Loans and Leases Recorded Investment Unpaid Principal Balance Commercial Commercial and Institutional 2 $ 4.0 $ 6.0 Commercial Real Estate 5 5.4 7.7 Total Commercial 7 9.4 13.7 Personal Private Client — — — Residential Real Estate 24 5.5 6.2 Total Personal 24 5.5 6.2 Total Loans and Leases 31 $ 14.9 $ 19.9 Note: Period end balances reflect all paydowns and charge-offs during the period. TDR modifications involve interest rate concessions, extensions of term, deferrals of principal and other modifications. Other modifications typically reflect other nonstandard terms which Northern Trust would not offer in non-troubled situations. During the three months ended March 31, 2017 , the majority of TDR modifications of loans within residential real estate were extension of term, other modifications, interest rate concessions and deferred principal. During the three months ended March 31, 2017 , the majority of TDR modifications within commercial real estate were extension of term, and other modifications. During the three months ended March 31, 2016 , the majority of TDR modifications of loans within residential real estate were deferred principal, extension of term, interest rate concessions, and other modifications. During the three months ended March 31, 2016 , the majority of TDR modifications within commercial and institutional, and commercial real estate classes were extension of term and other modifications. There were no loans modified in a TDR during the twelve months ended December 31, 2016 , which subsequently became nonperforming during the three months ended March 31, 2017 . There was one loan modified in a TDR during the twelve months ended December 31, 2015 , which subsequently became nonperforming during the three months ended March 31, 2016 . The total recorded investment and unpaid principal balance for these loans was approximately $ 0.1 million . All loans and leases modified in TDRs are evaluated for impairment. The nature and extent of impairment of TDRs, including those that have experienced a subsequent default, is considered in the determination of an appropriate level of allowance for credit losses. Northern Trust may obtain physical possession of residential real estate collateralizing a consumer mortgage loan via foreclosure on an in-substance repossession. As of March 31, 2017 , Northern Trust held foreclosed residential real estate properties with a carrying value of $5.9 million as a result of obtaining physical possession. In addition, as of March 31, 2017 , Northern Trust had consumer loans with a carrying value of $26.1 million collateralized by residential real estate property for which formal foreclosure proceedings were in process.

Allowance for Credit Losses

Allowance for Credit Losses	3 Months Ended
	Mar. 31, 2017
Receivables [Abstract]
Allowance for Credit Losses	Allowance for Credit Losses The allowance for credit losses, which represents management’s estimate of probable losses related to specific borrower relationships and inherent in the various loan and lease portfolios, undrawn commitments, and standby letters of credit, is determined by management through a disciplined credit review process. Northern Trust’s accounting policies related to the estimation of the allowance for credit losses and the charging off of loans, leases and other extensions of credit deemed uncollectible are consistent across both loan and lease segments. Loans, leases and other extensions of credit deemed uncollectible are charged to the allowance for credit losses. Subsequent recoveries, if any, are credited to the allowance. Determinations as to whether an uncollectible loan is charged-off or a specific allowance is established are based on management’s assessment as to the level of certainty regarding the amount of loss. The following table provides information regarding changes in the total allowance for credit losses by segment during the three months ended March 31, 2017 and 2016 . Table 48: Changes in the Allowance for Credit Losses Three Months Ended March 31, 2017 2016 (In Millions) Commercial Personal Total Commercial Personal Total Balance at Beginning of Period $ 104.9 $ 87.1 $ 192.0 $ 114.8 $ 118.5 $ 233.3 Charge-Offs (1.1 ) (3.6 ) (4.7 ) (3.5 ) (1.8 ) (5.3 ) Recoveries 1.6 1.1 2.7 1.2 1.4 2.6 Net (Charge-Offs) Recoveries 0.5 (2.5 ) (2.0 ) (2.3 ) (0.4 ) (2.7 ) Provision for Credit Losses 6.4 (7.4 ) (1.0 ) 2.7 (0.7 ) 2.0 Balance at End of Period $ 111.8 $ 77.2 $ 189.0 $ 115.2 $ 117.4 $ 232.6 The following table provides information regarding the recorded investments in loans and leases and the allowance for credit losses by segment as of March 31, 2017 and December 31, 2016 . Table 49: Recorded Investments in Loans and Leases March 31, 2017 December 31, 2016 (In Millions) Commercial Personal Total Commercial Personal Total Loans and Leases Specifically Evaluated for Impairment $ 73.6 $ 99.2 $ 172.8 $ 46.9 $ 109.2 $ 156.1 Evaluated for Inherent Impairment 15,453.8 17,845.2 33,299.0 15,855.4 17,810.6 33,666.0 Total Loans and Leases 15,527.4 17,944.4 33,471.8 15,902.3 17,919.8 33,822.1 Allowance for Credit Losses on Credit Exposures Specifically Evaluated for Impairment 7.9 0.8 8.7 — 2.1 2.1 Evaluated for Inherent Impairment 83.6 69.7 153.3 83.7 75.2 158.9 Allowance Assigned to Loans and Leases 91.5 70.5 162.0 83.7 77.3 161.0 Allowance for Undrawn Exposures Commitments and Standby Letters of Credit 20.3 6.7 27.0 21.2 9.8 31.0 Total Allowance for Credit Losses $ 111.8 $ 77.2 $ 189.0 $ 104.9 $ 87.1 $ 192.0

Pledged Assets

Pledged Assets	3 Months Ended
	Mar. 31, 2017
Transfers and Servicing [Abstract]
Pledged Assets	Pledged Assets Certain of Northern Trust’s subsidiaries, as required or permitted by law, pledge assets to secure public and trust deposits, repurchase agreements and Federal Home Loan Bank borrowings, as well as for other purposes, including support for securities settlement, primarily related to client activities, and for potential Federal Reserve Bank discount window borrowings. As of March 31, 2017 , securities and loans totaling $42.6 billion ( $31.5 billion of government-sponsored agency and other securities, $990.4 million of obligations of states and political subdivisions and $10.1 billion of loans) were pledged. This compares to $40.3 billion ( $29.7 billion of government-sponsored agency and other securities, $939.8 million of obligations of states and political subdivisions and $9.6 billion of loans) at December 31, 2016 . Collateral required for these purposes totaled $7.1 billion and $9.7 billion at March 31, 2017 and December 31, 2016 , respectively. Available for sale securities with a total fair value of $1.3 billion and $1.4 billion at March 31, 2017 and December 31, 2016 were included in the total pledged assets, which were pledged as collateral for agreements to repurchase securities sold transactions. The secured parties to these transactions have the right to repledge or sell these securities. Northern Trust is not permitted, by contract or custom, to repledge or sell collateral from agreements to resell securities purchased transactions. The total fair value of accepted collateral was $1.6 billion as of March 31, 2017 and $1.8 billion as of December 31, 2016 . There was no repledged or sold collateral at March 31, 2017 or December 31, 2016 . Deposits maintained to meet Federal Reserve Bank reserve requirements averaged $2.0 billion and $1.8 billion for the three months ended March 31, 2017 and 2016 .

Goodwill and Other Intangibles

Goodwill and Other Intangibles	3 Months Ended
	Mar. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangibles	Goodwill and Other Intangibles The carrying amounts of goodwill and other intangibles assets, reflecting the effect of foreign exchange rates on non-U.S.-dollar-denominated balances, by reporting segment at March 31, 2017 , and December 31, 2016 , were as follows: Table 50: Goodwill by Reporting Segment (In Millions) March 31, December 31, Corporate & Institutional Services $ 448.3 $ 448.4 Wealth Management 71.0 71.0 Total Goodwill $ 519.3 $ 519.4 The gross carrying amount and accumulated amortization of other intangible assets subject to amortization as of March 31, 2017 and December 31, 2016 , were as follows: Table 51: Other Intangible Assets (In Millions) March 31, December 31, Gross Carrying Amount $ 90.9 $ 89.0 Less: Accumulated Amortization 49.8 47.2 Net Book Value $ 41.1 $ 41.8 Other intangible assets consist primarily of the value of acquired client relationships and are included within other assets in the consolidated balance sheets. Amortization expense related to other intangible assets totaled $2.4 million and $2.1 million for the three months ended March 31, 2017 and 2016 , respectively. Amortization for the remainder of 2017 and for the years 2018 , 2019 , 2020 , and 2021 is estimated to be $6.7 million , $8.3 million , $8.2 million , $8.2 million and $5.9 million , respectively. On February 19, 2017, the Corporation entered into a definitive agreement with UBS AG to acquire UBS Asset Management’s fund administration servicing businesses in Luxembourg and Switzerland, for an initial purchase price of approximately $175 million in cash, subject to adjustment. The transaction is expected to close in the second half of 2017, subject to applicable regulatory and fund board approvals and other customary closing conditions.

Reporting Segments

Reporting Segments	3 Months Ended
	Mar. 31, 2017
Segment Reporting [Abstract]
Reporting Segments	Reporting Segments The following table shows the earnings contributions of Northern Trust’s reporting segments for the three -month periods ended March 31, 2017 and 2016 . Table 52: Results of Reporting Segments Three Months Ended March 31, Corporate & Wealth Treasury and Total ($ In Millions) 2017 2016 2017 2016 2017 2016 2017 2016 Noninterest Income Trust, Investment and Other Servicing Fees $ 462.9 $ 433.4 $ 345.3 $ 314.8 $ — $ — $ 808.2 $ 748.2 Foreign Exchange Trading Income 49.1 51.7 0.9 4.5 (1.9 ) 4.3 48.1 60.5 Other Noninterest Income 44.2 45.6 25.5 26.8 4.9 1.1 74.6 73.5 Net Interest Income* 166.5 138.4 177.0 158.5 18.9 17.1 362.4 314.0 Revenue* 722.7 669.1 548.7 504.6 21.9 22.5 1,293.3 1,196.2 Provision for Credit Losses 0.3 (3.2 ) (1.3 ) 5.2 — — (1.0 ) 2.0 Noninterest Expense 510.8 475.3 346.3 326.9 37.4 26.6 894.5 828.8 Income before Income Taxes* 211.6 197.0 203.7 172.5 (15.5 ) (4.1 ) 399.8 365.4 Provision for Income Taxes* 66.9 62.2 76.8 64.9 (20.0 ) (7.1 ) 123.7 120.0 Net Income $ 144.7 $ 134.8 $ 126.9 $ 107.6 $ 4.5 $ 3.0 $ 276.1 $ 245.4 Percentage of Consolidated Net Income 52 % 55 % 46 % 44 % 2 % 1 % 100 % 100 % Average Assets $ 77,803.5 $ 75,372.9 $ 26,661.8 $ 26,237.8 $ 12,011.1 $ 11,806.4 $ 116,476.4 $ 113,417.1 * Non-GAAP financial measures stated on a fully taxable equivalent basis (FTE). Total consolidated includes FTE adjustments of $8.9 million for 2017 and $6.2 million for 2016 . Further discussion of reporting segment results is provided within the “Reporting Segments” section of Management’s Discussion and Analysis of Financial Condition and Results of Operations.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Preferred Stock. The Corporation is authorized to issue 10 million shares of preferred stock without par value. The Board of Directors is authorized to fix the particular designations, preferences and relative, participating, optional and other special rights and qualifications, limitations or restrictions for each series of preferred stock issued. On August 8, 2016 , the Corporation issued and sold 500,000 depositary shares (the “Depositary Shares”), each representing a 1/100th ownership interest in a share of Series D Non-Cumulative Perpetual Preferred Stock (the “Series D Preferred Stock”). Shares of the Series D Preferred Stock have no par value and a liquidation preference of $100,000 (equivalent to $1,000 per depositary share). The aggregate proceeds from the public offering of the depositary shares, net of underwriting discounts, commissions and offering expenses, were $493.5 million . Dividends on the Series D Preferred Stock, which are not mandatory, will accrue and be payable on the liquidation preference amount, on a non-cumulative basis, at a rate per annum equal to (i) 4.60% from the original issue date of the Series D Preferred Stock to but excluding October 1, 2026 ; and (ii) a floating rate equal to Three-Month LIBOR plus 3.202% from and including October 1, 2026 . Fixed rate dividends will be payable in arrears on the 1st day of April and October of each year, commencing on April 1, 2017 , to and including October 1, 2026 , and floating rate dividends will be payable in arrears on the 1st day of January, April, July and October of each year, commencing on January 1, 2027 . The Series D Preferred Stock has no maturity date and is redeemable at the Corporation’s option, in whole or in part, on any dividend payment date on or after October 1, 2026 . The Series D Preferred Stock is redeemable at the Corporation’s option in whole, but not in part, including prior to October 1, 2026 , within 90 days of a regulatory capital treatment event, as described in the Series D Preferred Stock Certificate of Designation. On January 17, 2017 , the Corporation declared a cash dividend of $2,977.222222 per share of Series D Preferred Stock payable on April 1, 2017 , to stockholders of record as of March 15, 2017 . This initial dividend payment on the Series D preferred stock covers the period from the date of issuance of such stock through March 31, 2017. As of March 31, 2017 , the Corporation also had issued and outstanding 16 million depositary shares, each representing 1/1000th ownership interest in a share of Series C Non-Cumulative Perpetual Preferred Stock (“Series C Preferred Stock”), issued in August 2014. Equity related to Series C Preferred Stock as of March 31, 2017 and December 31, 2016 totaled $388.5 million . Series C Preferred Stock has no par value and has a liquidation preference of $25,000 ( $25 per depositary share). Dividends on the Series C Preferred Stock, which are not mandatory, accrue and are payable on the liquidation preference amount, on a non-cumulative basis, quarterly in arrears on the first day of January, April, July and October of each year, at a rate per annum equal to 5.85% . On January 17, 2017 , the Corporation declared a cash dividend of $365.625 per share of Series C Preferred Stock payable on April 1, 2017 , to stockholders of record as of March 15, 2017 . The Series C Preferred Stock has no maturity date and is redeemable at the Corporation’s option, in whole or in part, on any dividend payment date on or after October 1, 2019. The Series C Preferred stock is redeemable at the Corporation’s option, in whole, but not in part, including prior to October 1, 2019, within 90 days of a regulatory capital treatment event, as described in the Series C Preferred Stock Certificate of Designation. Shares of the Series C Preferred Stock and Series D Preferred Stock rank senior to the Corporation’s common stock, and will rank at least equally with any other series of preferred stock it may issue (except for any senior series that may be issued with the requisite consent of the holders of the Series C Preferred Stock and Series D Preferred Stock, respectively) and all other parity stock, with respect to the payment of dividends and distributions upon liquidation, dissolution or winding up. Common Stock. During the three months ended March 31, 2017 , the Corporation repurchased 811,730 shares of common stock, including 410,869 shares withheld related to share-based compensation, at a total cost of $70.1 million ( $86.39 average price per share). The Corporation’s current common stock repurchase authorization was approved by the Board of Directors in April 2015. The repurchased shares are used for general purposes by the Corporation, including management of the Corporation’s capital level and the issuance of shares under stock option and other incentive plans of the Corporation. The repurchase authorization approved by the Board of Directors has no expiration date. Under the Corporation’s 2016 Capital Plan, which was reviewed without objection by the Federal Reserve, the Corporation may repurchase up to $74.8 million of common stock after March 31, 2017 through June 2017 .

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) The following tables summarize the components of accumulated other comprehensive income (loss) (AOCI) at March 31, 2017 and 2016 , and changes during the three -month periods then ended. Table 53: Summary of Changes in Accumulated Other Comprehensive Income (Loss) (In Millions) Balance at March 31, 2017 Net Change Balance at December 31, 2016 Net Unrealized Gains (Losses) on Securities Available for Sale $ (13.1 ) $ 19.3 $ (32.4 ) Net Unrealized Gains (Losses) on Cash Flow Hedges 0.8 (5.3 ) 6.1 Net Foreign Currency Adjustments (16.5 ) 2.0 (18.5 ) Net Pension and Other Postretirement Benefit Adjustments (323.2 ) 2.0 (325.2 ) Total $ (352.0 ) $ 18.0 $ (370.0 ) (In Millions) Balance at March 31, 2016 Net Change Balance at December 31, 2015 Net Unrealized Gains (Losses) on Securities Available for Sale $ 43.7 $ 74.7 $ (31.0 ) Net Unrealized Gains (Losses) on Cash Flow Hedges 3.1 6.1 (3.0 ) Net Foreign Currency Adjustments (13.7 ) 3.9 (17.6 ) Net Pension and Other Postretirement Benefit Adjustments (317.0 ) 4.1 (321.1 ) Total $ (283.9 ) $ 88.8 $ (372.7 ) Table 54: Details of Changes in Accumulated Other Comprehensive Income (Loss) Three Months Ended March 31, 2017 2016 (In Millions) Before Tax Tax Effect After Tax Before Tax Tax Effect After Tax Unrealized Gains (Losses) on Securities Available for Sale Other Unrealized Gains (Losses) on Securities Available for Sale 30.9 (11.7 ) 19.2 120.5 (45.6 ) 74.9 Reclassification Adjustment for (Gains) Losses Included in Net Income 0.2 (0.1 ) 0.1 (0.3 ) 0.1 (0.2 ) Net Change 31.1 (11.8 ) 19.3 120.2 (45.5 ) 74.7 Unrealized Gains (Losses) on Cash Flow Hedges Unrealized Gains (Losses) on Cash Flow Hedges 8.7 (10.8 ) (2.1 ) 9.4 (3.7 ) 5.7 Reclassification Adjustment for (Gains) Losses Included in Net Income (5.1 ) 1.9 (3.2 ) 0.6 (0.2 ) 0.4 Net Change 3.6 (8.9 ) (5.3 ) 10.0 (3.9 ) 6.1 Foreign Currency Adjustments Foreign Currency Translation Adjustments 22.4 (1.5 ) 20.9 17.3 (0.3 ) 17.0 Long-Term Intra-Entity Foreign Currency Transaction Gains (Losses) — — — 4.2 (1.0 ) 3.2 Net Investment Hedge Gains (Losses) (30.5 ) 11.6 (18.9 ) (26.5 ) 10.2 (16.3 ) Reclassification Adjustment for (Gains) Losses Included in Net Income — — — — — — Net Change (8.1 ) 10.1 2.0 (5.0 ) 8.9 3.9 Pension and Other Postretirement Benefit Adjustments Net Actuarial Gain (Loss) (2.3 ) — (2.3 ) — — — Reclassification Adjustment for (Gains) Losses Included in Net Income 6.4 (2.1 ) 4.3 6.4 (2.3 ) 4.1 Net Change $ 4.1 $ (2.1 ) $ 2.0 $ 6.4 $ (2.3 ) $ 4.1 The following table provides the location and before-tax amounts of reclassifications out of AOCI during the three months ended March 31, 2017 . Table 55: Reclassification Adjustment out of Accumulated Other Comprehensive Income (Loss) (In Millions) Location of Reclassification Adjustments Recognized in Income Amount of Reclassification Adjustments Recognized in Income Three Months Ended March 31, 2017 Securities Available for Sale Realized (Gains) Losses on Securities Available for Sale Investment Security Gains (Losses), net $ 0.2 Realized Gains on Cash Flow Hedges Foreign Exchange Contracts Other Operating Income/Expense (5.1 ) Pension and Other Postretirement Benefit Adjustments Amortization of Net Actuarial Loss Employee Benefits 6.5 Amortization of Prior Service Cost Employee Benefits (0.1 ) Gross Reclassification Adjustment $ 6.4

Net Income Per Common Share Com

Net Income Per Common Share Computations	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
Net Income Per Common Share Computations	Net Income Per Common Share Computations The computations of net income per common share are presented in the following table. Table 56: Net Income per Common Share Three Months Ended March 31, ($ In Millions Except Per Common Share Information) 2017 2016 Basic Net Income Per Common Share Average Number of Common Shares Outstanding 229,059,540 228,619,089 Net Income $ 276.1 $ 245.4 Less: Dividends on Preferred Stock 20.7 5.9 Net Income Applicable to Common Stock 255.4 239.5 Less: Earnings Allocated to Participating Securities 4.5 4.1 Earnings Allocated to Common Shares Outstanding 250.9 235.4 Basic Net Income Per Common Share $ 1.10 $ 1.03 Diluted Net Income Per Common Share Average Number of Common Shares Outstanding 229,059,540 228,619,089 Plus: Dilutive Effect of Share-based Compensation 1,571,336 1,178,856 Average Common and Potential Common Shares 230,630,876 229,797,945 Earnings Allocated to Common and Potential Common Shares $ 250.9 $ 235.5 Diluted Net Income Per Common Share 1.09 1.03 Note: Common stock equivalents of 468,381 and 1,796,320 for the three months ended March 31, 2017 and 2016 , respectively, were not included in the computation of diluted net income per common share because their inclusion would have been antidilutive.

Net Interest Income

Net Interest Income	3 Months Ended
	Mar. 31, 2017
Banking and Thrift, Interest [Abstract]
Net Interest Income	Net Interest Income The components of net interest income were as follows: Table 57: Net Interest Income Three Months Ended March 31, (In Millions) 2017 2016 Interest Income Loans and Leases $ 213.4 $ 200.9 Securities — Taxable 143.2 103.3 — Non-Taxable 2.6 1.1 Interest-Bearing Due from and Deposits with Banks (1) 14.9 17.5 Federal Reserve and Other Central Bank Deposits 36.2 29.2 Total Interest Income 410.3 352.0 Interest Expense Deposits 27.6 22.2 Federal Funds Purchased 0.5 0.3 Securities Sold Under Agreements to Repurchase 0.9 0.4 Other Borrowings 7.6 2.7 Senior Notes 11.7 11.7 Long-Term Debt 7.4 6.1 Floating Rate Capital Debt 1.1 0.8 Total Interest Expense 56.8 44.2 Net Interest Income $ 353.5 $ 307.8 (1) Interest-Bearing Due from and Deposits with Banks includes the interest-bearing component of Cash and Due from Banks and Interest-Bearing Deposits with Banks as presented on the consolidated balance sheets.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income tax expense for the three months ended March 31, 2017 was $114.8 million , representing an effective tax rate of 29.4% . The prior-year three -month provision for income taxes was $113.8 million , representing an effective tax rate of 31.7% .

Pension and Postretirement Heal

Pension and Postretirement Health Care	3 Months Ended
	Mar. 31, 2017
Compensation and Retirement Disclosure [Abstract]
Pension and Postretirement Health Care	Pension and Postretirement Health Care The following tables set forth the net periodic pension and postretirement benefit expense for Northern Trust’s U.S. and non-U.S. pension plans, supplemental pension plan, and postretirement health care plan for the three months ended March 31, 2017 and 2016 . Table 58: Net Periodic Pension Expense (Benefit) Net Periodic Pension Expense U.S. Plan Three Months Ended March 31, (In Millions) 2017 2016 Service Cost $ 9.6 $ 9.3 Interest Cost 11.5 11.5 Expected Return on Plan Assets (23.5 ) (23.6 ) Amortization Net Actuarial Loss 4.8 4.7 Prior Service Cost (0.1 ) (0.1 ) Net Periodic Pension Expense $ 2.3 $ 1.8 Net Periodic Pension Expense Non-U.S. Plans Three Months Ended March 31, (In Millions) 2017 2016 Interest Cost $ 0.9 $ 1.3 Expected Return on Plan Assets (1.1 ) (1.3 ) Net Actuarial Loss Amortization 0.3 0.3 Net Periodic Pension Expense $ 0.1 $ 0.3 Net Periodic Pension Expense Supplemental Plan Three Months Ended March 31, (In Millions) 2017 2016 Service Cost $ 0.9 $ 0.9 Interest Cost 1.3 1.3 Amortization Net Actuarial Loss 1.4 1.5 Prior Service Cost — — Net Periodic Pension Expense $ 3.6 $ 3.7 Net Periodic Postretirement Expense Postretirement Health Care Plan Three Months Ended March 31, (In Millions) 2017 2016 Service Cost $ — $ — Interest Cost 0.4 0.4 Amortization Net Actuarial (Gain) — — Net Periodic Postretirement Expense $ 0.4 $ 0.4

Share-Based Compensation Plans

Share-Based Compensation Plans	3 Months Ended
	Mar. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation Plans	Share-Based Compensation Plans The Northern Trust Corporation 2012 Stock Plan provides for the grant of nonqualified stock options, incentive stock options, stock appreciation rights, stock awards, restricted stock units and performance stock units. Beginning with grants made on or after February 21, 2017, restricted stock unit and performance stock unit grants continue to vest in accordance with the original terms of the award if the applicable employee retires, after satisfying applicable age and service requirements. For all applicable periods, stock option grants continue to vest in accordance with the original terms of the award if the applicable employee retires, after satisfying applicable age and service requirements. In the first quarter of 2017 , the Corporation granted 468,381 non-qualified stock options with a total grant-date fair value of $9.0 million , 839,354 stock unit awards with a total grant-date value of $73.9 million , and 206,091 performance stock units with a total grant-date fair value of $18.1 million . Compensation expense for the three months ended March 31, 2017 of $21.6 million and $5.5 million was attributable to restricted stock units and stock options, respectively, granted to retirement-eligible employees that were expensed in their entirety on the date of grant. Compensation expense for the three months ended March 31, 2016 of $5.5 million was attributable to stock options granted to retirement-eligible employees that were expensed in their entirety on the date of grant. Compensation expense for the three months ended March 31, 2017 of $3.3 million was attributable to performance stock units granted to retirement-eligible employees that are expensed from the date of grant through the requisite service period which ends on June 30, 2017. Restricted stock unit award compensation expense for the three months ended March 31, 2017 and 2016 includes $2.5 million and $2.0 million , respectively, attributable to restricted stock units vested in full and were expensed in the entirety upon their date of grant. Total compensation expense for share-based payment arrangements and the associated tax impacts were as follows for the three months ended March 31, 2017 and 2016 . Table 59: Total Compensation Expense for Share-Based Payment Arrangements Three Months Ended March 31, (In Millions) 2017 2016 Restricted Stock Unit Awards $ 41.2 $ 15.3 Stock Options 6.3 6.4 Performance Stock Units 8.5 4.1 Total Share-Based Compensation Expense 56.0 25.8 Tax Benefits Recognized $ 21.2 $ 9.7

Variable Interest Entities

Variable Interest Entities	3 Months Ended
	Mar. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Variable Interest Entities	Variable Interest Entities Variable Interest Entities (VIEs) are defined within GAAP as entities that either have a total equity investment that is insufficient to permit the entity to finance its activities without additional subordinated financial support or whose equity investors lack the characteristics of a controlling financial interest. Investors that finance a VIE through debt or equity interests, or other counterparties that provide other forms of support, such as guarantees, subordinated fee arrangements, or certain types of derivative contracts, are variable interest holders in the entity. The variable interest holder, if any, that has both the power to direct the activities that most significantly impact the entity and a variable interest that could potentially be significant to the entity is deemed to be the VIE’s primary beneficiary and is required to consolidate the VIE. Leveraged Leases. In leveraged leasing transactions, Northern Trust acts as lessor of the underlying asset subject to the lease and typically funds 20 - 30% of the asset’s cost via an equity ownership in a trust with the remaining 70 - 80% provided by third-party non-recourse debt holders. In such transactions, the trusts, which are VIEs, are created to provide the lessee use of the property with substantially all of the rights and obligations of ownership. The lessee’s maintenance and operation of the leased property has a direct effect on the fair value of the underlying property, and the lessee also has the ability to increase the benefits it can receive and limit the losses it can suffer by the manner in which it uses the property. As a result, Northern Trust has determined that it is not the primary beneficiary of these VIEs given it lacks the power to direct the activities that most significantly impact the economic performance of the VIEs. Northern Trust’s maximum exposure to loss as a result of its involvement with the leveraged lease trust VIEs is limited to the carrying amounts of its leveraged lease investments. As of March 31, 2017 and December 31, 2016 , the carrying amounts of these investments, which are included in loans and leases in the consolidated balance sheets, were $145.9 million and $183.5 million , respectively. Northern Trust’s funding requirements relative to the VIEs are limited to its invested capital. Northern Trust has no other liquidity arrangements or obligations to purchase assets of the VIEs that would expose Northern Trust to a loss. Tax Credit Structures. Northern Trust invests in qualified affordable housing projects and community development entities (collectively, community development projects) that are designed to generate a return primarily through the realization of tax credits. The community development projects are formed as limited partnerships and limited liability companies (LLCs) in which Northern Trust invests as a limited partner/investor member through equity contributions. The economic performance of the community development projects, which are VIEs, is subject to the performance of their underlying investment and their ability to operate in compliance with the rules and regulations necessary for the qualification of tax credits generated by equity investments. Northern Trust has determined that it is not the primary beneficiary of any community development projects as it lacks the power to direct the activities that most significantly impact the economic performance of the underlying investments or to affect their ability to operate in compliance with the rules and regulations necessary for the qualification of tax credits generated by equity investments. This power is held by the general partners and managing members who exercise full and exclusive control of the operations of the VIEs. Northern Trust’s maximum exposure to loss as a result of its involvement with community development projects is limited to the carrying amount of its investments, including any undrawn commitments. As of March 31, 2017 and December 31, 2016 , the carrying amount of investments in community development projects that generate tax credits, included in other assets in the consolidated balance sheets, totaled $178.1 million and $186.5 million , respectively. As of March 31, 2017 and December 31, 2016 , liabilities related to undrawn commitments on investments in tax credit community development projects, included in other liabilities in the consolidated balance sheets, totaled $54.6 million and $56.7 million , respectively. Northern Trust’s funding requirements are limited to its invested capital and undrawn commitments for future equity contributions. Northern Trust has no exposure to loss from liquidity arrangements and no obligation to purchase assets of the community development projects. Affordable housing tax credits and other tax benefits attributable to community development projects totaled $12.1 million and $12.0 million for the three months ended March 31, 2017 and 2016 , respectively. Investment Funds. Northern Trust acts as asset manager for various funds in which clients of Northern Trust are investors. As an asset manager of funds, Northern Trust earns a competitively priced fee that is based on assets managed and varies with each fund’s investment objective. Based on its analysis, Northern Trust has determined that it is not the primary beneficiary of these VIEs under GAAP. Some of the funds for which Northern Trust acts as asset manager comply or operate in accordance with requirements that are similar to those in Rule 2a-7 of the Investment Company Act of 1940 for registered money market funds and therefore the funds are exempt from the consolidation requirements in Accounting Standards Codification 810-10. Northern Trust voluntarily waived $0.2 million and $7.7 million of money market mutual fund fees for the three months ended March 31, 2017 and 2016 , respectively. Northern Trust does not have any explicit arrangements to provide financial support to the funds. Any potential future support of the funds will be at the discretion of Northern Trust after an evaluation of the specific facts and circumstances.

Contingent Liabilities

Contingent Liabilities	3 Months Ended
	Mar. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Contingent Liabilities	Contingent Liabilities Commitments, Letters of Credit and Indemnifications. Northern Trust, in the normal course of business, enters into various types of commitments and issues letters of credit to meet the liquidity and credit enhancement needs of its clients. Legally binding commitments to extend credit generally have fixed expiration dates or other termination clauses. Since a significant portion of the commitments are expected to expire without being drawn upon, the total commitment amount does not necessarily represent future loans or liquidity requirements. Legally binding commitments to extend credit totaled $30.7 billion and $32.8 billion as of March 31, 2017 and December 31, 2016 , respectively. Standby letters of credit obligate Northern Trust to meet certain financial obligations of its clients, if, under the contractual terms of the agreement, the clients are unable to do so. These instruments are primarily issued to support public and private financial commitments, including commercial paper, bond financing, initial margin requirements on futures exchanges and similar transactions. Northern Trust is obligated to meet the entire financial obligation of these agreements and in certain cases is able to recover the amounts paid through recourse against collateral received or other participants. Standby letters of credit outstanding were $3.5 billion and $3.8 billion as of March 31, 2017 and December 31, 2016 , respectively. As part of its securities custody activities and at the direction of its clients, Northern Trust lends securities owned by clients to borrowers who are reviewed and approved by the Northern Trust Counterparty Risk Management Committee. In connection with these activities, Northern Trust has issued indemnifications to certain clients against certain losses that are a direct result of a borrower’s failure to return securities when due, should the value of such securities exceed the value of the collateral required to be posted. Borrowers are required to collateralize fully securities received with cash or marketable securities. As securities are loaned, collateral is maintained at a minimum of 100% of the fair value of the securities plus accrued interest. The collateral is revalued on a daily basis. The amount of securities loaned as of March 31, 2017 and December 31, 2016 subject to indemnification was $112.6 billion and $102.3 billion , respectively. Because of the credit quality of the borrowers and the requirement to collateralize fully securities borrowed, management believes that the exposure to credit loss from this activity is not significant and no liability was recorded as of March 31, 2017 or December 31, 2016 , related to these indemnifications. Legal Proceedings. In the normal course of business, the Corporation and its subsidiaries are routinely defendants in or parties to a number of pending and threatened legal actions, including, but not limited to, actions brought on behalf of various claimants or classes of claimants, regulatory matters, employment matters and challenges from tax authorities regarding the amount of taxes due. In certain of these actions and proceedings, claims for substantial monetary damages or adjustments to recorded tax liabilities are asserted. Based on current knowledge, after consultation with legal counsel and after taking into account current accruals, management does not believe that losses, if any, arising from pending litigation or threatened legal actions or regulatory matters will have a material adverse effect on the consolidated financial position or liquidity of the Corporation, although such matters could have a material adverse effect on the Corporation’s operating results for a particular period. Under GAAP, (i) an event is “probable” if the “future event or events are likely to occur”; (ii) an event is “reasonably possible” if “the chance of the future event or events occurring is more than remote but less than likely”; and (iii) an event is “remote” if “the chance of the future event or events occurring is slight.” For the reasons set out in this paragraph, the outcome of some matters is inherently difficult to predict and/or the range of loss cannot be reasonably estimated. This may be the case in matters that (i) will be decided by a jury, (ii) are in early stages, (iii) involve uncertainty as to the likelihood of a class being certified or the ultimate size of the class, (iv) are subject to appeals or motions, (v) involve significant factual issues to be resolved, including with respect to the amount of damages, (vi) do not specify the amount of damages sought or (vii) seek very large damages based on novel and complex damage and liability legal theories. Accordingly, the Corporation cannot reasonably estimate the eventual outcome of these pending matters, the timing of their ultimate resolution or what the eventual loss, fines or penalties, if any, related to each pending matter will be. In accordance with applicable accounting guidance, the Corporation records accruals for litigation and regulatory matters when those matters present loss contingencies that are both probable and reasonably estimable. When loss contingencies are not both probable and reasonably estimable, the Corporation does not record accruals. No material accruals have been recorded for pending litigation or threatened legal actions or regulatory matters. For a limited number of matters for which a loss is reasonably possible in future periods, whether in excess of an accrued liability or where there is no accrued liability, the Corporation is able to estimate a range of possible loss. As of March 31, 2017 , the Corporation has estimated the range of reasonably possible loss for these matters to be from zero to approximately $35 million in the aggregate. The Corporation’s estimate with respect to the aggregate range of reasonably possible loss is based upon currently available information and is subject to significant judgment and a variety of assumptions and known and unknown uncertainties. The matters underlying the estimated range will change from time to time, and actual results may vary significantly from the current estimate. In certain other pending matters, there may be a range of reasonably possible loss (including reasonably possible loss in excess of amounts accrued) that cannot be reasonably estimated for the reasons described above. Such matters are not included in the estimate of reasonably possible loss discussed above. In January 2015, the Public Prosecutor’s Office of France recommended that certain charges be brought against Northern Trust Fiduciary Services (Guernsey) Limited (NTFS), an indirect subsidiary of the Corporation, relating to the administration of two trusts for which NTFS serves as trustee. In April 2015, a French investigating magistrate judge charged NTFS with complicity in estate tax fraud. Charges also were brought against a number of other persons and entities related to this matter. The trial related to this matter concluded in October 2016. In January 2017, the French court found no estate tax fraud had occurred and NTFS and all other persons and entities charged were acquitted. The Public Prosecutor’s Office of France has appealed the court decision. The proceedings in the appellate court have not yet been scheduled. As trustee, NTFS provided no tax advice and had no involvement in the preparation or filing of the challenged estate tax filings. Visa Class B Common Shares. Northern Trust, as a member of Visa U.S.A. Inc. (Visa U.S.A.) and in connection with the 2007 restructuring of Visa U.S.A. and its affiliates and the 2008 initial public offering of Visa Inc. (Visa), received certain Visa Class B common shares. The Visa Class B common shares are subject to certain selling restrictions until the final resolution of the covered litigation noted below, at which time the shares are convertible into Visa Class A common shares based on a conversion rate dependent upon the ultimate cost of resolving the covered litigation. Certain members of Visa U.S.A. are obligated to indemnify Visa for losses resulting from certain litigation relating to interchange fees (the covered litigation). On October 19, 2012, Visa signed a settlement agreement with plaintiff representatives for binding settlement of the covered litigation. On January 14, 2014, the United States District Court for the Eastern District of New York entered a final judgment order approving the settlement with the class plaintiffs. A number of objectors appealed from that order and more than 30 opt-out cases have been filed by merchants in various federal district courts. On June 30, 2016, the United States Court of Appeals for the Second Circuit reversed the District Court's approval of the settlement and remanded the case to the District Court for further proceedings. In November 2016, a subset of plaintiffs filed a certiorari petition with the Supreme Court of the United States. In March 2017, the Supreme Court denied that petition. The ultimate resolution of the covered litigation and the timing for removal of the selling restrictions on the Visa Class B common shares are uncertain. In June 2016 and 2015, Northern Trust recorded a $123.1 million and $99.9 million net gain on the sale of 1.1 million and 1.0 million of its Visa Class B common shares, respectively. These sales do not affect Northern Trust’s risk related to the impact of the covered litigation on the rate at which such shares will ultimately convert into Visa Class A common shares. Northern Trust continued to hold approximately 4.1 million and 5.2 million Visa Class B common shares, which are recorded at their original cost basis of zero as of March 31, 2017 and 2016 , respectively.

Derivative Financial Instrument

Derivative Financial Instruments	3 Months Ended
	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Derivative Financial Instruments Northern Trust is a party to various derivative financial instruments that are used in the normal course of business to meet the needs of its clients, as part of its trading activity for its own account and as part of its risk management activities. These instruments include foreign exchange contracts, interest rate contracts, total return swap contracts, credit default swap contracts, and swaps related to the sale of certain Visa Class B common shares. Northern Trust’s primary risks associated with these instruments are the possibility that interest rates, foreign exchange rates, equity prices, or credit spreads could change in an unanticipated manner, resulting in higher costs or a loss in the underlying value of the instrument. These risks are mitigated by establishing limits, monitoring the level of actual positions taken against such established limits and monitoring the level of any interest rate sensitivity gaps created by such positions. When establishing position limits, market liquidity and volatility, as well as experience in each market, are taken into account. Credit risk associated with derivative instruments relates to the failure of the counterparty and the failure of Northern Trust to pay based on the contractual terms of the agreement, and is generally limited to the unrealized fair value gains and losses on these instruments, net of any cash collateral received or deposited. The amount of credit risk will increase or decrease during the lives of the instruments as interest rates, foreign exchange rates, equity prices or other underlying exposures fluctuate. Northern Trust’s risk is controlled by limiting such activity to an approved list of counterparties and by subjecting such activity to the same credit and quality controls as are followed in lending and investment activities. Credit Support Annexes and other similar agreements are currently in place with a number of Northern Trust’s counterparties which mitigate the aforementioned credit risk associated with derivative activity conducted with those counterparties by requiring that significant net unrealized fair value gains be supported by collateral placed with Northern Trust. All derivative financial instruments, whether designated as hedges or not, are recorded in the consolidated balance sheets at fair value within other assets or other liabilities. As noted in the discussions below, the manner in which changes in the fair value of a derivative is accounted for in the consolidated statements of income depends on whether the contract has been designated as a hedge and qualifies for hedge accounting under GAAP. Northern Trust has elected to net derivative assets and liabilities when legally enforceable master netting arrangements or similar agreements exist between Northern Trust and the counterparty. Derivative assets and liabilities recorded in the consolidated balance sheets were each reduced by $941.5 million and $1.7 billion as of March 31, 2017 and December 31, 2016 , respectively, as a result of master netting arrangements and similar agreements in place. Derivative assets and liabilities recorded at March 31, 2017 , also reflect reductions of $411.1 million and $207.2 million , respectively, as a result of cash collateral received from and deposited with derivative counterparties, respectively. This compares with reductions of derivative assets and liabilities of $461.3 million and $722.1 million , respectively, at December 31, 2016 . Additional cash collateral received from and deposited with derivative counterparties totaling $127.2 million and $126.2 million , respectively, as of March 31, 2017 , and $70.8 million and $324.5 million , respectively, as of December 31, 2016 , was not offset against derivative assets and liabilities in the consolidated balance sheets as the amounts exceeded the net derivative positions with those counterparties. Northern Trust centrally clears eligible interest rate derivative instruments as required under Title VII of the Dodd-Frank Wall Street Reform and Consumer Protection Act. Securities posted as collateral for these transactions totaled $52.2 million and $70.7 million at March 31, 2017 and December 31, 2016 , respectively, are not offset against derivative assets and liabilities in the consolidated balance sheets, and the counterparty receiving the securities as collateral does not have the right to repledge or sell the securities. Certain master netting arrangements Northern Trust enters into with derivative counterparties contain credit-risk-related contingent features in which the counterparty has the option to declare Northern Trust in default and accelerate cash settlement of net derivative liabilities with the counterparty in the event Northern Trust’s credit rating falls below specified levels. The aggregate fair value of all derivative instruments with credit-risk-related contingent features that were in a liability position was $271.2 million and $358.2 million at March 31, 2017 and December 31, 2016 , respectively. Cash collateral amounts deposited with derivative counterparties on those dates included $159.8 million and $317.5 million , respectively, posted against these liabilities, resulting in a net maximum amount of termination payments that could have been required at March 31, 2017 and December 31, 2016 , of $111.4 million and $40.7 million , respectively. Accelerated settlement of these liabilities would not have a material effect on the consolidated financial position or liquidity of Northern Trust. Foreign exchange contracts are agreements to exchange specific amounts of currencies at a future date, at a specified rate of exchange. Foreign exchange contracts are entered into primarily to meet the foreign exchange needs of clients. Foreign exchange contracts are also used for trading purposes and risk management. For risk management purposes, Northern Trust uses foreign exchange contracts to reduce its exposure to changes in foreign exchange rates relating to certain forecasted non-functional-currency-denominated revenue and expenditure transactions, foreign-currency-denominated assets and liabilities, including investment securities and net investments in non-U.S. affiliates. Interest rate contracts include swap and option contracts. Interest rate swap contracts involve the exchange of fixed and floating rate interest payment obligations without the exchange of the underlying principal amounts. Northern Trust enters into interest rate swap contracts with its clients and also may utilize such contracts to reduce or eliminate the exposure to changes in the cash flows or fair value of hedged assets or liabilities due to changes in interest rates. Interest rate option contracts may include caps, floors, collars and swaptions, and provide for the transfer or reduction of interest rate risk, typically in exchange for a fee. Northern Trust enters into option contracts primarily as a seller of interest rate protection to clients. Northern Trust receives a fee at the outset of the agreement for the assumption of the risk of an unfavorable change in interest rates. This assumed interest rate risk is then mitigated by entering into an offsetting position with an outside counterparty. Northern Trust may also purchase or enter into option contracts for risk management purposes including to reduce the exposure to changes in the cash flows of hedged assets due to changes in interest rates. Client-Related and Trading Derivative Instruments. Approximately 96% of Northern Trust’s derivatives outstanding at March 31, 2017 and December 31, 2016 , measured on a notional value basis, relate to client-related and trading activities. These activities consist principally of providing foreign exchange services to clients in connection with Northern Trust’s global custody business. However, in the normal course of business, Northern Trust also engages in trading of currencies for its own account. The following table shows the notional and fair values of client-related and trading derivative financial instruments. Notional amounts of derivative financial instruments do not represent credit risk, and are not recorded in the consolidated balance sheets. They are used merely to express the volume of this activity. Northern Trust’s credit-related risk of loss is limited to the positive fair value of the derivative instrument, which is significantly less than the notional amount. Table 60: Notional and Fair Values of Client-Related and Trading Derivative Financial Instruments March 31, 2017 December 31, 2016 Notional Value Fair Value Notional Value Fair Value (In Millions) Asset Liability Asset Liability Foreign Exchange Contracts $ 286,237.9 $ 1,851.8 $ 1,832.6 $ 273,213.1 $ 3,274.2 $ 3,221.7 Interest Rate Contracts 6,838.1 76.8 67.3 6,968.3 87.0 85.2 Total $ 293,076.0 $ 1,928.6 $ 1,899.9 $ 280,181.4 $ 3,361.2 $ 3,306.9 Changes in the fair value of client-related and trading derivative instruments are recognized currently in income. The following table shows the location and amount of gains and losses recorded in the consolidated statements of income for the three months ended March 31, 2017 and 2016 . Table 61: Location and Amount of Client-Related and Trading Derivative Gains and Losses Recorded in Income Amount of Derivative Gain Recognized in Income Location of Derivative Gain Recognized in Income Three Months Ended March 31, (In Millions) 2017 2016 Foreign Exchange Contracts Foreign Exchange Trading Income $ 48.1 $ 60.5 Interest Rate Contracts Security Commissions and Trading Income 1.2 4.1 Total $ 49.3 $ 64.6 Risk Management Instruments. Northern Trust uses derivative instruments to hedge its exposure to foreign currency, interest rate, equity price, and credit risk. Certain hedging relationships are formally designated and qualify for hedge accounting under GAAP as fair value, cash flow or net investment hedges. Other derivatives that are entered into for risk management purposes as economic hedges are not formally designated as hedges and changes in fair value are recognized currently in other operating income. In order to qualify for hedge accounting, a formal assessment is performed on a calendar-quarter basis to verify that derivatives used in designated hedging transactions continue to be highly effective in offsetting the changes in fair value or cash flows of the hedged item. If a derivative ceases to be highly effective, matures, is sold or is terminated, or if a hedged forecasted transaction is no longer probable of occurring, hedge accounting is terminated and the derivative is treated as if it were a trading instrument. The following table identifies the types and classifications of derivative instruments formally designated as hedges under GAAP and used by Northern Trust to manage risk, their notional and fair values, and the respective risks addressed. Table 62: Notional and Fair Value of Designated Risk Management Derivative Financial Instruments March 31, 2017 December 31, 2016 Derivative Instrument Risk Classification Notional Value Fair Value Notional Value Fair Value (In Millions) Asset Liability Asset Liability Fair Value Hedges Available for Sale Investment Securities Interest Rate Swap Contracts Interest Rate $ 3,670.3 $ 9.6 $ 11.0 $ 3,873.4 $ 88.3 $ 16.8 Senior Notes and Long-Term Subordinated Debt Interest Rate Swap Contracts Interest Rate 1,250.0 29.7 3.5 1,250.0 71.8 3.3 Cash Flow Hedges Forecasted Foreign Currency Denominated Transactions Foreign Exchange Contracts Foreign Currency 351.5 10.2 6.2 329.3 8.5 7.8 Foreign Currency Denominated Investment Securities Foreign Exchange Contracts Foreign Currency 1,193.9 — 27.7 1,431.6 151.5 0.8 Available for Sale Investment Securities Interest Rate Contracts Interest Rate 1,025.0 0.2 3.0 975.0 0.1 2.7 Net Investment Hedges Net Investments in Non-U.S. Affiliates Foreign Exchange Contracts Foreign Currency 2,190.0 18.1 7.5 2,083.6 174.6 10.8 Total $ 9,680.7 $ 67.8 $ 58.9 $ 9,942.9 $ 494.8 $ 42.2 Derivatives are designated as fair value hedges to limit Northern Trust’s exposure to changes in the fair value of assets and liabilities due to movements in interest rates. For a fair value hedge, changes in the fair value of the derivative instrument and changes in the fair value of the hedged asset or liability attributable to the hedged risk are recorded currently in income. The following table shows the location and amount of derivative gains and losses recognized in the consolidated statements of income related to fair value hedges for the three months ended March 31, 2017 and 2016 . Table 63: Location and Amount of Fair Value Hedge Derivative Gains and Losses Recorded in Income Location of Derivative Gain/(Loss) Recognized in Income Amount of Derivative Gain/(Loss) Recognized in Income Derivative Instrument Three Months Ended March 31, (In Millions) 2017 2016 Available for Sale Investment Securities Interest Rate Swap Contracts Interest Income $ (2.4 ) $ (34.7 ) Senior Notes and Long-Term Subordinated Debt Interest Rate Swap Contracts Interest Expense 3.1 47.4 Total $ 0.7 $ 12.7 Northern Trust applies the “shortcut” method of accounting, available under GAAP, to substantially all of its fair value hedges, which assumes there is no ineffectiveness in a hedge. For fair value hedges that do not qualify for the “shortcut” method of accounting, Northern Trust utilizes regression analysis, the “long-haul” method of accounting, in assessing whether the hedging relationships are highly effective at inception and quarterly thereafter. There was no ineffectiveness or changes in the fair value of hedged items recognized in income for fair value hedges accounted for under the “long-haul” method of accounting during the three month periods ended March 31, 2017 and 2016 . Derivatives are also designated as cash flow hedges in order to minimize the variability in cash flows of earning assets or forecasted transactions caused by movements in interest or foreign exchange rates. There was no ineffectiveness recognized in income for cash flow hedges during the three months ended March 31, 2017 and 2016 . As of March 31, 2017 , 23 months was the maximum length of time over which the exposure to variability in future cash flows of forecasted foreign-currency-denominated transactions was being hedged. The following table provides cash flow hedge derivative gains and losses recognized in AOCI and the amounts reclassified to income during the three months ended March 31, 2017 and 2016 . Table 64: Cash Flow Hedge Derivative Gains and Losses Recognized in AOCI and Reclassified to Income (In Millions) Foreign Exchange Contracts (Before Tax) Interest Rate Contracts (Before Tax) Three Months Ended March 31, 2017 2016 2017 2016 Net Gain/(Loss) Recognized in AOCI $ 8.9 $ 4.2 $ (0.2 ) $ 5.2 Net Gain/(Loss) Reclassified from AOCI to Net Income Other Operating Income 0.7 (1.1 ) — — Interest Income 4.4 — 0.1 0.9 Other Operating Expense (0.1 ) (0.4 ) — — Total $ 5.0 $ (1.5 ) $ 0.1 $ 0.9 There were no gains or losses reclassified into earnings during the three months ended March 31, 2017 and 2016 , as a result of the discontinuance of forecasted transactions that were no longer probable of occurring. It is estimated that a net gain of $2.9 million and a net loss of $0.4 million will be reclassified into net income within the next twelve months relating to cash flow hedges of foreign currency denominated transactions and cash flow hedges of foreign currency denominated investment securities, respectively. It is estimated that a net gain of $0.2 million will be reclassified into net income upon the receipt of interest payments on earning assets within the next twelve months relating to cash flow hedges of available for sale investment securities. Certain foreign exchange contracts and qualifying nonderivative instruments are designated as net investment hedges to minimize Northern Trust’s exposure to variability in the foreign currency translation of net investments in non-U.S. branches and subsidiaries. There was no ineffectiveness recorded during the three months ended March 31, 2017 and 2016 . Amounts recorded in AOCI are reclassified to net income only upon the sale or liquidation of an investment in a non-U.S. branch or subsidiary. The following table provides net investment hedge gains and losses recognized in AOCI during the three months ended March 31, 2017 and 2016 . Table 65: Net Investment Hedge Gains and Losses Recognized in AOCI Hedging Gain / (Loss) Recognized in OCI (Before Tax) Three Months Ended March 31, (In Millions) 2017 2016 Foreign Exchange Contracts $ (30.5 ) $ (26.5 ) Total $ (30.5 ) $ (26.5 ) Derivatives that are not formally designated as a hedge under GAAP are entered into for risk management purposes. Foreign exchange contracts are entered into to manage the foreign currency risk of non-U.S.-dollar-denominated assets and liabilities, the net investment in certain non-U.S. affiliates, commercial loans and forecasted foreign-currency-denominated transactions. Swaps related to sales of certain Visa Class B common shares were entered into which retains the risks associated with the ultimate conversion of the Visa Class B common shares into Visa Class A common shares. Credit default swaps were entered into to manage credit risk associated with certain loans and loan commitments. Total return swaps are entered into to manage the equity price risk associated with certain investments. The following table identifies the types of risk management derivative instruments not formally designated as hedges and their notional amounts and fair values. Table 66: Notional and Fair Values of Non-Designated Risk Management Derivative Instruments March 31, 2017 December 31, 2016 (In Millions) Notional Value Fair Value Notional Value Fair Value Asset Liability Asset Liability Foreign Exchange Contracts $ 441.6 $ 2.1 $ 0.6 $ 289.6 $ 0.8 $ 1.8 Other Financial Derivatives (1) 307.6 — 26.4 270.0 — 25.2 Total $ 749.2 $ 2.1 $ 27.0 $ 559.6 $ 0.8 $ 27.0 (1) This line includes swaps related to sales of certain Visa Class B common shares. Changes in the fair value of derivative instruments not formally designated as hedges are recognized currently in income. The following table provides the location and amount of gains and losses recorded in the consolidated statements of income for the three months ended March 31, 2017 and 2016 . Table 67: Location and Amount of Gains and Losses Recorded in Income for Non-Designated Risk Management Derivative Instruments (In Millions) Location of Derivative Gain / (Loss) Recognized in Income Amount of Derivative Gain / (Loss) Recognized in Income Three Months Ended March 31, 2017 2016 Foreign Exchange Contracts Other Operating Income $ 1.7 $ 2.7 Other Financial Derivatives (1) Other Operating Income (2.9 ) (0.8 ) Total $ (1.2 ) $ 1.9 (1) This line includes swaps related to sales of certain Visa Class B common shares, total return swap contracts, and credit default swap contracts.

Offsetting of Assets and Liabil

Offsetting of Assets and Liabilities	3 Months Ended
	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Offsetting of Assets and Liabilities	Offsetting of Assets and Liabilities The following tables provide information regarding the offsetting of derivative assets and securities purchased under agreements to resell within the consolidated balance sheets as of March 31, 2017 and December 31, 2016 . Table 68: Offsetting of Derivative Assets and Securities Purchased Under Agreements to Resell March 31, 2017 (In Millions) Gross Recognized Assets Gross Amounts Offset Net Amounts Presented Gross Amounts Not Offset Net Amount (3) Derivative Assets (1) Foreign Exchange Contracts Over the Counter (OTC) $ 1,414.1 $ 884.0 $ 530.1 $ — $ 530.1 Interest Rate Swaps OTC (10.3 ) 17.8 (28.1 ) — (28.1 ) Interest Rate Swaps Exchange Cleared 126.5 20.5 106.0 — 106.0 Cross Product Netting Adjustment — 19.2 — — — Cross Product Collateral Adjustment — 411.0 — — — Total Derivatives Subject to a Master Netting Arrangement 1,530.3 1,352.5 177.8 — 177.8 Total Derivatives Not Subject to a Master Netting Arrangement 468.2 — 468.2 — 468.2 Total Derivatives $ 1,998.5 $ 1,352.5 $ 646.0 $ — $ 646.0 Securities Purchased under Agreements to Resell (2) $ 1,933.8 $ — $ 1,933.8 $ 1,933.8 $ — December 31, 2016 (In Millions) Gross Recognized Assets Gross Amounts Offset Net Amounts Presented Gross Amounts Not Offset Net Amount (3) Derivative Assets (1) Foreign Exchange Contracts OTC $ 2,800.4 $ 1,651.9 $ 1,148.5 $ — $ 1,148.5 Interest Rate Swaps OTC 129.8 18.2 111.6 — 111.6 Interest Rate Swaps Exchange Cleared 117.4 21.8 95.6 — 95.6 Cross Product Netting Adjustment — 17.2 — — — Cross Product Collateral Adjustment — 461.3 — — — Total Derivatives Subject to a Master Netting Arrangement 3,047.6 2,170.4 877.2 — 877.2 Total Derivatives Not Subject to a Master Netting Arrangement 809.2 — 809.2 — 809.2 Total Derivatives 3,856.8 2,170.4 1,686.4 — 1,686.4 Securities Purchased under Agreements to Resell (2) $ 1,967.5 $ — $ 1,967.5 $ 1,967.5 $ — (1) Derivative assets are reported in other assets in the consolidated balance sheets. Other assets (excluding derivative assets) totaled $3.3 billion as of March 31, 2017 and December 31, 2016 , respectively. (2) Securities purchased under agreements to resell are reported in federal funds sold and securities purchased under agreements to resell in the consolidated balance sheets. There were no Federal funds sold and $6.8 million Federal funds sold as of March 31, 2017 and December 31, 2016 , respectively. (3) Northern Trust did not possess any cash collateral that was not offset in the consolidated balance sheets that could have been used to offset the net amounts presented in the consolidated balance sheets as of March 31, 2017 and December 31, 2016 . The following tables provide information regarding the offsetting of derivative liabilities and securities sold under agreements to repurchase within the consolidated balance sheets as of March 31, 2017 and December 31, 2016 . Table 69: Offsetting of Derivative Liabilities and Securities Sold Under Agreements to Repurchase March 31, 2017 (In Millions) Gross Recognized Liabilities Gross Amounts Offset Net Amounts Presented Gross Amounts Not Offset Net Amount (2) Derivative Liabilities (1) Foreign Exchange Contracts OTC $ 1,275.1 $ 884.0 $ 391.1 $ — $ 391.1 Interest Rate Swaps OTC 64.3 17.8 46.5 — 46.5 Interest Rate Swaps Exchange Cleared 20.5 20.5 — — — Other Financial Derivatives 26.4 — 26.4 — 26.4 Cross Product Netting Adjustment — 19.2 — — — Cross Product Collateral Adjustment — 207.2 — — — Total Derivatives Subject to a Master Netting Arrangement 1,386.3 1,148.7 237.6 — 237.6 Total Derivatives Not Subject to a Master Netting Arrangement 599.6 — 599.6 — 599.6 Total Derivatives 1,985.9 1,148.7 837.2 — 837.2 Securities Sold under Agreements to Repurchase $ 433.2 $ — $ 433.2 $ 433.2 $ — December 31, 2016 (In Millions) Gross Recognized Liabilities Gross Amounts Offset Net Amounts Presented Gross Amounts Not Offset Net Amount (2) Derivative Liabilities (1) Foreign Exchange Contracts OTC $ 2,634.4 $ 1,651.9 $ 982.5 $ — $ 982.5 Interest Rate Swaps OTC 86.2 18.2 68.0 — 68.0 Interest Rate Swaps Exchange Cleared 21.8 21.8 — — — Other Financial Derivatives 25.2 — 25.2 25.2 Cross Product Netting Adjustment — 17.2 — — — Cross Product Collateral Adjustment — 722.1 — — — Total Derivatives Subject to a Master Netting Arrangement 2,767.6 2,431.2 336.4 — 336.4 Total Derivatives Not Subject to a Master Netting Arrangement 608.5 — 608.5 — 608.5 Total Derivatives 3,376.1 2,431.2 944.9 — 944.9 Securities Sold under Agreements to Repurchase $ 473.7 $ — $ 473.7 $ 473.7 $ — (1) Derivative liabilities are reported in other liabilities in the consolidated balance sheets. Other liabilities (excluding derivative liabilities) totaled $2.2 billion and $2.7 billion as of March 31, 2017 and December 31, 2016 , respectively. (2) Northern Trust did not place any cash collateral with counterparties that was not offset in the consolidated balance sheets that could have been used to offset the net amounts presented in the consolidated balance sheets as of March 31, 2017 and December 31, 2016 . All of Northern Trust’s securities sold under agreements to repurchase (repurchase agreements) and securities purchased under agreements to resell (reverse repurchase agreements) involve the transfer of financial assets in exchange for cash subject to a right and obligation to repurchase those assets for an agreed upon amount. In the event of a repurchase failure, the cash or financial assets are available for offset. All of Northern Trust’s repurchase agreements and reverse repurchase agreements are subject to a master netting arrangement, which sets forth the rights and obligations for repurchase and offset. Under the master netting arrangement, Northern Trust is entitled to set off receivables from and collateral placed with a single counterparty against obligations owed to that counterparty. In addition, collateral held by Northern Trust can be offset against receivables from that counterparty. Derivative asset and liability positions with a single counterparty can be offset against each other in cases where legally enforceable master netting arrangements or similar agreements exist. Derivative assets and liabilities can be further offset by cash collateral received from, and deposited with, the transacting counterparty. The basis for this view is that, upon termination of transactions subject to a master netting arrangement or similar agreement, the individual derivative receivables do not represent resources to which general creditors have rights and individual derivative payables do not represent claims that are equivalent to the claims of general creditors. Northern Trust centrally clears those interest rate derivative instruments addressed under Title VII of the Dodd-Frank Wall Street Reform and Consumer Protection Act. These transactions are subject to an agreement similar to a master netting arrangement which has the same rights of offset as described above.

Recent Accounting Pronounceme29

Recent Accounting Pronouncements (Policies)	3 Months Ended
	Mar. 31, 2017
Accounting Changes and Error Corrections [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements On January 1, 2017, the Corporation adopted ASU 2016-05, “Derivatives and Hedging (Topics 815): Effects of Derivative Contract Novations on Existing Hedge Accounting Relationships (a consensus of the Emerging Issues Task Force)” (ASU 2016-05). ASU 2016-05 clarifies that a change in the counterparty to a derivative instrument that has been designated as the hedging instrument under Topic 815, does not, in and of itself, require dedesignation of that hedging relationship provided all other hedge accounting criteria continue to be met. Upon adoption of ASU 2016-05, the Corporation did not dedesignate any hedging relationships due to change in counterparty and therefore there was no impact to its consolidated financial condition or results of operations. On January 1, 2017, the Corporation adopted ASU 2016-06, “Derivatives and Hedging (Topic 815): Contingent Put and Call Options in Debt Instruments (a consensus of the Emerging Issues Task Force)” (ASU 2016-06). The amendments in ASU 2016-06 clarify what steps are required when assessing whether the economic characteristics and risks of call (put) options are clearly and closely related to the economic characteristics and risks of their debt hosts, which is one of the criteria for bifurcating an embedded derivative. The Corporation currently applies the approach for analyzing potential embedded derivative instruments in debt instruments detailed in ASU 2016-06 and therefore upon adoption there was no impact to its consolidated financial condition or results of operations. On January 1, 2017, the Corporation adopted ASU 2016-07, “Investments - Equity Method and Joint Ventures (Topic 323), Simplifying the Transition to the Equity Method of Accounting” (ASU 2016-07), which requires that when an investment qualifies for use of the equity method as a result of an increase in the level of ownership interest or degree of influence, the equity method investor add the cost of acquiring the additional interest in the investee to the current basis of the investor’s previously held interest and adopt the equity method of accounting as of the date the investment becomes qualified for equity method accounting. Upon adoption of ASU 2016-07, the Corporation did not hold an interest in an investee that subsequently qualified for the use of the equity method and therefore there was no impact to the Corporation’s consolidated financial condition or results of operations. On January 1, 2017, the Corporation adopted ASU 2016-17, “Consolidation (Topic 810): Interests Held through Related Parties That Are under Common Control” (ASU 2016-17). Under ASU 2016-17, a single decision maker evaluating whether it is the primary beneficiary of a variable interest entity will consider its indirect interests held by related parties that are under common control on a proportionate basis. Upon adoption of ASU 2016-17, there was no impact to the Corporation’s consolidated financial condition or results of operations.

Basis of Presentation (Tables)

Basis of Presentation (Tables)	3 Months Ended
	Mar. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of effects of the change in presentation	The table below shows the effect of the change in presentation on the Corporation’s consolidated statements of cash flows and related footnotes for the three months ended March 31, 2016 . Table 30: Change in Presentation Consolidated Statements of Cash Flows Three Months Ended March 31, 2016 (In Millions) Previously Reported Adjustment Revised Change in Interest-Bearing Deposits with Banks $ 716.7 $ 5.2 $ 721.9 Net Change in Federal Reserve Deposits 1,983.2 (1,983.2 ) — Net Change in Federal Reserve and Other Central Bank Deposits — 1,987.3 1,987.3 Net Cash Provided by Investing Activities 653.2 9.3 662.5 Effect of Foreign Currency Exchange Rates on Cash 202.9 0.2 203.1 Increase in Cash and Due from Banks 560.4 9.5 569.9 Cash and Due from Banks at Beginning of Year 6,444.6 (26.1 ) 6,418.5 Cash and Due from Banks at End of Period 7,005.0 (16.6 ) 6,988.4 Footnote 14 Net Interest Income Three Months Ended March 31, 2016 (In Millions) Previously Reported Adjustment Revised Interest-Bearing Due from and Deposits with Banks $ 23.7 $ (6.2 ) $ 17.5 Federal Reserve Deposits and Other 23.0 (23.0 ) — Federal Reserve and Other Central Bank Deposits $ — $ 29.2 $ 29.2 Adoption of ASU No. 2016-09. The Corporation adopted ASU No. 2016-09 on July 1, 2016 with an effective date of January 1, 2016, which resulted in a reclassification $3.6 million from additional paid-in capital to provision for income taxes, representing excess tax benefits previously recognized in additional paid-in-capital during the three months ended March 31, 2016 . Adoption of the standard impacted the Corporation’s previously reported quarterly results as follows: Three Months Ended March 31, 2016 ($ In Millions except per share data) As Reported As Adjusted Provision for Income Taxes $ 117.4 $ 113.8 Net Income 241.8 245.4 Earnings Allocated to Participating Securities 4.1 4.1 Net Income Applicable to Common Stock 235.9 239.5 Effective Tax Rate 32.7 % 31.7 % Basic Earnings per Share 1.01 1.03 Diluted Earnings per Share 1.01 1.03 Diluted Weighted Average Shares Outstanding (000s) 229,980 229,798 Additional Paid-In Capital 1,022.1 1,018.5 Retained Earnings 8,394.8 8,398.4

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Basis Hierarchy Leveling	The following tables present assets and liabilities measured at fair value on a recurring basis as of March 31, 2017 and December 31, 2016 , segregated by fair value hierarchy level. Table 32: Recurring Basis Hierarchy Leveling (In Millions) Level 1 Level 2 Level 3 Netting Assets/Liabilities at Fair Value March 31, 2017 Securities Available for Sale U.S. Government $ 6,830.2 $ — $ — $ — $ 6,830.2 Obligations of States and Political Subdivisions — 951.5 — — 951.5 Government Sponsored Agency — 17,936.4 — — 17,936.4 Non-U.S. Government — 218.1 — — 218.1 Corporate Debt — 3,559.0 — — 3,559.0 Covered Bonds — 884.9 — — 884.9 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds — 1,761.3 — — 1,761.3 Other Asset-Backed — 2,351.9 — — 2,351.9 Auction Rate — — 4.3 — 4.3 Commercial Mortgage-Backed — 456.2 — — 456.2 Other — 43.8 — — 43.8 Total Available for Sale 6,830.2 28,163.1 4.3 — 34,997.6 Trading Account — 1.4 — — 1.4 Total Available for Sale and Trading Securities 6,830.2 28,164.5 4.3 — 34,999.0 Other Assets Derivative Assets Foreign Exchange Contracts — 1,882.3 — — 1,882.3 Interest Rate Contracts — 116.2 — — 116.2 Total Derivative Assets — 1,998.5 — (1,352.5 ) 646.0 Other Liabilities Derivative Liabilities Foreign Exchange Contracts — 1,874.7 — — 1,874.7 Interest Rate Contracts — 84.8 — — 84.8 Other Financial Derivatives (1) — — 26.4 — 26.4 Total Derivative Liabilities $ — $ 1,959.5 $ 26.4 $ (1,148.7 ) $ 837.2 Note: Northern Trust has elected to net derivative assets and liabilities when legally enforceable master netting arrangements or similar agreements exist between Northern Trust and the counterparty. As of March 31, 2017 , derivative assets and liabilities shown above also include reductions of $411.0 million and $207.2 million , respectively, as a result of cash collateral received from and deposited with derivative counterparties. (1) This line consists of swaps related to the sale of certain Visa Class B common shares. (In Millions) Level 1 Level 2 Level 3 Netting Assets/Liabilities at Fair Value December 31, 2016 Securities Available for Sale U.S. Government $ 7,522.6 $ — $ — $ — $ 7,522.6 Obligations of States and Political Subdivisions — 885.2 — — 885.2 Government Sponsored Agency — 17,892.8 — — 17,892.8 Non-U.S. Government — 417.9 — — 417.9 Corporate Debt — 3,765.2 — — 3,765.2 Covered Bonds — 1,143.9 — — 1,143.9 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds — 1,340.7 — — 1,340.7 Other Asset-Backed — 2,085.1 — — 2,085.1 Auction Rate — — 4.7 — 4.7 Commercial Mortgage-Backed — 471.6 — — 471.6 Other — 50.1 — — 50.1 Total Available for Sale 7,522.6 28,052.5 4.7 — 35,579.8 Trading Account — 0.3 — — 0.3 Total Available for Sale and Trading Securities 7,522.6 28,052.8 4.7 — 35,580.1 Other Assets Derivative Assets Foreign Exchange Contracts — 3,609.6 — — 3,609.6 Interest Rate Contracts — 247.2 — — 247.2 Total Derivative Assets — 3,856.8 — (2,170.4 ) 1,686.4 Other Liabilities Derivative Liabilities Foreign Exchange Contracts — 3,242.9 — — 3,242.9 Interest Rate Contracts — 108.0 — — 108.0 Other Financial Derivatives (1) — — 25.2 — 25.2 Total Derivative Liabilities $ — $ 3,350.9 $ 25.2 $ (2,431.2 ) $ 944.9 Note: Northern Trust has elected to net derivative assets and liabilities when legally enforceable master netting arrangements or similar agreements exist between Northern Trust and the counterparty. As of December 31, 2016 , derivative assets and liabilities shown above also include reductions of $461.3 million and $722.1 million , respectively, as a result of cash collateral received from and deposited with derivative counterparties. (1) This line consists of swaps related to the sale of certain Visa Class B common shares.
Changes in Level 3 Assets	The following tables present the changes in Level 3 assets and liabilities for the three months ended March 31, 2017 and 2016 . Table 33: Changes in Level 3 Assets Level 3 Assets (In Millions) Auction Rate Securities Three Months Ended March 31, 2017 2016 Fair Value at January 1 $ 4.7 $ 17.1 Total Gains (Losses): Included in Earnings — — Included in Other Comprehensive Income (1) — (0.4 ) Purchases, Issues, Sales, and Settlements Sales — (0.1 ) Settlements (0.4 ) — Fair Value at March 31 $ 4.3 $ 16.6 (1) Unrealized gains (losses) are included in net unrealized gains (losses) on securities available for sale in the consolidated statements of comprehensive income.
Changes in Level 3 Liabilities	Table 34: Changes in Level 3 Liabilities Level 3 Liabilities (In Millions) Swaps Related to Sale of Certain Visa Class B Common Shares Three Months Ended March 31, 2017 2016 Fair Value at January 1 $ 25.2 $ 10.8 Total (Gains) Losses: Included in Earnings (1) 2.9 (0.3 ) Included in Other Comprehensive Income — — Purchases, Issues, Sales, and Settlements Purchases — — Settlements (1.7 ) (0.8 ) Fair Value at March 31 $ 26.4 $ 9.7 (1) (Gains) losses are recorded in other operating income in the consolidated statements of income.
Fair Value of Financial Instruments	The following tables summarize the fair values of all financial instruments. Table 36: Fair Value of Financial Instruments (In Millions) March 31, 2017 Book Value Total Fair Value Fair Value Level 1 Level 2 Level 3 Assets Cash and Due from Banks $ 4,649.2 $ 4,649.2 $ 4,649.2 $ — $ — Federal Reserve and Other Central Bank Deposits 25,959.5 25,959.5 — 25,959.5 — Interest-Bearing Deposits with Banks 5,247.8 5,247.8 — 5,247.8 — Federal Funds Sold and Resell Agreements 1,933.8 1,933.8 — 1,933.8 — Securities Available for Sale (Note) 34,997.6 34,997.6 6,830.2 28,163.1 4.3 Held to Maturity 8,938.4 8,933.4 6.0 8,927.4 — Trading Account 1.4 1.4 — 1.4 — Loans (excluding Leases) Held for Investment 33,056.5 33,151.9 — — 33,151.9 Held for Sale — — — — — Client Security Settlement Receivables 1,559.9 1,559.9 — 1,559.9 — Other Assets Federal Reserve and Federal Home Loan Bank Stock 158.1 158.1 — 158.1 — Community Development Investments 209.8 209.8 — 209.8 — Employee Benefit and Deferred Compensation 185.2 182.3 118.3 64.0 — Liabilities Deposits Demand, Noninterest-Bearing, Savings and Money Market $ 46,425.4 $ 46,425.4 $ 46,425.4 $ — $ — Savings Certificates and Other Time 1,346.8 1,351.4 — 1,351.4 — Non U.S. Offices Interest-Bearing 52,757.3 52,757.3 — 52,757.3 — Federal Funds Purchased 369.5 369.5 — 369.5 — Securities Sold under Agreements to Repurchase 433.2 433.2 — 433.2 — Other Borrowings 4,077.1 4,079.7 — 4,079.7 — Senior Notes 1,496.8 1,537.3 — 1,537.3 — Long Term Debt (excluding Leases) Subordinated Debt 1,302.5 1,315.5 — 1,315.5 — Floating Rate Capital Debt 277.4 252.6 — 252.6 — Other Liabilities Standby Letters of Credit 36.8 36.8 — — 36.8 Loan Commitments 37.5 37.5 — — 37.5 Derivative Instruments Asset/Liability Management Foreign Exchange Contracts Assets $ 30.5 $ 30.5 $ — $ 30.5 $ — Liabilities 42.1 42.1 — 42.1 — Interest Rate Contracts Assets 39.4 39.4 — 39.4 — Liabilities 17.5 17.5 — 17.5 — Other Financial Derivatives Liabilities (1) 26.4 26.4 — — 26.4 Client-Related and Trading Foreign Exchange Contracts Assets 1,851.8 1,851.8 — 1,851.8 — Liabilities 1,832.6 1,832.6 — 1,832.6 — Interest Rate Contracts Assets 76.8 76.8 — 76.8 — Liabilities 67.3 67.3 — 67.3 — Note: Refer to the table located on page 32 for the disaggregation of available for sale securities. (1) This line consists of swaps related to the sale of certain Visa Class B common shares. (In Millions) December 31, 2016 Book Value Total Fair Value Fair Value Level 1 Level 2 Level 3 Assets Cash and Due from Banks $ 5,332.0 $ 5,332.0 $ 5,332.0 $ — $ — Federal Reserve and Other Central Bank Deposits 26,674.2 26,674.2 — 26,674.2 — Interest-Bearing Deposits with Banks 4,800.6 4,800.6 — 4,800.6 — Federal Funds Sold and Resell Agreements 1,974.3 1,974.3 — 1,974.3 — Securities Available for Sale (Note) 35,579.8 35,579.8 7,522.6 28,052.5 4.7 Held to Maturity 8,921.1 8,905.1 15.0 8,890.1 — Trading Account 0.3 0.3 — 0.3 — Loans (excluding Leases) Held for Investment 33,354.1 33,471.3 — — 33,471.3 Held for Sale 13.4 13.4 — — 13.4 Client Security Settlement Receivables 1,043.7 1,043.7 — 1,043.7 — Other Assets Federal Reserve and Federal Home Loan Bank Stock 203.1 203.1 — 203.1 — Community Development Investments 218.9 215.5 — 215.5 — Employee Benefit and Deferred Compensation 166.2 162.5 107.2 55.3 — Liabilities Deposits Demand, Noninterest-Bearing, Savings and Money Market $ 46,671.9 $ 46,671.9 $ 46,671.9 $ — $ — Savings Certificates and Other Time 1,331.7 1,337.5 — 1,337.5 — Non U.S. Offices Interest-Bearing 53,648.1 53,648.1 — 53,648.1 — Federal Funds Purchased 204.8 204.8 — 204.8 — Securities Sold under Agreements to Repurchase 473.7 473.7 — 473.7 — Other Borrowings 5,109.5 5,113.4 — 5,113.4 — Senior Notes 1,496.6 1,535.5 — 1,535.5 — Long Term Debt (excluding Leases) Subordinated Debt 1,307.9 1,316.0 — 1,316.0 — Floating Rate Capital Debt 277.4 251.0 — 251.0 — Other Liabilities Standby Letters of Credit 37.2 37.2 — — 37.2 Loan Commitments 41.2 41.2 — — 41.2 Derivative Instruments Asset/Liability Management Foreign Exchange Contracts Assets $ 335.4 $ 335.4 $ — $ 335.4 $ — Liabilities 21.2 21.2 — 21.2 — Interest Rate Contracts Assets 160.2 160.2 — 160.2 — Liabilities 22.8 22.8 — 22.8 — Other Financial Derivatives Liabilities (1) 25.2 25.2 — — 25.2 Client-Related and Trading Foreign Exchange Contracts Assets 3,274.2 3,274.2 — 3,274.2 — Liabilities 3,221.7 3,221.7 — 3,221.7 — Interest Rate Contracts Assets 87.0 87.0 — 87.0 — Liabilities 85.2 85.2 — 85.2 — Note: Refer to the table located on page 33 for the disaggregation of available for sale securities. (1) This line consists of swaps related to the sale of certain Visa Class B common shares.
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Level 3 Nonrecurring Basis Significant Unobservable Inputs	The following presents the fair values of, and the valuation techniques, significant unobservable inputs, and quantitative information used to develop significant unobservable inputs for, Northern Trust’s Level 3 assets and liabilities as of March 31, 2017 and December 31, 2016 . Table 31: Level 3 Significant Unobservable Inputs March 31, 2017 Financial Instrument Fair Value Valuation Technique Unobservable Inputs Range of Inputs Auction Rate Securities $ 4.3 million Comparables Price $84 — 99 Swaps Related to Sale of Certain Visa Class B Common Shares $ 26.4 million Discounted Cash Flow Visa Class A Appreciation 7.0 % — 11.0% Conversion Rate 1.63x — 1.65x Expected Duration 1.25 — 4.25 years December 31, 2016 Financial Instrument Fair Value Valuation Technique Unobservable Inputs Range of Inputs Auction Rate Securities $ 4.7 million Comparables Price $84 — 99 Swap Related to Sale of Certain Visa Class B Common Shares $ 25.2 million Discounted Cash Flow Visa Class A Appreciation 7.0 % — 11.0% Conversion Rate 1.63x — 1.65x Expected Duration 1.50 — 4.50 years
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Level 3 Nonrecurring Basis Significant Unobservable Inputs	The following table provides the fair value of, and the valuation technique, significant unobservable inputs and quantitative information used to develop the significant unobservable inputs for, Northern Trust’s Level 3 assets that were measured at fair value on a nonrecurring basis as of March 31, 2017 and December 31, 2016 . Table 35: Level 3 Nonrecurring Basis Significant Unobservable Inputs March 31, 2017 Financial Instrument Fair Value Valuation Technique Unobservable Input Range of Discounts Applied Loans $28.7 million Market Approach Discount to reflect realizable value 15.0 % - 25.0% OREO $0.6 million Market Approach Discount to reflect realizable value 15.0 % - 20.0% December 31, 2016 Financial Instrument Fair Value Valuation Technique Unobservable Input Range of Discounts Applied Loans $6.7 million Market Approach Discount to reflect realizable value 15.0 % - 25.0% OREO $0.7 million Market Approach Discount to reflect realizable value 15.0 % - 20.0%

Securities (Tables)

Securities (Tables)	3 Months Ended
	Mar. 31, 2017
Schedule of Trading Securities and Other Trading Assets [Line Items]
Reconciliation of Amortized Cost to Fair Value of Securities Available for Sale	The following tables provide the amortized cost and fair values of securities at March 31, 2017 and December 31, 2016 . Table 37: Reconciliation of Amortized Cost to Fair Value of Securities Available for Sale Securities Available for Sale March 31, 2017 Amortized Cost Gross Unrealized Fair Value (In Millions) Gains Losses U.S. Government $ 6,815.5 $ 27.9 $ 13.2 $ 6,830.2 Obligations of States and Political Subdivisions 953.2 0.2 1.9 951.5 Government Sponsored Agency 17,947.4 52.6 63.6 17,936.4 Non-U.S. Government 219.8 — 1.7 218.1 Corporate Debt 3,578.0 3.6 22.6 3,559.0 Covered Bonds 887.3 1.1 3.5 884.9 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 1,761.0 3.1 2.8 1,761.3 Other Asset-Backed 2,349.0 4.4 1.5 2,351.9 Auction Rate 4.6 — 0.3 4.3 Commercial Mortgage-Backed 459.1 — 2.9 456.2 Other 43.8 — — 43.8 Total $ 35,018.7 $ 92.9 $ 114.0 $ 34,997.6 Securities Available for Sale December 31, 2016 Amortized Cost Gross Unrealized Fair Value (In Millions) Gains Losses U.S. Government $ 7,514.5 $ 22.4 $ 14.3 $ 7,522.6 Obligations of States and Political Subdivisions 890.8 — 5.6 885.2 Government Sponsored Agency 17,914.1 49.3 70.6 17,892.8 Non-U.S. Government 420.0 — 2.1 417.9 Corporate Debt 3,787.4 2.6 24.8 3,765.2 Covered Bonds 1,148.6 0.8 5.5 1,143.9 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 1,343.6 0.9 3.8 1,340.7 Other Asset-Backed 2,083.7 2.7 1.3 2,085.1 Auction Rate 5.0 — 0.3 4.7 Commercial Mortgage-Backed 474.1 — 2.5 471.6 Other 50.1 — — 50.1 Total $ 35,631.9 $ 78.7 $ 130.8 $ 35,579.8
Reconciliation of Amortized Cost to Fair Values of Securities Held to Maturity	Table 38: Reconciliation of Amortized Cost to Fair Value of Securities Held to Maturity Securities Held to Maturity March 31, 2017 Amortized Cost Gross Unrealized Fair Value (In Millions) Gains Losses U.S Government $ 6.0 $ — $ — $ 6.0 Obligations of States and Political Subdivisions 49.0 2.6 — 51.6 Government Sponsored Agency 6.8 0.5 — 7.3 Corporate Debt 252.6 0.1 0.4 252.3 Covered Bonds 2,295.6 11.6 2.7 2,304.5 Non-U.S. Government 3,282.6 6.6 0.4 3,288.8 Certificates of Deposit 306.5 — — 306.5 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 2,422.3 10.8 1.3 2,431.8 Other Asset-Backed 186.4 1.6 — 188.0 Other 130.6 — 34.0 96.6 Total $ 8,938.4 $ 33.8 $ 38.8 $ 8,933.4 Securities Held to Maturity December 31, 2016 Amortized Cost Gross Unrealized Fair Value (In Millions) Gains Losses U.S Government $ 15.0 $ — $ — $ 15.0 Obligations of States and Political Subdivisions 63.6 2.7 — 66.3 Government Sponsored Agency 7.4 0.5 — 7.9 Corporate Debt 231.2 0.2 0.4 231.0 Covered Bonds 2,051.6 10.1 3.7 2,058.0 Non-U.S. Government 3,517.5 4.9 2.3 3,520.1 Certificates of Deposit 606.0 0.2 0.1 606.1 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 2,154.7 10.5 2.8 2,162.4 Other Asset-Backed 143.4 0.1 — 143.5 Other 130.7 — 35.9 94.8 Total $ 8,921.1 $ 29.2 $ 45.2 $ 8,905.1
Securities Continuous Unrealized Loss Position	The following tables provide information regarding securities that had been in a continuous unrealized loss position for less than twelve months and for twelve months or longer as of March 31, 2017 and December 31, 2016 . Table 40: Securities with Unrealized Losses Securities with Unrealized Losses as of March 31, 2017 Less than 12 Months 12 Months or Longer Total (In Millions) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. Government $ 1,701.3 $ 13.2 $ — $ — $ 1,701.3 $ 13.2 Obligations of States and Political Subdivisions 750.1 1.9 — — 750.1 1.9 Government Sponsored Agency 7,455.5 51.5 2,433.8 12.1 9,889.3 63.6 Non-U.S. Government 1,729.3 2.1 — — 1,729.3 2.1 Corporate Debt 1,555.2 9.6 807.3 13.4 2,362.5 23.0 Covered Bonds 829.3 6.0 139.2 0.2 968.5 6.2 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 1,089.2 3.4 249.3 0.7 1,338.5 4.1 Other Asset-Backed 714.5 1.5 — — 714.5 1.5 Auction Rate 0.4 0.1 3.8 0.2 4.2 0.3 Commercial Mortgage-Backed 439.3 2.9 — — 439.3 2.9 Other 48.4 14.1 51.6 19.9 100.0 34.0 Total $ 16,312.5 $ 106.3 $ 3,685.0 $ 46.5 $ 19,997.5 $ 152.8 Securities with Unrealized Losses as of December 31, 2016 Less than 12 Months 12 Months or Longer Total (In Millions) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. Government $ 1,603.0 $ 14.3 $ — $ — $ 1,603.0 $ 14.3 Obligations of States and Political Subdivisions 865.3 5.6 — — 865.3 5.6 Government Sponsored Agency 8,252.5 58.5 2,121.0 12.1 10,373.5 70.6 Non-U.S. Government 2,957.1 4.4 — — 2,957.1 4.4 Corporate Debt 1,601.7 11.2 1,054.4 14.0 2,656.1 25.2 Covered Bonds 809.0 8.6 138.9 0.6 947.9 9.2 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 1,136.1 5.7 249.1 0.9 1,385.2 6.6 Other Asset-Backed 584.3 1.3 — — 584.3 1.3 Certificates of Deposit 81.4 0.1 — — 81.4 0.1 Auction Rate 0.4 0.1 4.3 0.2 4.7 0.3 Commercial Mortgage-Backed 471.5 2.5 — — 471.5 2.5 Other 50.5 17.9 59.7 18.0 110.2 35.9 Total $ 18,412.8 $ 130.2 $ 3,627.4 $ 45.8 $ 22,040.2 $ 176.0
Credit Related Impairment Losses Recognized in Earnings on Other Than Temporarily Impaired Securities	The table below provides the cumulative credit-related losses recognized in earnings on debt securities other-than-temporarily impaired. Table 41: Cumulative Credit-Related Losses on Securities Three Months Ended March 31, (In Millions) 2017 2016 Cumulative Credit-Related Losses on Securities Held — Beginning of Period $ 3.4 $ 5.2 Plus: Losses on Newly Identified Impairments — — Additional Losses on Previously Identified Impairments 0.1 — Less: Current and Prior Period Losses on Securities Sold During the Period — — Cumulative Credit-Related Losses on Securities Held — End of Period $ 3.5 $ 5.2
Available for Sale Investment Securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Remaining Maturity of Securities	The following table provides the remaining maturity of securities as of March 31, 2017 . Table 39: Remaining Maturity of Securities Available for Sale and Held to Maturity March 31, 2017 (In Millions) Amortized Cost Fair Value Available for Sale Due in One Year or Less $ 6,665.1 $ 6,660.1 Due After One Year Through Five Years 21,136.2 21,124.3 Due After Five Years Through Ten Years 6,015.5 6,017.7 Due After Ten Years 1,201.9 1,195.5 Total 35,018.7 34,997.6 Held to Maturity Due in One Year or Less 2,914.6 2,916.9 Due After One Year Through Five Years 5,764.1 5,783.4 Due After Five Years Through Ten Years 201.2 200.2 Due After Ten Years 58.5 32.9 Total $ 8,938.4 $ 8,933.4 Note: Mortgage-backed and asset-backed securities are included in the above table taking into account anticipated future prepayments.
Held-to-maturity Securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Remaining Maturity of Securities	The following table provides the remaining maturity of securities as of March 31, 2017 . Table 39: Remaining Maturity of Securities Available for Sale and Held to Maturity March 31, 2017 (In Millions) Amortized Cost Fair Value Available for Sale Due in One Year or Less $ 6,665.1 $ 6,660.1 Due After One Year Through Five Years 21,136.2 21,124.3 Due After Five Years Through Ten Years 6,015.5 6,017.7 Due After Ten Years 1,201.9 1,195.5 Total 35,018.7 34,997.6 Held to Maturity Due in One Year or Less 2,914.6 2,916.9 Due After One Year Through Five Years 5,764.1 5,783.4 Due After Five Years Through Ten Years 201.2 200.2 Due After Ten Years 58.5 32.9 Total $ 8,938.4 $ 8,933.4 Note: Mortgage-backed and asset-backed securities are included in the above table taking into account anticipated future prepayments.

Securities Sold Under Agreeme33

Securities Sold Under Agreements to Repurchase (Tables)	3 Months Ended
	Mar. 31, 2017
Banking and Thrift [Abstract]
Repurchase Agreements Accounted for as Secured Borrowings	The following table provides information regarding repurchase agreements that are accounted for as secured borrowings as of March 31, 2017 . Table 42: Repurchase Agreements Accounted for as Secured Borrowings March 31, 2017 (In Millions) Remaining Contractual Maturity of the Agreements Repurchase Agreements Overnight and Continuous U.S. Treasury and Agency Securities $ 433.2 Total Borrowings $ 433.2 Gross Amount of Recognized Liabilities for Repurchase Agreements in Note 21 $ 433.2 Amounts related to agreements not included in Note 21 $ —

Loans and Leases (Tables)

Loans and Leases (Tables)	3 Months Ended
	Mar. 31, 2017
Receivables [Abstract]
Amounts Outstanding for Loans and Leases by Segment and Class	Amounts outstanding for loans and leases, by segment and class, are shown below. Table 43: Loans and Leases (In Millions) March 31, December 31, Commercial Commercial and Institutional $ 9,487.3 $ 9,523.0 Commercial Real Estate 3,922.8 4,002.5 Non-U.S. 1,654.0 1,877.8 Lease Financing, net 253.6 293.9 Other 209.7 205.1 Total Commercial 15,527.4 15,902.3 Personal Private Client 10,375.8 10,052.0 Residential Real Estate 7,542.1 7,841.9 Other 26.5 25.9 Total Personal 17,944.4 17,919.8 Total Loans and Leases 33,471.8 33,822.1 Allowance for Credit Losses Assigned to Loans and Leases (162.0 ) (161.0 ) Net Loans and Leases $ 33,309.8 $ 33,661.1
Loan and Lease Segment and Class Balances Segregated by Borrower Ratings into "1 to 3", "4 to 5" and "6 to 9" (Watch List) Categories	Loan and lease segment and class balances as of March 31, 2017 and December 31, 2016 are provided below, segregated by borrower ratings into “1 to 3,” “4 to 5” and “6 to 9” (watch list), categories. Table 44: Borrower Ratings March 31, 2017 December 31, 2016 (In Millions) 1 to 3 Category 4 to 5 Category 6 to 9 Category (Watch List) Total 1 to 3 Category 4 to 5 Category 6 to 9 Category (Watch List) Total Commercial Commercial and Institutional $ 6,278.1 $ 3,080.6 $ 128.6 $ 9,487.3 $ 6,293.2 $ 3,108.5 $ 121.3 $ 9,523.0 Commercial Real Estate 1,742.3 2,157.6 22.9 3,922.8 1,825.7 2,134.8 42.0 4,002.5 Non-U.S. 379.9 1,272.8 1.3 1,654.0 602.8 1,273.5 1.5 1,877.8 Lease Financing, net 200.8 52.8 — 253.6 214.3 79.6 — 293.9 Other 113.4 95.5 0.8 209.7 135.5 67.9 1.7 205.1 Total Commercial 8,714.5 6,659.3 153.6 15,527.4 9,071.5 6,664.3 166.5 15,902.3 Personal Private Client 6,526.9 3,839.4 9.5 10,375.8 6,373.2 3,668.4 10.4 10,052.0 Residential Real Estate 2,564.4 4,664.3 313.4 7,542.1 2,617.8 4,913.9 310.2 7,841.9 Other 14.4 12.0 0.1 26.5 17.1 8.5 0.3 25.9 Total Personal 9,105.7 8,515.7 323.0 17,944.4 9,008.1 8,590.8 320.9 17,919.8 Total Loans and Leases $ 17,820.2 $ 15,175.0 $ 476.6 $ 33,471.8 $ 18,079.6 $ 15,255.1 $ 487.4 $ 33,822.1
Balances and Delinquency Status of Performing and Nonperforming Loans and Leases by Segment and Class as well as Total OREO and Nonperforming Asset Balances	The following tables provide balances and delinquency status of performing and nonperforming loans and leases by segment and class, as well as the total OREO and nonperforming asset balances, as of March 31, 2017 and December 31, 2016 . Table 45: Delinquency Status March 31, 2017 (In Millions) Current 30-59 Days Past Due 60-89 Days Past Due 90 Days or More Past Due Total Performing Nonperforming Total Loans and Leases Commercial Commercial and Institutional $ 9,398.5 $ 21.8 $ 2.4 $ 4.0 $ 9,426.7 $ 60.6 $ 9,487.3 Commercial Real Estate 3,887.8 15.8 3.0 4.1 3,910.7 12.1 3,922.8 Non-U.S. 1,654.0 — — — 1,654.0 — 1,654.0 Lease Financing, net 253.6 — — — 253.6 — 253.6 Other 209.7 — — — 209.7 — 209.7 Total Commercial 15,403.6 37.6 5.4 8.1 15,454.7 72.7 15,527.4 Personal Residential Real Estate 7,389.4 40.0 5.6 0.1 7,435.1 107.0 7,542.1 Private Client 10,216.4 155.0 2.5 1.7 10,375.6 0.2 10,375.8 Other 26.5 — — — 26.5 — 26.5 Total Personal 17,632.3 195.0 8.1 1.8 17,837.2 107.2 17,944.4 Total Loans and Leases $ 33,035.9 $ 232.6 $ 13.5 $ 9.9 $ 33,291.9 $ 179.9 $ 33,471.8 Other Real Estate Owned $ 6.9 Total Nonperforming Assets $ 186.8 December 31, 2016 (In Millions) Current 30-59 Days Past Due 60-89 Days Past Due 90 Days or More Past Due Total Performing Nonperforming Total Loans and Leases Commercial Commercial and Institutional $ 9,470.0 $ 5.3 $ 2.3 $ 11.7 $ 9,489.3 $ 33.7 $ 9,523.0 Commercial Real Estate 3,974.4 10.9 1.0 4.6 3,990.9 11.6 4,002.5 Non-U.S. 1,877.7 0.1 — — 1,877.8 — 1,877.8 Lease Financing, net 293.9 — — — 293.9 — 293.9 Other 205.1 — — — 205.1 — 205.1 Total Commercial 15,821.1 16.3 3.3 16.3 15,857.0 45.3 15,902.3 Personal Private Client 9,988.7 40.8 8.5 13.7 10,051.7 0.3 10,052.0 Residential Real Estate 7,675.7 44.5 6.1 1.0 7,727.3 114.6 7,841.9 Other 25.9 — — — 25.9 — 25.9 Total Personal 17,690.3 85.3 14.6 14.7 17,804.9 114.9 17,919.8 Total Loans and Leases $ 33,511.4 $ 101.6 $ 17.9 $ 31.0 $ 33,661.9 $ 160.2 $ 33,822.1 Other Real Estate Owned $ 5.2 Total Nonperforming Assets $ 165.4
Impaired Loans By Segment and Class	The following tables provide information related to impaired loans by segment and class. Table 46: Information about Impaired Loans as of the Period End As of March 31, 2017 As of December 31, 2016 (In Millions) Recorded Investment Unpaid Principal Balance Specific Allowance Recorded Investment Unpaid Principal Balance Specific Allowance With No Related Specific Allowance Commercial and Institutional $ 31.9 $ 34.5 $ — $ 32.2 $ 34.6 $ — Commercial Real Estate 11.6 14.1 — 14.7 18.6 — Lease Financing, net — — — — — — Private Client 0.1 0.1 — 0.3 0.3 — Residential Real Estate 91.8 127.5 — 101.2 138.4 — With a Related Specific Allowance Commercial and Institutional 27.3 27.6 7.2 — — — Commercial Real Estate 2.8 2.8 0.7 — — — Lease Financing, net — — — — — — Private Client — — — — — — Residential Real Estate 7.3 7.4 0.8 7.7 7.9 2.1 Total Commercial 73.6 79.0 7.9 46.9 53.2 — Personal 99.2 135.0 0.8 109.2 146.6 2.1 Total $ 172.8 $ 214.0 $ 8.7 $ 156.1 $ 199.8 $ 2.1 Three Months Ended March 31, 2017 2016 (In Millions) Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized With No Related Specific Allowance Commercial and Institutional $ 39.0 $ — $ 28.3 $ — Commercial Real Estate 14.9 0.1 17.7 0.1 Lease Financing, net — — 0.4 0.1 Private Client 0.2 — 0.3 — Residential Real Estate 101.7 0.5 99.6 0.4 With a Related Specific Allowance Commercial and Institutional 9.1 — 8.4 — Commercial Real Estate 0.9 — — — Lease Financing, net — — 2.1 — Private Client — — — — Residential Real Estate 2.4 — 1.5 — Total Commercial 63.9 0.1 56.9 0.2 Personal 104.3 0.5 101.4 0.4 Total $ 168.2 $ 0.6 $ 158.3 $ 0.6 Note: Average recorded investment in impaired loans is calculated as the average of the month-end impaired loan balances for the period.
Number of Loans and Leases Modified in TDRs and Total Recorded Investments and Unpaid Principal Balances	The following tables provide, by segment and class, the number of loans and leases modified in TDRs during the three - month periods ended March 31, 2017 and 2016 , and the recorded investments and unpaid principal balances as of March 31, 2017 and 2016 . Table 47: Modified Troubled Debt Restructurings ($ In Millions) Three Months Ended March 31, 2017 Number of Loans and Leases Recorded Investment Unpaid Principal Balance Commercial Commercial and Institutional — $ — $ — Commercial Real Estate 1 1.4 1.4 Total Commercial 1 1.4 1.4 Personal Private Client 1 — 0.1 Residential Real Estate 19 3.9 3.9 Total Personal 20 3.9 4.0 Total Loans and Leases 21 $ 5.3 $ 5.4 Note: Period end balances reflect all paydowns and charge-offs during the period. ($ In Millions) Three Months Ended March 31, 2016 Number of Loans and Leases Recorded Investment Unpaid Principal Balance Commercial Commercial and Institutional 2 $ 4.0 $ 6.0 Commercial Real Estate 5 5.4 7.7 Total Commercial 7 9.4 13.7 Personal Private Client — — — Residential Real Estate 24 5.5 6.2 Total Personal 24 5.5 6.2 Total Loans and Leases 31 $ 14.9 $ 19.9 Note: Period end balances reflect all paydowns and charge-offs during the period.

Allowance for Credit Losses (Ta

Allowance for Credit Losses (Tables)	3 Months Ended
	Mar. 31, 2017
Receivables [Abstract]
Changes in Allowance for Credit Losses by Segment	The following table provides information regarding changes in the total allowance for credit losses by segment during the three months ended March 31, 2017 and 2016 . Table 48: Changes in the Allowance for Credit Losses Three Months Ended March 31, 2017 2016 (In Millions) Commercial Personal Total Commercial Personal Total Balance at Beginning of Period $ 104.9 $ 87.1 $ 192.0 $ 114.8 $ 118.5 $ 233.3 Charge-Offs (1.1 ) (3.6 ) (4.7 ) (3.5 ) (1.8 ) (5.3 ) Recoveries 1.6 1.1 2.7 1.2 1.4 2.6 Net (Charge-Offs) Recoveries 0.5 (2.5 ) (2.0 ) (2.3 ) (0.4 ) (2.7 ) Provision for Credit Losses 6.4 (7.4 ) (1.0 ) 2.7 (0.7 ) 2.0 Balance at End of Period $ 111.8 $ 77.2 $ 189.0 $ 115.2 $ 117.4 $ 232.6
Allowances for Credit Losses and Recorded Investments in Loans and Leases by Segment	The following table provides information regarding the recorded investments in loans and leases and the allowance for credit losses by segment as of March 31, 2017 and December 31, 2016 . Table 49: Recorded Investments in Loans and Leases March 31, 2017 December 31, 2016 (In Millions) Commercial Personal Total Commercial Personal Total Loans and Leases Specifically Evaluated for Impairment $ 73.6 $ 99.2 $ 172.8 $ 46.9 $ 109.2 $ 156.1 Evaluated for Inherent Impairment 15,453.8 17,845.2 33,299.0 15,855.4 17,810.6 33,666.0 Total Loans and Leases 15,527.4 17,944.4 33,471.8 15,902.3 17,919.8 33,822.1 Allowance for Credit Losses on Credit Exposures Specifically Evaluated for Impairment 7.9 0.8 8.7 — 2.1 2.1 Evaluated for Inherent Impairment 83.6 69.7 153.3 83.7 75.2 158.9 Allowance Assigned to Loans and Leases 91.5 70.5 162.0 83.7 77.3 161.0 Allowance for Undrawn Exposures Commitments and Standby Letters of Credit 20.3 6.7 27.0 21.2 9.8 31.0 Total Allowance for Credit Losses $ 111.8 $ 77.2 $ 189.0 $ 104.9 $ 87.1 $ 192.0

Goodwill and Other Intangibles

Goodwill and Other Intangibles (Tables)	3 Months Ended
	Mar. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Changes by Reporting Segment in Carrying Amounts of Goodwill, including Effect of Foreign Exchange Rates on Non-U.S.-Dollar-Denominated Balances	The carrying amounts of goodwill and other intangibles assets, reflecting the effect of foreign exchange rates on non-U.S.-dollar-denominated balances, by reporting segment at March 31, 2017 , and December 31, 2016 , were as follows: Table 50: Goodwill by Reporting Segment (In Millions) March 31, December 31, Corporate & Institutional Services $ 448.3 $ 448.4 Wealth Management 71.0 71.0 Total Goodwill $ 519.3 $ 519.4
Other Intangible Assets Subject to Amortization	The gross carrying amount and accumulated amortization of other intangible assets subject to amortization as of March 31, 2017 and December 31, 2016 , were as follows: Table 51: Other Intangible Assets (In Millions) March 31, December 31, Gross Carrying Amount $ 90.9 $ 89.0 Less: Accumulated Amortization 49.8 47.2 Net Book Value $ 41.1 $ 41.8

Reporting Segments (Tables)

Reporting Segments (Tables)	3 Months Ended
	Mar. 31, 2017
Segment Reporting [Abstract]
Earnings Contribution of Northern Trust's Reporting Segments	The following table shows the earnings contributions of Northern Trust’s reporting segments for the three -month periods ended March 31, 2017 and 2016 . Table 52: Results of Reporting Segments Three Months Ended March 31, Corporate & Wealth Treasury and Total ($ In Millions) 2017 2016 2017 2016 2017 2016 2017 2016 Noninterest Income Trust, Investment and Other Servicing Fees $ 462.9 $ 433.4 $ 345.3 $ 314.8 $ — $ — $ 808.2 $ 748.2 Foreign Exchange Trading Income 49.1 51.7 0.9 4.5 (1.9 ) 4.3 48.1 60.5 Other Noninterest Income 44.2 45.6 25.5 26.8 4.9 1.1 74.6 73.5 Net Interest Income* 166.5 138.4 177.0 158.5 18.9 17.1 362.4 314.0 Revenue* 722.7 669.1 548.7 504.6 21.9 22.5 1,293.3 1,196.2 Provision for Credit Losses 0.3 (3.2 ) (1.3 ) 5.2 — — (1.0 ) 2.0 Noninterest Expense 510.8 475.3 346.3 326.9 37.4 26.6 894.5 828.8 Income before Income Taxes* 211.6 197.0 203.7 172.5 (15.5 ) (4.1 ) 399.8 365.4 Provision for Income Taxes* 66.9 62.2 76.8 64.9 (20.0 ) (7.1 ) 123.7 120.0 Net Income $ 144.7 $ 134.8 $ 126.9 $ 107.6 $ 4.5 $ 3.0 $ 276.1 $ 245.4 Percentage of Consolidated Net Income 52 % 55 % 46 % 44 % 2 % 1 % 100 % 100 % Average Assets $ 77,803.5 $ 75,372.9 $ 26,661.8 $ 26,237.8 $ 12,011.1 $ 11,806.4 $ 116,476.4 $ 113,417.1 * Non-GAAP financial measures stated on a fully taxable equivalent basis (FTE). Total consolidated includes FTE adjustments of $8.9 million for 2017 and $6.2 million for 2016 .

Accumulated Other Comprehensi38

Accumulated Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
Components of Accumulated Other Comprehensive Income (Loss) (AOCI)	The following tables summarize the components of accumulated other comprehensive income (loss) (AOCI) at March 31, 2017 and 2016 , and changes during the three -month periods then ended. Table 53: Summary of Changes in Accumulated Other Comprehensive Income (Loss) (In Millions) Balance at March 31, 2017 Net Change Balance at December 31, 2016 Net Unrealized Gains (Losses) on Securities Available for Sale $ (13.1 ) $ 19.3 $ (32.4 ) Net Unrealized Gains (Losses) on Cash Flow Hedges 0.8 (5.3 ) 6.1 Net Foreign Currency Adjustments (16.5 ) 2.0 (18.5 ) Net Pension and Other Postretirement Benefit Adjustments (323.2 ) 2.0 (325.2 ) Total $ (352.0 ) $ 18.0 $ (370.0 ) (In Millions) Balance at March 31, 2016 Net Change Balance at December 31, 2015 Net Unrealized Gains (Losses) on Securities Available for Sale $ 43.7 $ 74.7 $ (31.0 ) Net Unrealized Gains (Losses) on Cash Flow Hedges 3.1 6.1 (3.0 ) Net Foreign Currency Adjustments (13.7 ) 3.9 (17.6 ) Net Pension and Other Postretirement Benefit Adjustments (317.0 ) 4.1 (321.1 ) Total $ (283.9 ) $ 88.8 $ (372.7 )
Components of Changes in Accumulated Other Comprehensive Income (Loss)	Table 54: Details of Changes in Accumulated Other Comprehensive Income (Loss) Three Months Ended March 31, 2017 2016 (In Millions) Before Tax Tax Effect After Tax Before Tax Tax Effect After Tax Unrealized Gains (Losses) on Securities Available for Sale Other Unrealized Gains (Losses) on Securities Available for Sale 30.9 (11.7 ) 19.2 120.5 (45.6 ) 74.9 Reclassification Adjustment for (Gains) Losses Included in Net Income 0.2 (0.1 ) 0.1 (0.3 ) 0.1 (0.2 ) Net Change 31.1 (11.8 ) 19.3 120.2 (45.5 ) 74.7 Unrealized Gains (Losses) on Cash Flow Hedges Unrealized Gains (Losses) on Cash Flow Hedges 8.7 (10.8 ) (2.1 ) 9.4 (3.7 ) 5.7 Reclassification Adjustment for (Gains) Losses Included in Net Income (5.1 ) 1.9 (3.2 ) 0.6 (0.2 ) 0.4 Net Change 3.6 (8.9 ) (5.3 ) 10.0 (3.9 ) 6.1 Foreign Currency Adjustments Foreign Currency Translation Adjustments 22.4 (1.5 ) 20.9 17.3 (0.3 ) 17.0 Long-Term Intra-Entity Foreign Currency Transaction Gains (Losses) — — — 4.2 (1.0 ) 3.2 Net Investment Hedge Gains (Losses) (30.5 ) 11.6 (18.9 ) (26.5 ) 10.2 (16.3 ) Reclassification Adjustment for (Gains) Losses Included in Net Income — — — — — — Net Change (8.1 ) 10.1 2.0 (5.0 ) 8.9 3.9 Pension and Other Postretirement Benefit Adjustments Net Actuarial Gain (Loss) (2.3 ) — (2.3 ) — — — Reclassification Adjustment for (Gains) Losses Included in Net Income 6.4 (2.1 ) 4.3 6.4 (2.3 ) 4.1 Net Change $ 4.1 $ (2.1 ) $ 2.0 $ 6.4 $ (2.3 ) $ 4.1
Reclassification Out of Accumulated Other Comprehensive Income (Loss)	The following table provides the location and before-tax amounts of reclassifications out of AOCI during the three months ended March 31, 2017 . Table 55: Reclassification Adjustment out of Accumulated Other Comprehensive Income (Loss) (In Millions) Location of Reclassification Adjustments Recognized in Income Amount of Reclassification Adjustments Recognized in Income Three Months Ended March 31, 2017 Securities Available for Sale Realized (Gains) Losses on Securities Available for Sale Investment Security Gains (Losses), net $ 0.2 Realized Gains on Cash Flow Hedges Foreign Exchange Contracts Other Operating Income/Expense (5.1 ) Pension and Other Postretirement Benefit Adjustments Amortization of Net Actuarial Loss Employee Benefits 6.5 Amortization of Prior Service Cost Employee Benefits (0.1 ) Gross Reclassification Adjustment $ 6.4

Net Income Per Common Share C39

Net Income Per Common Share Computations (Tables)	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
Computations of Net Income per Common Share	The computations of net income per common share are presented in the following table. Table 56: Net Income per Common Share Three Months Ended March 31, ($ In Millions Except Per Common Share Information) 2017 2016 Basic Net Income Per Common Share Average Number of Common Shares Outstanding 229,059,540 228,619,089 Net Income $ 276.1 $ 245.4 Less: Dividends on Preferred Stock 20.7 5.9 Net Income Applicable to Common Stock 255.4 239.5 Less: Earnings Allocated to Participating Securities 4.5 4.1 Earnings Allocated to Common Shares Outstanding 250.9 235.4 Basic Net Income Per Common Share $ 1.10 $ 1.03 Diluted Net Income Per Common Share Average Number of Common Shares Outstanding 229,059,540 228,619,089 Plus: Dilutive Effect of Share-based Compensation 1,571,336 1,178,856 Average Common and Potential Common Shares 230,630,876 229,797,945 Earnings Allocated to Common and Potential Common Shares $ 250.9 $ 235.5 Diluted Net Income Per Common Share 1.09 1.03 Note: Common stock equivalents of 468,381 and 1,796,320 for the three months ended March 31, 2017 and 2016 , respectively, were not included in the computation of diluted net income per common share because their inclusion would have been antidilutive.

Net Interest Income (Tables)

Net Interest Income (Tables)	3 Months Ended
	Mar. 31, 2017
Banking and Thrift, Interest [Abstract]
Components of Net Interest Income	The components of net interest income were as follows: Table 57: Net Interest Income Three Months Ended March 31, (In Millions) 2017 2016 Interest Income Loans and Leases $ 213.4 $ 200.9 Securities — Taxable 143.2 103.3 — Non-Taxable 2.6 1.1 Interest-Bearing Due from and Deposits with Banks (1) 14.9 17.5 Federal Reserve and Other Central Bank Deposits 36.2 29.2 Total Interest Income 410.3 352.0 Interest Expense Deposits 27.6 22.2 Federal Funds Purchased 0.5 0.3 Securities Sold Under Agreements to Repurchase 0.9 0.4 Other Borrowings 7.6 2.7 Senior Notes 11.7 11.7 Long-Term Debt 7.4 6.1 Floating Rate Capital Debt 1.1 0.8 Total Interest Expense 56.8 44.2 Net Interest Income $ 353.5 $ 307.8 (1) Interest-Bearing Due from and Deposits with Banks includes the interest-bearing component of Cash and Due from Banks and Interest-Bearing Deposits with Banks as presented on the consolidated balance sheets.

Pension and Postretirement He41

Pension and Postretirement Health Care (Tables)	3 Months Ended
	Mar. 31, 2017
Compensation and Retirement Disclosure [Abstract]
Components of Company's Net Periodic Benefit Cost	The following tables set forth the net periodic pension and postretirement benefit expense for Northern Trust’s U.S. and non-U.S. pension plans, supplemental pension plan, and postretirement health care plan for the three months ended March 31, 2017 and 2016 . Table 58: Net Periodic Pension Expense (Benefit) Net Periodic Pension Expense U.S. Plan Three Months Ended March 31, (In Millions) 2017 2016 Service Cost $ 9.6 $ 9.3 Interest Cost 11.5 11.5 Expected Return on Plan Assets (23.5 ) (23.6 ) Amortization Net Actuarial Loss 4.8 4.7 Prior Service Cost (0.1 ) (0.1 ) Net Periodic Pension Expense $ 2.3 $ 1.8 Net Periodic Pension Expense Non-U.S. Plans Three Months Ended March 31, (In Millions) 2017 2016 Interest Cost $ 0.9 $ 1.3 Expected Return on Plan Assets (1.1 ) (1.3 ) Net Actuarial Loss Amortization 0.3 0.3 Net Periodic Pension Expense $ 0.1 $ 0.3 Net Periodic Pension Expense Supplemental Plan Three Months Ended March 31, (In Millions) 2017 2016 Service Cost $ 0.9 $ 0.9 Interest Cost 1.3 1.3 Amortization Net Actuarial Loss 1.4 1.5 Prior Service Cost — — Net Periodic Pension Expense $ 3.6 $ 3.7 Net Periodic Postretirement Expense Postretirement Health Care Plan Three Months Ended March 31, (In Millions) 2017 2016 Service Cost $ — $ — Interest Cost 0.4 0.4 Amortization Net Actuarial (Gain) — — Net Periodic Postretirement Expense $ 0.4 $ 0.4

Share-Based Compensation Plans

Share-Based Compensation Plans (Tables)	3 Months Ended
	Mar. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Compensation Expense for Share-Based Payment Arrangements and Associated Tax Impacts	Total compensation expense for share-based payment arrangements and the associated tax impacts were as follows for the three months ended March 31, 2017 and 2016 . Table 59: Total Compensation Expense for Share-Based Payment Arrangements Three Months Ended March 31, (In Millions) 2017 2016 Restricted Stock Unit Awards $ 41.2 $ 15.3 Stock Options 6.3 6.4 Performance Stock Units 8.5 4.1 Total Share-Based Compensation Expense 56.0 25.8 Tax Benefits Recognized $ 21.2 $ 9.7

Derivative Financial Instrume43

Derivative Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Notional and Fair Value Amounts of Client-related and Trading Derivative Financial Instruments	The following table shows the notional and fair values of client-related and trading derivative financial instruments. Notional amounts of derivative financial instruments do not represent credit risk, and are not recorded in the consolidated balance sheets. They are used merely to express the volume of this activity. Northern Trust’s credit-related risk of loss is limited to the positive fair value of the derivative instrument, which is significantly less than the notional amount. Table 60: Notional and Fair Values of Client-Related and Trading Derivative Financial Instruments March 31, 2017 December 31, 2016 Notional Value Fair Value Notional Value Fair Value (In Millions) Asset Liability Asset Liability Foreign Exchange Contracts $ 286,237.9 $ 1,851.8 $ 1,832.6 $ 273,213.1 $ 3,274.2 $ 3,221.7 Interest Rate Contracts 6,838.1 76.8 67.3 6,968.3 87.0 85.2 Total $ 293,076.0 $ 1,928.6 $ 1,899.9 $ 280,181.4 $ 3,361.2 $ 3,306.9
Location and Amount of Gains and Losses Recorded in Consolidated Statements of Income	The following table shows the location and amount of gains and losses recorded in the consolidated statements of income for the three months ended March 31, 2017 and 2016 . Table 61: Location and Amount of Client-Related and Trading Derivative Gains and Losses Recorded in Income Amount of Derivative Gain Recognized in Income Location of Derivative Gain Recognized in Income Three Months Ended March 31, (In Millions) 2017 2016 Foreign Exchange Contracts Foreign Exchange Trading Income $ 48.1 $ 60.5 Interest Rate Contracts Security Commissions and Trading Income 1.2 4.1 Total $ 49.3 $ 64.6
Types and Classifications of Derivative Instruments	The following table identifies the types and classifications of derivative instruments formally designated as hedges under GAAP and used by Northern Trust to manage risk, their notional and fair values, and the respective risks addressed. Table 62: Notional and Fair Value of Designated Risk Management Derivative Financial Instruments March 31, 2017 December 31, 2016 Derivative Instrument Risk Classification Notional Value Fair Value Notional Value Fair Value (In Millions) Asset Liability Asset Liability Fair Value Hedges Available for Sale Investment Securities Interest Rate Swap Contracts Interest Rate $ 3,670.3 $ 9.6 $ 11.0 $ 3,873.4 $ 88.3 $ 16.8 Senior Notes and Long-Term Subordinated Debt Interest Rate Swap Contracts Interest Rate 1,250.0 29.7 3.5 1,250.0 71.8 3.3 Cash Flow Hedges Forecasted Foreign Currency Denominated Transactions Foreign Exchange Contracts Foreign Currency 351.5 10.2 6.2 329.3 8.5 7.8 Foreign Currency Denominated Investment Securities Foreign Exchange Contracts Foreign Currency 1,193.9 — 27.7 1,431.6 151.5 0.8 Available for Sale Investment Securities Interest Rate Contracts Interest Rate 1,025.0 0.2 3.0 975.0 0.1 2.7 Net Investment Hedges Net Investments in Non-U.S. Affiliates Foreign Exchange Contracts Foreign Currency 2,190.0 18.1 7.5 2,083.6 174.6 10.8 Total $ 9,680.7 $ 67.8 $ 58.9 $ 9,942.9 $ 494.8 $ 42.2
Gains/Losses of Derivative Financial Instruments	The following table shows the location and amount of derivative gains and losses recognized in the consolidated statements of income related to fair value hedges for the three months ended March 31, 2017 and 2016 . Table 63: Location and Amount of Fair Value Hedge Derivative Gains and Losses Recorded in Income Location of Derivative Gain/(Loss) Recognized in Income Amount of Derivative Gain/(Loss) Recognized in Income Derivative Instrument Three Months Ended March 31, (In Millions) 2017 2016 Available for Sale Investment Securities Interest Rate Swap Contracts Interest Income $ (2.4 ) $ (34.7 ) Senior Notes and Long-Term Subordinated Debt Interest Rate Swap Contracts Interest Expense 3.1 47.4 Total $ 0.7 $ 12.7
Cash Flow Hedge Derivative Gains and Losses Recognized in AOCI and the Amounts Reclassified to Earnings	The following table provides cash flow hedge derivative gains and losses recognized in AOCI and the amounts reclassified to income during the three months ended March 31, 2017 and 2016 . Table 64: Cash Flow Hedge Derivative Gains and Losses Recognized in AOCI and Reclassified to Income (In Millions) Foreign Exchange Contracts (Before Tax) Interest Rate Contracts (Before Tax) Three Months Ended March 31, 2017 2016 2017 2016 Net Gain/(Loss) Recognized in AOCI $ 8.9 $ 4.2 $ (0.2 ) $ 5.2 Net Gain/(Loss) Reclassified from AOCI to Net Income Other Operating Income 0.7 (1.1 ) — — Interest Income 4.4 — 0.1 0.9 Other Operating Expense (0.1 ) (0.4 ) — — Total $ 5.0 $ (1.5 ) $ 0.1 $ 0.9
Net Investment Hedge Gains and Losses Recognized in AOCI	The following table provides net investment hedge gains and losses recognized in AOCI during the three months ended March 31, 2017 and 2016 . Table 65: Net Investment Hedge Gains and Losses Recognized in AOCI Hedging Gain / (Loss) Recognized in OCI (Before Tax) Three Months Ended March 31, (In Millions) 2017 2016 Foreign Exchange Contracts $ (30.5 ) $ (26.5 ) Total $ (30.5 ) $ (26.5 )
Types of Risk Management Derivative Instruments Not Formally Designated as Hedges, Including Notional Amounts and Fair Values	The following table identifies the types of risk management derivative instruments not formally designated as hedges and their notional amounts and fair values. Table 66: Notional and Fair Values of Non-Designated Risk Management Derivative Instruments March 31, 2017 December 31, 2016 (In Millions) Notional Value Fair Value Notional Value Fair Value Asset Liability Asset Liability Foreign Exchange Contracts $ 441.6 $ 2.1 $ 0.6 $ 289.6 $ 0.8 $ 1.8 Other Financial Derivatives (1) 307.6 — 26.4 270.0 — 25.2 Total $ 749.2 $ 2.1 $ 27.0 $ 559.6 $ 0.8 $ 27.0 (1) This line includes swaps related to sales of certain Visa Class B common shares.
Gains/Losses of Derivative Financial Instruments	The following table provides the location and amount of gains and losses recorded in the consolidated statements of income for the three months ended March 31, 2017 and 2016 . Table 67: Location and Amount of Gains and Losses Recorded in Income for Non-Designated Risk Management Derivative Instruments (In Millions) Location of Derivative Gain / (Loss) Recognized in Income Amount of Derivative Gain / (Loss) Recognized in Income Three Months Ended March 31, 2017 2016 Foreign Exchange Contracts Other Operating Income $ 1.7 $ 2.7 Other Financial Derivatives (1) Other Operating Income (2.9 ) (0.8 ) Total $ (1.2 ) $ 1.9 (1) This line includes swaps related to sales of certain Visa Class B common shares

Offsetting of Assets and Liab44

Offsetting of Assets and Liabilities (Tables)	3 Months Ended
	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of offsetting derivative assets and securities purchased under agreements to resell	The following tables provide information regarding the offsetting of derivative assets and securities purchased under agreements to resell within the consolidated balance sheets as of March 31, 2017 and December 31, 2016 . Table 68: Offsetting of Derivative Assets and Securities Purchased Under Agreements to Resell March 31, 2017 (In Millions) Gross Recognized Assets Gross Amounts Offset Net Amounts Presented Gross Amounts Not Offset Net Amount (3) Derivative Assets (1) Foreign Exchange Contracts Over the Counter (OTC) $ 1,414.1 $ 884.0 $ 530.1 $ — $ 530.1 Interest Rate Swaps OTC (10.3 ) 17.8 (28.1 ) — (28.1 ) Interest Rate Swaps Exchange Cleared 126.5 20.5 106.0 — 106.0 Cross Product Netting Adjustment — 19.2 — — — Cross Product Collateral Adjustment — 411.0 — — — Total Derivatives Subject to a Master Netting Arrangement 1,530.3 1,352.5 177.8 — 177.8 Total Derivatives Not Subject to a Master Netting Arrangement 468.2 — 468.2 — 468.2 Total Derivatives $ 1,998.5 $ 1,352.5 $ 646.0 $ — $ 646.0 Securities Purchased under Agreements to Resell (2) $ 1,933.8 $ — $ 1,933.8 $ 1,933.8 $ — December 31, 2016 (In Millions) Gross Recognized Assets Gross Amounts Offset Net Amounts Presented Gross Amounts Not Offset Net Amount (3) Derivative Assets (1) Foreign Exchange Contracts OTC $ 2,800.4 $ 1,651.9 $ 1,148.5 $ — $ 1,148.5 Interest Rate Swaps OTC 129.8 18.2 111.6 — 111.6 Interest Rate Swaps Exchange Cleared 117.4 21.8 95.6 — 95.6 Cross Product Netting Adjustment — 17.2 — — — Cross Product Collateral Adjustment — 461.3 — — — Total Derivatives Subject to a Master Netting Arrangement 3,047.6 2,170.4 877.2 — 877.2 Total Derivatives Not Subject to a Master Netting Arrangement 809.2 — 809.2 — 809.2 Total Derivatives 3,856.8 2,170.4 1,686.4 — 1,686.4 Securities Purchased under Agreements to Resell (2) $ 1,967.5 $ — $ 1,967.5 $ 1,967.5 $ — (1) Derivative assets are reported in other assets in the consolidated balance sheets. Other assets (excluding derivative assets) totaled $3.3 billion as of March 31, 2017 and December 31, 2016 , respectively. (2) Securities purchased under agreements to resell are reported in federal funds sold and securities purchased under agreements to resell in the consolidated balance sheets. There were no Federal funds sold and $6.8 million Federal funds sold as of March 31, 2017 and December 31, 2016 , respectively. (3) Northern Trust did not possess any cash collateral that was not offset in the consolidated balance sheets that could have been used to offset the net amounts presented in the consolidated balance sheets as of March 31, 2017 and December 31, 2016 .
Schedule of offsetting derivative liabilities and securities sold under agreements to repurchase	The following tables provide information regarding the offsetting of derivative liabilities and securities sold under agreements to repurchase within the consolidated balance sheets as of March 31, 2017 and December 31, 2016 . Table 69: Offsetting of Derivative Liabilities and Securities Sold Under Agreements to Repurchase March 31, 2017 (In Millions) Gross Recognized Liabilities Gross Amounts Offset Net Amounts Presented Gross Amounts Not Offset Net Amount (2) Derivative Liabilities (1) Foreign Exchange Contracts OTC $ 1,275.1 $ 884.0 $ 391.1 $ — $ 391.1 Interest Rate Swaps OTC 64.3 17.8 46.5 — 46.5 Interest Rate Swaps Exchange Cleared 20.5 20.5 — — — Other Financial Derivatives 26.4 — 26.4 — 26.4 Cross Product Netting Adjustment — 19.2 — — — Cross Product Collateral Adjustment — 207.2 — — — Total Derivatives Subject to a Master Netting Arrangement 1,386.3 1,148.7 237.6 — 237.6 Total Derivatives Not Subject to a Master Netting Arrangement 599.6 — 599.6 — 599.6 Total Derivatives 1,985.9 1,148.7 837.2 — 837.2 Securities Sold under Agreements to Repurchase $ 433.2 $ — $ 433.2 $ 433.2 $ — December 31, 2016 (In Millions) Gross Recognized Liabilities Gross Amounts Offset Net Amounts Presented Gross Amounts Not Offset Net Amount (2) Derivative Liabilities (1) Foreign Exchange Contracts OTC $ 2,634.4 $ 1,651.9 $ 982.5 $ — $ 982.5 Interest Rate Swaps OTC 86.2 18.2 68.0 — 68.0 Interest Rate Swaps Exchange Cleared 21.8 21.8 — — — Other Financial Derivatives 25.2 — 25.2 25.2 Cross Product Netting Adjustment — 17.2 — — — Cross Product Collateral Adjustment — 722.1 — — — Total Derivatives Subject to a Master Netting Arrangement 2,767.6 2,431.2 336.4 — 336.4 Total Derivatives Not Subject to a Master Netting Arrangement 608.5 — 608.5 — 608.5 Total Derivatives 3,376.1 2,431.2 944.9 — 944.9 Securities Sold under Agreements to Repurchase $ 473.7 $ — $ 473.7 $ 473.7 $ — (1) Derivative liabilities are reported in other liabilities in the consolidated balance sheets. Other liabilities (excluding derivative liabilities) totaled $2.2 billion and $2.7 billion as of March 31, 2017 and December 31, 2016 , respectively. (2) Northern Trust did not place any cash collateral with counterparties that was not offset in the consolidated balance sheets that could have been used to offset the net amounts presented in the consolidated balance sheets as of March 31, 2017 and December 31, 2016 .

Basis of Presentation ( Effect

Basis of Presentation ( Effect of the Change in Presentation on Consolidated Statements of Cash Flows and Related Footnotes) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Change in Interest-Bearing Deposits with Banks	$ (327.8)	$ 721.9
Net Change in Federal Reserve Deposits		0
Net Change in Federal Reserve and Other Central Bank Deposits	767.1	1,987.3
Net Cash Provided by Investing Activities	1,026.5	662.5
Effect of Foreign Currency Exchange Rates on Cash	213.6	203.1
Increase in Cash and Due from Banks	(682.8)	569.9
Cash and Due from Banks at Beginning of Year	5,332	6,418.5
Cash and Due from Banks at End of Period	4,649.2	6,988.4
Interest-Bearing Deposits with Banks	5,247.8	17.5	$ 4,800.6
Federal Reserve Bank Stock		0
Federal Reserve and Other Central Bank Deposits	$ 25,959.5	29.2	$ 26,674.2
Change In Presentation Of Federal Reserve and Foreign Bank Deposits | Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Change in Interest-Bearing Deposits with Banks		716.7
Net Change in Federal Reserve Deposits		1,983.2
Net Change in Federal Reserve and Other Central Bank Deposits		0
Net Cash Provided by Investing Activities		653.2
Effect of Foreign Currency Exchange Rates on Cash		202.9
Increase in Cash and Due from Banks		560.4
Cash and Due from Banks at Beginning of Year		6,444.6
Cash and Due from Banks at End of Period		7,005
Interest-Bearing Deposits with Banks		23.7
Federal Reserve Bank Stock		23
Federal Reserve and Other Central Bank Deposits		0
Change In Presentation Of Federal Reserve and Foreign Bank Deposits | Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Change in Interest-Bearing Deposits with Banks		5.2
Net Change in Federal Reserve Deposits		(1,983.2)
Net Change in Federal Reserve and Other Central Bank Deposits		1,987.3
Net Cash Provided by Investing Activities		9.3
Effect of Foreign Currency Exchange Rates on Cash		0.2
Increase in Cash and Due from Banks		9.5
Cash and Due from Banks at Beginning of Year		(26.1)
Cash and Due from Banks at End of Period		(16.6)
Interest-Bearing Deposits with Banks		(6.2)
Federal Reserve Bank Stock		(23)
Federal Reserve and Other Central Bank Deposits		$ 29.2

Basis of Presentation (Adoption

Basis of Presentation (Adoption of ASU No. 2016-09) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
New Accounting Pronouncement, Early Adoption [Line Items]
Provision for Income Taxes	$ (114.8)	$ (113.8)
Net Income	276.1	245.4
Earnings Allocated to Participating Securities	4.5	4.1
Net Income Applicable to Common Stock	$ 255.4	$ 239.5
Effective Tax Rate	29.40%	31.70%
Basic Earnings per Share	$ 1.10	$ 1.03
Diluted Earnings per Share	$ 1.09	$ 1.03
Diluted Weighted Average Shares Outstanding (000s)	230,630,876	229,797,945
Additional Paid-In Capital	$ 1,010.2		$ 1,035.8
Retained Earnings	$ 9,074.4		$ 8,908.4
Accounting Standards Update 2016-09
New Accounting Pronouncement, Early Adoption [Line Items]
Provision for Income Taxes		$ 3.6
Accounting Standards Update 2016-09 | As Reported
New Accounting Pronouncement, Early Adoption [Line Items]
Provision for Income Taxes		117.4
Net Income		241.8
Earnings Allocated to Participating Securities		4.1
Net Income Applicable to Common Stock		$ 235.9
Effective Tax Rate		32.70%
Basic Earnings per Share		$ 1.01
Diluted Earnings per Share		$ 1.01
Diluted Weighted Average Shares Outstanding (000s)		229,980,000
Additional Paid-In Capital		$ 1,022.1
Retained Earnings		8,394.8
Accounting Standards Update 2016-09 | As Adjusted
New Accounting Pronouncement, Early Adoption [Line Items]
Provision for Income Taxes		113.8
Net Income		245.4
Earnings Allocated to Participating Securities		4.1
Net Income Applicable to Common Stock		$ 239.5
Effective Tax Rate		31.70%
Basic Earnings per Share		$ 1.03
Diluted Earnings per Share		$ 1.03
Diluted Weighted Average Shares Outstanding (000s)		229,798,000
Additional Paid-In Capital		$ 1,018.5
Retained Earnings		$ 8,398.4

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) shares in Millions	3 Months Ended
	Mar. 31, 2017USD ($)Securities	Mar. 31, 2016USD ($)	Dec. 31, 2016USD ($)Securities	Jun. 30, 2016shares	Jun. 30, 2015shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for Sale	$ 34,997,600,000		$ 35,579,800,000
Trading account securities	1,400,000		$ 300,000
Transfers into Level 3 assets	0	$ 0
Transfers out of Level 3 assets	0	0
Transfers into Level 3 liabilities	0	0
Transfers out of Level 3 liabilities	$ 0	0
Visa Class B
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Shares issued | shares				1.1	1
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of available for sale securities portfolio | Securities	1,434		1,409
Available for Sale	$ 28,200,000,000		$ 28,100,000,000
Level 2 | External Pricing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of available for sale securities portfolio | Securities	1,434		1,409
Trading account securities	$ 1,400,000		$ 300,000
Fair Value, Measurements, Nonrecurring | Level 3 | Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	28,700,000	10,100,000	6,700,000
Fair Value, Measurements, Nonrecurring | Level 3 | OREO
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 600,000	$ 2,500,000	$ 700,000

Fair Value Measurements (Level

Fair Value Measurements (Level 3 Significant Unobservable Inputs) (Details) - Fair Value, Measurements, Recurring - Level 3 - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Swaps Related to Sale of Certain Visa Class B Common Shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value swaps	$ 26.4	$ 25.2
Swaps Related to Sale of Certain Visa Class B Common Shares | Group One
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation technique	Discounted Cash Flow	Discounted Cash Flow
Unobservable inputs	Visa Class A Appreciation	Visa Class A Appreciation
Swaps Related to Sale of Certain Visa Class B Common Shares | Group Two
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unobservable inputs	Conversion Rate	Conversion Rate
Swaps Related to Sale of Certain Visa Class B Common Shares | Group Three
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unobservable inputs	Expected Duration	Expected Duration
Swaps Related to Sale of Certain Visa Class B Common Shares | Lower Limit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instrument visa class A appreciation	7.00%	7.00%
Financial instrument conversion rate	1.63%	1.63%
Financial instrument expected conversion rate	1 year 3 months	1 year 6 months
Swaps Related to Sale of Certain Visa Class B Common Shares | Upper Limit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instrument visa class A appreciation	11.00%	11.00%
Financial instrument conversion rate	1.65%	1.65%
Financial instrument expected conversion rate	4 years 3 months	4 years 6 months
Auction Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value auction rate securities	$ 4.3	$ 4.7
Auction Rate | Group One
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation technique	Comparables	Comparables
Unobservable inputs	Price	Price
Auction Rate | Lower Limit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments fair value assumptions price per share	$ 84	$ 84
Auction Rate | Upper Limit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments fair value assumptions price per share	$ 99	$ 99

Fair Value Measurements (Recurr

Fair Value Measurements (Recurring Basis Hierarchy Leveling) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	$ 34,997.6	$ 35,579.8
Trading Account	1.4	0.3
Derivative Assets	1,998.5	3,856.8
Net Amount	646	1,686.4
Derivative Liabilities	837.2	944.9
Gross amounts offset, total derivatives subject to a master netting arrangement, assets	1,352.5	2,170.4
Gross amounts offset, total derivatives subject to a master netting arrangement, liabilities	1,148.7	2,431.2
Cross Product Collateral Adjustment
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Gross amounts offset, total derivatives subject to a master netting arrangement, assets	411	461.3
Gross amounts offset, total derivatives subject to a master netting arrangement, liabilities	207.2	722.1
Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	28,200	28,100
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total Available for Sale and Trading Securities	34,999	35,580.1
Fair Value, Measurements, Recurring | Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	34,997.6	35,579.8
Trading Account	1.4	0.3
Fair Value, Measurements, Recurring | Securities | U.S. Government
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	6,830.2	7,522.6
Fair Value, Measurements, Recurring | Securities | Obligations of States and Political Subdivisions
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	951.5	885.2
Fair Value, Measurements, Recurring | Securities | Government Sponsored Agency
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	17,936.4	17,892.8
Fair Value, Measurements, Recurring | Securities | Non-U.S. Government
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	218.1	417.9
Fair Value, Measurements, Recurring | Securities | Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	3,559	3,765.2
Fair Value, Measurements, Recurring | Securities | Covered Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	884.9	1,143.9
Fair Value, Measurements, Recurring | Securities | Sub-Sovereign, Supranational and Non-U.S. Agency Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	1,761.3
Fair Value, Measurements, Recurring | Securities | Other Asset-Backed
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	2,351.9	2,085.1
Fair Value, Measurements, Recurring | Securities | Auction Rate
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	4.3	4.7
Fair Value, Measurements, Recurring | Securities | Commercial Mortgage-Backed
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	456.2	471.6
Fair Value, Measurements, Recurring | Securities | Other
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	43.8	50.1
Fair Value, Measurements, Recurring | Other Assets
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative assets, subject to netting arrangement	(1,352.5)	(2,170.4)
Net Amount	646	1,686.4
Fair Value, Measurements, Recurring | Other Assets | Foreign Exchange Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Net Amount	1,882.3	3,609.6
Fair Value, Measurements, Recurring | Other Assets | Interest Rate Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Net Amount	116.2	247.2
Fair Value, Measurements, Recurring | Other Liabilities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	837.2	944.9
Derivative liabilities, subject to netting arrangements	(1,148.7)	(2,431.2)
Fair Value, Measurements, Recurring | Other Liabilities | Foreign Exchange Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	1,874.7	3,242.9
Fair Value, Measurements, Recurring | Other Liabilities | Interest Rate Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	84.8	108
Fair Value, Measurements, Recurring | Other Liabilities | Other Financial Derivatives
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	26.4	25.2
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total Available for Sale and Trading Securities	6,830.2	7,522.6
Fair Value, Measurements, Recurring | Level 1 | Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	6,830.2	7,522.6
Fair Value, Measurements, Recurring | Level 1 | Securities | U.S. Government
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	6,830.2	7,522.6
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total Available for Sale and Trading Securities	28,164.5	28,052.8
Fair Value, Measurements, Recurring | Level 2 | Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	28,163.1	28,052.5
Trading Account	1.4	0.3
Fair Value, Measurements, Recurring | Level 2 | Securities | Obligations of States and Political Subdivisions
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	951.5	885.2
Fair Value, Measurements, Recurring | Level 2 | Securities | Government Sponsored Agency
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	17,936.4	17,892.8
Fair Value, Measurements, Recurring | Level 2 | Securities | Non-U.S. Government
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	218.1	417.9
Fair Value, Measurements, Recurring | Level 2 | Securities | Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	3,559	3,765.2
Fair Value, Measurements, Recurring | Level 2 | Securities | Covered Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	884.9	1,143.9
Fair Value, Measurements, Recurring | Level 2 | Securities | Sub-Sovereign, Supranational and Non-U.S. Agency Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	1,761.3	1,340.7
Fair Value, Measurements, Recurring | Level 2 | Securities | Other Asset-Backed
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	2,351.9	2,085.1
Fair Value, Measurements, Recurring | Level 2 | Securities | Commercial Mortgage-Backed
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	456.2	471.6
Fair Value, Measurements, Recurring | Level 2 | Securities | Other
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	43.8	50.1
Fair Value, Measurements, Recurring | Level 2 | Other Assets
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Assets	1,998.5	3,856.8
Fair Value, Measurements, Recurring | Level 2 | Other Assets | Foreign Exchange Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Assets	1,882.3	3,609.6
Fair Value, Measurements, Recurring | Level 2 | Other Assets | Interest Rate Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Assets	116.2	247.2
Fair Value, Measurements, Recurring | Level 2 | Other Liabilities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	1,959.5	3,350.9
Fair Value, Measurements, Recurring | Level 2 | Other Liabilities | Foreign Exchange Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	1,874.7	3,242.9
Fair Value, Measurements, Recurring | Level 2 | Other Liabilities | Interest Rate Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	84.8	108
Fair Value, Measurements, Recurring | Level 2 | Other Liabilities | Other Financial Derivatives
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total Available for Sale and Trading Securities	4.3	4.7
Fair Value, Measurements, Recurring | Level 3 | Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	4.3	4.7
Fair Value, Measurements, Recurring | Level 3 | Securities | Auction Rate
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value	4.3	4.7
Fair Value, Measurements, Recurring | Level 3 | Other Liabilities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	26.4	25.2
Fair Value, Measurements, Recurring | Level 3 | Other Liabilities | Other Financial Derivatives
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	$ 26.4	$ 25.2

Fair Value Measurements (Change

Fair Value Measurements (Changes in Level 3 Assets) (Details) - Auction Rate - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value assets beginning balance	$ 4.7	$ 17.1
Total Gains (Losses):
Included in Earnings	0	0
Included in Other Comprehensive Income (1)	0	(0.4)
Purchases, Issues, Sales, and Settlements
Sales	0	(0.1)
Settlements	(0.4)	0
Fair value assets ending balance	$ 4.3	$ 16.6

Fair Value Measurements (Chan51

Fair Value Measurements (Changes in Level 3 Liabilities) (Details) - Swaps Related to Sale of Certain Visa Class B Common Shares - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value liabilities beginning balance	$ 25.2	$ 10.8
Total (Gains) Losses:
Included in Earnings (1)	2.9	(0.3)
Included in Other Comprehensive Income	0	0
Purchases, Issues, Sales, and Settlements
Purchases	0	0
Settlements	(1.7)	(0.8)
Fair value liabilities ending balance	$ 26.4	$ 9.7

Fair Value Measurements (Nonrec

Fair Value Measurements (Nonrecurring Basis Significant Unobservable Inputs) (Details) - Fair Value, Measurements, Nonrecurring - Level 3 - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 28.7	$ 6.7	$ 10.1
Valuation Technique	Market Approach	Market Approach
Unobservable Input	Discount to reflect realizable value	Discount to reflect realizable value
OREO
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 0.6	$ 0.7	$ 2.5
Valuation Technique	Market Approach	Market Approach
Unobservable Input	Discount to reflect realizable value	Discount to reflect realizable value
Lower Limit | Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range of Discounts Applied	15.00%	15.00%
Lower Limit | OREO
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range of Discounts Applied	15.00%	15.00%
Upper Limit | Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range of Discounts Applied	25.00%	25.00%
Upper Limit | OREO
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range of Discounts Applied	20.00%	20.00%

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value of Financial Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Assets
Cash and Due from Banks	$ 4,649.2	$ 5,332	$ 6,988.4	$ 6,418.5
Federal Reserve and Other Central Bank Deposits	25,959.5	26,674.2	29.2
Interest-Bearing Deposits with Banks	5,247.8	4,800.6	$ 17.5
Federal Funds Sold and Securities Purchased under Agreements to Resell	1,933.8	1,974.3
Securities
Available for Sale (Note)	34,997.6	35,579.8
Held to Maturity	8,938.4	8,921.1
Trading Account	1.4	0.3
Loans (excluding Leases)
Client Security Settlement Receivables	1,559.9	1,043.7
Deposits
Savings Certificates and Other Time	1,346.8	1,331.7
Non U.S. Offices Interest-Bearing	52,757.3	53,648.1
Federal Funds Purchased	369.5	204.8
Securities Sold Under Agreements to Repurchase	433.2	473.7
Other Borrowings	4,077.1	5,109.5
Senior Notes	1,496.8	1,496.6
Long Term Debt (excluding Leases)
Floating Rate Capital Debt	277.4	277.4
Derivative Instruments
Fair value asset	1,530.3	3,047.6
Fair value liability	1,386.3	2,767.6
Other Financial Derivatives
Derivative Instruments
Fair value liability	26.4	25.2
Asset And Liability Management
Derivative Instruments
Fair value asset	67.8	494.8
Fair value liability	58.9	42.2
Client Related and Trading
Derivative Instruments
Fair value asset	1,928.6	3,361.2
Fair value liability	1,899.9	3,306.9
Client Related and Trading | Foreign Exchange Contracts
Derivative Instruments
Fair value asset	1,851.8	3,274.2
Fair value liability	1,832.6	3,221.7
Client Related and Trading | Interest Rate Contracts
Derivative Instruments
Fair value asset	76.8	87
Fair value liability	67.3	85.2
Level 2
Securities
Available for Sale (Note)	28,200	28,100
Carrying (Reported) Amount, Fair Value Disclosure
Assets
Cash and Due from Banks	4,649.2	5,332
Federal Reserve and Other Central Bank Deposits	25,959.5	26,674.2
Interest-Bearing Deposits with Banks	5,247.8	4,800.6
Federal Funds Sold and Securities Purchased under Agreements to Resell	1,933.8	1,974.3
Securities
Available for Sale (Note)	34,997.6	35,579.8
Held to Maturity	8,938.4	8,921.1
Trading Account	1.4	0.3
Loans (excluding Leases)
Held for Investment	33,056.5	33,354.1
Held for Sale	0	13.4
Client Security Settlement Receivables	1,559.9	1,043.7
Other Assets
Federal Reserve and Federal Home Loan Bank Stock	158.1	203.1
Community Development Investments	209.8	218.9
Employee Benefit and Deferred Compensation	185.2	166.2
Deposits
Demand, Noninterest-Bearing, Savings and Money Market	46,425.4	46,671.9
Savings Certificates and Other Time	1,346.8	1,331.7
Non U.S. Offices Interest-Bearing	52,757.3	53,648.1
Federal Funds Purchased	369.5	204.8
Securities Sold Under Agreements to Repurchase	433.2	473.7
Other Borrowings	4,077.1	5,109.5
Senior Notes	1,496.8	1,496.6
Long Term Debt (excluding Leases)
Subordinated Debt	1,302.5	1,307.9
Floating Rate Capital Debt	277.4	277.4
Other Liabilities
Standby Letters of Credit	36.8	37.2
Loan Commitments	37.5	41.2
Carrying (Reported) Amount, Fair Value Disclosure | Asset And Liability Management | Foreign Exchange Contracts
Derivative Instruments
Fair value asset	30.5	335.4
Fair value liability	42.1	21.2
Carrying (Reported) Amount, Fair Value Disclosure | Asset And Liability Management | Interest Rate Contracts
Derivative Instruments
Fair value asset	39.4	160.2
Fair value liability	17.5	22.8
Carrying (Reported) Amount, Fair Value Disclosure | Asset And Liability Management | Other Financial Derivatives
Derivative Instruments
Fair value liability	26.4	25.2
Carrying (Reported) Amount, Fair Value Disclosure | Client Related and Trading | Foreign Exchange Contracts
Derivative Instruments
Fair value asset	1,851.8	3,274.2
Fair value liability	1,832.6	3,221.7
Carrying (Reported) Amount, Fair Value Disclosure | Client Related and Trading | Interest Rate Contracts
Derivative Instruments
Fair value asset	76.8	87
Fair value liability	67.3	85.2
Estimate of Fair Value, Fair Value Disclosure
Assets
Cash and Due from Banks	4,649.2	5,332
Federal Reserve and Other Central Bank Deposits	25,959.5	26,674.2
Interest-Bearing Deposits with Banks	5,247.8	4,800.6
Federal Funds Sold and Securities Purchased under Agreements to Resell	1,933.8	1,974.3
Securities
Available for Sale (Note)	34,997.6	35,579.8
Held to Maturity	8,933.4	8,905.1
Trading Account	1.4	0.3
Loans (excluding Leases)
Held for Investment	33,151.9	33,471.3
Held for Sale	0	13.4
Client Security Settlement Receivables	1,559.9	1,043.7
Other Assets
Federal Reserve and Federal Home Loan Bank Stock	158.1	203.1
Community Development Investments	209.8	215.5
Employee Benefit and Deferred Compensation	182.3	162.5
Deposits
Demand, Noninterest-Bearing, Savings and Money Market	46,425.4	46,671.9
Savings Certificates and Other Time	1,351.4	1,337.5
Non U.S. Offices Interest-Bearing	52,757.3	53,648.1
Federal Funds Purchased	369.5	204.8
Securities Sold Under Agreements to Repurchase	433.2	473.7
Other Borrowings	4,079.7	5,113.4
Senior Notes	1,537.3	1,535.5
Long Term Debt (excluding Leases)
Subordinated Debt	1,315.5	1,316
Floating Rate Capital Debt	252.6	251
Other Liabilities
Standby Letters of Credit	36.8	37.2
Loan Commitments	37.5	41.2
Estimate of Fair Value, Fair Value Disclosure | Asset And Liability Management | Foreign Exchange Contracts
Derivative Instruments
Fair value asset	30.5	335.4
Fair value liability	42.1	21.2
Estimate of Fair Value, Fair Value Disclosure | Asset And Liability Management | Interest Rate Contracts
Derivative Instruments
Fair value asset	39.4	160.2
Fair value liability	17.5	22.8
Estimate of Fair Value, Fair Value Disclosure | Asset And Liability Management | Other Financial Derivatives
Derivative Instruments
Fair value liability	26.4	25.2
Estimate of Fair Value, Fair Value Disclosure | Client Related and Trading | Foreign Exchange Contracts
Derivative Instruments
Fair value asset	1,851.8	3,274.2
Fair value liability	1,832.6	3,221.7
Estimate of Fair Value, Fair Value Disclosure | Client Related and Trading | Interest Rate Contracts
Derivative Instruments
Fair value asset	76.8	87
Fair value liability	67.3	85.2
Estimate of Fair Value, Fair Value Disclosure | Level 1
Assets
Cash and Due from Banks	4,649.2	5,332
Securities
Available for Sale (Note)	6,830.2	7,522.6
Held to Maturity	6	15
Other Assets
Employee Benefit and Deferred Compensation	118.3	107.2
Deposits
Demand, Noninterest-Bearing, Savings and Money Market	46,425.4	46,671.9
Estimate of Fair Value, Fair Value Disclosure | Level 2
Assets
Federal Reserve and Other Central Bank Deposits	25,959.5	26,674.2
Interest-Bearing Deposits with Banks	5,247.8	4,800.6
Federal Funds Sold and Securities Purchased under Agreements to Resell	1,933.8	1,974.3
Securities
Available for Sale (Note)	28,163.1	28,052.5
Held to Maturity	8,927.4	8,890.1
Trading Account	1.4	0.3
Loans (excluding Leases)
Client Security Settlement Receivables	1,559.9	1,043.7
Other Assets
Federal Reserve and Federal Home Loan Bank Stock	158.1	203.1
Community Development Investments	209.8	215.5
Employee Benefit and Deferred Compensation	64	55.3
Deposits
Savings Certificates and Other Time	1,351.4	1,337.5
Non U.S. Offices Interest-Bearing	52,757.3	53,648.1
Federal Funds Purchased	369.5	204.8
Securities Sold Under Agreements to Repurchase	433.2	473.7
Other Borrowings	4,079.7	5,113.4
Senior Notes	1,537.3	1,535.5
Long Term Debt (excluding Leases)
Subordinated Debt	1,315.5	1,316
Floating Rate Capital Debt	252.6	251
Estimate of Fair Value, Fair Value Disclosure | Level 2 | Asset And Liability Management | Foreign Exchange Contracts
Derivative Instruments
Fair value asset	30.5	335.4
Fair value liability	42.1	21.2
Estimate of Fair Value, Fair Value Disclosure | Level 2 | Asset And Liability Management | Interest Rate Contracts
Derivative Instruments
Fair value asset	39.4	160.2
Fair value liability	17.5	22.8
Estimate of Fair Value, Fair Value Disclosure | Level 2 | Asset And Liability Management | Other Financial Derivatives
Derivative Instruments
Fair value liability	0	0
Estimate of Fair Value, Fair Value Disclosure | Level 2 | Client Related and Trading | Foreign Exchange Contracts
Derivative Instruments
Fair value asset	1,851.8	3,274.2
Fair value liability	1,832.6	3,221.7
Estimate of Fair Value, Fair Value Disclosure | Level 2 | Client Related and Trading | Interest Rate Contracts
Derivative Instruments
Fair value asset	76.8	87
Fair value liability	67.3	85.2
Estimate of Fair Value, Fair Value Disclosure | Level 3
Securities
Available for Sale (Note)	4.3	4.7
Loans (excluding Leases)
Held for Investment	33,151.9	33,471.3
Held for Sale	0	13.4
Other Liabilities
Standby Letters of Credit	36.8	37.2
Loan Commitments	37.5	41.2
Estimate of Fair Value, Fair Value Disclosure | Level 3 | Asset And Liability Management | Other Financial Derivatives
Derivative Instruments
Fair value liability	$ 26.4	$ 25.2

Securities (Narrative) (Details

Securities (Narrative) (Details)	3 Months Ended
	Mar. 31, 2017USD ($)Investment	Mar. 31, 2016USD ($)	Dec. 31, 2016USD ($)
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investment Security Gains, net	$ 300,000	$ (300,000)
Other Than Temporary Impairment Losses	100,000	0
Gross proceeds from sale of securities	541,300,000	513,600,000
Gross realized securities losses	$ 200,000
Gross realized securities gains		300,000
Number of securities in an unrealized loss position | Investment	1,074
Total fair value	$ 19,997,500,000		$ 22,040,200,000
Total unrealized losses	152,800,000		$ 176,000,000
Net impairment losses recognized in earnings		$ 0
Government Sponsored Agency
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total unrealized losses	63,600,000
Corporate Debt
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total unrealized losses	$ 23,000,000
Percent of corporate debt portfolio	35.00%
Other | Community Reinvestment Act CRA
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total unrealized losses	$ 34,000,000
Auction Rate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total unrealized losses	$ 300,000

Securities (Reconciliation of A

Securities (Reconciliation of Amortized Cost to Fair Value of Securities Available for Sale) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Investment Holdings [Line Items]
Amortized Cost	$ 35,018.7	$ 35,631.9
Gross unrealized, gains	92.9	78.7
Gross unrealized, losses	114	130.8
Fair Value	34,997.6	35,579.8
U.S. Government
Investment Holdings [Line Items]
Amortized Cost	6,815.5	7,514.5
Gross unrealized, gains	27.9	22.4
Gross unrealized, losses	13.2	14.3
Fair Value	6,830.2	7,522.6
Obligations of States and Political Subdivisions
Investment Holdings [Line Items]
Amortized Cost	953.2	890.8
Gross unrealized, gains	0.2	0
Gross unrealized, losses	1.9	5.6
Fair Value	951.5	885.2
Government Sponsored Agency
Investment Holdings [Line Items]
Amortized Cost	17,947.4	17,914.1
Gross unrealized, gains	52.6	49.3
Gross unrealized, losses	63.6	70.6
Fair Value	17,936.4	17,892.8
Non-U.S. Government
Investment Holdings [Line Items]
Amortized Cost	219.8	420
Gross unrealized, gains	0	0
Gross unrealized, losses	1.7	2.1
Fair Value	218.1	417.9
Corporate Debt
Investment Holdings [Line Items]
Amortized Cost	3,578	3,787.4
Gross unrealized, gains	3.6	2.6
Gross unrealized, losses	22.6	24.8
Fair Value	3,559	3,765.2
Covered Bonds
Investment Holdings [Line Items]
Amortized Cost	887.3	1,148.6
Gross unrealized, gains	1.1	0.8
Gross unrealized, losses	3.5	5.5
Fair Value	884.9	1,143.9
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds
Investment Holdings [Line Items]
Amortized Cost	1,761	1,343.6
Gross unrealized, gains	3.1	0.9
Gross unrealized, losses	2.8	3.8
Fair Value	1,761.3	1,340.7
Other Asset-Backed
Investment Holdings [Line Items]
Amortized Cost	2,349	2,083.7
Gross unrealized, gains	4.4	2.7
Gross unrealized, losses	1.5	1.3
Fair Value	2,351.9	2,085.1
Auction Rate
Investment Holdings [Line Items]
Amortized Cost	4.6	5
Gross unrealized, gains	0	0
Gross unrealized, losses	0.3	0.3
Fair Value	4.3	4.7
Commercial Mortgage-Backed
Investment Holdings [Line Items]
Amortized Cost	459.1	474.1
Gross unrealized, gains	0	0
Gross unrealized, losses	2.9	2.5
Fair Value	456.2	471.6
Other
Investment Holdings [Line Items]
Amortized Cost	43.8	50.1
Gross unrealized, gains	0	0
Gross unrealized, losses	0	0
Fair Value	$ 43.8	$ 50.1

Securities (Reconciliation of56

Securities (Reconciliation of Amortized Cost to Fair Value of Securities Held to Maturity) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Schedule of Held-to-maturity Securities [Line Items]
Total	$ 8,938.4	$ 8,921.1
Gross Unrealized Gains	33.8	29.2
Gross Unrealized Losses	38.8	45.2
Fair Value	8,933.4	8,905.1
U.S. Government
Schedule of Held-to-maturity Securities [Line Items]
Total	6	15
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	6	15
Obligations of States and Political Subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Total	49	63.6
Gross Unrealized Gains	2.6	2.7
Gross Unrealized Losses	0	0
Fair Value	51.6	66.3
Government Sponsored Agency
Schedule of Held-to-maturity Securities [Line Items]
Total	6.8	7.4
Gross Unrealized Gains	0.5	0.5
Gross Unrealized Losses	0	0
Fair Value	7.3	7.9
Corporate Debt
Schedule of Held-to-maturity Securities [Line Items]
Total	252.6	231.2
Gross Unrealized Gains	0.1	0.2
Gross Unrealized Losses	0.4	0.4
Fair Value	252.3	231
Covered Bonds
Schedule of Held-to-maturity Securities [Line Items]
Total	2,295.6	2,051.6
Gross Unrealized Gains	11.6	10.1
Gross Unrealized Losses	2.7	3.7
Fair Value	2,304.5	2,058
Non-U.S. Government
Schedule of Held-to-maturity Securities [Line Items]
Total	3,282.6	3,517.5
Gross Unrealized Gains	6.6	4.9
Gross Unrealized Losses	0.4	2.3
Fair Value	3,288.8	3,520.1
Certificates of Deposit
Schedule of Held-to-maturity Securities [Line Items]
Total	306.5	606
Gross Unrealized Gains	0	0.2
Gross Unrealized Losses	0	0.1
Fair Value	306.5	606.1
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds
Schedule of Held-to-maturity Securities [Line Items]
Total	2,422.3	2,154.7
Gross Unrealized Gains	10.8	10.5
Gross Unrealized Losses	1.3	2.8
Fair Value	2,431.8	2,162.4
Other Asset-Backed
Schedule of Held-to-maturity Securities [Line Items]
Total	186.4	143.4
Gross Unrealized Gains	1.6	0.1
Gross Unrealized Losses	0	0
Fair Value	188	143.5
Other
Schedule of Held-to-maturity Securities [Line Items]
Total	130.6	130.7
Gross Unrealized Gains	0	0
Gross Unrealized Losses	34	35.9
Fair Value	$ 96.6	$ 94.8

Securities (Remaining Maturity

Securities (Remaining Maturity of Securities Available for Sale and Held to Maturity) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Available for Sale - Cost
Due in One Year or Less	$ 6,665.1
Due After One Year Through Five Years	21,136.2
Due After Five Years Through Ten Years	6,015.5
Due After Ten Years	1,201.9
Total	35,018.7
Held to Maturity - Amortized Cost
Due in One Year or Less	2,914.6
Due After One Year Through Five Years	5,764.1
Due After Five Years Through Ten Years	201.2
Due After Ten Years	58.5
Total	8,938.4	$ 8,921.1
Available for Sale - Value
Due in One Year or Less	6,660.1
Due After One Year Through Five Years	21,124.3
Due After Five Years Through Ten Years	6,017.7
Due After Ten Years	1,195.5
Total	34,997.6
Held to Maturity - Fair Value
Due in One Year or Less	2,916.9
Due After One Year Through Five Years	5,783.4
Due After Five Years Through Ten Years	200.2
Due After Ten Years	32.9
Total	$ 8,933.4	$ 8,905.1

Securities (Securities with Unr

Securities (Securities with Unrealized Losses) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Gain (Loss) on Investments [Line Items]
Less than 12 months, fair value	$ 16,312.5	$ 18,412.8
Less than 12 months, unrealized losses	106.3	130.2
12 months or longer fair value	3,685	3,627.4
12 months or longer unrealized losses	46.5	45.8
Total fair value	19,997.5	22,040.2
Total unrealized losses	152.8	176
U.S. Government
Gain (Loss) on Investments [Line Items]
Less than 12 months, fair value	1,701.3	1,603
Less than 12 months, unrealized losses	13.2	14.3
12 months or longer fair value	0	0
12 months or longer unrealized losses	0	0
Total fair value	1,701.3	1,603
Total unrealized losses	13.2	14.3
Obligations of States and Political Subdivisions
Gain (Loss) on Investments [Line Items]
Less than 12 months, fair value	750.1	865.3
Less than 12 months, unrealized losses	1.9	5.6
12 months or longer fair value	0	0
12 months or longer unrealized losses	0	0
Total fair value	750.1	865.3
Total unrealized losses	1.9	5.6
Government Sponsored Agency
Gain (Loss) on Investments [Line Items]
Less than 12 months, fair value	7,455.5	8,252.5
Less than 12 months, unrealized losses	51.5	58.5
12 months or longer fair value	2,433.8	2,121
12 months or longer unrealized losses	12.1	12.1
Total fair value	9,889.3	10,373.5
Total unrealized losses	63.6	70.6
Non-U.S. Government
Gain (Loss) on Investments [Line Items]
Less than 12 months, fair value	1,729.3	2,957.1
Less than 12 months, unrealized losses	2.1	4.4
12 months or longer fair value	0	0
12 months or longer unrealized losses	0	0
Total fair value	1,729.3	2,957.1
Total unrealized losses	2.1	4.4
Corporate Debt
Gain (Loss) on Investments [Line Items]
Less than 12 months, fair value	1,555.2	1,601.7
Less than 12 months, unrealized losses	9.6	11.2
12 months or longer fair value	807.3	1,054.4
12 months or longer unrealized losses	13.4	14
Total fair value	2,362.5	2,656.1
Total unrealized losses	23	25.2
Covered Bonds
Gain (Loss) on Investments [Line Items]
Less than 12 months, fair value	829.3	809
Less than 12 months, unrealized losses	6	8.6
12 months or longer fair value	139.2	138.9
12 months or longer unrealized losses	0.2	0.6
Total fair value	968.5	947.9
Total unrealized losses	6.2	9.2
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds
Gain (Loss) on Investments [Line Items]
Less than 12 months, fair value	1,089.2	1,136.1
Less than 12 months, unrealized losses	3.4	5.7
12 months or longer fair value	249.3	249.1
12 months or longer unrealized losses	0.7	0.9
Total fair value	1,338.5	1,385.2
Total unrealized losses	4.1	6.6
Other Asset-Backed
Gain (Loss) on Investments [Line Items]
Less than 12 months, fair value	714.5	584.3
Less than 12 months, unrealized losses	1.5	1.3
12 months or longer fair value	0	0
12 months or longer unrealized losses	0	0
Total fair value	714.5	584.3
Total unrealized losses	1.5	1.3
Certificates of Deposit
Gain (Loss) on Investments [Line Items]
Less than 12 months, fair value		81.4
Less than 12 months, unrealized losses		0.1
12 months or longer fair value		0
12 months or longer unrealized losses		0
Total fair value		81.4
Total unrealized losses		0.1
Auction Rate
Gain (Loss) on Investments [Line Items]
Less than 12 months, fair value	0.4	0.4
Less than 12 months, unrealized losses	0.1	0.1
12 months or longer fair value	3.8	4.3
12 months or longer unrealized losses	0.2	0.2
Total fair value	4.2	4.7
Total unrealized losses	0.3	0.3
Commercial Mortgage-Backed
Gain (Loss) on Investments [Line Items]
Less than 12 months, fair value	439.3	471.5
Less than 12 months, unrealized losses	2.9	2.5
12 months or longer fair value	0	0
12 months or longer unrealized losses	0	0
Total fair value	439.3	471.5
Total unrealized losses	2.9	2.5
Other
Gain (Loss) on Investments [Line Items]
Less than 12 months, fair value	48.4	50.5
Less than 12 months, unrealized losses	14.1	17.9
12 months or longer fair value	51.6	59.7
12 months or longer unrealized losses	19.9	18
Total fair value	100	110.2
Total unrealized losses	$ 34	$ 35.9

Securities (Cumulative Credit-R

Securities (Cumulative Credit-Related Losses on Securities) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Cumulative Credit-Related Losses on Securities Held — Beginning of Period	$ 3.4	$ 5.2
Plus: Losses on Newly Identified Impairments	0	0
Additional Losses on Previously Identified Impairments	0.1	0
Less: Current and Prior Period Losses on Securities Sold During the Period	0	0
Cumulative Credit-Related Losses on Securities Held — End of Period	$ 3.5	$ 5.2

Securities Sold Under Agreeme60

Securities Sold Under Agreements to Repurchase (Repurchase Agreements Accounted for as Secured Borrowings) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Gross Amount of Recognized Liabilities for Repurchase Agreements in Note 21	$ 237.6	$ 336.4
Overnight and Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Borrowings	433.2
Gross Amount of Recognized Liabilities for Repurchase Agreements in Note 21	433.2
Amounts related to agreements not included in Note 21	0
Overnight and Continuous | U.S. Treasury and Agency Securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Borrowings	$ 433.2

Loans and Leases (Narrative) (D

Loans and Leases (Narrative) (Details)	3 Months Ended
	Mar. 31, 2017USD ($)payment_periodLoan	Mar. 31, 2016USD ($)Loan	Dec. 31, 2016USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Collateral required on Residential real estate loan, lower limit	65.00%
Collateral required on Residential real estate loan, upper limit	80.00%
Draw period for credit line products	10 years
Other U.S. loans and non-U.S. loans, short duration advances	$ 920,100,000		$ 1,400,000,000
Demand deposits	74,800,000		88,100,000
Loans classified as held for sale	0		13,400,000
Leases classified as held for sale	32,300,000		43,000,000
Interest income that would have been recorded for nonperforming loans	2,300,000	$ 2,100,000
Undrawn loan commitments and standby letters of credit	5,000,000		2,300,000
Total loans and leases	$ 33,471,800,000		33,822,100,000
Performing status, minimum period of time	6 months
Foreclosed residential real estate properties with carrying value	$ 5,900,000
Consumer loans with carrying value collateralized by residential real estate property	$ 26,100,000
Lower Limit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Days contractually past due for interest and principal and the loan is not well-secured and in the process of collection	90 days
Upper Limit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of payment periods | payment_period	6
Limit of individual homogeneous loans collective evaluation for impairment and excluded from impaired loan disclosures (less than)	$ 1,000,000
Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equity credit lines	$ 1,100,000,000		$ 1,200,000,000
Percentage of total equity credit lines	92.00%		91.00%
Nonperforming Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	$ 79,900,000		$ 85,200,000
Performing Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	$ 37,900,000		$ 42,400,000
Performing Financing Receivable | Lower Limit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period for which troubled debt restructurings with modified terms is performing before ceasing to be classified as impaired loan	6 months
Residential Real Estate | Re-Defaulted
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans and Leases | Loan	0	1
Recorded investment		$ 100,000

Loans and Leases (Loans and Lea

Loans and Leases (Loans and Leases) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	$ 33,471.8	$ 33,822.1
Allowance for Credit Losses Assigned to Loans and Leases	(162)	(161)
Net Loans and Leases	33,309.8	33,661.1
Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	15,527.4	15,902.3
Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	9,487.3	9,523
Commercial | Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	3,922.8	4,002.5
Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	1,654	1,877.8
Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	253.6	293.9
Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	209.7	205.1
Personal
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	17,944.4	17,919.8
Personal | Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	7,542.1	7,841.9
Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	10,375.8	10,052
Personal | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	$ 26.5	$ 25.9

Loans and Leases (Borrower Rati

Loans and Leases (Borrower Ratings) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	$ 33,471.8	$ 33,822.1
1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	17,820.2	18,079.6
4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	15,175	15,255.1
6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	476.6	487.4
Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	15,527.4	15,902.3
Commercial | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	8,714.5	9,071.5
Commercial | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	6,659.3	6,664.3
Commercial | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	153.6	166.5
Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	9,487.3	9,523
Commercial | Commercial and Institutional | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	6,278.1	6,293.2
Commercial | Commercial and Institutional | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	3,080.6	3,108.5
Commercial | Commercial and Institutional | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	128.6	121.3
Commercial | Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	3,922.8	4,002.5
Commercial | Real Estate | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	1,742.3	1,825.7
Commercial | Real Estate | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	2,157.6	2,134.8
Commercial | Real Estate | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	22.9	42
Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	253.6	293.9
Commercial | Lease Financing, net | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	200.8	214.3
Commercial | Lease Financing, net | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	52.8	79.6
Commercial | Lease Financing, net | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	0	0
Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	1,654	1,877.8
Commercial | Non-U.S. | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	379.9	602.8
Commercial | Non-U.S. | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	1,272.8	1,273.5
Commercial | Non-U.S. | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	1.3	1.5
Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	209.7	205.1
Commercial | Other | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	113.4	135.5
Commercial | Other | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	95.5	67.9
Commercial | Other | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	0.8	1.7
Personal
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	17,944.4	17,919.8
Personal | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	9,105.7	9,008.1
Personal | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	8,515.7	8,590.8
Personal | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	323	320.9
Personal | Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	7,542.1	7,841.9
Personal | Real Estate | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	2,564.4	2,617.8
Personal | Real Estate | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	4,664.3	4,913.9
Personal | Real Estate | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	313.4	310.2
Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	10,375.8	10,052
Personal | Private Client | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	6,526.9	6,373.2
Personal | Private Client | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	3,839.4	3,668.4
Personal | Private Client | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	9.5	10.4
Personal | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	26.5	25.9
Personal | Other | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	14.4	17.1
Personal | Other | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	12	8.5
Personal | Other | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	$ 0.1	$ 0.3

Loans and Leases (Delinquency S

Loans and Leases (Delinquency Status) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	$ 33,471.8	$ 33,822.1
Other Real Estate Owned	6.9	5.2
Total Nonperforming Assets	186.8	165.4
Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	15,527.4	15,902.3
Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	9,487.3	9,523
Commercial | Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	3,922.8	4,002.5
Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	1,654	1,877.8
Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	253.6	293.9
Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	209.7	205.1
Personal
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	17,944.4	17,919.8
Personal | Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	7,542.1	7,841.9
Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	10,375.8	10,052
Personal | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	26.5	25.9
Performing Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Current	33,035.9	33,511.4
Total Loans and Leases	33,291.9	33,661.9
Performing Financing Receivable | 30-59 Days Past Due
Financing Receivable, Recorded Investment [Line Items]
Past Due	232.6	101.6
Performing Financing Receivable | 60-89 Days Past Due
Financing Receivable, Recorded Investment [Line Items]
Past Due	13.5	17.9
Performing Financing Receivable | 90 Days or More Past Due
Financing Receivable, Recorded Investment [Line Items]
Past Due	9.9	31
Performing Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Current	15,403.6	15,821.1
Total Loans and Leases	15,454.7	15,857
Performing Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Current	9,398.5	9,470
Total Loans and Leases	9,426.7	9,489.3
Performing Financing Receivable | Commercial | Real Estate
Financing Receivable, Recorded Investment [Line Items]
Current	3,887.8	3,974.4
Total Loans and Leases	3,910.7	3,990.9
Performing Financing Receivable | Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Current	1,654	1,877.7
Total Loans and Leases	1,654	1,877.8
Performing Financing Receivable | Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Current	253.6	293.9
Total Loans and Leases	253.6	293.9
Performing Financing Receivable | Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Current	209.7	205.1
Total Loans and Leases	209.7	205.1
Performing Financing Receivable | Commercial | 30-59 Days Past Due
Financing Receivable, Recorded Investment [Line Items]
Past Due	37.6	16.3
Performing Financing Receivable | Commercial | 30-59 Days Past Due | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Past Due	21.8	5.3
Performing Financing Receivable | Commercial | 30-59 Days Past Due | Real Estate
Financing Receivable, Recorded Investment [Line Items]
Past Due	15.8	10.9
Performing Financing Receivable | Commercial | 30-59 Days Past Due | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Past Due		0.1
Performing Financing Receivable | Commercial | 60-89 Days Past Due
Financing Receivable, Recorded Investment [Line Items]
Past Due	5.4	3.3
Performing Financing Receivable | Commercial | 60-89 Days Past Due | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Past Due	2.4	2.3
Performing Financing Receivable | Commercial | 60-89 Days Past Due | Real Estate
Financing Receivable, Recorded Investment [Line Items]
Past Due	3	1
Performing Financing Receivable | Commercial | 90 Days or More Past Due
Financing Receivable, Recorded Investment [Line Items]
Past Due	8.1	16.3
Performing Financing Receivable | Commercial | 90 Days or More Past Due | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Past Due	4	11.7
Performing Financing Receivable | Commercial | 90 Days or More Past Due | Real Estate
Financing Receivable, Recorded Investment [Line Items]
Past Due	4.1	4.6
Performing Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Current	17,632.3	17,690.3
Total Loans and Leases	17,837.2	17,804.9
Performing Financing Receivable | Personal | Real Estate
Financing Receivable, Recorded Investment [Line Items]
Current	7,389.4	7,675.7
Total Loans and Leases	7,435.1	7,727.3
Performing Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Current	10,216.4	9,988.7
Total Loans and Leases	10,375.6	10,051.7
Performing Financing Receivable | Personal | Other
Financing Receivable, Recorded Investment [Line Items]
Current	26.5	25.9
Total Loans and Leases	26.5	25.9
Performing Financing Receivable | Personal | 30-59 Days Past Due
Financing Receivable, Recorded Investment [Line Items]
Past Due	195	85.3
Performing Financing Receivable | Personal | 30-59 Days Past Due | Real Estate
Financing Receivable, Recorded Investment [Line Items]
Past Due	40	44.5
Performing Financing Receivable | Personal | 30-59 Days Past Due | Private Client
Financing Receivable, Recorded Investment [Line Items]
Past Due	155	40.8
Performing Financing Receivable | Personal | 60-89 Days Past Due
Financing Receivable, Recorded Investment [Line Items]
Past Due	8.1	14.6
Performing Financing Receivable | Personal | 60-89 Days Past Due | Real Estate
Financing Receivable, Recorded Investment [Line Items]
Past Due	5.6	6.1
Performing Financing Receivable | Personal | 60-89 Days Past Due | Private Client
Financing Receivable, Recorded Investment [Line Items]
Past Due	2.5	8.5
Performing Financing Receivable | Personal | 90 Days or More Past Due
Financing Receivable, Recorded Investment [Line Items]
Past Due	1.8	14.7
Performing Financing Receivable | Personal | 90 Days or More Past Due | Real Estate
Financing Receivable, Recorded Investment [Line Items]
Past Due	0.1	1
Performing Financing Receivable | Personal | 90 Days or More Past Due | Private Client
Financing Receivable, Recorded Investment [Line Items]
Past Due	1.7	13.7
Nonperforming Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	179.9	160.2
Nonperforming Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	72.7	45.3
Nonperforming Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	60.6	33.7
Nonperforming Financing Receivable | Commercial | Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	12.1	11.6
Nonperforming Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	107.2	114.9
Nonperforming Financing Receivable | Personal | Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	107	114.6
Nonperforming Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	$ 0.2	$ 0.3

Loans and Leases (Information a

Loans and Leases (Information about Impaired Loans as of the Period End) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 172.8		$ 156.1
Unpaid principal balance	214		199.8
Specific allowance	8.7		2.1
Average recorded investment	168.2	$ 158.3
Interest income recognized	0.6	0.6
Commercial
Financing Receivable, Impaired [Line Items]
Recorded Investment	73.6		46.9
Unpaid principal balance	79		53.2
Specific allowance	7.9		0
Average recorded investment	63.9	56.9
Interest income recognized	0.1	0.2
Commercial | Commercial and Institutional
Financing Receivable, Impaired [Line Items]
With no related specific reserve, recorded investment	31.9		32.2
With a related specific reserve, recorded investment	27.3		0
With no related specific reserve, unpaid principal balance	34.5		34.6
With a related specific reserve, unpaid principal balance	27.6		0
Specific allowance	7.2		0
With no related specific reserve, average recorded investment	39	28.3
With a related specific reserve, average recorded investment	9.1	8.4
With no related specific reserve, interest income recognized	0	0
With a related specific reserve, interest income recognized	0	0
Commercial | Real Estate
Financing Receivable, Impaired [Line Items]
With no related specific reserve, recorded investment	11.6		14.7
With a related specific reserve, recorded investment	2.8		0
With no related specific reserve, unpaid principal balance	14.1		18.6
With a related specific reserve, unpaid principal balance	2.8		0
Specific allowance	0.7		0
With no related specific reserve, average recorded investment	14.9	17.7
With a related specific reserve, average recorded investment	0.9	0
With no related specific reserve, interest income recognized	0.1	0.1
With a related specific reserve, interest income recognized	0	0
Commercial | Lease Financing, net
Financing Receivable, Impaired [Line Items]
With no related specific reserve, recorded investment	0		0
With a related specific reserve, recorded investment	0		0
With no related specific reserve, unpaid principal balance	0		0
With a related specific reserve, unpaid principal balance	0		0
Specific allowance	0		0
With no related specific reserve, average recorded investment	0	0.4
With a related specific reserve, average recorded investment	0	2.1
With no related specific reserve, interest income recognized	0	0.1
With a related specific reserve, interest income recognized	0	0
Personal
Financing Receivable, Impaired [Line Items]
Recorded Investment	99.2		109.2
Unpaid principal balance	135		146.6
Specific allowance	0.8		2.1
Average recorded investment	104.3	101.4
Interest income recognized	0.5	0.4
Personal | Real Estate
Financing Receivable, Impaired [Line Items]
With no related specific reserve, recorded investment	91.8		101.2
With a related specific reserve, recorded investment	7.3		7.7
With no related specific reserve, unpaid principal balance	127.5		138.4
With a related specific reserve, unpaid principal balance	7.4		7.9
Specific allowance	0.8		2.1
With no related specific reserve, average recorded investment	101.7	99.6
With a related specific reserve, average recorded investment	2.4	1.5
With no related specific reserve, interest income recognized	0.5	0.4
With a related specific reserve, interest income recognized	0	0
Personal | Private Client
Financing Receivable, Impaired [Line Items]
With no related specific reserve, recorded investment	0.1		0.3
With a related specific reserve, recorded investment	0		0
With no related specific reserve, unpaid principal balance	0.1		0.3
With a related specific reserve, unpaid principal balance	0		0
Specific allowance	0		$ 0
With no related specific reserve, average recorded investment	0.2	0.3
With a related specific reserve, average recorded investment	0	0
With no related specific reserve, interest income recognized	0	0
With a related specific reserve, interest income recognized	$ 0	$ 0

Loans and Leases (Troubled Debt

Loans and Leases (Troubled Debt Restructurings) (Details) - Lease Financing, net $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)Contract	Mar. 31, 2016USD ($)Contract
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases | Contract	21	31
Recorded Investment	$ 5.3	$ 14.9
Unpaid Principal Balance	$ 5.4	$ 19.9
Commercial
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases | Contract	1	7
Recorded Investment	$ 1.4	$ 9.4
Unpaid Principal Balance	$ 1.4	$ 13.7
Commercial | Commercial and Institutional
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases | Contract	0	2
Recorded Investment	$ 0	$ 4
Unpaid Principal Balance	$ 0	$ 6
Commercial | Real Estate
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases | Contract	1	5
Recorded Investment	$ 1.4	$ 5.4
Unpaid Principal Balance	$ 1.4	$ 7.7
Personal
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases | Contract	20	24
Recorded Investment	$ 3.9	$ 5.5
Unpaid Principal Balance	$ 4	$ 6.2
Personal | Real Estate
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases | Contract	19	24
Recorded Investment	$ 3.9	$ 5.5
Unpaid Principal Balance	$ 3.9	$ 6.2
Personal | Private Client
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases | Contract	1	0
Recorded Investment	$ 0	$ 0
Unpaid Principal Balance	$ 0.1	$ 0

Allowance for Credit Losses (Ch

Allowance for Credit Losses (Changes in Allowance for Credit Losses) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 192	$ 233.3
Charge-Offs	(4.7)	(5.3)
Recoveries	2.7	2.6
Net (Charge-Offs) Recoveries	(2)	(2.7)
Provision for Credit Losses	(1)	2
Balance at end of period	189	232.6
Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	104.9	114.8
Charge-Offs	(1.1)	(3.5)
Recoveries	1.6	1.2
Net (Charge-Offs) Recoveries	0.5	(2.3)
Provision for Credit Losses	6.4	2.7
Balance at end of period	111.8	115.2
Personal
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	87.1	118.5
Charge-Offs	(3.6)	(1.8)
Recoveries	1.1	1.4
Net (Charge-Offs) Recoveries	(2.5)	(0.4)
Provision for Credit Losses	(7.4)	(0.7)
Balance at end of period	$ 77.2	$ 117.4

Allowance for Credit Losses (Re

Allowance for Credit Losses (Recorded Investments in Loans and Leases) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Loans and Leases
Specifically Evaluated for Impairment	$ 172.8	$ 156.1
Evaluated for Inherent Impairment	33,299	33,666
Total Loans and Leases	33,471.8	33,822.1
Allowance for Credit Losses on Credit Exposures
Specifically Evaluated for Impairment	8.7	2.1
Evaluated for Inherent Impairment	153.3	158.9
Allowance Assigned to Loans and Leases	162	161
Allowance for Undrawn Exposures
Commitments and Standby Letters of Credit	27	31
Total Allowance for Credit Losses	189	192	$ 232.6	$ 233.3
Commercial
Loans and Leases
Specifically Evaluated for Impairment	73.6	46.9
Evaluated for Inherent Impairment	15,453.8	15,855.4
Total Loans and Leases	15,527.4	15,902.3
Allowance for Credit Losses on Credit Exposures
Specifically Evaluated for Impairment	7.9	0
Evaluated for Inherent Impairment	83.6	83.7
Allowance Assigned to Loans and Leases	91.5	83.7
Allowance for Undrawn Exposures
Commitments and Standby Letters of Credit	20.3	21.2
Total Allowance for Credit Losses	111.8	104.9	115.2	114.8
Personal
Loans and Leases
Specifically Evaluated for Impairment	99.2	109.2
Evaluated for Inherent Impairment	17,845.2	17,810.6
Total Loans and Leases	17,944.4	17,919.8
Allowance for Credit Losses on Credit Exposures
Specifically Evaluated for Impairment	0.8	2.1
Evaluated for Inherent Impairment	69.7	75.2
Allowance Assigned to Loans and Leases	70.5	77.3
Allowance for Undrawn Exposures
Commitments and Standby Letters of Credit	6.7	9.8
Total Allowance for Credit Losses	$ 77.2	$ 87.1	$ 117.4	$ 118.5

Pledged Assets (Narrative) (Det

Pledged Assets (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Financial Instruments Owned and Pledged as Collateral [Line Items]
Amount of securities and loans pledged	$ 42,600,000,000		$ 40,300,000,000
Fair value of accepted collateral	1,600,000,000		1,800,000,000
Amount of securities re pledged or sold collateral	0		0
Average deposits maintained to meet Federal Reserve Bank reserve requirements	2,000,000,000	$ 1,800,000,000
US Government Agencies Debt Securities And Other Securities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Amount of securities and loans pledged	31,500,000,000		29,700,000,000
Obligations of States and Political Subdivisions
Financial Instruments Owned and Pledged as Collateral [Line Items]
Amount of securities and loans pledged	990,400,000		939,800,000
Loans
Financial Instruments Owned and Pledged as Collateral [Line Items]
Amount of securities and loans pledged	10,100,000,000		9,600,000,000
Collateral Requirements
Financial Instruments Owned and Pledged as Collateral [Line Items]
Amount of securities and loans pledged	7,100,000,000		9,700,000,000
Available for Sale Investment Securities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Amount of securities and loans pledged	$ 1,300,000,000		$ 1,400,000,000

Goodwill and Other Intangible70

Goodwill and Other Intangibles (Narrative) (Details) - USD ($) $ in Millions	Feb. 19, 2017	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Net Book Value		$ 41.1		$ 41.8
Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense related to other intangible assets		2.4	$ 2.1
Estimated future amortization expense for 2017		6.7
Estimated future amortization expense for 2018		8.3
Estimated future amortization expense for 2019		8.2
Estimated future amortization expense for 2020		8.2
Estimated future amortization expense for 2021		$ 5.9
UBS Asset Management Fund Administration Servicing Business
Acquired Finite-Lived Intangible Assets [Line Items]
Cash paid	$ 175

Goodwill and Other Intangible71

Goodwill and Other Intangibles (Goodwill by Reporting Segment) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill	$ 519.3	$ 519.4
Corporate & Institutional Services
Goodwill [Line Items]
Goodwill	448.3	448.4
Wealth Management
Goodwill [Line Items]
Goodwill	$ 71	$ 71

Goodwill and Other Intangible72

Goodwill and Other Intangibles (Other Intangible Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Gross Carrying Amount	$ 90.9	$ 89
Less: Accumulated Amortization	49.8	47.2
Net Book Value	$ 41.1	$ 41.8

Reporting Segments (Results of

Reporting Segments (Results of Reporting Segments) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	$ 808.2	$ 748.2
Foreign Exchange Trading Income	48.1	60.5
Other Noninterest Income	74.6	73.5
Net Interest Income	362.4	314
Revenue	1,293.3	1,196.2
Provision for Credit Losses	(1)	2
Noninterest Expense	894.5	828.8
Income before Income Taxes	399.8	365.4
Provision for Income Taxes	123.7	120
Net Income	$ 276.1	$ 245.4
Percentage of Consolidated Net Income	100.00%	100.00%
Average Assets	$ 116,476.4	$ 113,417.1
FTE adjustments	8.9	6.2
Corporate & Institutional Services
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	462.9	433.4
Foreign Exchange Trading Income	49.1	51.7
Other Noninterest Income	44.2	45.6
Net Interest Income	166.5	138.4
Revenue	722.7	669.1
Provision for Credit Losses	0.3	(3.2)
Noninterest Expense	510.8	475.3
Income before Income Taxes	211.6	197
Provision for Income Taxes	66.9	62.2
Net Income	$ 144.7	$ 134.8
Percentage of Consolidated Net Income	52.00%	55.00%
Average Assets	$ 77,803.5	$ 75,372.9
Wealth Management
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	345.3	314.8
Foreign Exchange Trading Income	0.9	4.5
Other Noninterest Income	25.5	26.8
Net Interest Income	177	158.5
Revenue	548.7	504.6
Provision for Credit Losses	(1.3)	5.2
Noninterest Expense	346.3	326.9
Income before Income Taxes	203.7	172.5
Provision for Income Taxes	76.8	64.9
Net Income	$ 126.9	$ 107.6
Percentage of Consolidated Net Income	46.00%	44.00%
Average Assets	$ 26,661.8	$ 26,237.8
Treasury and Other
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	0	0
Foreign Exchange Trading Income	(1.9)	4.3
Other Noninterest Income	4.9	1.1
Net Interest Income	18.9	17.1
Revenue	21.9	22.5
Provision for Credit Losses	0	0
Noninterest Expense	37.4	26.6
Income before Income Taxes	(15.5)	(4.1)
Provision for Income Taxes	(20)	(7.1)
Net Income	$ 4.5	$ 3
Percentage of Consolidated Net Income	2.00%	1.00%
Average Assets	$ 12,011.1	$ 11,806.4

Stockholders' Equity (Narrative

Stockholders' Equity (Narrative) (Details) - USD ($)	Jan. 18, 2017	Jan. 17, 2017	Aug. 08, 2016	Mar. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)				10,000,000	10,000,000
Preferred stock, without par value				$ 0	$ 0
Stock repurchase, shares				811,730
Stock repurchase, share-based compensation plan, shares				410,869
Stock repurchase, aggregate cost				$ 70,100,000
Average price paid per share for common stock repurchased				$ 86.39
Upper Limit
Class of Stock [Line Items]
Stock repurchase authorized amount				$ 74,800,000
Series D Preferred Stock, Depositary Shares
Class of Stock [Line Items]
Shares issued (in shares)			500,000
Preferred stock, liquidation preference			$ 100,000
Depository shares, liquidation preference per share			$ 1,000
Preferred stock, annual dividend rate			4.60%
Preferred stock, dividend payment rate, variable rate			3.202%
Preferred stock, without par value			$ 0
Per share ownership interest, percentage			1.00%
Series D Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividends, per share, cash paid		$ 2,977.222222
Preferred stock			$ 493,500,000	$ 493,500,000
Dividends payable, date to be paid	Apr. 1, 2017
Dividends payable, date of record	Mar. 15, 2017
Series C Preferred Stock, Depositary Shares
Class of Stock [Line Items]
Shares issued (in shares)				16,000,000
Preferred stock, liquidation preference				$ 25,000	$ 25,000
Depository shares, liquidation preference per share				$ 25	$ 25
Preferred stock				$ 388,500,000	$ 388,500,000
Preferred stock, without par value				$ 0	$ 0
Per share ownership interest, percentage				0.10%	0.10%
Series C Preferred Stock
Class of Stock [Line Items]
Preferred stock, annual dividend rate				5.85%
Preferred stock				$ 388,500,000	$ 388,500,000
Preferred stock, dividends per share, declared	$ 365.625

Accumulated Other Comprehensi75

Accumulated Other Comprehensive Income (Loss) (Summary of Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 9,770.4
Net Change	18	$ 88.8
Ending balance	9,977.7	8,832.8
Net Unrealized Gains (Losses) on Securities Available for Sale
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(32.4)	(31)
Net Change	19.3	74.7
Ending balance	(13.1)	43.7
Net Unrealized Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	6.1	(3)
Net Change	(5.3)	6.1
Ending balance	0.8	3.1
Net Foreign Currency Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(18.5)	(17.6)
Net Change	2	3.9
Ending balance	(16.5)	(13.7)
Net Pension and Other Postretirement Benefit Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(325.2)	(321.1)
Net Change	2	4.1
Ending balance	(323.2)	(317)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(370)	(372.7)
Net Change	18	88.8
Ending balance	$ (352)	$ (283.9)

Accumulated Other Comprehensi76

Accumulated Other Comprehensive Income (Loss) (Details of Changes In Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
After Tax
Other Comprehensive Income (Loss)	$ 18	$ 88.8
Other Unrealized Gains (Losses) on Securities Available for Sale
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	30.9	120.5
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	(11.7)	(45.6)
After Tax
Other comprehensive income (loss), before reclassification, after tax	19.2	74.9
Net Unrealized Gains (Losses) on Securities Available for Sale
Before Tax
Reclassification Adjustment for (Gains) Losses Included in Net Income	0.2	(0.3)
Net Change	31.1	120.2
Tax Effect
Reclassification Adjustment for (Gains) Losses Included in Net Income	(0.1)	0.1
Net Change	(11.8)	(45.5)
After Tax
Reclassification Adjustment for (Gains) Losses Included in Net Income	0.1	(0.2)
Other Comprehensive Income (Loss)	19.3	74.7
Net Unrealized Gains (Losses) on Cash Flow Hedges
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	8.7	9.4
Reclassification Adjustment for (Gains) Losses Included in Net Income	(5.1)	0.6
Net Change	3.6	10
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	(10.8)	(3.7)
Reclassification Adjustment for (Gains) Losses Included in Net Income	1.9	(0.2)
Net Change	(8.9)	(3.9)
After Tax
Other comprehensive income (loss), before reclassification, after tax	(2.1)	5.7
Reclassification Adjustment for (Gains) Losses Included in Net Income	(3.2)	0.4
Other Comprehensive Income (Loss)	(5.3)	6.1
Net Foreign Currency Adjustments
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	22.4	17.3
Reclassification Adjustment for (Gains) Losses Included in Net Income	0	0
Net Change	(8.1)	(5)
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	(1.5)	(0.3)
Reclassification Adjustment for (Gains) Losses Included in Net Income	0	0
Net Change	10.1	8.9
After Tax
Other comprehensive income (loss), before reclassification, after tax	20.9	17
Reclassification Adjustment for (Gains) Losses Included in Net Income	0	0
Other Comprehensive Income (Loss)	2	3.9
Long-Term Intra-Entity Foreign Currency Transaction Gains (Losses)
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	0	4.2
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	0	(1)
After Tax
Other comprehensive income (loss), before reclassification, after tax	0	3.2
Net Investment Hedge Gains (Losses)
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	(30.5)	(26.5)
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	11.6	10.2
After Tax
Other comprehensive income (loss), before reclassification, after tax	(18.9)	(16.3)
Net Pension and Other Postretirement Benefit Adjustments
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	(2.3)	0
Reclassification Adjustment for (Gains) Losses Included in Net Income	6.4	6.4
Net Change	4.1	6.4
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	0	0
Reclassification Adjustment for (Gains) Losses Included in Net Income	(2.1)	(2.3)
Net Change	(2.1)	(2.3)
After Tax
Other comprehensive income (loss), before reclassification, after tax	(2.3)	0
Reclassification Adjustment for (Gains) Losses Included in Net Income	4.3	4.1
Other Comprehensive Income (Loss)	$ 2	$ 4.1

Accumulated Other Comprehensi77

Accumulated Other Comprehensive Income (Loss) (Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment Security Gains (Losses), net (Note)	$ (0.3)	$ 0.3
Other Operating Income	39.7	38.1
Net Unrealized Gains (Losses) on Securities Available for Sale
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification Adjustment for (Gains) Losses Included in Net Income	0.2	(0.3)
Net Unrealized Gains (Losses) on Securities Available for Sale | Net Gain/(Loss) Reclassified from AOCI to Net Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment Security Gains (Losses), net (Note)	0.2
Net Unrealized Gains (Losses) on Cash Flow Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification Adjustment for (Gains) Losses Included in Net Income	(5.1)	0.6
Net Unrealized Gains (Losses) on Cash Flow Hedges | Net Gain/(Loss) Reclassified from AOCI to Net Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Operating Income	(5.1)
Amortization of Net Actuarial Loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification Adjustment for (Gains) Losses Included in Net Income	6.5
Amortization of Prior Service Cost
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification Adjustment for (Gains) Losses Included in Net Income	(0.1)
Net Pension and Other Postretirement Benefit Adjustments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification Adjustment for (Gains) Losses Included in Net Income	$ 6.4	$ 6.4

Net Income Per Common Share C78

Net Income Per Common Share Computations (Net Income Per Common Share) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Basic Net Income Per Common Share
Average Number of Common Shares Outstanding — Basic (in shares)	229,059,540	228,619,089
Net Income	$ 276.1	$ 245.4
Less: Dividends on Preferred Stock	20.7	5.9
Net Income Applicable to Common Stock	255.4	239.5
Less: Earnings Allocated to Participating Securities	4.5	4.1
Earnings Allocated to Common Shares Outstanding	$ 250.9	$ 235.4
Basic Earnings per Share	$ 1.10	$ 1.03
Diluted Net Income Per Common Share
Average Number of Common Shares Outstanding — Basic (in shares)	229,059,540	228,619,089
Plus: Dilutive Effect of Share-based Compensation (in shares)	1,571,336	1,178,856
Diluted (in shares)	230,630,876	229,797,945
Earnings Allocated to Common and Potential Common Shares	$ 250.9	$ 235.5
Diluted Earnings per Share	$ 1.09	$ 1.03
Common stock equivalents not included in the computation of diluted earnings per share because their inclusion would have been antidilutive (in shares)	468,381	1,796,320

Net Interest Income (Net Intere

Net Interest Income (Net Interest Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Interest Income
Loans and Leases	$ 213.4	$ 200.9
Securities — Taxable	143.2	103.3
Securities - Non-Taxable	2.6	1.1
Interest-Bearing Due from and Deposits with Banks	14.9	17.5
Federal Reserve and Other Central Bank Deposits	36.2	29.2
Total Interest Income	410.3	352
Interest Expense
Deposits	27.6	22.2
Federal Funds Purchased	0.5	0.3
Securities Sold Under Agreements to Repurchase	0.9	0.4
Other Borrowings	7.6	2.7
Senior Notes	11.7	11.7
Long-Term Debt	7.4	6.1
Floating Rate Capital Debt	1.1	0.8
Total Interest Expense	56.8	44.2
Net Interest Income	$ 353.5	$ 307.8

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Provision for Income Taxes	$ 114.8	$ 113.8
Effective Tax Rate	29.40%	31.70%

Pension and Postretirement He81

Pension and Postretirement Health Care (Net Periodic Pension Expense (Benefit)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
U.S. Plan
Defined Benefit plan Net periodic benefit cost
Service Cost	$ 9.6	$ 9.3
Interest Cost	11.5	11.5
Expected Return on Plan Assets	(23.5)	(23.6)
Amortization
Net Actuarial Loss (Gain)	4.8	4.7
Prior Service Cost	(0.1)	(0.1)
Net Periodic Pension Expense	2.3	1.8
Non U.S. Plans
Defined Benefit plan Net periodic benefit cost
Interest Cost	0.9	1.3
Expected Return on Plan Assets	(1.1)	(1.3)
Amortization
Net Actuarial Loss (Gain)	0.3	0.3
Net Periodic Pension Expense	0.1	0.3
Supplemental Plan
Defined Benefit plan Net periodic benefit cost
Service Cost	0.9	0.9
Interest Cost	1.3	1.3
Amortization
Net Actuarial Loss (Gain)	1.4	1.5
Prior Service Cost	0	0
Net Periodic Pension Expense	3.6	3.7
Postretirement Health Care Plan
Defined Benefit plan Net periodic benefit cost
Service Cost	0	0
Interest Cost	0.4	0.4
Amortization
Net Actuarial Loss (Gain)	0	0
Net Periodic Pension Expense	$ 0.4	$ 0.4

Share-Based Compensation Plan82

Share-Based Compensation Plans (Narrative) (Details) - USD ($) $ / shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 56	$ 25.8
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, grants in period (in shares)	468,381
Options, grants date fair value	$ 9
Share based compensation expense, employees expensed in entirety	$ 5.5	5.5
Share-based compensation expense	$ 6.3	6.4
Restricted Stock Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Other than options, grants in period (in shares)	839,354
Other than options, grants in period fair value	$ 73.9
Share based compensation expense, employees expensed in entirety	$ 21.6
Share-based compensation expense	41.2	15.3
Share-based compensation expense for fully vested equity options	$ 2.5	$ 2
Performance Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Other than options, grants in period (in shares)	206,091
Other than options, grants in period fair value	$ 18.1
Share-based compensation expense	$ 3.3

Share-Based Compensation Plan83

Share-Based Compensation Plans (Compensation Expense for Share-Based Arrangements and Tax Impacts) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 56	$ 25.8
Tax Benefits Recognized	21.2	9.7
Restricted Stock Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	41.2	15.3
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	6.3	6.4
Performance Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 8.5	$ 4.1

Variable Interest Entities (Nar

Variable Interest Entities (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Tax Credit Structures
Variable Interest Entity [Line Items]
Carrying amounts	$ 178,100,000		$ 186,500,000
Exposure to loss from liquidity arrangements and obligations to purchase assets	0
Liabilities related to undrawn commitments	54,600,000		56,700,000
Affordable housing tax credits and other tax benefits	12,100,000	$ 12,000,000
Leveraged Leasing Transactions
Variable Interest Entity [Line Items]
Carrying amounts	145,900,000		$ 183,500,000
Exposure to loss from liquidity arrangements and obligations to purchase assets	$ 0
Leveraged Leasing Transactions | Lower Limit
Variable Interest Entity [Line Items]
Funding of assets cost via equity interest	20.00%
Funding of asset's cost via third party non recourse debt holders	70.00%
Leveraged Leasing Transactions | Upper Limit
Variable Interest Entity [Line Items]
Funding of assets cost via equity interest	30.00%
Funding of asset's cost via third party non recourse debt holders	80.00%
Accounting Standards Update 2015-02
Variable Interest Entity [Line Items]
Money market mutual funds fees waived	$ 200,000	$ 7,700,000

Contingent Liabilities (Narrati

Contingent Liabilities (Narrative) (Details) shares in Millions	Jan. 14, 2014case	Jun. 30, 2016USD ($)shares	Jun. 30, 2015USD ($)shares	Jan. 31, 2015trust	Mar. 31, 2017USD ($)shares	Dec. 31, 2016USD ($)	Mar. 31, 2016USD ($)shares
Loss Contingencies [Line Items]
Commitments and letters of credit					$ 30,700,000,000	$ 32,800,000,000
Standby letters of credit outstanding					$ 3,500,000,000	3,800,000,000
Minimum securities lending related collateral percentage					100.00%
Number of opt-out cases filed by merchants | case	30
Visa Class B
Loss Contingencies [Line Items]
Visa redemption gain		$ 123,100,000	$ 99,900,000
Shares issued | shares		1.1	1
Remaining Visa shares held by Northern Trust | shares					4.1		5.2
Remaining Visa shares held by Northern Trust, original cost basis					$ 0		$ 0
Northern Trust Fiduciary Services (Guernsey) Limited | Subsidiaries
Loss Contingencies [Line Items]
Number of administrated trusts serving as trustee on | trust				2
Indemnification Agreement
Loss Contingencies [Line Items]
Collateralized securities loaned, subject to indemnification					112,600,000,000	102,300,000,000
Credit loss liability					0	$ 0
Upper Limit
Loss Contingencies [Line Items]
Possible loss in future periods in excess of accrual					35,000,000
Pending Litigation
Loss Contingencies [Line Items]
Loss contingency accrual					0		0
Threatened Litigation
Loss Contingencies [Line Items]
Loss contingency accrual					$ 0		$ 0

Derivative Financial Instrume86

Derivative Financial Instruments (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Derivative [Line Items]
Derivative assets recorded on the consolidated balance sheet, reduced as a result of master netting agreements	$ 900,000,000
Derivative liabilities recorded on the consolidated balance sheet, reduced as a result of master netting agreements			$ 1,700,000,000
Derivative asset, fair value, amount offset against collateral	177,800,000		877,200,000
Gross Amount of Recognized Liabilities for Repurchase Agreements in Note 21	237,600,000		336,400,000
Gains or losses reclassified into earnings	$ 0	$ 0
Maximum length of time over which exposure was being hedged	23 months
Securities posted as collateral	$ 52,200,000		70,700,000
Aggregate fair value of all derivative instruments with credit-risk-related contingent features that are in a liability position	271,200,000		358,200,000
Collateral deposited with derivative counterparties for derivatives instruments with credit-risk-related contingent features that are in a liability position	159,800,000		317,500,000
Termination payments that could have been required for derivative instruments with credit-risk-related contingent features	111,400,000		40,700,000
Ineffectiveness or changes in the fair value of hedged items recognized in earnings for fair value hedges	0	0
Ineffectiveness recognized in earnings for cash flow hedges	0	0
Ineffectiveness from net investment hedges	0	$ 0
Net Investment Hedges
Derivative [Line Items]
Derivative assets recorded on the consolidated balance sheet, reduced as a result of master netting agreements	941,500,000
Derivative liabilities recorded on the consolidated balance sheet, reduced as a result of master netting agreements			1,700,000,000
Derivative asset, fair value, amount offset against collateral	411,100,000		461,300,000
Gross Amount of Recognized Liabilities for Repurchase Agreements in Note 21	207,200,000		722,100,000
This amount represents additional cash collateral received from derivative counterparties not offset against derivative assets	127,200,000		70,800,000
This amount represents additional cash collateral deposited with derivative counterparties not offset against derivative liabilities	$ 126,200,000		$ 324,500,000
Client Related and Trading
Derivative [Line Items]
Percentage of derivatives outstanding related to client-related and trading activities	96.00%		96.00%
Foreign Currency Denominate
Derivative [Line Items]
Estimated net gain (loss) to be reclassified into net income within the next twelve months relating to cash flow hedges	$ 2,900,000
Foreign Currency Denominated Investment Securities
Derivative [Line Items]
Estimated net gain (loss) to be reclassified into net income within the next twelve months relating to cash flow hedges	(400,000)
Available for Sale Investment Securities
Derivative [Line Items]
Estimated net gain (loss) to be reclassified into net income within the next twelve months relating to cash flow hedges	$ 200,000

Derivative Financial Instrume87

Derivative Financial Instruments (Notional and Fair Values of Client-Related and Trading Derivative Financial Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Fair value asset	$ 1,530.3	$ 3,047.6
Fair value liability	1,386.3	2,767.6
Client Related and Trading
Derivative [Line Items]
Notional Value	293,076	280,181.4
Fair value asset	1,928.6	3,361.2
Fair value liability	1,899.9	3,306.9
Client Related and Trading | Foreign Exchange Contracts
Derivative [Line Items]
Notional Value	286,237.9	273,213.1
Fair value asset	1,851.8	3,274.2
Fair value liability	1,832.6	3,221.7
Client Related and Trading | Interest Rate Contracts
Derivative [Line Items]
Notional Value	6,838.1	6,968.3
Fair value asset	76.8	87
Fair value liability	$ 67.3	$ 85.2

Derivative Financial Instrume88

Derivative Financial Instruments (Location and Amount of Gains and Losses Recorded in Income) (Details) - Client Related and Trading - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Gain Recognized in Income	$ 49.3	$ 64.6
Foreign Exchange Contracts | Foreign Exchange Trading Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Gain Recognized in Income	48.1	60.5
Interest Rate Contracts | Security Commissions and Trading Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Gain Recognized in Income	$ 1.2	$ 4.1

Derivative Financial Instrume89

Derivative Financial Instruments (Notional and Fair Value of Designated Risk Management Derivative Financial Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Fair value asset	$ 1,530.3	$ 3,047.6
Fair value liability	1,386.3	2,767.6
Asset And Liability Management
Derivative [Line Items]
Notional Value	9,680.7	9,942.9
Fair value asset	67.8	494.8
Fair value liability	58.9	42.2
Asset And Liability Management | Fair Value Hedges | Senior Notes and Long-Term Subordinated Debt | Interest Rate Swap Contracts
Derivative [Line Items]
Notional Value	1,250	1,250
Fair value asset	29.7	71.8
Fair value liability	3.5	3.3
Asset And Liability Management | Fair Value Hedges | Available for Sale Investment Securities | Interest Rate Swap Contracts
Derivative [Line Items]
Notional Value	3,670.3	3,873.4
Fair value asset	9.6	88.3
Fair value liability	11	16.8
Asset And Liability Management | Cash Flow Hedges | Forecasted Foreign Currency Denominated Transactions | Foreign Exchange Contracts
Derivative [Line Items]
Notional Value	351.5	329.3
Fair value asset	10.2	8.5
Fair value liability	6.2	7.8
Asset And Liability Management | Cash Flow Hedges | Foreign Currency Denominated Investment Securities | Foreign Exchange Contracts
Derivative [Line Items]
Notional Value	1,193.9	1,431.6
Fair value asset	0	151.5
Fair value liability	27.7	0.8
Asset And Liability Management | Cash Flow Hedges | Available for Sale Investment Securities | Interest Rate Contracts
Derivative [Line Items]
Notional Value	1,025	975
Fair value asset	0.2	0.1
Fair value liability	3	2.7
Asset And Liability Management | Net Investment Hedges | Net Investments in Non-U.S. Affiliates | Foreign Exchange Contracts
Derivative [Line Items]
Notional Value	2,190	2,083.6
Fair value asset	18.1	174.6
Fair value liability	$ 7.5	$ 10.8

Derivative Financial Instrume90

Derivative Financial Instruments (Location and Amount of Derivative Gains and Losses Recorded in Income) (Details) - Asset And Liability Management - Fair Value Hedges - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Gain Recognized in Income	$ 0.7	$ 12.7
Available for Sale Investment Securities | Interest Rate Swap Contracts | Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Gain Recognized in Income	(2.4)	(34.7)
Senior Notes and Long-Term Subordinated Debt | Interest Rate Swap Contracts | Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Gain Recognized in Income	$ 3.1	$ 47.4

Derivative Financial Instrume91

Derivative Financial Instruments (Cash Flow Hedge Derivative Gains and Losses Recognized in AOCI and Reclassified to Earnings) (Details) - Asset And Liability Management - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Foreign Exchange Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Net Gain/(Loss) Recognized in AOCI	$ 8.9	$ 4.2
Net Gain/(Loss) Reclassified from AOCI to Net Income
Net Gain/(Loss) Reclassified from AOCI to Net Income	5	(1.5)
Interest Rate Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Net Gain/(Loss) Recognized in AOCI	(0.2)	5.2
Net Gain/(Loss) Reclassified from AOCI to Net Income
Net Gain/(Loss) Reclassified from AOCI to Net Income	0.1	0.9
Net Gain/(Loss) Reclassified from AOCI to Net Income | Foreign Exchange Contracts
Net Gain/(Loss) Reclassified from AOCI to Net Income
Other Operating Income	0.7	(1.1)
Interest Income	4.4	0
Other Operating Expense	(0.1)	(0.4)
Net Gain/(Loss) Reclassified from AOCI to Net Income | Interest Rate Contracts
Net Gain/(Loss) Reclassified from AOCI to Net Income
Other Operating Income	0	0
Interest Income	0.1	0.9
Other Operating Expense	$ 0	$ 0

Derivative Financial Instrume92

Derivative Financial Instruments (Net Investment Hedge Gains and Losses Recognized in AOCI) (Details) - Net Investment Hedges - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Derivative [Line Items]
Hedging Gain / (Loss) Recognized in OCI (Before Tax)	$ (30.5)	$ (26.5)
Foreign Exchange Contracts
Derivative [Line Items]
Hedging Gain / (Loss) Recognized in OCI (Before Tax)	$ (30.5)	$ (26.5)

Derivative Financial Instrume93

Derivative Financial Instruments (Notional and Fair Values of Non-Designated Risk Management Derivative Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Fair value asset	$ 1,530.3	$ 3,047.6
Fair value liability	1,386.3	2,767.6
Nondesignated
Derivative [Line Items]
Notional Value	749.2	559.6
Fair value asset	2.1	0.8
Fair value liability	27	27
Nondesignated | Foreign Exchange Contracts
Derivative [Line Items]
Notional Value	441.6	289.6
Fair value asset	2.1	0.8
Fair value liability	0.6	1.8
Nondesignated | Other Financial Derivatives
Derivative [Line Items]
Notional Value	307.6	270
Fair value asset	0	0
Fair value liability	$ 26.4	$ 25.2

Derivative Financial Instrume94

Derivative Financial Instruments (Location and Amount of Gains and Losses Recorded in Income for Non-Designated Risk Management Derivative Instruments) (Details) - Nondesignated - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Gain Recognized in Income	$ (1.2)	$ 1.9
Foreign Exchange Contracts | Others Operating Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Gain Recognized in Income	1.7	2.7
Other Financial Derivatives | Others Operating Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Gain Recognized in Income	$ (2.9)	$ (0.8)

Offsetting of Assets and Liab95

Offsetting of Assets and Liabilities (Offsetting of Derivative Assets and Securities Purchased Under Agreements to Resell) (Details) - USD ($)	Mar. 31, 2017	Dec. 31, 2016
Offsetting Assets [Line Items]
Gross recognized assets, total derivatives subject to a master netting arrangement	$ 1,530,300,000	$ 3,047,600,000
Gross amounts offset, total derivatives subject to a master netting arrangement	1,352,500,000	2,170,400,000
Net amounts presented, total derivatives subject to a master netting arrangements	177,800,000	877,200,000
Net amount, total derivatives not subject to a master netting arrangement	177,800,000	877,200,000
Total Derivatives Not Subject to a Master Netting Arrangement	(468,200,000)	(809,200,000)
Gross recognized assets, total derivatives	1,998,500,000	3,856,800,000
Net Amount	646,000,000	1,686,400,000
Gross recognized assets, securities purchased under agreement to resell	1,933,800,000	1,967,500,000
Net amounts presented, securities purchased under agreements to resell	1,933,800,000	1,967,500,000
Gross amounts not offset, securities purchased under agreements to resell	1,933,800,000	1,967,500,000
Other assets excluding derivatives and non financial instruments	3,300,000,000	3,300,000,000
Federal funds sold	0	6,800,000
Cash collateral possessed that was not offset	0	0
Foreign Exchange Contracts | Over the Counter Derivative
Offsetting Assets [Line Items]
Gross recognized assets, total derivatives subject to a master netting arrangement	1,414,100,000	2,800,400,000
Gross amounts offset, total derivatives subject to a master netting arrangement	884,000,000	1,651,900,000
Net amounts presented, total derivatives subject to a master netting arrangements	530,100,000	1,148,500,000
Net amount, total derivatives not subject to a master netting arrangement	530,100,000	1,148,500,000
Interest Rate Swap Contracts | Over the Counter Derivative
Offsetting Assets [Line Items]
Gross recognized assets, total derivatives subject to a master netting arrangement	(10,300,000)	129,800,000
Gross amounts offset, total derivatives subject to a master netting arrangement	17,800,000	18,200,000
Net amounts presented, total derivatives subject to a master netting arrangements	(28,100,000)	111,600,000
Net amount, total derivatives not subject to a master netting arrangement	(28,100,000)	111,600,000
Interest Rate Swap Contracts | Exchange Cleared
Offsetting Assets [Line Items]
Gross recognized assets, total derivatives subject to a master netting arrangement	126,500,000	117,400,000
Gross amounts offset, total derivatives subject to a master netting arrangement	20,500,000	21,800,000
Net amounts presented, total derivatives subject to a master netting arrangements	106,000,000	95,600,000
Net amount, total derivatives not subject to a master netting arrangement	106,000,000	95,600,000
Cross Product Netting Adjustment
Offsetting Assets [Line Items]
Gross amounts offset, total derivatives subject to a master netting arrangement	19,200,000	17,200,000
Cross Product Collateral Adjustment
Offsetting Assets [Line Items]
Gross amounts offset, total derivatives subject to a master netting arrangement	$ 411,000,000	$ 461,300,000

Offsetting of Assets and Liab96

Offsetting of Assets and Liabilities (Offsetting of Derivative Liabilities and Securities Sold Under Agreements to Repurchase) (Details) - USD ($)	Mar. 31, 2017	Dec. 31, 2016
Offsetting Liabilities [Line Items]
Gross recognized liabilities, total derivatives subject to a master netting arrangement	$ 1,386,300,000	$ 2,767,600,000
Gross amounts offset, total derivatives subject to a master netting arrangement	1,148,700,000	2,431,200,000
Net amounts presented, total derivatives subject to a master netting arrangement	237,600,000	336,400,000
Net amount, total derivatives subject to a master netting arrangement	237,600,000	336,400,000
Total Derivatives Not Subject to a Master Netting Arrangement	599,600,000	608,500,000
Gross recognized liabilities, total derivatives	1,985,900,000	3,376,100,000
Derivative Liabilities	837,200,000	944,900,000
Gross recognized liabilities, securities sold under agreements to repurchase	433,200,000	473,700,000
Net amounts presented, securities sold under agreements to repurchase	433,200,000	473,700,000
Gross amounts not offset, securities sold under agreements to repurchase	433,200,000	473,700,000
Other liabilities	2,200,000,000	2,700,000,000
Cash collateral possessed that was not offset	0	0
Foreign Exchange Contracts | Over the Counter Derivative
Offsetting Liabilities [Line Items]
Gross recognized liabilities, total derivatives subject to a master netting arrangement	1,275,100,000	2,634,400,000
Gross amounts offset, total derivatives subject to a master netting arrangement	884,000,000	1,651,900,000
Net amounts presented, total derivatives subject to a master netting arrangement	391,100,000	982,500,000
Net amount, total derivatives subject to a master netting arrangement	391,100,000	982,500,000
Interest Rate Swap Contracts | Over the Counter Derivative
Offsetting Liabilities [Line Items]
Gross recognized liabilities, total derivatives subject to a master netting arrangement	64,300,000	86,200,000
Gross amounts offset, total derivatives subject to a master netting arrangement	17,800,000	18,200,000
Net amounts presented, total derivatives subject to a master netting arrangement	46,500,000	68,000,000
Net amount, total derivatives subject to a master netting arrangement	46,500,000	68,000,000
Interest Rate Swap Contracts | Exchange Cleared
Offsetting Liabilities [Line Items]
Gross recognized liabilities, total derivatives subject to a master netting arrangement	20,500,000	21,800,000
Gross amounts offset, total derivatives subject to a master netting arrangement	20,500,000	21,800,000
Other Financial Derivatives
Offsetting Liabilities [Line Items]
Gross recognized liabilities, total derivatives subject to a master netting arrangement	26,400,000	25,200,000
Net amounts presented, total derivatives subject to a master netting arrangement	26,400,000	25,200,000
Net amount, total derivatives subject to a master netting arrangement	26,400,000	25,200,000
Cross Product Netting Adjustment
Offsetting Liabilities [Line Items]
Gross amounts offset, total derivatives subject to a master netting arrangement	19,200,000	17,200,000
Cross Product Collateral Adjustment
Offsetting Liabilities [Line Items]
Gross amounts offset, total derivatives subject to a master netting arrangement	$ 207,200,000	$ 722,100,000