Amphenol (APH) 10-K 21 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
Document and Entity Information
Entity Registrant Name	AMPHENOL CORP /DE/
Entity Central Index Key	820,313
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 17,320
Entity Common Stock, Shares Outstanding		305,483,780
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Statements of Income
Net sales	$ 7,011.3	$ 6,286.4	$ 5,568.7
Cost of sales	4,701.4	4,246.4	3,789.2
Gross profit	2,309.9	2,040	1,779.5
Acquisition-related expenses	4	36.6	5.7
Selling, general and administrative expenses	878.3	798.2	669.1
Operating income	1,427.6	1,205.2	1,104.7
Interest expense	(92.3)	(72.6)	(68.3)
Other income, net	17.1	8.5	16.4
Income before income taxes	1,352.4	1,141.1	1,052.8
Provision for income taxes	(691.7)	(308.5)	(280.5)
Net income	660.7	832.6	772.3
Less: Net income attributable to noncontrolling interests	(10.2)	(9.7)	(8.8)
Net income attributable to Amphenol Corporation	$ 650.5	$ 822.9	$ 763.5
Net income per common share — Basic (in dollars per share)	$ 2.13	$ 2.67	$ 2.47
Weighted average common shares outstanding — Basic (in shares)	305.7	308.3	309.1
Net income per common share — Diluted (in dollars per share)	$ 2.06	$ 2.61	$ 2.41
Weighted average common shares outstanding — Diluted (in shares)	316.5	315.2	316.5
Dividends declared per common share (in dollars per share)	$ 0.7	$ 0.58	$ 0.53

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Statements of Comprehensive Income
Net income	$ 660.7	$ 832.6	$ 772.3
Total other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	243.3	(110.7)	(152.7)
Unrealized gain (loss) on cash flow hedges	(0.1)	1.6	(0.4)
Defined benefit plan adjustment	27.8	(12.5)	8.2
Total other comprehensive income (loss), net of tax	271	(121.6)	(144.9)
Total comprehensive income	931.7	711	627.4
Less: Comprehensive income attributable to noncontrolling interests	(13.2)	(7.6)	(7.6)
Comprehensive income attributable to Amphenol Corporation	$ 918.5	$ 703.4	$ 619.8

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current Assets:
Cash and cash equivalents	$ 1,719.1	$ 1,034.6
Short-term investments	34.6	138.6
Total cash, cash equivalents and short-term investments	1,753.7	1,173.2
Accounts receivable, less allowance for doubtful accounts of $23.0 and $23.6, respectively	1,598.6	1,349.3
Inventories:
Raw materials and supplies	386.2	319.8
Work in process	358	313.4
Finished goods	362.7	295.7
Inventories	1,106.9	928.9
Other current assets	196.8	139.8
Total current assets	4,656	3,591.2
Property, plant and equipment:
Land	32.6	28.1
Buildings and improvements	322.3	281.7
Machinery and equipment	1,662	1,408.8
Property, plant and equipment, gross	2,016.9	1,718.6
Accumulated depreciation	(1,200.1)	(1,007.2)
Property, plant and equipment, net	816.8	711.4
Goodwill	4,042.6	3,678.8
Intangibles, net and other long-term assets	488.5	517.3
Total assets	10,003.9	8,498.7
Current Liabilities:
Accounts payable	875.6	678.2
Accrued salaries, wages and employee benefits	151.6	131.8
Accrued income taxes	154.2	125.1
Accrued dividends	58.1	49.3
Other accrued expenses	338.8	275.6
Current portion of long-term debt	1.1	375.2
Total current liabilities	1,579.4	1,635.2
Long-term debt, less current portion	3,541.5	2,635.5
Accrued pension and postretirement benefit obligations	272	288.4
Deferred income taxes	241.2	77.7
Other long-term liabilities	326.4	138.8
Commitments and contingent liabilities
Equity:
Class A Common Stock, $.001 par value; 1,000.0 shares authorized; 305.7 and 308.3 shares issued and outstanding at December 31, 2017 and 2016, respectively	0.3	0.3
Additional paid-in capital	1,249	1,020.9
Retained earnings	2,941.5	3,122.7
Accumulated other comprehensive loss	(201)	(469)
Total shareholders' equity attributable to Amphenol Corporation	3,989.8	3,674.9
Noncontrolling interests	53.6	48.2
Total equity	4,043.4	3,723.1
Total liabilities and equity	$ 10,003.9	$ 8,498.7

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Millions, $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Consolidated Balance Sheets
Accounts receivable, allowance for doubtful accounts	$ 23	$ 23.6
Class A Common Stock, par value (in dollars per share)	$ 0.001	$ 0.001
Class A Common Stock, shares authorized	1,000	1,000
Class A Common Stock, shares issued	305.7	308.3
Class A Common Stock, shares outstanding	305.7	308.3

Consolidated Statements of Chan

Consolidated Statements of Changes in Equity - USD ($) shares in Millions, $ in Millions	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock	Noncontrolling Interests	Total
Balance at beginning of period at Dec. 31, 2014	$ 0.3	$ 659.4	$ 2,453.5	$ (205.8)		$ 30.5	$ 2,937.9
Balance (in shares) at Dec. 31, 2014	310
Increase (Decrease) In Shareholders' Equity
Net income			763.5			8.8	772.3
Other comprehensive income (loss)				(143.7)		(1.2)	(144.9)
Acquisition resulting in noncontrolling interest						7.9	7.9
Distributions to shareholders of noncontrolling interests						(6.1)	(6.1)
Purchase of treasury stock					$ (248.9)		(248.9)
Retirement of treasury stock			(248.9)		248.9
Retirement of treasury stock (in shares)	(5)
Stock options exercised, including tax benefit		79.7					79.7
Stock options exercised, including tax benefit (in shares)	3
Dividends declared			(163.7)				(163.7)
Stock-based compensation expense		44.2					44.2
Balance at end of period at Dec. 31, 2015	$ 0.3	783.3	2,804.4	(349.5)		39.9	3,278.4
Balance (in shares) at Dec. 31, 2015	308
Increase (Decrease) In Shareholders' Equity
Net income			822.9			9.7	832.6
Other comprehensive income (loss)				(119.5)		(2.1)	(121.6)
Acquisition resulting in noncontrolling interest						7.5	7.5
Distributions to shareholders of noncontrolling interests						(6.8)	(6.8)
Purchase of treasury stock					(325.8)		(325.8)
Retirement of treasury stock			(325.8)		325.8
Retirement of treasury stock (in shares)	(6)
Stock options exercised, including tax benefit		190					190
Stock options exercised, including tax benefit (in shares)	6
Dividends declared			(178.8)				(178.8)
Stock-based compensation expense		47.6					47.6
Balance at end of period at Dec. 31, 2016	$ 0.3	1,020.9	3,122.7	(469)		48.2	$ 3,723.1
Balance (in shares) at Dec. 31, 2016	308						308.3
Increase (Decrease) In Shareholders' Equity
Net income			650.5			10.2	$ 660.7
Other comprehensive income (loss)				268		3	271
Acquisition resulting in noncontrolling interest						11.1	11.1
Purchase of noncontrolling interest		(5.5)				(10.3)	(15.8)
Distributions to shareholders of noncontrolling interests						(8.6)	(8.6)
Purchase of treasury stock					(618)		(618)
Retirement of treasury stock			(618)		$ 618
Retirement of treasury stock (in shares)	(8)
Stock options exercised		183.9					183.9
Stock options exercised (in shares)	6
Dividends declared			(213.7)				(213.7)
Stock-based compensation expense		49.7					49.7
Balance at end of period at Dec. 31, 2017	$ 0.3	$ 1,249	$ 2,941.5	$ (201)		$ 53.6	$ 4,043.4
Balance (in shares) at Dec. 31, 2017	306						305.7

Consolidated Statements of Cha7

Consolidated Statements of Changes in Equity (Parenthetical) - $ / shares	3 Months Ended												12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Statements of Changes in Equity
Dividends declared per common share (in dollars per share)	$ 0.19	$ 0.19	$ 0.16	$ 0.16	$ 0.16	$ 0.14	$ 0.14	$ 0.14	$ 0.14	$ 0.14	$ 0.125	$ 0.125	$ 0.7	$ 0.58	$ 0.53

Consolidated Statements of Cash

Consolidated Statements of Cash Flow - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash from operating activities:
Net income	$ 660.7	$ 832.6	$ 772.3
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	226.8	217	171.6
Stock-based compensation expense	49.7	47.6	44.2
Deferred income tax provision (benefit)	186.3	(29.9)	12.9
Excess tax benefits from stock-based compensation payment arrangements		(44.4)	(16.2)
Net change in operating assets and liabilities:
Accounts receivable, net	(146.5)	(165.9)	(22.3)
Inventories	(100.4)	(14.2)	(5.2)
Other current assets	(75.9)	29.9	47.7
Accounts payable	140.5	47.8	(17.5)
Accrued income taxes	11.2	91.7	16.5
Other accrued liabilities	13	61.9	27.7
Accrued pension and postretirement benefits	5	2.5	8.7
Other long-term assets and liabilities	(173.8)	(1)	9.9
Net cash provided by operating activities	1,144.2	1,077.6	1,030.5
Cash from investing activities:
Capital expenditures	(226.6)	(190.8)	(172.1)
Proceeds from disposals of property, plant and equipment	4.1	7.1	8.7
Purchases of short-term investments	(40.2)	(232.4)	(134.7)
Sales and maturities of short-term investments	148	108.5	470.6
Acquisitions, net of cash acquired	(265.5)	(1,305.1)	(199.8)
Net cash used in investing activities	(380.2)	(1,612.7)	(27.3)
Cash from financing activities:
Proceeds from issuance of senior notes, net	749.3
Long-term borrowings under credit facilities			132.6
Repayments of long-term debt	(375)		(217.7)
Borrowings under commercial paper program, net	154.1	183.2	238.7
Payment of costs related to debt financing	(5.2)	(3)
Purchase and retirement of treasury stock	(618)	(325.8)	(248.9)
Proceeds from exercise of stock options	184.1	147.2	64.4
Excess tax benefits from stock-based compensation payment arrangements		44.4	16.2
Distributions to and purchases of noncontrolling interests	(24.4)	(6.8)	(6.1)
Dividend payments	(205)	(172.7)	(159.3)
Net cash used in financing activities	(140.1)	(133.5)	(180.1)
Effect of exchange rate changes on cash and cash equivalents	60.6	(34)	(54.8)
Net change in cash and cash equivalents	684.5	(702.6)	768.3
Cash and cash equivalents balance, beginning of year	1,034.6	1,737.2	968.9
Cash and cash equivalents balance, end of year	1,719.1	1,034.6	1,737.2
Cash paid during the year for:
Interest	84.3	68.5	64.1
Income taxes	$ 325.2	$ 246.8	$ 250.7

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	Note 1—Summary of Significant Accounting Policies Business Amphenol Corporation (together with its subsidiaries, “Amphenol”, the “Company”, “we”, “our”, or “us”) is one of the world’s largest designers, manufacturers and marketers of electrical, electronic and fiber optic connectors, interconnect systems, antennas, sensors and sensor-based products and coaxial and high-speed specialty cable. The Company sells its products to customer locations worldwide. The Company operates through two reportable business segments: · Interconnect Products and Assemblies – The Interconnect Products and Assemblies segment primarily designs, manufactures and markets a broad range of connector and connector systems, value-add products and other products, including antennas and sensors, used in a broad range of applications in a diverse set of end markets. · Cable Products and Solutions – The Cable Products and Solutions segment primarily designs, manufactures and markets cable, value-add products and components for use primarily in the broadband communications and information technology markets as well as certain applications in other markets. Use of Estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. The Company’s management evaluates these significant estimates and assumptions that affect the consolidated financial statements and related disclosures. Actual results could differ from those estimates. All normal recurring adjustments necessary for a fair presentation in conformity with accounting principles generally accepted in the United States of America have been included. Change in Presentation C Principles of Consolidation The consolidated financial statements are prepared in U.S. dollars and include the accounts of the Company and its wholly-owned and majority-owned subsidiaries. All material intercompany balances and transactions have been eliminated in consolidation. The results of companies acquired are included in the Consolidated Financial Statements from the effective date of acquisition. Cash and Cash Equivalents Cash and cash equivalents consist of cash and liquid investments with an original maturity of less than three months. The carrying amounts approximate fair values of those instruments, the majority of which are in non-U.S. bank accounts. Short-term Investments Short-term investments consist primarily of certificates of deposit with original maturities of twelve months or less. The carrying amounts approximate fair values of those instruments, the majority of which are in non-U.S. bank accounts. Accounts Receivable Accounts receivable is stated at net realizable value. The Company regularly reviews accounts receivable balances and adjusts the receivable reserves as necessary whenever events or circumstances indicate the carrying value may not be recoverable. Inventories Inventories are stated at the lower of standard cost, which approximates average cost, or net realizable value. The principal components of cost included in inventories are materials, direct labor and manufacturing overhead. The Company regularly reviews inventory quantities on hand and evaluates the realizability of inventories and adjusts the carrying value as necessary based on forecasted product demand. Depreciable Assets Property, plant and equipment are carried at cost less accumulated depreciation. Depreciation is recorded on a straight-line basis over the respective asset lives determined on a composite basis by asset group or on a specific item basis using the estimated useful lives of such assets, which range from 3 to 12 years for machinery and equipment and 20 to 40 years for buildings. Leasehold building improvements are depreciated over the shorter of the lease term or estimated useful life. The Company periodically reviews fixed asset lives. Depreciation expense is included in both Cost of sales and Selling, general and administrative expenses in the Consolidated Statements of Income based on the specific categorization and use of the underlying asset being depreciated. The Company assesses the impairment of property and equipment subject to depreciation, whenever events or changes in circumstances indicate the carrying value may not be recoverable. Factors the Company considers important, which could trigger an impairment review, include significant changes in the manner of the use of the asset, significant changes in historical trends in operating performance, significant changes in projected operating performance, and significant negative economic trends. There have been no impairments recorded as a result of such reviews during any of the periods presented. Goodwill The Company performs its annual evaluation for the impairment of goodwill for the Company’s two reporting units on an annual basis as of each July 1 or more frequently if an event occurs or circumstances change that would indicate that a reporting unit’s carrying amount may be impaired. The Company has defined its reporting units as the two reportable business segments “Interconnect Products and Assemblies” and “Cable Products and Solutions”, as the components of these reportable business segments have similar economic characteristics. In 2017 and 2016, as part of our annual evaluation, the Company utilized the option to first assess qualitative factors to determine whether it was necessary to perform the quantitative goodwill impairment assessment. As part of this assessment, the Company reviews qualitative factors, which include but are not limited to, economic, market and industry conditions, as well as the financial performance of each reporting unit. In accordance with applicable guidance, an entity is not required to calculate the fair value of a reporting unit if, after assessing these qualitative factors, the Company determines that it is more likely than not that the fair value of its reporting units is greater than its respective carrying amount. As of July 1, 2017 and 2016, the Company determined that it was more likely than not that the fair value of its reporting units exceeded their respective carrying amounts and therefore, a quantitative assessment was not required. The Company has not recognized any goodwill impairment in 2017, 2016 or 2015 in connection with its annual impairment test. Intangible Assets Intangible assets are included in Intangibles, net and other long-term assets and consist primarily of proprietary technology, customer relationships and license agreements and are generally amortized over the estimated periods of benefit. The Company assesses and reviews its long-lived assets, other than goodwill, for potential impairment including identifiable intangible assets subject to amortization, whenever significant events or significant changes in circumstances indicate the carrying amount may not be recoverable. Factors the Company considers important, which could trigger an impairment review, include significant changes in the manner of the use of the asset, changes in historical trends in operating performance, significant changes in projected operating performance, anticipated future cash flows and significant negative economic trends. Indefinite-lived intangible assets that are not subject to amortization are reviewed at least annually for impairment. In the third quarter of 2017, the Company performed its annual assessment of these identifiable indefinite-lived intangible assets. Based on our qualitative assessment, the Company determined that it was more likely than not that the fair value of the indefinite-lived intangible assets exceeded their respective carrying amounts. There have been no impairments recorded in 2017, 2016 or 2015 as a result of such reviews. Revenue Recognition The Company’s primary source of revenues is from product sales to its customers. Revenue from sales of the Company’s products is recognized at the time the goods are delivered, title passes, and the risks and rewards of ownership pass to the customer, provided the earning process is complete and revenue is measurable. Such recognition generally occurs when the products reach the shipping point, the sales price is fixed and determinable, and collection is reasonably assured. Delivery is determined by the Company’s shipping terms, which are primarily freight on board (“FOB”) shipping point. Revenue is recorded at the net amount to be received after deductions for estimated discounts, allowances and returns. These estimates and related reserves are determined and adjusted as needed based upon historical experience, contract terms and other related factors. The shipping costs for the majority of the Company’s sales are paid directly by the Company’s customers. In the broadband communications market (approximately 6% of net sales in 2017), the Company pays for shipping costs to the majority of its customers. Shipping costs are also paid by the Company for certain customers in the Interconnect Products and Assemblies segment. Amounts billed to customers related to shipping costs are immaterial and are included in Net sales. Shipping costs incurred to transport products to the customer which are not reimbursed are included in Selling, general and administrative expenses. Retirement Pension Plans Costs for retirement pension plans include current service costs and amortization of prior service costs over the average working life expectancy. It is the Company’s policy to fund current pension costs taking into consideration minimum funding requirements and maximum tax deductible limitations. The expense of retiree medical benefit programs is recognized during the employees’ service with the Company. The recognition of expense for retirement pension plans and medical benefit programs is significantly impacted by estimates made by management such as discount rates used to value certain liabilities, expected return on assets, mortality projections and future health care costs. The Company uses third-party specialists to assist management in appropriately measuring the expense and obligations associated with pension and other postretirement plan benefits. Stock-Based Compensation The Company accounts for its stock option and restricted share awards based on the fair value of the award at the date of grant and recognizes compensation expense over the service period that the awards are expected to vest. The Company recognizes expense for stock-based compensation with graded vesting on a straight-line basis over the vesting period of the entire award. Stock-based compensation expense includes the estimated effects of forfeitures, which are adjusted over the requisite service period to the extent actual forfeitures differ or are expected to differ from such estimates. Changes in estimated forfeitures are recognized in the period of change and impact the amount of expense to be recognized in future periods. The fair value of stock options has been estimated at the date of grant using the Black-Scholes option-pricing model with the following weighted average assumptions: 2017 2016 2015 Risk free interest rate 1.7 % 1.3 % 1.4 % Expected life 4.6 years 4.6 years 4.6 years Expected volatility 13.0 % 15.0 % 17.0 % Expected dividend yield 1.0 % 1.0 % 1.0 % Income Taxes Deferred income taxes are provided for revenue and expenses which are recognized in different periods for income tax and financial statement reporting purposes. The Company recognizes the effects of changes in tax laws and rates on deferred income taxes in the period in which legislation is enacted. Deferred income taxes are provided on undistributed earnings of foreign subsidiaries in the period in which the Company determines it no longer intends to permanently reinvest such earnings outside the United States. As of December 31, 2017, the Company has not provided for deferred income taxes on undistributed foreign earnings related to certain geographies of approximately $492.8, as it is the Company’s intention to permanently reinvest such earnings outside the United States. The amount of taxes that would be payable if these undistributed foreign earnings were to be repatriated would not be material. In addition, the Company remains indefinitely reinvested with respect to its financial statement basis in excess of tax basis of its investments in foreign subsidiaries. It is not practicable to determine the deferred tax liability with respect to such basis differences. Deferred tax assets are regularly assessed for recoverability based on both historical and anticipated earnings levels and a valuation allowance is recorded when it is more likely than not that these amounts will not be recovered. The tax effects of an uncertain tax position taken or expected to be taken in income tax returns are recognized only if it is “more likely than not” to be sustained on examination by the taxing authorities, based on its technical merits as of the reporting date. The tax benefits recognized in the financial statements from such a position are measured based on the largest benefit that has a greater than fifty percent likelihood of being realized upon ultimate settlement. The Company includes estimated interest and penalties related to unrecognized tax benefits in the provision for income taxes. As a result of the Tax Cuts and Jobs Act (“Tax Act”), the Company has recorded (i) a provisional income tax charge related to the deemed repatriation of the accumulated unremitted earnings and profits of foreign subsidiaries, (ii) a provisional income tax charge related to changes in the Company’s permanent reinvestment assertion with regards to prior accumulated unremitted earnings from certain foreign subsidiaries, partially offset by (iii) a provisional income tax benefit associated with the remeasurement of its net deferred tax liabilities due to the U.S. federal corporate tax rate reduction, and included these amounts in its consolidated financial statements for the year ended December 31, 2017. Beginning in 2018, the Tax Act also includes a global intangible low-taxed income ("GILTI") provision, which as currently interpreted by the Company, requires a tax on foreign earnings in excess of a deemed return on tangible assets of foreign subsidiaries. The Company has elected an accounting policy to account for GILTI as a period cost if incurred, rather than recognizing deferred taxes for temporary basis differences expected to reverse as GILTI. Other provisions of the Tax Act that impact future tax years continue to be assessed. In December 2017, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”) to address the application of U.S. GAAP in situations where a registrant does not have the necessary information available, prepared, or analyzed in reasonable detail to complete the accounting for certain income tax effects of the Tax Act. In 2017, the Company recorded provisional income tax charges as a result of the Tax Act. Due to the timing of the Tax Act’s enactment and the complexity of its provisions, the Company has not completed its accounting for the impact of the Tax Act. The Company will analyze guidance and technical interpretations of the provisions of the Tax Act, as well as refine, analyze and update the underlying data, computations and assumptions used to prepare these provisional amounts. The Company will complete its accounting in 2018 once the Company has obtained, prepared, and fully analyzed all the necessary information. We will record any necessary adjustments in the period in which such adjustments are identified. Refer to Note 4 of the Notes to the Consolidated Financial Statements for further discussion on the Tax Act. Foreign Currency Translation The financial position and results of operations of the Company’s significant foreign subsidiaries are measured using local currency as the functional currency. Assets and liabilities of such subsidiaries have been translated into U.S. dollars at current exchange rates and related revenues and expenses have been translated at weighted average exchange rates. The aggregate effect of translation adjustments is included as a component of Accumulated other comprehensive income (loss) within equity. Transaction gains and losses related to operating assets and liabilities are included in Cost of sales. Research and Development Costs incurred in connection with the development of new products and applications are expensed as incurred. Research and development expenses for the creation of new and improved products and processes were $193.7, $166.1 and $124.7, for the years 2017, 2016 and 2015, respectively, and are included in Selling, general and administrative expenses. Acquisitions The Company accounts for acquisitions using the acquisition method of accounting, which requires that assets acquired and liabilities assumed be recognized at fair value as of the acquisition date. The purchase price of acquisitions is allocated to the tangible and identifiable intangible assets acquired and liabilities assumed based on estimated fair values, and any excess purchase price over the identifiable assets acquired and liabilities assumed is recorded as goodwill. Any subsequent adjustments to the purchase price allocation prior to the completion of the measurement period will be reflected as an adjustment to goodwill in the period in which the adjustments are identified. The Company may use independent valuation specialists to assist in determining the estimated fair values of assets acquired and liabilities assumed, which could require certain significant management assumptions and estimates. Environmental Obligations The Company recognizes the potential cost for environmental remediation activities when site assessments are made, remediation efforts are probable and related amounts can be reasonably estimated; potential insurance reimbursements are not recorded. The Company assesses its environmental liabilities as necessary and appropriate through regular reviews of contractual commitments, site assessments, feasibility studies and formal remedial design and action plans. Net Income per Common Share Basic income per common share is based on the net income attributable to Amphenol Corporation for the year divided by the weighted average number of common shares outstanding. Diluted income per common share assumes the exercise of outstanding dilutive stock options using the treasury stock method. Derivative Financial Instruments Derivative financial instruments, which are periodically used by the Company in the management of its interest rate and foreign currency exposures, are accounted for as cash flow hedges. Gains and losses on derivatives designated as cash flow hedges resulting from changes in fair value are recorded in Accumulated other comprehensive income (loss), and subsequently reflected in Cost of sales in the Consolidated Statements of Income in a manner that matches the timing of the actual income or expense of such instruments with the hedged transaction. Any ineffective portion of the change in the fair value of designated hedging instruments is included in the Consolidated Statements of Income. Recent Accounting Pronouncements Recently Adopted Accounting Standards In July 2015, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update No. (“ASU”) 2015-11, Simplifying the Measurement of Inventory (“ASU 2015-11”), which requires inventory to be measured at the lower of cost and net realizable value, thereby simplifying the previous guidance of measuring inventory at the lower of cost or market. The Company adopted ASU 2015-11 in the first quarter of 2017 and it did not have a material impact on our consolidated financial statements. In March 2016, the FASB issued ASU 2016‑09 , Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (“ASU 2016‑09”), which simplifies certain provisions associated with the accounting for stock compensation. The Company adopted ASU 2016‑09 on January 1, 2017, which requires any excess tax benefits and tax deficiencies to be recorded as a discrete income tax item in the statement of income in the period in which they occur. For the year ended December 31, 2017, this change resulted in the recognition of tax benefits of approximately $66.6 (or $0.21 per share) within the provision for income taxes in the accompanying Consolidated Statements of Income. Under previous accounting guidance, these tax benefits would have been recorded directly to equity. Since this provision of the standard was applied prospectively, there was no impact to prior periods. As of January 1, 2017, the Company did not have any unrecognized excess tax benefits in which the related tax deduction did not reduce income taxes payable and therefore, there was no cumulative-effect adjustment to beginning retained earnings. The ASU also eliminated the requirement to reclassify cash flows related to excess tax benefits from operating activities to financing activities in the statement of cash flows, but rather requires such excess tax benefits and deficiencies to be classified within operating activities, consistent with other cash flows related to income taxes. The Company adopted this provision prospectively, and prior year amounts in the Statements of Cash Flow have not been adjusted. As permitted, the Company elected to continue its existing accounting practice of estimating forfeitures when recognizing stock-based compensation expense. Other provisions of this standard did not and are not expected to have a material impact on our consolidated financial statements. T he impact of this guidance on our consolidated financial statements could result in significant fluctuations in our effective tax rate in the future, since the provision for income taxes will be impacted by the timing and intrinsic value of future stock-based compensation award exercises. In January 2017, the FASB issued ASU 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (“ASU 2017-04”), which eliminates Step 2 of the two-step goodwill impairment assessment process requiring an entity to calculate any impairment as the difference between a reporting unit’s implied fair value of goodwill and the carrying value of the goodwill. Rather, ASU 2017-04 would now require any goodwill impairment charges to be calculated as the difference between a reporting unit’s fair value and its carrying value, with the loss being limited to its carrying value. The Company early adopted ASU 2017-04 in the third quarter of 2017 in conjunction with its annual impairment assessment and concluded that a Step 1 assessment was not required given the results of our annual impairment assessment discussed in Note 1 herein. As such, ASU 2017-04 did not have any impact on the Company’s consolidated financial statements. Recently Issued Accounting Standards Not Yet Adopted In May 2014, the FASB issued ASU 2014‑09, Revenue from Contracts with Customers (“ASU 2014‑09” and collectively with its subsequent amendments, “Topic 606”), which stipulates that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for such goods or services. To achieve this core principle, an entity should apply the following steps: (1) identify the contract(s) with a customer, (2) identify the performance obligations in the contract(s), (3) determine the transaction price(s), (4) allocate the transaction price(s) to the performance obligations in the contract(s), and (5) recognize revenue when (or as) the entity satisfies a performance obligation. The guidance also requires enhanced disclosures regarding the nature, amount, timing and uncertainty of revenue and cash flows arising from an entity’s contracts with customers. The guidance under ASU 2014‑09 shall apply for annual reporting periods beginning after December 15, 2017, including interim reporting periods within that period. Since 2014, the FASB has issued various related updates including, but not limited to, ASU 2016‑08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) , which clarified the implementation guidance on principal versus agent considerations, and ASU 2016‑10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing , which clarified the implementation guidance regarding performance obligations and licensing arrangements. The Company had an implementation plan involving teams across our organization to review and implement the requirements of Topic 606. We have completed the review of our existing contracts and the related revenue streams, and based on our review, the vast majority of our revenue will be recognized on a “point-in-time” basis which is consistent with current practice, while a nominal amount of our revenue will be recognized “over time” under the new standard. The Company made system reporting changes to incorporate the impact of the new standard into our financial reporting processes; implemented the related internal controls, policies, and processes; and drafted the required disclosures. The Company adopted Topic 606 in the first quarter of 2018 using the modified retrospective approach. We will expand our financial statement disclosures in the first quarter of 2018 to comply with this new standard, including the disaggregation of revenue and performance obligations, among other requirements. We have quantified the cumulative effect adjustment of applying this new standard on existing, uncompleted contracts as of January 1, 2018, and have determined that the cumulative effect is not material. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) (“ASU 2016‑02”), which amends, among other things, the existing guidance by requiring lessees to recognize lease assets (right-to-use) and liabilities (for reasonably certain lease payments) arising from operating leases on the balance sheet. For leases with a term of twelve months or less, ASU 2016‑02 permits an entity to make an accounting policy election to recognize such leases as lease expense, generally on a straight-line basis over the lease term. ASU 2016‑02 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted. ASU 2016-02 requires a modified retrospective transition application, whereas the effect of the standard would need to be reflected as of the beginning of the earliest period presented in the financial statements. The Company has begun evaluating ASU 2016‑02, including the review and implementation of the necessary changes to our existing processes and systems that will be required to implement this new standard. While we expect the adoption of ASU 2016-02 to have an impact on our consolidated balance sheet, we currently do not expect ASU 2016-02 to have a material effect on either our consolidated income statement or consolidated statement of cash flow. We plan to adopt ASU 2016-02 in the first quarter of 2019. In March 2017, the FASB issued ASU 2017‑07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost (“ASU 2017‑07”), requiring employers to provide more details about the components of costs related to retirement benefits. Specifically, ASU 2017‑07 requires employers to report the service costs for providing pensions to employees in the same line item as other employee compensation costs, while the other pension-related costs such as interest costs, amortization of pension-related costs from prior periods, and the gains or losses on plan assets, should be reported separately and outside of the subtotal of operating income. ASU 2017‑07 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017, with early adoption permitted only if adopted in the first quarter of the Company’s fiscal year. We will adopt this new standard in the first quarter of 2018. The Company has evaluated ASU 2017‑07 and we do not expect the reclassification to be material. In May 2017, the FASB issued ASU 2017‑09, Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting (“ASU 2017‑09”), which provides guidance to determine which changes to the terms or conditions of share-based payment awards require an entity to apply modification accounting in Topic 718. ASU 2017‑09 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017, with early adoption permitted, and requires prospective application to changes in terms or conditions of awards occurring on or after the adoption date. The Company has evaluated ASU 2017‑09 and we do not believe it will have a material impact on our consolidated financial statements. In February 2018, the FASB issued ASU 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income (“ASU 2018-02”), which amends the standard on comprehensive income by providing an option for an entity to reclassify stranded tax effects of the Tax Act from accumulated other comprehensive income directly to retained earnings. The stranded tax effects result from the remeasurement of net deferred tax positions which were originally recorded in comprehensive income but whose remeasurement was reflected in the income statement in 2017. ASU 2018-02 only applies to the effects of the Tax Act and is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted. ASU 2018-02 may be applied either in the period of adoption or on a retrospective basis to any period in which the impacts of the Tax Act are recognized. The Company is currently evaluating ASU 2018-02 and its impact on our consolidated financial statements.

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2017
Long-Term Debt
Long-Term Debt	Note 2—Long-Term Debt Long-term debt consists of the following: December 31, 2017 December 31, 2016 Carrying Approximate Carrying Approximate Maturity Amount Fair Value (1) Amount Fair Value (1) Revolving Credit Facility March 2021 $ — $ — $ — $ — Commercial Paper Program (less unamortized discount of $0.3 and $0.4 at December 31, 2017 and 2016, respectively) March 2021 1,175.4 1,175.4 1,018.9 1,018.9 4.00% Senior Notes (less unamortized discount of $0.5 and $0.6 at December 31, 2017 and 2016, respectively) February 2022 499.5 522.5 499.4 523.7 2.55% Senior Notes (less unamortized discount of $0.2 and $0.5 at December 31, 2017 and 2016, respectively) January 2019 749.8 752.8 749.5 758.3 1.55% Senior Notes (less unamortized discount of $0.1 at December 31, 2016) September 2017 — — 374.9 375.4 3.125% Senior Notes (less unamortized discount of $0.2 and $0.2 at December 31, 2017 and 2016, respectively) September 2021 374.8 381.2 374.8 380.4 2.20% Senior Notes (less unamortized discount of $0.2 at December 31, 2017) April 2020 399.8 398.0 — — 3.20% Senior Notes (less unamortized discount of $0.4 at December 31, 2017) April 2024 349.6 351.9 — — Notes payable to foreign banks and other debt 2018-2032 6.6 6.6 5.5 5.5 Less unamortized deferred debt issuance costs (12.9) — (12.3) — Total debt 3,542.6 3,588.4 3,010.7 3,062.2 Less current portion 1.1 1.1 375.2 375.7 Total long-term debt $ 3,541.5 $ 3,587.3 $ 2,635.5 $ 2,686.5 (1) The fair value of the Company’s Senior Notes is based on recent bid prices in an active market, and therefore is classified as Level 1 in the fair value hierarchy (Note 3). Revolving Credit Facility The Company has a $2,000.0 unsecured credit facility (the “Revolving Credit Facility”), which matures March 2021 and gives the Company the ability to borrow at a spread over LIBOR. The Company may utilize the Revolving Credit Facility for general corporate purposes. The carrying value of any borrowings under the Revolving Credit Facility would approximate their fair value due primarily to their market interest rates and would be classified as Level 2 in the fair value hierarchy (Note 3). At December 31, 2017, there were no borrowings under the Revolving Credit Facility. The Revolving Credit Facility requires payment of certain annual agency and commitment fees and requires that the Company satisfy certain financial covenants. Commercial Paper The Company has a commercial paper program (the “Commercial Paper Program”) pursuant to which the Company issues short-term unsecured commercial paper notes (“Commercial Paper”) in one or more private placements. Amounts available under the Commercial Paper Program are borrowed, repaid and re-borrowed from time to time. The maturities of the Commercial Paper vary, but may not exceed 397 days from the date of issue. The Commercial Paper is sold under customary terms in the commercial paper market and may be issued at a discount from par, or, alternatively, may be sold at par, and bears varying interest rates on a fixed or floating basis. The Commercial Paper Program is rated A-2 by Standard & Poor’s and P-2 by Moody’s and is backstopped by the Revolving Credit Facility. The maximum aggregate principal amount of the Commercial Paper outstanding under the Commercial Paper Program at any time is $2,000.0. The Commercial Paper is classified as long-term debt in the accompanying Consolidated Balance Sheets since the Company has the intent and ability to refinance the Commercial Paper on a long-term basis using the Revolving Credit Facility. The Commercial Paper is actively traded and is therefore classified as Level 1 in the fair value hierarchy (Note 3). The carrying value of Commercial Paper borrowings approximates their fair value. The average interest rate on the Commercial Paper as of December 31, 2017 and 2016 was 1.71% and 1.06%, respectively. Senior Notes All of the Company’s outstanding senior notes (“Senior Notes”) are unsecured and rank equally in right of payment with the Company’s other unsecured senior indebtedness. Interest on each series of Senior Notes is payable semiannually. The Company may, at its option, redeem some or all of any series of Senior Notes at any time subject to certain terms and conditions, which include paying 100% of the principal amount, plus accrued and unpaid interest, if any, to the date of repurchase, and, with certain exceptions, a make-whole premium. On April 5, 2017, the Company issued $400.0 principal amount of unsecured 2.20% Senior Notes due April 1, 2020 at 99.922% of face value (the “2020 Senior Notes”) and $350.0 principal amount of unsecured 3.20% Senior Notes due April 1, 2024 at 99.888% of face value (the “ 2024 Senior Notes” and, together with the 2020 Senior Notes, the “Notes” ). Interest on each of these series of Notes is payable semiannually on April 1 and October 1 of each year, commencing on October 1, 2017. The Company may, at its option, redeem some or all of the 2020 Senior Notes at any time by paying 100% of the principal amount, plus accrued and unpaid interest, if any, to the date of repurchase, and if redeemed prior to the date of maturity, a make-whole premium. The Company may, at its option, redeem some or all of the 2024 Senior Notes at any time by paying 100% of the principal amount, plus accrued and unpaid interest, if any, to the date of repurchase, and if redeemed prior to February 1, 2024, a make-whole premium. For the year ended December 31, 2017, the Company incurred approximately $5.2 of costs related to the issuances of the Notes, which are amortized to interest expense over the respective terms of the debt. In September 2017, the Company used the net proceeds from the Notes to repay all of its outstanding $375.0 principal amount of 1.55% Senior Notes that were due September 15, 2017, with the remainder of the net proceeds being used for general corporate purposes. As of December 31, 2016, such 1.55% Senior Notes were recorded, net of the related unamortized discount and debt issuance costs, within Current portion of long-term debt in the accompanying Consolidated Balance Sheets. The maturity of the Company’s debt (exclusive of unamortized deferred debt issuance costs as of December 31, 2017) over each of the next five years ending December 31 and thereafter, is as follows: 2018 $ 1.1 2019 751.0 2020 400.7 2021 1,551.2 2022 500.2 Thereafter 351.3 $ 3,555.5 At December 31, 2017, the Company had approximately $30.0 of uncommitted standby letter of credit facilities, of which $21.7 were issued.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Measurements
Fair Value Measurements	Note 3—Fair Value Measurements Fair value is determined based on the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants. These requirements establish market or observable inputs as the preferred source of values. Assumptions based on hypothetical transactions are used in the absence of market inputs. The Company does not have any non-financial instruments accounted for at fair value on a recurring basis. The valuation techniques required are based upon observable and unobservable inputs. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect the Company’s market assumptions. These two types of inputs create the following fair value hierarchy: Level 1 Quoted prices for identical instruments in active markets. Level 2 Quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations whose inputs are observable or whose significant value drivers are observable. Level 3 Significant inputs to the valuation model are unobservable. The Company believes that the assets or liabilities subject to such standards with fair value disclosure requirements are short-term investments and derivative instruments. Substantially all of the Company’s short-term investments consist of certificates of deposit with original maturities of twelve months or less and as such, are considered as Level 1 in the fair value hierarchy as they are traded in active markets for identical assets. The carrying amounts of these instruments, the majority of which are in non-U.S. bank accounts, approximate their fair value. The Company’s derivative instruments represent foreign exchange rate forward contracts, which are valued using bank quotations based on market observable inputs such as forward and spot rates and are therefore classified as Level 2 in the fair value hierarchy. The impact of the credit risk related to these financial assets is immaterial. The fair values of the Company’s financial and non-financial assets and liabilities subject to such standards at December 31, 2017 and December 31, 2016 are as follows: Fair Value Measurements Quoted Prices in Significant Significant Active Markets Observable Unobservable for Identical Inputs Inputs 2017 Total Assets (Level 1) (Level 2) (Level 3) Short-term investments $ 34.6 $ 34.6 $ — $ — Forward contracts 2.3 — 2.3 — Total $ 36.9 $ 34.6 $ 2.3 $ — 2016 Short-term investments $ 138.6 $ 138.6 $ — $ — Forward contracts 8.4 — 8.4 — Total $ 147.0 $ 138.6 $ 8.4 $ — The Company does not have any significant financial or non-financial assets and liabilities that are measured at fair value on a non-recurring basis. For the years ended December 31, 2017 and 2016, a gain (loss) of $(0.1) and $1.6, respectively, was recognized in Accumulated other comprehensive loss associated with foreign exchange rate forward contracts. The amounts reclassified from Accumulated other comprehensive loss to foreign exchange gain (loss) in the accompanying Consolidated Statements of Income during 2017 and 2016 was not material. The fair values of the forward contracts are recorded within Other current assets, Intangibles, net and other long-term assets, Other accrued expenses or Other long-term liabilities in the accompanying Consolidated Balance Sheets, depending on their value and remaining contractual period.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Taxes
Income Taxes	Note 4—Income Taxes The components of income before income taxes and the provision for income taxes are as follows: Year Ended December 31, 2017 2016 2015 Income before income taxes: United States $ 153.0 $ 87.7 $ 134.4 Foreign 1,199.4 1,053.4 918.4 $ 1,352.4 $ 1,141.1 $ 1,052.8 Current tax provision: United States $ 200.0 $ 74.6 $ 39.5 Foreign 305.4 263.8 228.1 505.4 338.4 267.6 Deferred tax provision (benefit): United States 51.0 (32.3) 13.3 Foreign 135.3 2.4 (0.4) 186.3 (29.9) 12.9 Total provision for income taxes $ 691.7 $ 308.5 $ 280.5 On December 22, 2017, the United States federal government enacted the Tax Act, marking a change from a worldwide tax system to a modified territorial tax system in the United States. As part of this change, the Tax Act, among other changes, provides for a transition tax on the accumulated unremitted foreign earnings and profits of the Company’s foreign subsidiaries (“Transition Tax”) and a reduction of the U.S. federal corporate income tax rate from 35% to 21%. As a result, in the fourth quarter of 2017, the Company recorded an income tax charge of $398.5 (“Tax Act Charge”) that was comprised of (i) the Transition Tax of $259.4, (ii) a charge of $176.6 related to changes in the Company’s permanent reinvestment assertion with regards to prior accumulated unremitted earnings from certain foreign subsidiaries, partially offset by (iii) a tax benefit of $37.5 associated with the remeasurement of the Company’s U.S. net deferred tax liabilities due to the U.S. federal corporate tax rate reduction. These three components of the Tax Act Charge are provisional amounts recorded in accordance with Staff Accounting Bulletin No. 118 (“SAB 118”), which addresses the application of U.S. GAAP in situations where a registrant does not have the necessary information available, prepared, or analyzed in reasonable detail to complete the accounting for certain income tax effects of the Tax Act. Due to the timing of the Tax Act’s enactment and the complexity of its provisions, the Company has not completed its accounting for the impact of the Tax Act. The Company will analyze guidance and technical interpretations of the provisions of the Tax Act, as well as refine, analyze and update the underlying data, computations and assumptions used to prepare these provisional amounts. The Company will complete its accounting in 2018 once the Company has obtained, prepared and fully analyzed all the necessary information. At December 31, 2017, the Company had $139.6 of foreign tax loss carryforwards, $3.5 of U.S. federal loss carryforwards, and $45.9 of U.S. state tax loss carryforwards, of which $98.6, $3.5 and $45.9, respectively, will either expire or be refunded at various dates through 2037 and the balance can be carried forward indefinitely. The Company had $2.8 of foreign tax credit carryforwards, $32.7 of U.S. federal tax credit carryforwards, and $12.4 of U.S. state tax credit carryforwards, of which $2.8, $32.7 and $6.8, respectively, will either expire or be refunded at various dates through 2037 and the balance can be carried forward indefinitely. A valuation allowance of $39.6 and $37.2 at December 31, 2017 and 2016, respectively, has been recorded which relates to the U.S. federal and state and foreign net operating loss carryforwards and U.S. state tax credits. The net change in the valuation allowance for deferred tax assets was an increase of $2.4 in 2017, which related to foreign net operating loss and U.S. state credit carryforwards. The net change in the valuation allowance for deferred tax assets was an increase of $18.7 in 2016, which was related to foreign net operating loss, U.S. federal net operating loss and state credit carryforwards. Differences between the U.S. statutory federal tax rate and the Company’s effective income tax rate are analyzed below: Year Ended December 31, 2017 2016 2015 U.S. statutory federal tax rate 35.0 % 35.0 % 35.0 % State and local taxes 0.2 0.1 0.1 Foreign earnings and dividends taxed at different rates (9.1) (9.7) (8.8) Valuation allowance 0.1 0.7 0.3 Tax Act - transition tax 19.2 — — Tax Act - remeasurement of deferred tax liabilities, net (2.8) — — Tax Act - change in indefinite reinvestment assertion 13.1 — — Excess tax benefits related to stock-based compensation (4.9) — — Impact of acquisition-related expenses — 0.5 0.1 Other, net 0.3 0.4 (0.1) Effective tax rate 51.1 % 27.0 % 26.6 % The components of the Company’s deferred tax assets and liabilities are comprised of the following: December 31, 2017 2016 Deferred tax assets relating to: Accrued liabilities and reserves $ 31.7 $ 36.8 Operating loss and tax credit carryforwards 84.2 58.8 Pensions 27.8 64.7 Inventories 35.1 45.3 Employee benefits 29.8 43.4 Total deferred tax assets 208.6 249.0 Valuation allowance (39.6) (37.2) Total deferred tax assets, net of valuation allowances 169.0 211.8 Deferred tax liabilities relating to: Goodwill 135.5 185.9 Depreciation and amortization 61.8 67.6 Unremitted foreign earnings 176.6 — Contingent consideration 4.3 6.6 Total deferred tax liabilities 378.2 260.1 Net deferred tax liability $ 209.2 $ 48.3 Classification of deferred tax assets and liabilities, as reflected on the Consolidated Balance Sheets: Intangibles, net and other long-term assets $ 32.0 $ 29.4 Deferred income taxes 241.2 77.7 Net deferred tax liability, long-term $ 209.2 $ 48.3 A tabular reconciliation of the gross amounts of unrecognized tax benefits excluding interest and penalties at the beginning and end of the year for 2017, 2016 and 2015 is shown below. The gross increases for tax positions in prior periods recorded in 2016 included $78.7 related to acquisitions. 2017 2016 2015 Unrecognized tax benefits as of January 1 $ 106.2 $ 29.8 $ 27.7 Gross increases for tax positions in prior periods 32.7 81.9 0.3 Gross increases for tax positions in current period 2.4 7.0 2.1 Settlements (11.0) (10.8) — Lapse of statute of limitations (3.0) (1.7) (0.3) Unrecognized tax benefits as of December 31 $ 127.3 $ 106.2 $ 29.8 The Company includes estimated interest and penalties related to unrecognized tax benefits in the provision for income taxes. During the years ended December 31, 2017, 2016 and 2015, the provision for income taxes included a net expense of $3.7, $6.5 and $1.5, respectively, in estimated interest and penalties. As of December 31, 2017, 2016 and 2015, the liability for unrecognized tax benefits included $39.3, $35.3 and $6.0, respectively, for tax-related interest and penalties. The Company operates in the U.S. and numerous foreign taxable jurisdictions, and at any point in time has numerous audits underway at various stages of completion. With few exceptions, the Company is subject to income tax examinations by tax authorities for the years 2013 and after. The Company is generally not able to precisely estimate the ultimate settlement amounts or timing until the close of an audit. The Company evaluates its tax positions and establishes liabilities for uncertain tax positions that may be challenged by tax authorities and may not be fully sustained, despite the Company’s belief that the underlying tax positions are fully supportable. As of December 31, 2017 and 2016, the amount of the liability for unrecognized tax benefits, including penalties and interest, which if recognized would impact the effective tax rate, was approximately $130.1 and $138.7, respectively, which is included in Other long-term liabilities in the accompanying Consolidated Balance Sheets . Unrecognized tax benefits are reviewed on an ongoing basis and are adjusted for changing facts and circumstances, including progress of tax audits and the closing of statutes of limitation. Based on information currently available, management anticipates that over the next twelve-month period, audit activity could be completed and statutes of limitation may close relating to existing unrecognized tax benefits of approximately $38.4.

Equity

Equity	12 Months Ended
	Dec. 31, 2017
Equity
Equity	Note 5—Equity Stock-Based Compensation: The Company’s income before income taxes was reduced by $49.7, $47.6 and $44.2 for the years ended December 31, 2017, 2016 and 2015, respectively, related to the expense incurred for stock-based compensation plans, which is included in Selling, general and administrative expenses in the accompanying Consolidated Statements of Income. In addition, for the years ended December 31, 2017, 2016 and 2015, the Company recognized income tax benefits in the provision for income taxes in the accompanying Consolidated Statements of Income associated with stock-based compensation of $78.3, $11.4 and $11.3, respectively. The income tax benefit during the year ended December 31, 2017 includes the excess tax benefit of $66.6 from option exercises during the year in accordance with the adoption of ASU 2016-09. Under previous accounting guidance, these excess tax benefits would have been recorded directly to equity. Stock Options In May 2017, the Company adopted the 2017 Stock Purchase and Option Plan for Key Employees of Amphenol and Subsidiaries (the “2017 Employee Option Plan”). The Company also continues to maintain the 2009 Stock Purchase and Option Plan for Key Employees of Amphenol and Subsidiaries, as amended (the “2009 Employee Option Plan”) and the 2000 Stock Purchase and Option Plan for Key Employees of Amphenol and Subsidiaries, as amended (the “2000 Employee Option Plan”). No additional stock options will be granted under the 2009 Employee Option Plan. The 2000 Employee Option Plan expired in May 2011, except that the terms continue with respect to any outstanding options granted thereunder. A committee of the Company’s Board of Directors has been authorized to grant stock options pursuant to the 2017 Employee Option Plan. The number of shares of the Company’s Class A Common Stock (“Common Stock”) reserved for issuance under the 2017 Employee Option Plan is 30,000,000 shares. As of December 31, 2017, there were 22,991,400 shares of Common Stock available for the granting of additional stock options under the 2017 Employee Option Plan. Options granted under the 2017 Employee Option Plan and the 2009 Employee Option Plan generally vest ratably over a period of five years from the date of grant and are generally exercisable over a period of ten years from the date of grant. Options granted under the 2000 Employee Option Plan are fully vested and are generally exercisable over a period of ten years from the date of grant. In 2004, the Company adopted the 2004 Stock Option Plan for Directors of Amphenol Corporation (the “2004 Directors Option Plan”). The 2004 Directors Option Plan is administered by the Company’s Board of Directors. The 2004 Directors Option Plan expired in May 2014, except that the terms continue with respect to any outstanding options granted thereunder. Options were last granted under the 2004 Directors Option Plan in May 2011. Options granted under the 2004 Directors Option Plan are fully vested and are generally exercisable over a period of ten years from the date of grant. Stock option activity for 2015, 2016 and 2017 was as follows: Weighted Average Aggregate Weighted Remaining Intrinsic Average Contractual Value Options Exercise Price Term (in years) (in millions) Options outstanding at January 1, 2015 27,787,920 $ 31.60 7.09 Options granted 6,490,200 57.85 Options exercised (2,718,745) 23.71 Options forfeited (422,900) 41.73 Options outstanding at December 31, 2015 31,136,475 37.62 6.92 Options granted 7,560,450 57.72 Options exercised (5,703,254) 25.80 Options forfeited (727,280) 50.17 Options outstanding at December 31, 2016 32,266,391 44.14 7.03 Options granted 7,029,600 72.98 Options exercised (5,773,287) 31.87 Options forfeited (300,340) 55.16 Options outstanding at December 31, 2017 33,222,364 $ 52.27 7.05 $ 1,180.3 Vested and non-vested options expected to vest at December 31, 2017 31,214,883 $ 51.61 6.96 $ 1,129.8 Exercisable options at December 31, 2017 13,621,924 $ 39.48 5.40 $ 658.2 A summary of the status of the Company’s non-vested options as of December 31, 2017 and changes during the year then ended is as follows: Weighted Average Fair Value Options at Grant Date Non-vested options at January 1, 2017 18,725,570 $ 7.99 Options granted 7,029,600 8.78 Options vested (5,854,390) 7.91 Options forfeited (300,340) 8.10 Non-vested options at December 31, 2017 19,600,440 $ 8.29 The weighted average fair value at the grant date of options granted during 2016 and 2015 was $7.39 and $8.47, respectively. During the years ended December 31, 2017, 2016 and 2015, the following activity occurred under the Company’s option plans: 2017 2016 2015 Total intrinsic value of stock options exercised $ 268.7 $ 197.2 $ 88.1 Total fair value of stock options vested 46.3 43.1 39.9 As of December 31, 2017, the total compensation cost related to non-vested options not yet recognized was approximately $120.3, with a weighted average expected amortization period of 3.30 years. The grant date fair value of each option grant under the 2000 Employee Option Plan, the 2009 Employee Option Plan , the 2017 Employee Option Plan and the 2004 Directors Option Plan is estimated using the Black-Scholes option pricing model. The grant date fair value of each share grant is determined based on the closing share price of the Company’s Common Stock on the date of the grant. The fair value is then amortized on a straight-line basis over the requisite service period of the awards, which is generally the vesting period. Use of a valuation model for option grants requires management to make certain assumptions with respect to selected model inputs. Expected share price volatility is calculated based on the historical volatility of the Common Stock and implied volatility derived from related exchange traded options. The average expected life is based on the contractual term of the option and expected exercise and historical post-vesting termination experience. The risk-free interest rate is based on U.S. Treasury zero-coupon issuances with a remaining term equal to the expected life assumed at the date of grant. The expected annual dividend per share is based on the Company’s dividend rate. Restricted Stock In 2012, the Company adopted the 2012 Restricted Stock Plan for Directors of Amphenol Corporation (the “2012 Directors Restricted Stock Plan”). The 2012 Directors Restricted Stock Plan is administered by the Company’s Board of Directors. As of December 31, 2017, the number of restricted shares available for grant under the 2012 Directors Restricted Stock Plan was 124,164. Restricted shares granted under the 2012 Directors Restricted Stock Plan generally vest on the first anniversary of the grant date. Grants under the 2012 Directors Restricted Stock Plan entitle the holder to receive shares of the Company’s Common Stock without payment. Restricted share activity for 2015, 2016 and 2017 was as follows: Weighted Average Fair Value Remaining Restricted at Grant Amortization Shares Date Term (in years) Restricted shares outstanding at January 1, 2015 18,340 $ 47.72 0.39 Restricted shares granted 17,948 57.85 Shares vested and issued (19,032) 47.98 Restricted shares outstanding at December 31, 2015 17,256 57.97 0.39 Restricted shares granted 16,905 57.99 Shares vested and issued (17,256) 57.97 Restricted shares outstanding at December 31, 2016 16,905 57.99 0.38 Restricted shares granted 12,905 73.25 Shares vested and issued (16,905) 57.99 Restricted shares outstanding at December 31, 2017 12,905 $ 73.25 0.37 The total fair value of restricted share awards that vested during 2017, 2016, and 2015 was $1.0, $1.0, and $0.9, respectively. As of December 31, 2017, the total compensation cost related to non-vested restricted shares not yet recognized was approximately $0.4 with a weighted average expected amortization period of 0.37 years. Stock Repurchase Program: In January 2015, the Company’s Board of Directors authorized a stock repurchase program under which the Company could repurchase up to 10 million shares of its Common Stock during the two-year period ended January 20, 2017 (the “2015 Stock Repurchase Program”). During the years ended December 31, 2016 and 2015, the Company repurchased 5.5 million and 4.5 million shares of its Common Stock for $325.8 and $248.9, respectively. These treasury shares have been retired by the Company and Common Stock and retained earnings were reduced accordingly. At December 31, 2016, the Company had repurchased all of the shares authorized under the 2015 Stock Repurchase Program. On January 24, 2017, the Company’s Board of Directors authorized a new stock repurchase program under which the Company may purchase up to $1,000.0 of the Company’s Common Stock during the two-year period ending January 24, 2019 in accordance with the requirements of Rule 10b-18 of the Exchange Act (the “2017 Stock Repurchase Program”). During the year ended December 31, 2017, the Company repurchased 8.4 million shares of its Common Stock for $618.0. These treasury shares have been retired by the Company and Common Stock and retained earnings were reduced accordingly . From January 1, 2018 through January 31, 2018, the Company repurchased approximately 1.1 million additional shares of Common Stock for $105.5, leaving approximately $276.5 available to purchase under the 2017 Stock Repurchase Program. The price and timing of any future purchases under the 2017 Stock Repurchase Program will depend on factors such as levels of cash generation from operations, the volume of stock option exercises by employees, cash requirements for acquisitions, dividends, economic and market conditions and stock price. Dividends: Contingent upon declaration by the Board of Directors, the Company generally pays a quarterly dividend on shares of its Common Stock. The following table summarizes the declared quarterly dividends per share for each of the three years ended December 31, 2017, 2016 and 2015: 2017 2016 2015 First Quarter $ 0.16 $ 0.14 $ 0.125 Second Quarter 0.16 0.14 0.125 Third Quarter 0.19 0.14 0.14 Fourth Quarter 0.19 0.16 0.14 Dividends declared and paid for the years ended December 31, 2017, 2016 and 2015 were as follows: 2017 2016 2015 Dividends declared $ 213.7 $ 178.8 $ 163.7 Dividends paid (including those declared in the prior year) 205.0 172.7 159.3 Accumulated Other Comprehensive Income (Loss): Balances of related after-tax components comprising Accumulated other comprehensive income (loss) included in equity at December 31, 2017, 2016 and 2015 are as follows: Foreign Unrealized Defined Accumulated Currency Gain (Loss) Benefit Other Translation on Cash Plan Comprehensive Adjustments Flow Hedges Adjustment Income (Loss) Balance at January 1, 2015 $ (13.4) $ (1.3) $ (191.1) $ (205.8) Other comprehensive income (loss) before reclassifications, net of tax of nil, $0.1 and $5.5, respectively (151.5) (0.4) (10.0) (161.9) Amounts reclassified from Accumulated other comprehensive income (loss) to earnings, net of tax of ($10.1) — — 18.2 18.2 Balance at December 31, 2015 (164.9) (1.7) (182.9) (349.5) Other comprehensive income (loss) before reclassifications, net of tax of nil, ($0.3) and $12.3, respectively (108.6) 1.6 (28.8) (135.8) Amounts reclassified from Accumulated other comprehensive income (loss) to earnings, net of tax of ($8.9) — — 16.3 16.3 Balance at December 31, 2016 (273.5) (0.1) (195.4) (469.0) Other comprehensive income (loss) before reclassifications, net of tax of nil, $0.1 and ($3.4), respectively 240.3 (0.1) 10.7 250.9 Amounts reclassified from Accumulated other comprehensive income (loss) to earnings, net of tax of ($9.1) — — 17.1 17.1 Balance at December 31, 2017 $ (33.2) $ (0.2) $ (167.6) $ (201.0) The amounts reclassified from Accumulated other comprehensive income (loss) for defined benefit plan liabilities, are included within Cost of sales and Selling, general and administrative expenses and for unrealized gain (loss) on cash flow hedges, are included in Cost of sales within the Company’s Consolidated Statements of Income.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share
Earnings Per Share	Note 6—Earnings Per Share Basic earnings per share (“EPS”) is computed by dividing net income attributable to Amphenol Corporation by the weighted average number of common shares outstanding. Diluted EPS is computed by dividing net income attributable to Amphenol Corporation by the weighted average number of common shares and dilutive common shares outstanding, which relates to stock options. Additionally, the prospective adoption of ASU 2016-09 in 2017 had the effect of increasing the Company’s 2017 diluted weighted average common shares outstanding by approximately two million shares. A reconciliation of the basic weighted average common shares outstanding to diluted weighted average common shares outstanding for the years ended December 31, 2017, 2016 and 2015 is as follows: (dollars and shares in millions, except per share data) 2017 2016 2015 Net income attributable to Amphenol Corporation shareholders $ 650.5 $ 822.9 $ 763.5 Basic weighted average common shares outstanding 305.7 308.3 309.1 Effect of dilutive stock options 10.8 6.9 7.4 Diluted weighted average common shares outstanding 316.5 315.2 316.5 Earnings per share attributable to Amphenol Corporation shareholders: Basic $ 2.13 $ 2.67 $ 2.47 Diluted $ 2.06 $ 2.61 $ 2.41 Excluded from the computations above were anti-dilutive common shares of 1.6 million, 8.5 million and 6.3 million for the years ended December 31, 2017, 2016 and 2015, respectively.

Benefit Plans and Other Postret

Benefit Plans and Other Postretirement Benefits	12 Months Ended
	Dec. 31, 2017
Benefit Plans and Other Postretirement Benefits
Benefit Plans and Other Postretirement Benefits	Note 7—Benefit Plans and Other Postretirement Benefits Defined Benefit Plans The Company and certain of its domestic subsidiaries have defined benefit pension plans (the “U.S. Plans”), which cover certain U.S. employees and which represent the majority of the plan assets and benefit obligations of the aggregate defined benefit plans of the Company. The U.S. Plans’ benefits are generally based on years of service and compensation and are generally noncontributory. Certain U.S. employees not covered by the U.S. Plans are covered by defined contribution plans. Certain foreign subsidiaries have defined benefit plans covering their employees (the “International Plans” and together with the U.S. Plans, the “Plans”). The largest international pension plan, in accordance with local regulations, is unfunded and had a projected benefit obligation of approximately $93.0 and $81.7 at December 31, 2017 and 2016, respectively. Total required contributions to be made during 2018 for the unfunded International Plans are included in Other accrued expenses in the accompanying Consolidated Balance Sheets and in the tables below. The following is a summary of the Company’s defined benefit plans’ funded status as of the most recent actuarial valuations as of December 31 of each year; for each year presented below, projected benefit obligations exceed assets. U.S. Plans International Plans Total 2017 2016 2017 2016 2017 2016 Change in projected benefit obligation : Projected benefit obligation at beginning of year $ 469.8 $ 460.8 $ 233.5 $ 174.4 $ 703.3 $ 635.2 Service cost 6.7 6.2 2.9 2.8 9.6 9.0 Interest cost 15.3 15.4 4.7 5.5 20.0 20.9 Acquisitions — — — 47.4 — 47.4 Plan amendments — 3.7 — — — 3.7 Actuarial (gain) loss 21.1 11.6 (2.2) 28.0 18.9 39.6 Foreign exchange translation — — 26.7 (17.3) 26.7 (17.3) Benefits paid (26.2) (27.9) (10.6) (7.3) (36.8) (35.2) Projected benefit obligation at end of year 486.7 469.8 255.0 233.5 741.7 703.3 Change in plan assets : Fair value of plan assets at beginning of year 342.1 333.2 97.8 59.0 439.9 392.2 Actual return on plan assets 57.2 20.4 5.2 11.4 62.4 31.8 Employer contributions 16.5 16.4 6.0 5.8 22.5 22.2 Acquisitions — — — 36.7 — 36.7 Foreign exchange translation — — 9.9 (7.8) 9.9 (7.8) Benefits paid (26.2) (27.9) (10.6) (7.3) (36.8) (35.2) Fair value of plan assets at end of year 389.6 342.1 108.3 97.8 497.9 439.9 Underfunded status at end of year $ 97.1 $ 127.7 $ 146.7 $ 135.7 $ 243.8 $ 263.4 Amounts recognized on the balance sheet as of December 31: Other accrued expenses $ — $ — $ 3.1 $ 2.8 $ 3.1 $ 2.8 Accrued pension and postretirement benefit obligations 97.1 127.7 143.6 132.9 240.7 260.6 Underfunded status at end of year $ 97.1 $ 127.7 $ 146.7 $ 135.7 $ 243.8 $ 263.4 Accumulated other comprehensive loss, net $ (110.5) $ (129.3) $ (53.9) $ (62.5) $ (164.4) $ (191.8) Weighted average assumptions used to determine projected benefit obligations: Discount rate 3.48 % 3.93 % 2.21 % 2.28 % Rate of compensation increase 3.00 % 3.00 % 1.70 % 1.63 % The accumulated benefit obligation for the Company’s defined benefit pension plans was $731.2 and $691.1 at December 31, 2017 and 2016, respectively. As of December 31, 2017 and 2016, the accumulated benefit obligation for the U.S. Plans was $484.4 and $465.8 and for the International Plans was $246.8 and $225.3, respectively. All of the Company’s U.S. Plans and substantially all of the International Plans have accumulated benefit obligations in excess of plan assets as of December 31, 2017 and 2016. The following is a summary of the components of net pension expense for the Company’s defined benefit plans for the years ended December 31, 2017, 2016 and 2015: U.S. Plans International Plans Total 2017 2016 2015 2017 2016 2015 2017 2016 2015 Components of net pension expense : Service cost $ 6.7 $ 6.2 $ 6.5 $ 2.9 $ 2.8 $ 2.8 $ 9.6 $ 9.0 $ 9.3 Interest cost 15.3 15.4 17.4 4.7 5.5 5.4 20.0 20.9 22.8 Expected return on plan assets (27.2) (26.2) (25.9) (3.5) (3.9) (3.2) (30.7) (30.1) (29.1) Amortization of prior service cost 2.7 2.4 2.3 — — — 2.7 2.4 2.3 Amortization of actuarial losses 18.3 18.6 21.5 4.6 3.4 4.2 22.9 22.0 25.7 Net pension expense $ 15.8 $ 16.4 $ 21.8 $ 8.7 $ 7.8 $ 9.2 $ 24.5 $ 24.2 $ 31.0 Weighted average assumptions used to determine net periodic benefit cost: Discount rate 3.93 % 4.11 % 3.75 % 2.28 % 2.96 % 2.91 % Expected long-term return on assets 7.75 % 7.75 % 8.00 % 3.80 % 4.29 % 5.47 % Rate of compensation increase 3.00 % 3.00 % 3.00 % 1.63 % 1.61 % 1.45 % The pension expense for the Plans is calculated based upon a number of actuarial assumptions established on January 1 of the applicable year, including mortality projections as well as a weighted average discount rate, rate of increase in future compensation levels and an expected long-term rate of return on the respective Plans’ assets which are detailed in the table above. The discount rate used by the Company for valuing pension liabilities is based on a review of high quality corporate bond yields with maturities approximating the remaining life of the projected benefit obligations. The weighted average discount rate for the U.S. Plans on this basis was 3.48% and 3.93% at December 31, 2017 and 2016, respectively. The decrease in the discount rate for the U.S. Plans resulted in an increase in the benefit obligation of approximately $24.0 at December 31, 2017. The weighted average discount rate for the International Plans was 2.21% and 2.28% at December 31, 2017 and 2016, respectively. The decrease in the discount rate for the International Plans did not have a material impact on the benefit obligation at December 31, 2017. At December 31, 2015, the Company elected to further refine its approach for calculating its service and interest costs beginning in 2016 by applying a split discount rate approach under which specific spot rates along the selected yield curve are applied to the relevant projected cash flows as the Company believes this method more precisely measures its obligations. The mortality assumptions used by the Company reflect commonly used mortality tables and improvement scales for each plan and increased life expectancies for plan participants. The Company’s investment strategy for the Plans’ assets is to achieve a rate of return on plan assets equal to or greater than the average for the respective investment classification through prudent allocation and periodic rebalancing between fixed income and equity instruments. The current investment policy includes a strategy to maintain an adequate level of diversification, subject to portfolio risks. In developing the expected long-term rate of return assumption for the U.S. Plans, the Company evaluated input from its external actuaries and investment consultants as well as consideration of long-term inflation assumptions. Projected returns by such consultants are based on broad equity and bond indices. The Company also considered its historical compounded return of approximately 8.75%, which has been in excess of these broad equity and bond benchmark indices. As described above, the expected long-term rate of return on the U.S. Plans’ assets is based on an asset allocation assumption of approximately 60% with equity managers (with an expected long-term rate of return of approximately 8-9%) and 40% with fixed income managers (with an expected long-term rate of return of approximately 5-6%). The Company believes that the long-term asset allocation on average will approximate 60% with equity managers and 40% with fixed income managers. The Company regularly reviews the actual asset allocation and periodically rebalances investments to its targeted allocation when considered appropriate. The Company’s Plan assets, the vast majority of which relate to the U.S. Plans, are reported at fair value and classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The process requires judgment and may have an effect on the placement of the Plan assets within the fair value measurement hierarchy. The fair values of the Company’s pension Plans’ assets at December 31, 2017 and 2016 by asset category are as follows (refer to Note 3 for definitions of Level 1, 2 and 3 inputs): Assets Measured at Net Asset Asset Category Total Level 1 Level 2 Level 3 Value (a) December 31, 2017 Equity securities: U.S. equities — large cap $ 141.5 $ 106.6 $ 34.9 $ — $ — U.S. equities — small/mid cap and other 22.0 — 22.0 — — International equities — growth 35.6 30.4 5.2 — — International equities — other 95.5 — 40.7 — 54.8 Alternative investment funds 12.9 — — — 12.9 Fixed income securities: U.S. fixed income securities — short term 6.1 — — — 6.1 U.S. fixed income securities — intermediate term 61.4 61.4 — — — U.S. fixed income securities — high yield 21.9 — 21.9 — — International fixed income securities — other 47.4 — 47.4 — — Insurance contracts 37.9 — — 37.9 — Real estate funds 7.0 — — 7.0 — Cash and cash equivalents 8.7 8.7 — — — Total $ 497.9 $ 207.1 $ 172.1 $ 44.9 $ 73.8 December 31, 2016 Equity securities: U.S. equities — large cap $ 118.8 $ 88.7 $ 30.1 $ — $ — U.S. equities — small/mid cap and other 25.8 — 25.8 — — International equities — growth 46.5 46.5 — — — International equities — other 60.6 7.0 33.9 — 19.7 Alternative investment funds 12.6 — — — 12.6 Fixed income securities: U.S. fixed income securities — short term 6.0 — — — 6.0 U.S. fixed income securities — intermediate term 58.4 58.4 — — — U.S. fixed income securities — high yield 22.2 — 22.2 — — International fixed income securities — other 43.0 — 43.0 — — Insurance contracts 34.0 — — 34.0 — Cash and cash equivalents 12.0 12.0 — — — Total $ 439.9 $ 212.6 $ 155.0 $ 34.0 $ 38.3 (a) Certain investments measured at fair value using the net asset value (NAV) practical expedient have been removed from the fair value hierarchy but included in the table above in order to permit the reconciliation of the fair value hierarchy to total plan assets. Equity securities consist primarily of publicly traded U.S. and non-U.S. equities. Publicly traded securities are valued at the last trade or closing price reported in the active market in which the individual securities are traded. Certain equity securities held in commingled funds are valued at unitized net asset value (“NAV”) based on the fair value of the underlying net assets owned by the funds. Alternative investment funds include investments in hedge funds including fund of fund products. Fixed income securities consist primarily of government securities and corporate bonds. They are valued at the closing price in the active market or at quotes obtained from brokers/dealers or pricing services. Certain fixed income securities held within commingled funds are valued at NAV as determined by the custodian of the funds based on the fair value of the underlying net assets of the funds. The Level 3 pension plan assets as of December 31, 2017 and 2016 included in the table above consist primarily of contracts with insurance companies related to certain international plans. The insurance contracts generally include guarantees in accordance with the policy purchased. Our valuation of Level 3 assets is based on insurance company or third-party actuarial valuations, representing an estimation of the surrender or market values of the insurance contract between the Company and the insurance companies. Our Level 3 pension plan assets also include certain investments in commingled real estate funds which are valued at net asset value, although based on unobservable inputs. The following table sets forth a summary of changes of the fair value of the Level 3 pension plan assets for the years ended December 31, 2017 and 2016: 2017 2016 Balance on January 1 $ 34.0 $ — Additions due to acquisition — 34.3 Unrealized gains (losses), net 0.6 2.7 Purchases, sales and settlements, net 5.8 (0.9) Foreign currency translation 4.5 (2.1) Balance on December 31 $ 44.9 $ 34.0 The amounts, before tax, included in Accumulated other comprehensive loss at December 31, 2017 and 2016 that have not yet been recognized as expense were as follows: U.S. International Plans Plans Total 2017 2016 2017 2016 2017 2016 Net loss $ 167.7 $ 194.7 $ 70.0 $ 71.0 $ 237.7 $ 265.7 Net prior service cost 7.7 10.5 — — 7.7 10.5 The estimated amounts before tax for net loss and prior service cost for the Plans that will be amortized from Accumulated other comprehensive loss into net periodic benefit cost over the next fiscal year are expected to be $23.4 and $2.3, respectively. The Company made cash contributions to the Plans of $22.5, $22.2, and $20.9 in 2017, 2016, and 2015, respectively, and estimates that, based on current actuarial calculations and the Company’s funding intentions, it will make aggregate cash contributions to the Plans in 2018 of approximately $90.0, of which approximately $80.0 represents voluntary contributions made in January 2018 to substantially fund the U.S. Plans. The timing and amount of cash contributions in subsequent years will depend on a number of factors, including the investment performance of the Plans’ assets. Benefit payments related to the Plans above, including those amounts to be paid out of Company assets and reflecting future expected service as appropriate, are expected to be as follows: U.S. International Plans Plans Total 2018 $ 24.8 $ 7.5 $ 32.3 2019 25.8 7.1 32.9 2020 26.9 7.3 34.2 2021 27.8 9.2 37.0 2022 28.9 9.4 38.3 2023-2027 151.2 51.1 202.3 The Company also has an unfunded Supplemental Employee Retirement Plan (“SERP”), which provides for the payment of the portion of annual pension which cannot be paid from the retirement plan as a result of regulatory limitations on average compensation for purposes of the benefit computation. The obligation related to the SERP is included in the accompanying Consolidated Balance Sheets and in the tables above. Certain foreign subsidiaries of the Company offer certain benefits under local statutory plans which are excluded from the tables above. The net liability for such plans was $16.6 and $13.9 as of December 31, 2017 and 2016, respectively, the majority of which is included within Accrued pension and postretirement benefit obligations in the accompanying Consolidated Balance Sheets. Other Postretirement Benefit Plans The Company maintains self-insurance programs for that portion of its health care and workers compensation costs not covered by insurance. The Company also provides certain health care and life insurance benefits to certain eligible retirees in the U.S. through postretirement benefit (“OPEB”) programs. The Company’s share of the cost of such plans for most participants is fixed, and any increase in the cost of such plans will be the responsibility of the retirees. The Company funds the benefit costs for such plans on a pay-as-you-go basis. Since the Company’s obligation for postretirement medical plans is fixed and since the benefit obligation and the net postretirement benefit expense are not material in relation to the Company’s financial condition or results of operations, the Company believes any change in medical costs from that estimated will not have a significant impact on the Company. Summary information on the Company’s OPEB plans as of December 31, 2017 and 2016 is as follows: 2017 2016 Change in benefit obligation : Benefit obligation at beginning of year $ 13.6 $ 13.2 Interest cost 0.4 0.4 Benefits paid (0.9) (0.9) Actuarial loss — 0.9 Benefit obligation at end of year $ 13.1 $ 13.6 Amounts recognized on the balance sheet as of December 31: Other accrued expenses $ 1.2 $ 1.2 Accrued pension and postretirement benefit obligations 11.9 12.4 Unfunded status at end of year $ 13.1 $ 13.6 Accumulated other comprehensive loss, net $ (3.2) $ (3.6) Weighted average assumptions used to determine projected benefit obligations: Discount rate 3.29 % 3.65 % The accumulated benefit obligation for the Company’s OPEB plans was equal to its projected benefit obligation at December 31, 2017 and 2016. 2017 2016 2015 Components of net postretirement benefit expense : Service cost $ — $ — $ 0.1 Interest cost 0.4 0.4 0.4 Amortization of actuarial losses 0.5 0.7 0.3 Net postretirement benefit expense $ 0.9 $ 1.1 $ 0.8 Weighted average assumptions used to determine net postretirement benefit expense : Discount rate 3.65 % 3.71 % 3.50 % The health care cost trend rate, which represents the annual rate of covered benefit cost increases assumed for the following year, was 7.75% and 8.25% as of December 31, 2017 and 2016, respectively, and is expected to gradually decrease to a rate of 4.75% by calendar year 2024. A one percentage point change in the assumed health care cost trend rate would not result in a material impact on either the postretirement benefit obligation or the postretirement benefit expense. As of December 31, 2017, the amounts before tax for unrecognized net loss, net prior service cost and net transition obligation included in Accumulated other comprehensive loss related to OPEB plans that have not yet been recognized as expense are $5.1, nil and nil, respectively. As of December 31, 2016, the amounts before tax for unrecognized net loss, net prior service cost and net transition obligation in Accumulated other comprehensive loss related to OPEB plans that have not yet been recognized as expense were $5.7, nil and nil, respectively. The estimated amounts before tax for net loss, prior service cost and net transition obligation for the OPEB plans that will be amortized from Accumulated other comprehensive loss into net periodic benefit cost over the next fiscal year are expected to be $0.6, nil and nil, respectively. Benefit payments for the OPEB plan, including those amounts to be paid out of Company assets and reflecting future expected service as appropriate are expected to be between $1.2 and $1.5 per year for the next ten years. Defined Contribution Plans The Company offers various defined contribution plans for certain U.S. and foreign employees. Participation in these plans is based on certain eligibility requirements. The Company matches the majority of employee contributions to the U.S. defined contribution plans with cash contributions up to a maximum of 5% of eligible compensation. The Company provided matching contributions to the U.S. defined contribution plans of approximately $6.9, $5.0 and $4.2 in 2017, 2016 and 2015, respectively.

Leases

Leases	12 Months Ended
	Dec. 31, 2017
Leases
Leases	Note 8—Leases At December 31, 2017, the Company was committed under operating leases for buildings, office space, automobiles and equipment, which expire at various dates. Total rent expense under operating leases for the years 2017, 2016 and 2015 were approximately $58.5, $50.5 and $41.0, respectively. Minimum lease payments under non-cancelable operating leases are as follows: 2018 $ 53.2 2019 37.3 2020 23.7 2021 15.5 2022 10.2 Beyond 2022 21.3 Total minimum obligation $ 161.2

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2017
Acquisitions
Acquisitions	Note 9—Acquisitions On January 8, 2016, the Company acquired all of the share capital of FCI Asia Pte. Ltd. (“FCI”) for a purchase price of approximately $1,178.6, net of cash acquired. The acquisition was funded by cash, cash equivalents and short-term investments that were held outside of the United States. The purchase price was allocated to the tangible and identifiable intangible assets acquired and liabilities assumed of FCI based upon their estimated fair values. In the fourth quarter of 2016, the Company completed its analysis of the fair value of the net assets acquired through the use of independent valuations and management’s estimates. Headquartered in Singapore, FCI, a global leader in interconnect solutions for the information technology and data communications, industrial, mobile networks, automotive and mobile devices markets, is reported as part of the Company’s Interconnect Products and Assemblies segment. FCI is a leading supplier of high-speed backplane and mezzanine connectors, power interconnect solutions and a wide variety of board-mounted interconnects. The accompanying Consolidated Statements of Income include the results of FCI since the date of acquisition. Excluding the impact of acquisitions as well as the negative impact of foreign exchange of approximately $61.3 for the year ended December 31, 2016, compared to the year ended December 31, 2015, the Company’s net sales increased approximately 2% in the year ended December 31, 2016, compared to the year ended December 31, 2015. Pro Forma Financial Information The following table summarizes the unaudited pro forma combined financial information assuming that the FCI acquisition had occurred on January 1, 2015, and its results had been included in our financial results for all of 2016 and 2015. The pro forma combined amounts are based upon available information and reflect a reasonable estimate of the effects of the FCI acquisition for the periods presented on the basis set forth herein. The following unaudited pro forma combined financial information is presented for informational purposes only and does not purport to represent what the financial position or results of operations would have been had the FCI acquisition in fact occurred on the date assumed, nor is it necessarily indicative of the results that may be expected in future periods. Year ended December 31, Pro forma: 2016 2015 Net sales $ 6,296.1 $ 6,137.3 Net income attributable to Amphenol Corporation 856.2 799.3 Net income per common share - Diluted 2.72 2.53 The unaudited pro forma Net income attributable to Amphenol Corporation has been calculated using actual historical information and is adjusted for certain pro forma adjustments based on the assumption that the FCI acquisition and the application of fair value adjustments to intangible assets occurred on January 1, 2015. For the year ended December 31, 2016, the pro forma financial information excluded acquisition-related expenses, net of tax, of $33.1, which are included in the reported results, but excluded from the pro forma amounts above due to their nonrecurring nature. For the year ended December 31, 2015, the pro forma financial information reflects the following adjustments, net of tax: (a) acquisition-related expenses of $5.7, which were included in the reported results, but excluded from the pro forma amounts above due to their nonrecurring nature, (b) amortization expense related to the acquired intangible assets of $8.8 that was not reflected in the historical results, but has been included in the pro forma amounts, (c) interest income of approximately $11.6 earned on the cash, cash equivalents and short-term investments used to fund the FCI acquisition that was included in the historical results, but excluded from the pro forma amounts, and (d) other income of $4.8 that was included in the historical results of FCI, but excluded from the pro forma amounts due to their nonrecurring nature. Other Acquisitions The Company completed several other acquisitions throughout 2017 and is in the process of completing its analyses of the fair value of the assets acquired and liabilities assumed. The Company anticipates that the final assessments of values will not differ materially from the preliminary assessments. These 2017 acquisitions, along with the other non-FCI 2016 acquisitions, were not material to the Company either individually or in the aggregate. Acquisition-related Expenses In 2017, the Company incurred approximately $4.0 ($3.7 after-tax) of acquisition-related expenses in the second quarter related to external transaction costs. In 2016, the Company incurred approximately $30.3 ($27.3 after-tax) of acquisition-related expenses related to the acquisition of FCI in the first quarter of 2016, primarily related to external transaction costs, amortization related to the value associated with acquired backlog and post-closing restructuring charges; and approximately $6.3 ($5.8 after-tax) of acquisition-related transaction expenses incurred in the third quarter of 2016. In 2015, the Company incurred approximately $5.7 ($5.7 after-tax) of acquisition-related expenses related to professional fees and other external expenses primarily related to the FCI acquisition which was announced in the second quarter of 2015. Such acquisition-related expenses are separately presented in the accompanying Consolidated Statements of Income.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill and Other Intangible Assets
Goodwill and Other Intangible Assets	Note 10—Goodwill and Other Intangible Assets The changes in the carrying amount of goodwill by segment were as follows: Interconnect Cable Products and Products and Assemblies Solutions Total Goodwill at December 31, 2015 $ 2,569.2 $ 123.7 $ 2,692.9 Acquisition-related 1,008.7 22.6 1,031.3 Foreign currency translation (45.4) — (45.4) Goodwill at December 31, 2016 3,532.5 146.3 3,678.8 Acquisition-related 233.6 0.2 233.8 Foreign currency translation 130.0 — 130.0 Goodwill at December 31, 2017 $ 3,896.1 $ 146.5 $ 4,042.6 Other than goodwill noted above, the following is a summary of the Company’s intangible assets as of December 31, 2017 and 2016: December 31, 2017 December 31, 2016 Weighted Gross Net Gross Net Average Carrying Accumulated Carrying Carrying Accumulated Carrying Life (years) Amount Amortization Amount Amount Amortization Amount Customer relationships 10 $ 398.1 $ 199.8 $ 198.3 $ 381.1 $ 159.1 $ 222.0 Proprietary technology 11 107.5 50.7 56.8 106.7 40.9 65.8 Backlog and other 2 34.0 33.6 0.4 34.0 33.5 0.5 Total intangible assets (definite-lived) 10 539.6 284.1 255.5 521.8 233.5 288.3 Trade names (indefinite-lived) - 186.1 — 186.1 186.1 — 186.1 $ 725.7 $ 284.1 $ 441.6 $ 707.9 $ 233.5 $ 474.4 Intangible assets are included in Intangibles, net and other long-term assets in the accompanying Consolidated Balance Sheets. The aggregate amortization expense for the years ended December 31, 2017, 2016 and 2015 was approximately $48.6, $54.6 and $34.7, respectively. The 2016 amortization expense includes $8.0 related to the amortization of acquired backlog. Amortization expense relating to the Company’s current intangible assets estimated for each of the next five fiscal years is approximately $46.5 in 2018, $42.6 in 2019, $37.2 in 2020, $32.0 in 2021 and $24.2 in 2022.

Reportable Business Segments an

Reportable Business Segments and International Operations	12 Months Ended
	Dec. 31, 2017
Reportable Business Segments
Reportable Business Segments	Note 11—Reportable Business Segments and International Operations The Company has two reportable business segments: (i) Interconnect Products and Assemblies and (ii) Cable Products and Solutions. The Company organizes its reportable business segments based upon similar economic characteristics and business groupings of products, services, and customers. These reportable business segments are determined based upon how the Company reviews its businesses, assesses operating performance and makes investing and resource allocation decisions. The Interconnect Products and Assemblies segment primarily designs, manufactures and markets a broad range of connector and connector systems, value-add products and other products, including antennas and sensors, used in a broad range of applications in a diverse set of end markets. The Cable Products and Solutions segment primarily designs, manufactures and markets cable, value-add products and components for use primarily in the broadband communications and information technology markets as well as certain applications in other markets. The accounting policies of the segments are the same as those for the Company as a whole and are described in Note 1 herein. The Company evaluates the performance of business units on, among other things, profit or loss from operations before interest, headquarters’ expense allocations, stock-based compensation expense, income taxes, amortization related to certain intangible assets and nonrecurring gains and losses. Interconnect Products Cable Products Total Reportable and Assemblies and Solutions Business Segments 2017 2016 2015 2017 2016 2015 2017 2016 2015 Net sales: External $ 6,606.9 $ 5,922.3 $ 5,239.1 $ 404.4 $ 364.1 $ 329.6 $ 7,011.3 $ 6,286.4 $ 5,568.7 Intersegment 9.7 6.9 7.2 40.7 30.0 21.6 50.4 36.9 28.8 Depreciation and amortization 214.7 206.8 162.3 6.3 4.9 3.0 221.0 211.7 165.3 Segment operating income 1,475.2 1,280.3 1,158.3 54.2 52.8 40.3 1,529.4 1,333.1 1,198.6 Segment assets (excluding goodwill) 5,732.6 4,587.5 4,580.4 200.3 197.1 163.5 5,932.9 4,784.6 4,743.9 Capital expenditures 220.4 186.2 167.1 5.6 4.0 4.5 226.0 190.2 171.6 Reconciliation of segment operating income to consolidated income before income taxes: 2017 2016 2015 Segment operating income $ 1,529.4 $ 1,333.1 $ 1,198.6 Interest expense (92.3) (72.6) (68.3) Other income, net 17.1 8.5 16.4 Stock-based compensation expense (49.7) (47.6) (44.2) Acquisition-related expenses (4.0) (36.6) (5.7) Other operating expenses (48.1) (43.7) (44.0) Income before income taxes $ 1,352.4 $ 1,141.1 $ 1,052.8 Reconciliation of segment assets to consolidated total assets: 2017 2016 Segment assets, excluding goodwill $ 5,932.9 $ 4,784.6 Goodwill 4,042.6 3,678.8 Other assets 28.4 35.3 Consolidated total assets $ 10,003.9 $ 8,498.7 Net sales by geographic area for the years ended December 31, 2017, 2016 and 2015 and property, plant and equipment, net by geographic area as of December 31 were as follows: 2017 2016 2015 Net sales United States $ 1,978.4 $ 1,740.7 $ 1,696.3 China 2,067.3 1,865.6 1,675.5 Other international locations 2,965.6 2,680.1 2,196.9 Total $ 7,011.3 $ 6,286.4 $ 5,568.7 Property, plant and equipment, net United States $ 212.7 $ 209.2 $ 214.4 China 244.7 200.1 151.4 Other international locations 359.4 302.1 243.7 Total $ 816.8 $ 711.4 $ 609.5 Net sales by geographic area are based on the customer location to which the product is shipped. No single customer represented 10% or more of the Company’s net sales for the years ended December 31, 2017 and 2016. During the year ended December 31, 2015, aggregate sales to the Company’s largest customer, including sales of products to EMS companies and subcontractors that the Company believes are manufacturing products on their behalf, represented approximately 11% of the Company’s net sales, all of which are included within the Interconnect Products and Assemblies segment. It is impracticable to disclose net sales by product or group of products.

Other Income, net

Other Income, net	12 Months Ended
	Dec. 31, 2017
Other Income, net
Other Income, net	Note 12—Other Income, net The components of Other income, net are set forth below: Year Ended December 31, 2017 2016 2015 Agency and commitment fees $ (3.1) $ (3.0) $ (2.0) Interest income 20.2 11.5 18.4 $ 17.1 $ 8.5 $ 16.4

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies
Commitments and Contingencies	Note 13—Commitments and Contingencies The Company has been named as a defendant in several legal actions arising from normal business activities. The Company records a loss contingency liability when a loss is considered probable and the amount can be reasonably estimated. Although the potential liability with respect to certain of such legal actions cannot be reasonably estimated, none of such matters is expected to have a material adverse effect on the Company’s financial condition, results of operations or cash flows. The Company’s legal costs associated with defending itself are recorded to expense as incurred. Certain operations of the Company are subject to environmental laws and regulations which govern the discharge of pollutants into the air and water, as well as the handling and disposal of solid and hazardous wastes. The Company believes that its operations are currently in substantial compliance with applicable environmental laws and regulations and that the costs of continuing compliance will not have a material adverse effect on the Company’s financial condition, results of operations or cash flows. The Company also has purchase obligations related to commitments to purchase certain goods and services. At December 31, 2017, the Company had purchase commitments of $286.9 in 2018, $56.2 in 2019 and 2020, combined, and $2.5 beyond 2020.

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2017
Selected Quarterly Financial Data (Unaudited)
Selected Quarterly Financial Data (Unaudited)	Note 14—Selected Quarterly Financial Data (Unaudited) Three Months Ended March 31, June 30, September 30, December 31, 2017 Net sales $ 1,560.1 $ 1,666.5 $ 1,840.8 $ 1,943.9 Gross profit 515.9 552.6 606.1 635.4 Operating income 314.1 336.2 (2) 377.9 399.4 Net income (loss) 227.3 (1) 253.6 (2) 280.3 (3) (100.4) (4) Net income (loss) attributable to Amphenol Corporation 224.9 (1) 251.5 (2) 277.5 (3) (103.4) (4) Net income (loss) per common share—Basic 0.73 (1) 0.82 (2) 0.91 (3) (0.34) (4) Net income (loss) per common share—Diluted 0.71 (1) 0.80 (2) 0.88 (3) (0.34) (4) 2016 Net sales $ 1,451.2 $ 1,548.2 $ 1,635.9 $ 1,651.1 Gross profit 459.2 497.3 537.3 546.1 Operating income 239.4 (5) 300.3 326.3 (6) 339.1 Net income 158.4 (5) 208.7 227.1 (6) 238.3 Net income attributable to Amphenol Corporation 156.6 (5) 206.5 224.3 (6) 235.4 Net income per common share—Basic 0.51 (5) 0.67 0.73 (6) 0.76 Net income per common share—Diluted 0.50 (5) 0.65 0.71 (6) 0.75 (1) Net income and net income per common share includes excess tax benefits related to stock-based compensation of $8.0 as a result of the adoption of ASU 2016-09 in 2017. The excess tax benefits had the effect of increasing Net income, Net income attributable to Amphenol Corporation, and Net income per common share-Diluted by $8.0, $8.0 and $0.02 per share, respectively, for the three months ended March 31, 2017. (2) Operating income, net income and net income per common share includes acquisition-related expenses of $4.0 ($3.7 after-tax, or $0.01 per share) primarily related to 2017 acquisitions and excess tax benefits related to stock-based compensation of $21.2 ($0.07 per share). These items had the aggregate effect of decreasing Operating income by $4.0, while increasing Net income, Net income attributable to Amphenol Corporation, and Net income per common share-Diluted by $17.5, $17.5 and $0.06 per share, respectively, for the three months ended June 30, 2017. (3) Net income and net income per common share includes excess tax benefits related to stock-based compensation of $16.6. The excess tax benefits had the effect of increasing Net income, Net income attributable to Amphenol Corporation, and Net income per common share-Diluted by $16.6, $16.6 and $0.05 per share, respectively, for the three months ended September 30, 2017. (4) Net loss and net loss per common share includes the provisional Tax Act Charge of $398.5 ($1.26 per share) related to the enactment of the Tax Cuts and Jobs Act, partially offset by the excess tax benefits related to stock-based compensation of $20.8 ($0.07 per share). In addition, (5) Operating income, net income and net income per common share includes acquisition-related expenses primarily related to the acquisition of FCI which closed in January 2016. These acquisition-related expenses had the effect of decreasing Operating income, Net income, Net income attributable to Amphenol Corporation, and Net income per common share-Diluted by $30.3, $27.3, $27.3 and $0.09 per share, respectively, for the three months ended March 31, 2016. (6) Operating income, net income and net income per common share includes acquisition-related expenses. These acquisition-related expenses had the effect of decreasing Operating income, Net income, Net income attributable to Amphenol Corporation, and Net income per common share-Diluted by $6.3, $5.8, $5.8 and $0.02 per share, respectively, for the three months ended September 30, 2016.

SCHEDULE II VALUATION AND QUALI

SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS	12 Months Ended
	Dec. 31, 2017
SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS
SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS	SCHEDULE II AMPHENOL CORPORATION AND SUBSIDIARIES VALUATION AND QUALIFYING ACCOUNTS For the years ended December 31, 2017, 2016 and 2015 (Dollars in millions) Balance at Charged to Balance at beginning cost and Additions end of of period expenses (Deductions) period Allowance for doubtful accounts: Year ended 2017 $ 23.6 $ 1.8 $ (2.4) $ 23.0 Year ended 2016 25.6 6.0 (8.0) 23.6 Year ended 2015 20.2 3.7 1.7 25.6 Valuation allowance on deferred tax assets: Year ended 2017 $ 37.2 $ 2.5 $ (0.1) $ 39.6 Year ended 2016 18.5 4.8 13.9 37.2 Year ended 2015 15.5 3.0 — 18.5

Summary of Significant Accoun24

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Summary of Significant Accounting Policies
Business	Business Amphenol Corporation (together with its subsidiaries, “Amphenol”, the “Company”, “we”, “our”, or “us”) is one of the world’s largest designers, manufacturers and marketers of electrical, electronic and fiber optic connectors, interconnect systems, antennas, sensors and sensor-based products and coaxial and high-speed specialty cable. The Company sells its products to customer locations worldwide. The Company operates through two reportable business segments: · Interconnect Products and Assemblies – The Interconnect Products and Assemblies segment primarily designs, manufactures and markets a broad range of connector and connector systems, value-add products and other products, including antennas and sensors, used in a broad range of applications in a diverse set of end markets. · Cable Products and Solutions – The Cable Products and Solutions segment primarily designs, manufactures and markets cable, value-add products and components for use primarily in the broadband communications and information technology markets as well as certain applications in other markets.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. The Company’s management evaluates these significant estimates and assumptions that affect the consolidated financial statements and related disclosures. Actual results could differ from those estimates. All normal recurring adjustments necessary for a fair presentation in conformity with accounting principles generally accepted in the United States of America have been included.
Change in Presentation	Change in Presentation C
Principles of Consolidation	Principles of Consolidation The consolidated financial statements are prepared in U.S. dollars and include the accounts of the Company and its wholly-owned and majority-owned subsidiaries. All material intercompany balances and transactions have been eliminated in consolidation. The results of companies acquired are included in the Consolidated Financial Statements from the effective date of acquisition.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist of cash and liquid investments with an original maturity of less than three months. The carrying amounts approximate fair values of those instruments, the majority of which are in non-U.S. bank accounts.
Short-term Investments	Short-term Investments Short-term investments consist primarily of certificates of deposit with original maturities of twelve months or less. The carrying amounts approximate fair values of those instruments, the majority of which are in non-U.S. bank accounts.
Accounts Receivable	Accounts Receivable Accounts receivable is stated at net realizable value. The Company regularly reviews accounts receivable balances and adjusts the receivable reserves as necessary whenever events or circumstances indicate the carrying value may not be recoverable.
Inventories	Inventories Inventories are stated at the lower of standard cost, which approximates average cost, or net realizable value. The principal components of cost included in inventories are materials, direct labor and manufacturing overhead. The Company regularly reviews inventory quantities on hand and evaluates the realizability of inventories and adjusts the carrying value as necessary based on forecasted product demand.
Depreciable Assets	Depreciable Assets Property, plant and equipment are carried at cost less accumulated depreciation. Depreciation is recorded on a straight-line basis over the respective asset lives determined on a composite basis by asset group or on a specific item basis using the estimated useful lives of such assets, which range from 3 to 12 years for machinery and equipment and 20 to 40 years for buildings. Leasehold building improvements are depreciated over the shorter of the lease term or estimated useful life. The Company periodically reviews fixed asset lives. Depreciation expense is included in both Cost of sales and Selling, general and administrative expenses in the Consolidated Statements of Income based on the specific categorization and use of the underlying asset being depreciated. The Company assesses the impairment of property and equipment subject to depreciation, whenever events or changes in circumstances indicate the carrying value may not be recoverable. Factors the Company considers important, which could trigger an impairment review, include significant changes in the manner of the use of the asset, significant changes in historical trends in operating performance, significant changes in projected operating performance, and significant negative economic trends. There have been no impairments recorded as a result of such reviews during any of the periods presented.
Goodwill	Goodwill The Company performs its annual evaluation for the impairment of goodwill for the Company’s two reporting units on an annual basis as of each July 1 or more frequently if an event occurs or circumstances change that would indicate that a reporting unit’s carrying amount may be impaired. The Company has defined its reporting units as the two reportable business segments “Interconnect Products and Assemblies” and “Cable Products and Solutions”, as the components of these reportable business segments have similar economic characteristics. In 2017 and 2016, as part of our annual evaluation, the Company utilized the option to first assess qualitative factors to determine whether it was necessary to perform the quantitative goodwill impairment assessment. As part of this assessment, the Company reviews qualitative factors, which include but are not limited to, economic, market and industry conditions, as well as the financial performance of each reporting unit. In accordance with applicable guidance, an entity is not required to calculate the fair value of a reporting unit if, after assessing these qualitative factors, the Company determines that it is more likely than not that the fair value of its reporting units is greater than its respective carrying amount. As of July 1, 2017 and 2016, the Company determined that it was more likely than not that the fair value of its reporting units exceeded their respective carrying amounts and therefore, a quantitative assessment was not required. The Company has not recognized any goodwill impairment in 2017, 2016 or 2015 in connection with its annual impairment test.
Intangible Assets	Intangible Assets Intangible assets are included in Intangibles, net and other long-term assets and consist primarily of proprietary technology, customer relationships and license agreements and are generally amortized over the estimated periods of benefit. The Company assesses and reviews its long-lived assets, other than goodwill, for potential impairment including identifiable intangible assets subject to amortization, whenever significant events or significant changes in circumstances indicate the carrying amount may not be recoverable. Factors the Company considers important, which could trigger an impairment review, include significant changes in the manner of the use of the asset, changes in historical trends in operating performance, significant changes in projected operating performance, anticipated future cash flows and significant negative economic trends. Indefinite-lived intangible assets that are not subject to amortization are reviewed at least annually for impairment. In the third quarter of 2017, the Company performed its annual assessment of these identifiable indefinite-lived intangible assets. Based on our qualitative assessment, the Company determined that it was more likely than not that the fair value of the indefinite-lived intangible assets exceeded their respective carrying amounts. There have been no impairments recorded in 2017, 2016 or 2015 as a result of such reviews.
Revenue Recognition	Revenue Recognition The Company’s primary source of revenues is from product sales to its customers. Revenue from sales of the Company’s products is recognized at the time the goods are delivered, title passes, and the risks and rewards of ownership pass to the customer, provided the earning process is complete and revenue is measurable. Such recognition generally occurs when the products reach the shipping point, the sales price is fixed and determinable, and collection is reasonably assured. Delivery is determined by the Company’s shipping terms, which are primarily freight on board (“FOB”) shipping point. Revenue is recorded at the net amount to be received after deductions for estimated discounts, allowances and returns. These estimates and related reserves are determined and adjusted as needed based upon historical experience, contract terms and other related factors. The shipping costs for the majority of the Company’s sales are paid directly by the Company’s customers. In the broadband communications market (approximately 6% of net sales in 2017), the Company pays for shipping costs to the majority of its customers. Shipping costs are also paid by the Company for certain customers in the Interconnect Products and Assemblies segment. Amounts billed to customers related to shipping costs are immaterial and are included in Net sales. Shipping costs incurred to transport products to the customer which are not reimbursed are included in Selling, general and administrative expenses.
Retirement Pension Plans	Retirement Pension Plans Costs for retirement pension plans include current service costs and amortization of prior service costs over the average working life expectancy. It is the Company’s policy to fund current pension costs taking into consideration minimum funding requirements and maximum tax deductible limitations. The expense of retiree medical benefit programs is recognized during the employees’ service with the Company. The recognition of expense for retirement pension plans and medical benefit programs is significantly impacted by estimates made by management such as discount rates used to value certain liabilities, expected return on assets, mortality projections and future health care costs. The Company uses third-party specialists to assist management in appropriately measuring the expense and obligations associated with pension and other postretirement plan benefits.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for its stock option and restricted share awards based on the fair value of the award at the date of grant and recognizes compensation expense over the service period that the awards are expected to vest. The Company recognizes expense for stock-based compensation with graded vesting on a straight-line basis over the vesting period of the entire award. Stock-based compensation expense includes the estimated effects of forfeitures, which are adjusted over the requisite service period to the extent actual forfeitures differ or are expected to differ from such estimates. Changes in estimated forfeitures are recognized in the period of change and impact the amount of expense to be recognized in future periods. The fair value of stock options has been estimated at the date of grant using the Black-Scholes option-pricing model with the following weighted average assumptions: 2017 2016 2015 Risk free interest rate 1.7 % 1.3 % 1.4 % Expected life 4.6 years 4.6 years 4.6 years Expected volatility 13.0 % 15.0 % 17.0 % Expected dividend yield 1.0 % 1.0 % 1.0 %
Income Taxes	Income Taxes Deferred income taxes are provided for revenue and expenses which are recognized in different periods for income tax and financial statement reporting purposes. The Company recognizes the effects of changes in tax laws and rates on deferred income taxes in the period in which legislation is enacted. Deferred income taxes are provided on undistributed earnings of foreign subsidiaries in the period in which the Company determines it no longer intends to permanently reinvest such earnings outside the United States. As of December 31, 2017, the Company has not provided for deferred income taxes on undistributed foreign earnings related to certain geographies of approximately $492.8, as it is the Company’s intention to permanently reinvest such earnings outside the United States. The amount of taxes that would be payable if these undistributed foreign earnings were to be repatriated would not be material. In addition, the Company remains indefinitely reinvested with respect to its financial statement basis in excess of tax basis of its investments in foreign subsidiaries. It is not practicable to determine the deferred tax liability with respect to such basis differences. Deferred tax assets are regularly assessed for recoverability based on both historical and anticipated earnings levels and a valuation allowance is recorded when it is more likely than not that these amounts will not be recovered. The tax effects of an uncertain tax position taken or expected to be taken in income tax returns are recognized only if it is “more likely than not” to be sustained on examination by the taxing authorities, based on its technical merits as of the reporting date. The tax benefits recognized in the financial statements from such a position are measured based on the largest benefit that has a greater than fifty percent likelihood of being realized upon ultimate settlement. The Company includes estimated interest and penalties related to unrecognized tax benefits in the provision for income taxes. As a result of the Tax Cuts and Jobs Act (“Tax Act”), the Company has recorded (i) a provisional income tax charge related to the deemed repatriation of the accumulated unremitted earnings and profits of foreign subsidiaries, (ii) a provisional income tax charge related to changes in the Company’s permanent reinvestment assertion with regards to prior accumulated unremitted earnings from certain foreign subsidiaries, partially offset by (iii) a provisional income tax benefit associated with the remeasurement of its net deferred tax liabilities due to the U.S. federal corporate tax rate reduction, and included these amounts in its consolidated financial statements for the year ended December 31, 2017. Beginning in 2018, the Tax Act also includes a global intangible low-taxed income ("GILTI") provision, which as currently interpreted by the Company, requires a tax on foreign earnings in excess of a deemed return on tangible assets of foreign subsidiaries. The Company has elected an accounting policy to account for GILTI as a period cost if incurred, rather than recognizing deferred taxes for temporary basis differences expected to reverse as GILTI. Other provisions of the Tax Act that impact future tax years continue to be assessed. In December 2017, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”) to address the application of U.S. GAAP in situations where a registrant does not have the necessary information available, prepared, or analyzed in reasonable detail to complete the accounting for certain income tax effects of the Tax Act. In 2017, the Company recorded provisional income tax charges as a result of the Tax Act. Due to the timing of the Tax Act’s enactment and the complexity of its provisions, the Company has not completed its accounting for the impact of the Tax Act. The Company will analyze guidance and technical interpretations of the provisions of the Tax Act, as well as refine, analyze and update the underlying data, computations and assumptions used to prepare these provisional amounts. The Company will complete its accounting in 2018 once the Company has obtained, prepared, and fully analyzed all the necessary information. We will record any necessary adjustments in the period in which such adjustments are identified. Refer to Note 4 of the Notes to the Consolidated Financial Statements for further discussion on the Tax Act.
Foreign Currency Translation	Foreign Currency Translation The financial position and results of operations of the Company’s significant foreign subsidiaries are measured using local currency as the functional currency. Assets and liabilities of such subsidiaries have been translated into U.S. dollars at current exchange rates and related revenues and expenses have been translated at weighted average exchange rates. The aggregate effect of translation adjustments is included as a component of Accumulated other comprehensive income (loss) within equity. Transaction gains and losses related to operating assets and liabilities are included in Cost of sales.
Research and Development	Research and Development Costs incurred in connection with the development of new products and applications are expensed as incurred. Research and development expenses for the creation of new and improved products and processes were $193.7, $166.1 and $124.7, for the years 2017, 2016 and 2015, respectively, and are included in Selling, general and administrative expenses.
Acquisitions	Acquisitions The Company accounts for acquisitions using the acquisition method of accounting, which requires that assets acquired and liabilities assumed be recognized at fair value as of the acquisition date. The purchase price of acquisitions is allocated to the tangible and identifiable intangible assets acquired and liabilities assumed based on estimated fair values, and any excess purchase price over the identifiable assets acquired and liabilities assumed is recorded as goodwill. Any subsequent adjustments to the purchase price allocation prior to the completion of the measurement period will be reflected as an adjustment to goodwill in the period in which the adjustments are identified. The Company may use independent valuation specialists to assist in determining the estimated fair values of assets acquired and liabilities assumed, which could require certain significant management assumptions and estimates.
Environmental Obligations	Environmental Obligations The Company recognizes the potential cost for environmental remediation activities when site assessments are made, remediation efforts are probable and related amounts can be reasonably estimated; potential insurance reimbursements are not recorded. The Company assesses its environmental liabilities as necessary and appropriate through regular reviews of contractual commitments, site assessments, feasibility studies and formal remedial design and action plans.
Net Income per Common Share	Net Income per Common Share Basic income per common share is based on the net income attributable to Amphenol Corporation for the year divided by the weighted average number of common shares outstanding. Diluted income per common share assumes the exercise of outstanding dilutive stock options using the treasury stock method.
Derivative Financial Instruments	Derivative Financial Instruments Derivative financial instruments, which are periodically used by the Company in the management of its interest rate and foreign currency exposures, are accounted for as cash flow hedges. Gains and losses on derivatives designated as cash flow hedges resulting from changes in fair value are recorded in Accumulated other comprehensive income (loss), and subsequently reflected in Cost of sales in the Consolidated Statements of Income in a manner that matches the timing of the actual income or expense of such instruments with the hedged transaction. Any ineffective portion of the change in the fair value of designated hedging instruments is included in the Consolidated Statements of Income.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Adopted Accounting Standards In July 2015, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update No. (“ASU”) 2015-11, Simplifying the Measurement of Inventory (“ASU 2015-11”), which requires inventory to be measured at the lower of cost and net realizable value, thereby simplifying the previous guidance of measuring inventory at the lower of cost or market. The Company adopted ASU 2015-11 in the first quarter of 2017 and it did not have a material impact on our consolidated financial statements. In March 2016, the FASB issued ASU 2016‑09 , Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (“ASU 2016‑09”), which simplifies certain provisions associated with the accounting for stock compensation. The Company adopted ASU 2016‑09 on January 1, 2017, which requires any excess tax benefits and tax deficiencies to be recorded as a discrete income tax item in the statement of income in the period in which they occur. For the year ended December 31, 2017, this change resulted in the recognition of tax benefits of approximately $66.6 (or $0.21 per share) within the provision for income taxes in the accompanying Consolidated Statements of Income. Under previous accounting guidance, these tax benefits would have been recorded directly to equity. Since this provision of the standard was applied prospectively, there was no impact to prior periods. As of January 1, 2017, the Company did not have any unrecognized excess tax benefits in which the related tax deduction did not reduce income taxes payable and therefore, there was no cumulative-effect adjustment to beginning retained earnings. The ASU also eliminated the requirement to reclassify cash flows related to excess tax benefits from operating activities to financing activities in the statement of cash flows, but rather requires such excess tax benefits and deficiencies to be classified within operating activities, consistent with other cash flows related to income taxes. The Company adopted this provision prospectively, and prior year amounts in the Statements of Cash Flow have not been adjusted. As permitted, the Company elected to continue its existing accounting practice of estimating forfeitures when recognizing stock-based compensation expense. Other provisions of this standard did not and are not expected to have a material impact on our consolidated financial statements. T he impact of this guidance on our consolidated financial statements could result in significant fluctuations in our effective tax rate in the future, since the provision for income taxes will be impacted by the timing and intrinsic value of future stock-based compensation award exercises. In January 2017, the FASB issued ASU 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (“ASU 2017-04”), which eliminates Step 2 of the two-step goodwill impairment assessment process requiring an entity to calculate any impairment as the difference between a reporting unit’s implied fair value of goodwill and the carrying value of the goodwill. Rather, ASU 2017-04 would now require any goodwill impairment charges to be calculated as the difference between a reporting unit’s fair value and its carrying value, with the loss being limited to its carrying value. The Company early adopted ASU 2017-04 in the third quarter of 2017 in conjunction with its annual impairment assessment and concluded that a Step 1 assessment was not required given the results of our annual impairment assessment discussed in Note 1 herein. As such, ASU 2017-04 did not have any impact on the Company’s consolidated financial statements. Recently Issued Accounting Standards Not Yet Adopted In May 2014, the FASB issued ASU 2014‑09, Revenue from Contracts with Customers (“ASU 2014‑09” and collectively with its subsequent amendments, “Topic 606”), which stipulates that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for such goods or services. To achieve this core principle, an entity should apply the following steps: (1) identify the contract(s) with a customer, (2) identify the performance obligations in the contract(s), (3) determine the transaction price(s), (4) allocate the transaction price(s) to the performance obligations in the contract(s), and (5) recognize revenue when (or as) the entity satisfies a performance obligation. The guidance also requires enhanced disclosures regarding the nature, amount, timing and uncertainty of revenue and cash flows arising from an entity’s contracts with customers. The guidance under ASU 2014‑09 shall apply for annual reporting periods beginning after December 15, 2017, including interim reporting periods within that period. Since 2014, the FASB has issued various related updates including, but not limited to, ASU 2016‑08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) , which clarified the implementation guidance on principal versus agent considerations, and ASU 2016‑10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing , which clarified the implementation guidance regarding performance obligations and licensing arrangements. The Company had an implementation plan involving teams across our organization to review and implement the requirements of Topic 606. We have completed the review of our existing contracts and the related revenue streams, and based on our review, the vast majority of our revenue will be recognized on a “point-in-time” basis which is consistent with current practice, while a nominal amount of our revenue will be recognized “over time” under the new standard. The Company made system reporting changes to incorporate the impact of the new standard into our financial reporting processes; implemented the related internal controls, policies, and processes; and drafted the required disclosures. The Company adopted Topic 606 in the first quarter of 2018 using the modified retrospective approach. We will expand our financial statement disclosures in the first quarter of 2018 to comply with this new standard, including the disaggregation of revenue and performance obligations, among other requirements. We have quantified the cumulative effect adjustment of applying this new standard on existing, uncompleted contracts as of January 1, 2018, and have determined that the cumulative effect is not material. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) (“ASU 2016‑02”), which amends, among other things, the existing guidance by requiring lessees to recognize lease assets (right-to-use) and liabilities (for reasonably certain lease payments) arising from operating leases on the balance sheet. For leases with a term of twelve months or less, ASU 2016‑02 permits an entity to make an accounting policy election to recognize such leases as lease expense, generally on a straight-line basis over the lease term. ASU 2016‑02 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted. ASU 2016-02 requires a modified retrospective transition application, whereas the effect of the standard would need to be reflected as of the beginning of the earliest period presented in the financial statements. The Company has begun evaluating ASU 2016‑02, including the review and implementation of the necessary changes to our existing processes and systems that will be required to implement this new standard. While we expect the adoption of ASU 2016-02 to have an impact on our consolidated balance sheet, we currently do not expect ASU 2016-02 to have a material effect on either our consolidated income statement or consolidated statement of cash flow. We plan to adopt ASU 2016-02 in the first quarter of 2019. In March 2017, the FASB issued ASU 2017‑07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost (“ASU 2017‑07”), requiring employers to provide more details about the components of costs related to retirement benefits. Specifically, ASU 2017‑07 requires employers to report the service costs for providing pensions to employees in the same line item as other employee compensation costs, while the other pension-related costs such as interest costs, amortization of pension-related costs from prior periods, and the gains or losses on plan assets, should be reported separately and outside of the subtotal of operating income. ASU 2017‑07 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017, with early adoption permitted only if adopted in the first quarter of the Company’s fiscal year. We will adopt this new standard in the first quarter of 2018. The Company has evaluated ASU 2017‑07 and we do not expect the reclassification to be material. In May 2017, the FASB issued ASU 2017‑09, Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting (“ASU 2017‑09”), which provides guidance to determine which changes to the terms or conditions of share-based payment awards require an entity to apply modification accounting in Topic 718. ASU 2017‑09 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017, with early adoption permitted, and requires prospective application to changes in terms or conditions of awards occurring on or after the adoption date. The Company has evaluated ASU 2017‑09 and we do not believe it will have a material impact on our consolidated financial statements. In February 2018, the FASB issued ASU 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income (“ASU 2018-02”), which amends the standard on comprehensive income by providing an option for an entity to reclassify stranded tax effects of the Tax Act from accumulated other comprehensive income directly to retained earnings. The stranded tax effects result from the remeasurement of net deferred tax positions which were originally recorded in comprehensive income but whose remeasurement was reflected in the income statement in 2017. ASU 2018-02 only applies to the effects of the Tax Act and is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted. ASU 2018-02 may be applied either in the period of adoption or on a retrospective basis to any period in which the impacts of the Tax Act are recognized. The Company is currently evaluating ASU 2018-02 and its impact on our consolidated financial statements.

Summary of Significant Accoun25

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Summary of Significant Accounting Policies
Schedule of fair value of stock options estimated at the date of grant using the Black-Scholes option-pricing model with the following weighted-average assumptions	2017 2016 2015 Risk free interest rate 1.7 % 1.3 % 1.4 % Expected life 4.6 years 4.6 years 4.6 years Expected volatility 13.0 % 15.0 % 17.0 % Expected dividend yield 1.0 % 1.0 % 1.0 %

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Long-Term Debt
Schedule of debt	December 31, 2017 December 31, 2016 Carrying Approximate Carrying Approximate Maturity Amount Fair Value (1) Amount Fair Value (1) Revolving Credit Facility March 2021 $ — $ — $ — $ — Commercial Paper Program (less unamortized discount of $0.3 and $0.4 at December 31, 2017 and 2016, respectively) March 2021 1,175.4 1,175.4 1,018.9 1,018.9 4.00% Senior Notes (less unamortized discount of $0.5 and $0.6 at December 31, 2017 and 2016, respectively) February 2022 499.5 522.5 499.4 523.7 2.55% Senior Notes (less unamortized discount of $0.2 and $0.5 at December 31, 2017 and 2016, respectively) January 2019 749.8 752.8 749.5 758.3 1.55% Senior Notes (less unamortized discount of $0.1 at December 31, 2016) September 2017 — — 374.9 375.4 3.125% Senior Notes (less unamortized discount of $0.2 and $0.2 at December 31, 2017 and 2016, respectively) September 2021 374.8 381.2 374.8 380.4 2.20% Senior Notes (less unamortized discount of $0.2 at December 31, 2017) April 2020 399.8 398.0 — — 3.20% Senior Notes (less unamortized discount of $0.4 at December 31, 2017) April 2024 349.6 351.9 — — Notes payable to foreign banks and other debt 2018-2032 6.6 6.6 5.5 5.5 Less unamortized deferred debt issuance costs (12.9) — (12.3) — Total debt 3,542.6 3,588.4 3,010.7 3,062.2 Less current portion 1.1 1.1 375.2 375.7 Total long-term debt $ 3,541.5 $ 3,587.3 $ 2,635.5 $ 2,686.5 (1) The fair value of the Company’s Senior Notes is based on recent bid prices in an active market, and therefore is classified as Level 1 in the fair value hierarchy (Note 3).
Schedule of maturity of the Company's debt (exclusive of unamortized deferred debt issuance costs) over each of the next five years and thereafter	2018 $ 1.1 2019 751.0 2020 400.7 2021 1,551.2 2022 500.2 Thereafter 351.3 $ 3,555.5

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Measurements
Fair values of financial and non-financial assets and liabilities	Fair Value Measurements Quoted Prices in Significant Significant Active Markets Observable Unobservable for Identical Inputs Inputs 2017 Total Assets (Level 1) (Level 2) (Level 3) Short-term investments $ 34.6 $ 34.6 $ — $ — Forward contracts 2.3 — 2.3 — Total $ 36.9 $ 34.6 $ 2.3 $ — 2016 Short-term investments $ 138.6 $ 138.6 $ — $ — Forward contracts 8.4 — 8.4 — Total $ 147.0 $ 138.6 $ 8.4 $ —

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Taxes
Schedule of income before income taxes	Year Ended December 31, 2017 2016 2015 Income before income taxes: United States $ 153.0 $ 87.7 $ 134.4 Foreign 1,199.4 1,053.4 918.4 $ 1,352.4 $ 1,141.1 $ 1,052.8 Current tax provision: United States $ 200.0 $ 74.6 $ 39.5 Foreign 305.4 263.8 228.1 505.4 338.4 267.6 Deferred tax provision (benefit): United States 51.0 (32.3) 13.3 Foreign 135.3 2.4 (0.4) 186.3 (29.9) 12.9 Total provision for income taxes $ 691.7 $ 308.5 $ 280.5
Schedule of provision for income taxes	Year Ended December 31, 2017 2016 2015 Income before income taxes: United States $ 153.0 $ 87.7 $ 134.4 Foreign 1,199.4 1,053.4 918.4 $ 1,352.4 $ 1,141.1 $ 1,052.8 Current tax provision: United States $ 200.0 $ 74.6 $ 39.5 Foreign 305.4 263.8 228.1 505.4 338.4 267.6 Deferred tax provision (benefit): United States 51.0 (32.3) 13.3 Foreign 135.3 2.4 (0.4) 186.3 (29.9) 12.9 Total provision for income taxes $ 691.7 $ 308.5 $ 280.5
Schedule of differences between the U.S. statutory federal tax rate and the Company's effective income tax rate	Year Ended December 31, 2017 2016 2015 U.S. statutory federal tax rate 35.0 % 35.0 % 35.0 % State and local taxes 0.2 0.1 0.1 Foreign earnings and dividends taxed at different rates (9.1) (9.7) (8.8) Valuation allowance 0.1 0.7 0.3 Tax Act - transition tax 19.2 — — Tax Act - remeasurement of deferred tax liabilities, net (2.8) — — Tax Act - change in indefinite reinvestment assertion 13.1 — — Excess tax benefits related to stock-based compensation (4.9) — — Impact of acquisition-related expenses — 0.5 0.1 Other, net 0.3 0.4 (0.1) Effective tax rate 51.1 % 27.0 % 26.6 %
Schedule of deferred tax assets and liabilities	December 31, 2017 2016 Deferred tax assets relating to: Accrued liabilities and reserves $ 31.7 $ 36.8 Operating loss and tax credit carryforwards 84.2 58.8 Pensions 27.8 64.7 Inventories 35.1 45.3 Employee benefits 29.8 43.4 Total deferred tax assets 208.6 249.0 Valuation allowance (39.6) (37.2) Total deferred tax assets, net of valuation allowances 169.0 211.8 Deferred tax liabilities relating to: Goodwill 135.5 185.9 Depreciation and amortization 61.8 67.6 Unremitted foreign earnings 176.6 — Contingent consideration 4.3 6.6 Total deferred tax liabilities 378.2 260.1 Net deferred tax liability $ 209.2 $ 48.3 Classification of deferred tax assets and liabilities, as reflected on the Consolidated Balance Sheets: Intangibles, net and other long-term assets $ 32.0 $ 29.4 Deferred income taxes 241.2 77.7 Net deferred tax liability, long-term $ 209.2 $ 48.3
Schedule of reconciliation of gross amounts of unrecognized tax benefits excluding interest and penalties	2017 2016 2015 Unrecognized tax benefits as of January 1 $ 106.2 $ 29.8 $ 27.7 Gross increases for tax positions in prior periods 32.7 81.9 0.3 Gross increases for tax positions in current period 2.4 7.0 2.1 Settlements (11.0) (10.8) — Lapse of statute of limitations (3.0) (1.7) (0.3) Unrecognized tax benefits as of December 31 $ 127.3 $ 106.2 $ 29.8

Equity (Tables)

Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity
Schedule of stock option activity	Weighted Average Aggregate Weighted Remaining Intrinsic Average Contractual Value Options Exercise Price Term (in years) (in millions) Options outstanding at January 1, 2015 27,787,920 $ 31.60 7.09 Options granted 6,490,200 57.85 Options exercised (2,718,745) 23.71 Options forfeited (422,900) 41.73 Options outstanding at December 31, 2015 31,136,475 37.62 6.92 Options granted 7,560,450 57.72 Options exercised (5,703,254) 25.80 Options forfeited (727,280) 50.17 Options outstanding at December 31, 2016 32,266,391 44.14 7.03 Options granted 7,029,600 72.98 Options exercised (5,773,287) 31.87 Options forfeited (300,340) 55.16 Options outstanding at December 31, 2017 33,222,364 $ 52.27 7.05 $ 1,180.3 Vested and non-vested options expected to vest at December 31, 2017 31,214,883 $ 51.61 6.96 $ 1,129.8 Exercisable options at December 31, 2017 13,621,924 $ 39.48 5.40 $ 658.2
Summary of status of non-vested options and changes during the year	Weighted Average Fair Value Options at Grant Date Non-vested options at January 1, 2017 18,725,570 $ 7.99 Options granted 7,029,600 8.78 Options vested (5,854,390) 7.91 Options forfeited (300,340) 8.10 Non-vested options at December 31, 2017 19,600,440 $ 8.29
Summary of activity in the option plans	2017 2016 2015 Total intrinsic value of stock options exercised $ 268.7 $ 197.2 $ 88.1 Total fair value of stock options vested 46.3 43.1 39.9
Schedule of restricted stock activity	Weighted Average Fair Value Remaining Restricted at Grant Amortization Shares Date Term (in years) Restricted shares outstanding at January 1, 2015 18,340 $ 47.72 0.39 Restricted shares granted 17,948 57.85 Shares vested and issued (19,032) 47.98 Restricted shares outstanding at December 31, 2015 17,256 57.97 0.39 Restricted shares granted 16,905 57.99 Shares vested and issued (17,256) 57.97 Restricted shares outstanding at December 31, 2016 16,905 57.99 0.38 Restricted shares granted 12,905 73.25 Shares vested and issued (16,905) 57.99 Restricted shares outstanding at December 31, 2017 12,905 $ 73.25 0.37
Schedules of dividends	The following table summarizes the declared quarterly dividends per share for each of the three years ended December 31, 2017, 2016 and 2015: 2017 2016 2015 First Quarter $ 0.16 $ 0.14 $ 0.125 Second Quarter 0.16 0.14 0.125 Third Quarter 0.19 0.14 0.14 Fourth Quarter 0.19 0.16 0.14 Dividends declared and paid for the years ended December 31, 2017, 2016 and 2015 were as follows: 2017 2016 2015 Dividends declared $ 213.7 $ 178.8 $ 163.7 Dividends paid (including those declared in the prior year) 205.0 172.7 159.3
Schedule of components comprising Accumulated other comprehensive income (loss) included in equity	Foreign Unrealized Defined Accumulated Currency Gain (Loss) Benefit Other Translation on Cash Plan Comprehensive Adjustments Flow Hedges Adjustment Income (Loss) Balance at January 1, 2015 $ (13.4) $ (1.3) $ (191.1) $ (205.8) Other comprehensive income (loss) before reclassifications, net of tax of nil, $0.1 and $5.5, respectively (151.5) (0.4) (10.0) (161.9) Amounts reclassified from Accumulated other comprehensive income (loss) to earnings, net of tax of ($10.1) — — 18.2 18.2 Balance at December 31, 2015 (164.9) (1.7) (182.9) (349.5) Other comprehensive income (loss) before reclassifications, net of tax of nil, ($0.3) and $12.3, respectively (108.6) 1.6 (28.8) (135.8) Amounts reclassified from Accumulated other comprehensive income (loss) to earnings, net of tax of ($8.9) — — 16.3 16.3 Balance at December 31, 2016 (273.5) (0.1) (195.4) (469.0) Other comprehensive income (loss) before reclassifications, net of tax of nil, $0.1 and ($3.4), respectively 240.3 (0.1) 10.7 250.9 Amounts reclassified from Accumulated other comprehensive income (loss) to earnings, net of tax of ($9.1) — — 17.1 17.1 Balance at December 31, 2017 $ (33.2) $ (0.2) $ (167.6) $ (201.0)

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share
Schedule of the reconciliation of basic weighted average common shares outstanding to diluted weighted average common shares outstanding	(dollars and shares in millions, except per share data) 2017 2016 2015 Net income attributable to Amphenol Corporation shareholders $ 650.5 $ 822.9 $ 763.5 Basic weighted average common shares outstanding 305.7 308.3 309.1 Effect of dilutive stock options 10.8 6.9 7.4 Diluted weighted average common shares outstanding 316.5 315.2 316.5 Earnings per share attributable to Amphenol Corporation shareholders: Basic $ 2.13 $ 2.67 $ 2.47 Diluted $ 2.06 $ 2.61 $ 2.41

Benefit Plans and Other Postr31

Benefit Plans and Other Postretirement Benefits (Tables)	12 Months Ended
	Dec. 31, 2017
Pension Benefits
Defined Benefit Plan Disclosure
Schedule of change in projected benefit obligation and plan assets	U.S. Plans International Plans Total 2017 2016 2017 2016 2017 2016 Change in projected benefit obligation : Projected benefit obligation at beginning of year $ 469.8 $ 460.8 $ 233.5 $ 174.4 $ 703.3 $ 635.2 Service cost 6.7 6.2 2.9 2.8 9.6 9.0 Interest cost 15.3 15.4 4.7 5.5 20.0 20.9 Acquisitions — — — 47.4 — 47.4 Plan amendments — 3.7 — — — 3.7 Actuarial (gain) loss 21.1 11.6 (2.2) 28.0 18.9 39.6 Foreign exchange translation — — 26.7 (17.3) 26.7 (17.3) Benefits paid (26.2) (27.9) (10.6) (7.3) (36.8) (35.2) Projected benefit obligation at end of year 486.7 469.8 255.0 233.5 741.7 703.3 Change in plan assets : Fair value of plan assets at beginning of year 342.1 333.2 97.8 59.0 439.9 392.2 Actual return on plan assets 57.2 20.4 5.2 11.4 62.4 31.8 Employer contributions 16.5 16.4 6.0 5.8 22.5 22.2 Acquisitions — — — 36.7 — 36.7 Foreign exchange translation — — 9.9 (7.8) 9.9 (7.8) Benefits paid (26.2) (27.9) (10.6) (7.3) (36.8) (35.2) Fair value of plan assets at end of year 389.6 342.1 108.3 97.8 497.9 439.9 Underfunded status at end of year $ 97.1 $ 127.7 $ 146.7 $ 135.7 $ 243.8 $ 263.4 Amounts recognized on the balance sheet as of December 31: Other accrued expenses $ — $ — $ 3.1 $ 2.8 $ 3.1 $ 2.8 Accrued pension and postretirement benefit obligations 97.1 127.7 143.6 132.9 240.7 260.6 Underfunded status at end of year $ 97.1 $ 127.7 $ 146.7 $ 135.7 $ 243.8 $ 263.4 Accumulated other comprehensive loss, net $ (110.5) $ (129.3) $ (53.9) $ (62.5) $ (164.4) $ (191.8) Weighted average assumptions used to determine projected benefit obligations: Discount rate 3.48 % 3.93 % 2.21 % 2.28 % Rate of compensation increase 3.00 % 3.00 % 1.70 % 1.63 %
Schedule of amounts recognized in the balance sheet	U.S. Plans International Plans Total 2017 2016 2017 2016 2017 2016 Change in projected benefit obligation : Projected benefit obligation at beginning of year $ 469.8 $ 460.8 $ 233.5 $ 174.4 $ 703.3 $ 635.2 Service cost 6.7 6.2 2.9 2.8 9.6 9.0 Interest cost 15.3 15.4 4.7 5.5 20.0 20.9 Acquisitions — — — 47.4 — 47.4 Plan amendments — 3.7 — — — 3.7 Actuarial (gain) loss 21.1 11.6 (2.2) 28.0 18.9 39.6 Foreign exchange translation — — 26.7 (17.3) 26.7 (17.3) Benefits paid (26.2) (27.9) (10.6) (7.3) (36.8) (35.2) Projected benefit obligation at end of year 486.7 469.8 255.0 233.5 741.7 703.3 Change in plan assets : Fair value of plan assets at beginning of year 342.1 333.2 97.8 59.0 439.9 392.2 Actual return on plan assets 57.2 20.4 5.2 11.4 62.4 31.8 Employer contributions 16.5 16.4 6.0 5.8 22.5 22.2 Acquisitions — — — 36.7 — 36.7 Foreign exchange translation — — 9.9 (7.8) 9.9 (7.8) Benefits paid (26.2) (27.9) (10.6) (7.3) (36.8) (35.2) Fair value of plan assets at end of year 389.6 342.1 108.3 97.8 497.9 439.9 Underfunded status at end of year $ 97.1 $ 127.7 $ 146.7 $ 135.7 $ 243.8 $ 263.4 Amounts recognized on the balance sheet as of December 31: Other accrued expenses $ — $ — $ 3.1 $ 2.8 $ 3.1 $ 2.8 Accrued pension and postretirement benefit obligations 97.1 127.7 143.6 132.9 240.7 260.6 Underfunded status at end of year $ 97.1 $ 127.7 $ 146.7 $ 135.7 $ 243.8 $ 263.4 Accumulated other comprehensive loss, net $ (110.5) $ (129.3) $ (53.9) $ (62.5) $ (164.4) $ (191.8) Weighted average assumptions used to determine projected benefit obligations: Discount rate 3.48 % 3.93 % 2.21 % 2.28 % Rate of compensation increase 3.00 % 3.00 % 1.70 % 1.63 %
Schedule of weighted average assumptions used to determine projected benefit obligations	U.S. Plans International Plans Total 2017 2016 2017 2016 2017 2016 Change in projected benefit obligation : Projected benefit obligation at beginning of year $ 469.8 $ 460.8 $ 233.5 $ 174.4 $ 703.3 $ 635.2 Service cost 6.7 6.2 2.9 2.8 9.6 9.0 Interest cost 15.3 15.4 4.7 5.5 20.0 20.9 Acquisitions — — — 47.4 — 47.4 Plan amendments — 3.7 — — — 3.7 Actuarial (gain) loss 21.1 11.6 (2.2) 28.0 18.9 39.6 Foreign exchange translation — — 26.7 (17.3) 26.7 (17.3) Benefits paid (26.2) (27.9) (10.6) (7.3) (36.8) (35.2) Projected benefit obligation at end of year 486.7 469.8 255.0 233.5 741.7 703.3 Change in plan assets : Fair value of plan assets at beginning of year 342.1 333.2 97.8 59.0 439.9 392.2 Actual return on plan assets 57.2 20.4 5.2 11.4 62.4 31.8 Employer contributions 16.5 16.4 6.0 5.8 22.5 22.2 Acquisitions — — — 36.7 — 36.7 Foreign exchange translation — — 9.9 (7.8) 9.9 (7.8) Benefits paid (26.2) (27.9) (10.6) (7.3) (36.8) (35.2) Fair value of plan assets at end of year 389.6 342.1 108.3 97.8 497.9 439.9 Underfunded status at end of year $ 97.1 $ 127.7 $ 146.7 $ 135.7 $ 243.8 $ 263.4 Amounts recognized on the balance sheet as of December 31: Other accrued expenses $ — $ — $ 3.1 $ 2.8 $ 3.1 $ 2.8 Accrued pension and postretirement benefit obligations 97.1 127.7 143.6 132.9 240.7 260.6 Underfunded status at end of year $ 97.1 $ 127.7 $ 146.7 $ 135.7 $ 243.8 $ 263.4 Accumulated other comprehensive loss, net $ (110.5) $ (129.3) $ (53.9) $ (62.5) $ (164.4) $ (191.8) Weighted average assumptions used to determine projected benefit obligations: Discount rate 3.48 % 3.93 % 2.21 % 2.28 % Rate of compensation increase 3.00 % 3.00 % 1.70 % 1.63 %
Schedule of components of net pension expense	U.S. Plans International Plans Total 2017 2016 2015 2017 2016 2015 2017 2016 2015 Components of net pension expense : Service cost $ 6.7 $ 6.2 $ 6.5 $ 2.9 $ 2.8 $ 2.8 $ 9.6 $ 9.0 $ 9.3 Interest cost 15.3 15.4 17.4 4.7 5.5 5.4 20.0 20.9 22.8 Expected return on plan assets (27.2) (26.2) (25.9) (3.5) (3.9) (3.2) (30.7) (30.1) (29.1) Amortization of prior service cost 2.7 2.4 2.3 — — — 2.7 2.4 2.3 Amortization of actuarial losses 18.3 18.6 21.5 4.6 3.4 4.2 22.9 22.0 25.7 Net pension expense $ 15.8 $ 16.4 $ 21.8 $ 8.7 $ 7.8 $ 9.2 $ 24.5 $ 24.2 $ 31.0 Weighted average assumptions used to determine net periodic benefit cost: Discount rate 3.93 % 4.11 % 3.75 % 2.28 % 2.96 % 2.91 % Expected long-term return on assets 7.75 % 7.75 % 8.00 % 3.80 % 4.29 % 5.47 % Rate of compensation increase 3.00 % 3.00 % 3.00 % 1.63 % 1.61 % 1.45 %
Schedule of weighted average assumptions used to determine net benefit cost/expense	U.S. Plans International Plans Total 2017 2016 2015 2017 2016 2015 2017 2016 2015 Components of net pension expense : Service cost $ 6.7 $ 6.2 $ 6.5 $ 2.9 $ 2.8 $ 2.8 $ 9.6 $ 9.0 $ 9.3 Interest cost 15.3 15.4 17.4 4.7 5.5 5.4 20.0 20.9 22.8 Expected return on plan assets (27.2) (26.2) (25.9) (3.5) (3.9) (3.2) (30.7) (30.1) (29.1) Amortization of prior service cost 2.7 2.4 2.3 — — — 2.7 2.4 2.3 Amortization of actuarial losses 18.3 18.6 21.5 4.6 3.4 4.2 22.9 22.0 25.7 Net pension expense $ 15.8 $ 16.4 $ 21.8 $ 8.7 $ 7.8 $ 9.2 $ 24.5 $ 24.2 $ 31.0 Weighted average assumptions used to determine net periodic benefit cost: Discount rate 3.93 % 4.11 % 3.75 % 2.28 % 2.96 % 2.91 % Expected long-term return on assets 7.75 % 7.75 % 8.00 % 3.80 % 4.29 % 5.47 % Rate of compensation increase 3.00 % 3.00 % 3.00 % 1.63 % 1.61 % 1.45 %
Fair values of Company's pension plan assets by asset category	Assets Measured at Net Asset Asset Category Total Level 1 Level 2 Level 3 Value (a) December 31, 2017 Equity securities: U.S. equities — large cap $ 141.5 $ 106.6 $ 34.9 $ — $ — U.S. equities — small/mid cap and other 22.0 — 22.0 — — International equities — growth 35.6 30.4 5.2 — — International equities — other 95.5 — 40.7 — 54.8 Alternative investment funds 12.9 — — — 12.9 Fixed income securities: U.S. fixed income securities — short term 6.1 — — — 6.1 U.S. fixed income securities — intermediate term 61.4 61.4 — — — U.S. fixed income securities — high yield 21.9 — 21.9 — — International fixed income securities — other 47.4 — 47.4 — — Insurance contracts 37.9 — — 37.9 — Real estate funds 7.0 — — 7.0 — Cash and cash equivalents 8.7 8.7 — — — Total $ 497.9 $ 207.1 $ 172.1 $ 44.9 $ 73.8 December 31, 2016 Equity securities: U.S. equities — large cap $ 118.8 $ 88.7 $ 30.1 $ — $ — U.S. equities — small/mid cap and other 25.8 — 25.8 — — International equities — growth 46.5 46.5 — — — International equities — other 60.6 7.0 33.9 — 19.7 Alternative investment funds 12.6 — — — 12.6 Fixed income securities: U.S. fixed income securities — short term 6.0 — — — 6.0 U.S. fixed income securities — intermediate term 58.4 58.4 — — — U.S. fixed income securities — high yield 22.2 — 22.2 — — International fixed income securities — other 43.0 — 43.0 — — Insurance contracts 34.0 — — 34.0 — Cash and cash equivalents 12.0 12.0 — — — Total $ 439.9 $ 212.6 $ 155.0 $ 34.0 $ 38.3 (a) Certain investments measured at fair value using the net asset value (NAV) practical expedient have been removed from the fair value hierarchy but included in the table above in order to permit the reconciliation of the fair value hierarchy to total plan assets.
Reconciliation of fair value measurements using significant unobservable inputs (Level 3)	2017 2016 Balance on January 1 $ 34.0 $ — Additions due to acquisition — 34.3 Unrealized gains (losses), net 0.6 2.7 Purchases, sales and settlements, net 5.8 (0.9) Foreign currency translation 4.5 (2.1) Balance on December 31 $ 44.9 $ 34.0
Schedule of amounts, before tax, included in Accumulated other comprehensive loss that have not yet been recognized as expense	U.S. International Plans Plans Total 2017 2016 2017 2016 2017 2016 Net loss $ 167.7 $ 194.7 $ 70.0 $ 71.0 $ 237.7 $ 265.7 Net prior service cost 7.7 10.5 — — 7.7 10.5
Benefit payments related to the pension plans, including amounts to be paid out of Company assets and reflecting future expected service	U.S. International Plans Plans Total 2018 $ 24.8 $ 7.5 $ 32.3 2019 25.8 7.1 32.9 2020 26.9 7.3 34.2 2021 27.8 9.2 37.0 2022 28.9 9.4 38.3 2023-2027 151.2 51.1 202.3
Other Postretirement Benefits
Defined Benefit Plan Disclosure
Schedule of change in projected benefit obligation and plan assets	2017 2016 Change in benefit obligation : Benefit obligation at beginning of year $ 13.6 $ 13.2 Interest cost 0.4 0.4 Benefits paid (0.9) (0.9) Actuarial loss — 0.9 Benefit obligation at end of year $ 13.1 $ 13.6 Amounts recognized on the balance sheet as of December 31: Other accrued expenses $ 1.2 $ 1.2 Accrued pension and postretirement benefit obligations 11.9 12.4 Unfunded status at end of year $ 13.1 $ 13.6 Accumulated other comprehensive loss, net $ (3.2) $ (3.6) Weighted average assumptions used to determine projected benefit obligations: Discount rate 3.29 % 3.65 %
Schedule of amounts recognized in the balance sheet	2017 2016 Change in benefit obligation : Benefit obligation at beginning of year $ 13.6 $ 13.2 Interest cost 0.4 0.4 Benefits paid (0.9) (0.9) Actuarial loss — 0.9 Benefit obligation at end of year $ 13.1 $ 13.6 Amounts recognized on the balance sheet as of December 31: Other accrued expenses $ 1.2 $ 1.2 Accrued pension and postretirement benefit obligations 11.9 12.4 Unfunded status at end of year $ 13.1 $ 13.6 Accumulated other comprehensive loss, net $ (3.2) $ (3.6) Weighted average assumptions used to determine projected benefit obligations: Discount rate 3.29 % 3.65 %
Schedule of weighted average assumptions used to determine projected benefit obligations	2017 2016 Change in benefit obligation : Benefit obligation at beginning of year $ 13.6 $ 13.2 Interest cost 0.4 0.4 Benefits paid (0.9) (0.9) Actuarial loss — 0.9 Benefit obligation at end of year $ 13.1 $ 13.6 Amounts recognized on the balance sheet as of December 31: Other accrued expenses $ 1.2 $ 1.2 Accrued pension and postretirement benefit obligations 11.9 12.4 Unfunded status at end of year $ 13.1 $ 13.6 Accumulated other comprehensive loss, net $ (3.2) $ (3.6) Weighted average assumptions used to determine projected benefit obligations: Discount rate 3.29 % 3.65 %
Schedule of components of net pension expense	2017 2016 2015 Components of net postretirement benefit expense : Service cost $ — $ — $ 0.1 Interest cost 0.4 0.4 0.4 Amortization of actuarial losses 0.5 0.7 0.3 Net postretirement benefit expense $ 0.9 $ 1.1 $ 0.8 Weighted average assumptions used to determine net postretirement benefit expense : Discount rate 3.65 % 3.71 % 3.50 %
Schedule of weighted average assumptions used to determine net benefit cost/expense	2017 2016 2015 Components of net postretirement benefit expense : Service cost $ — $ — $ 0.1 Interest cost 0.4 0.4 0.4 Amortization of actuarial losses 0.5 0.7 0.3 Net postretirement benefit expense $ 0.9 $ 1.1 $ 0.8 Weighted average assumptions used to determine net postretirement benefit expense: Discount rate 3.65 % 3.71 % 3.50 %

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2017
Leases
Schedule of minimum lease payments under non-cancelable operating leases	2018 $ 53.2 2019 37.3 2020 23.7 2021 15.5 2022 10.2 Beyond 2022 21.3 Total minimum obligation $ 161.2

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2017
Acquisitions
Pro forma financial information	Year ended December 31, Pro forma: 2016 2015 Net sales $ 6,296.1 $ 6,137.3 Net income attributable to Amphenol Corporation 856.2 799.3 Net income per common share - Diluted 2.72 2.53

Goodwill and Other Intangible34

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Other Intangible Assets
Schedule of changes in the carrying amount of goodwill by segment	Interconnect Cable Products and Products and Assemblies Solutions Total Goodwill at December 31, 2015 $ 2,569.2 $ 123.7 $ 2,692.9 Acquisition-related 1,008.7 22.6 1,031.3 Foreign currency translation (45.4) — (45.4) Goodwill at December 31, 2016 3,532.5 146.3 3,678.8 Acquisition-related 233.6 0.2 233.8 Foreign currency translation 130.0 — 130.0 Goodwill at December 31, 2017 $ 3,896.1 $ 146.5 $ 4,042.6
Summary of the Company's intangible assets	December 31, 2017 December 31, 2016 Weighted Gross Net Gross Net Average Carrying Accumulated Carrying Carrying Accumulated Carrying Life (years) Amount Amortization Amount Amount Amortization Amount Customer relationships 10 $ 398.1 $ 199.8 $ 198.3 $ 381.1 $ 159.1 $ 222.0 Proprietary technology 11 107.5 50.7 56.8 106.7 40.9 65.8 Backlog and other 2 34.0 33.6 0.4 34.0 33.5 0.5 Total intangible assets (definite-lived) 10 539.6 284.1 255.5 521.8 233.5 288.3 Trade names (indefinite-lived) - 186.1 — 186.1 186.1 — 186.1 $ 725.7 $ 284.1 $ 441.6 $ 707.9 $ 233.5 $ 474.4

Reportable Business Segments 35

Reportable Business Segments and International Operations (Tables)	12 Months Ended
	Dec. 31, 2017
Reportable Business Segments
Schedule of segment reporting information by segment	Interconnect Products Cable Products Total Reportable and Assemblies and Solutions Business Segments 2017 2016 2015 2017 2016 2015 2017 2016 2015 Net sales: External $ 6,606.9 $ 5,922.3 $ 5,239.1 $ 404.4 $ 364.1 $ 329.6 $ 7,011.3 $ 6,286.4 $ 5,568.7 Intersegment 9.7 6.9 7.2 40.7 30.0 21.6 50.4 36.9 28.8 Depreciation and amortization 214.7 206.8 162.3 6.3 4.9 3.0 221.0 211.7 165.3 Segment operating income 1,475.2 1,280.3 1,158.3 54.2 52.8 40.3 1,529.4 1,333.1 1,198.6 Segment assets (excluding goodwill) 5,732.6 4,587.5 4,580.4 200.3 197.1 163.5 5,932.9 4,784.6 4,743.9 Capital expenditures 220.4 186.2 167.1 5.6 4.0 4.5 226.0 190.2 171.6
Schedule of the reconciliation of segment operating income to consolidated income before income taxes	2017 2016 2015 Segment operating income $ 1,529.4 $ 1,333.1 $ 1,198.6 Interest expense (92.3) (72.6) (68.3) Other income, net 17.1 8.5 16.4 Stock-based compensation expense (49.7) (47.6) (44.2) Acquisition-related expenses (4.0) (36.6) (5.7) Other operating expenses (48.1) (43.7) (44.0) Income before income taxes $ 1,352.4 $ 1,141.1 $ 1,052.8
Schedule of the reconciliation of segment assets to consolidated total assets	2017 2016 Segment assets, excluding goodwill $ 5,932.9 $ 4,784.6 Goodwill 4,042.6 3,678.8 Other assets 28.4 35.3 Consolidated total assets $ 10,003.9 $ 8,498.7
Schedule of revenues and long-lived assets by geographical area	2017 2016 2015 Net sales United States $ 1,978.4 $ 1,740.7 $ 1,696.3 China 2,067.3 1,865.6 1,675.5 Other international locations 2,965.6 2,680.1 2,196.9 Total $ 7,011.3 $ 6,286.4 $ 5,568.7 Property, plant and equipment, net United States $ 212.7 $ 209.2 $ 214.4 China 244.7 200.1 151.4 Other international locations 359.4 302.1 243.7 Total $ 816.8 $ 711.4 $ 609.5

Other Income, net (Tables)

Other Income, net (Tables)	12 Months Ended
	Dec. 31, 2017
Other Income, net
Schedule of components of other income, net	Year Ended December 31, 2017 2016 2015 Agency and commitment fees $ (3.1) $ (3.0) $ (2.0) Interest income 20.2 11.5 18.4 $ 17.1 $ 8.5 $ 16.4

Selected Quarterly Financial 37

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Selected Quarterly Financial Data (Unaudited)
Schedule of selected quarterly financial data (unaudited)	Three Months Ended March 31, June 30, September 30, December 31, 2017 Net sales $ 1,560.1 $ 1,666.5 $ 1,840.8 $ 1,943.9 Gross profit 515.9 552.6 606.1 635.4 Operating income 314.1 336.2 (2) 377.9 399.4 Net income (loss) 227.3 (1) 253.6 (2) 280.3 (3) (100.4) (4) Net income (loss) attributable to Amphenol Corporation 224.9 (1) 251.5 (2) 277.5 (3) (103.4) (4) Net income (loss) per common share—Basic 0.73 (1) 0.82 (2) 0.91 (3) (0.34) (4) Net income (loss) per common share—Diluted 0.71 (1) 0.80 (2) 0.88 (3) (0.34) (4) 2016 Net sales $ 1,451.2 $ 1,548.2 $ 1,635.9 $ 1,651.1 Gross profit 459.2 497.3 537.3 546.1 Operating income 239.4 (5) 300.3 326.3 (6) 339.1 Net income 158.4 (5) 208.7 227.1 (6) 238.3 Net income attributable to Amphenol Corporation 156.6 (5) 206.5 224.3 (6) 235.4 Net income per common share—Basic 0.51 (5) 0.67 0.73 (6) 0.76 Net income per common share—Diluted 0.50 (5) 0.65 0.71 (6) 0.75 (1) Net income and net income per common share includes excess tax benefits related to stock-based compensation of $8.0 as a result of the adoption of ASU 2016-09 in 2017. The excess tax benefits had the effect of increasing Net income, Net income attributable to Amphenol Corporation, and Net income per common share-Diluted by $8.0, $8.0 and $0.02 per share, respectively, for the three months ended March 31, 2017. (2) Operating income, net income and net income per common share includes acquisition-related expenses of $4.0 ($3.7 after-tax, or $0.01 per share) primarily related to 2017 acquisitions and excess tax benefits related to stock-based compensation of $21.2 ($0.07 per share). These items had the aggregate effect of decreasing Operating income by $4.0, while increasing Net income, Net income attributable to Amphenol Corporation, and Net income per common share-Diluted by $17.5, $17.5 and $0.06 per share, respectively, for the three months ended June 30, 2017. (3) Net income and net income per common share includes excess tax benefits related to stock-based compensation of $16.6. The excess tax benefits had the effect of increasing Net income, Net income attributable to Amphenol Corporation, and Net income per common share-Diluted by $16.6, $16.6 and $0.05 per share, respectively, for the three months ended September 30, 2017. (4) Net loss and net loss per common share includes the provisional Tax Act Charge of $398.5 ($1.26 per share) related to the enactment of the Tax Cuts and Jobs Act, partially offset by the excess tax benefits related to stock-based compensation of $20.8 ($0.07 per share). In addition, (5) Operating income, net income and net income per common share includes acquisition-related expenses primarily related to the acquisition of FCI which closed in January 2016. These acquisition-related expenses had the effect of decreasing Operating income, Net income, Net income attributable to Amphenol Corporation, and Net income per common share-Diluted by $30.3, $27.3, $27.3 and $0.09 per share, respectively, for the three months ended March 31, 2016. (6) Operating income, net income and net income per common share includes acquisition-related expenses. These acquisition-related expenses had the effect of decreasing Operating income, Net income, Net income attributable to Amphenol Corporation, and Net income per common share-Diluted by $6.3, $5.8, $5.8 and $0.02 per share, respectively, for the three months ended September 30, 2016.

Summary of Significant Accoun38

Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2017segment
Summary of Significant Accounting Policies
Number of reportable business segments	2

Summary of Significant Accoun39

Summary of Significant Accounting Policies, Depreciable Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Depreciable Assets
Impairments	$ 0	$ 0	$ 0
Machinery and Equipment | Minimum
Depreciable Assets
Estimated useful life	3 years
Machinery and Equipment | Maximum
Depreciable Assets
Estimated useful life	12 years
Buildings | Minimum
Depreciable Assets
Estimated useful life	20 years
Buildings | Maximum
Depreciable Assets
Estimated useful life	40 years

Summary of Significant Accoun40

Summary of Significant Accounting Policies, Other (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)segmentitem	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Summary of Significant Accounting Policies
Number of reporting units | item	2
Number of reportable business segments | segment	2
Goodwill impairment	$ 0	$ 0	$ 0
Impairment of intangible assets	$ 0	$ 0	$ 0
Revenue Recognition
Percentage of net sales attributable to broadband communication market (as a percent)	6.00%
Weighted-average assumptions:
Risk free interest rate (as a percent)	1.70%	1.30%	1.40%
Expected life	4 years 7 months 6 days	4 years 7 months 6 days	4 years 7 months 6 days
Expected volatility (as a percent)	13.00%	15.00%	17.00%
Expected dividend yield (as a percent)	1.00%	1.00%	1.00%
Income tax
Undistributed foreign earnings	$ 492.8
Research and Development
Research and development expenses for the creation of new and improved products and processes	$ 193.7	$ 166.1	$ 124.7

Summary of Significant Accoun41

Summary of Significant Accounting Policies, Recent Accounting Pronouncements (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 01, 2017
New Accounting Pronouncements
Income tax expense (benefit)					$ 691.7	$ 308.5	$ 280.5
Impact of ASU 2016-09
New Accounting Pronouncements
Income tax expense (benefit)	$ (20.8)	$ (16.6)	$ (21.2)	$ (8)	$ (66.6)
Increase in diluted earnings per share (in dollars per share)					$ 0.21
Cumulative-effect adjustment to retained earnings								$ 0

Long-Term Debt, Schedule of Deb

Long-Term Debt, Schedule of Debt (Details) - USD ($) $ in Millions	Dec. 31, 2017	Apr. 05, 2017	Dec. 31, 2016
Long-Term Debt
Less deferred debt issuance costs	$ (12.9)		$ (12.3)
Total debt	3,542.6		3,010.7
Less current portion	1.1		375.2
Total long-term debt	3,541.5		2,635.5
Quoted Prices in Active Markets for Identical Assets (Level 1)
Long-Term Debt
Total debt, Approximate Fair Value	3,588.4		3,062.2
Less short-term debt, Approximate Fair Value	1.1		375.7
Long-term debt, Approximate Fair Value	3,587.3		2,686.5
Commercial Paper Program
Long-Term Debt
Debt carrying amount, net of unamortized discount before deferred debt issuance costs	1,175.4		1,018.9
Unamortized discount	0.3		0.4
Commercial Paper Program | Quoted Prices in Active Markets for Identical Assets (Level 1)
Long-Term Debt
Total debt, Approximate Fair Value	$ 1,175.4		1,018.9
4.00% Senior Notes due February 2022
Long-Term Debt
Stated interest rate (as a percent)	4.00%
Debt carrying amount, net of unamortized discount before deferred debt issuance costs	$ 499.5		499.4
Unamortized discount	0.5		0.6
4.00% Senior Notes due February 2022 | Quoted Prices in Active Markets for Identical Assets (Level 1)
Long-Term Debt
Total debt, Approximate Fair Value	$ 522.5		523.7
2.55% Senior Notes due January 2019
Long-Term Debt
Stated interest rate (as a percent)	2.55%
Debt carrying amount, net of unamortized discount before deferred debt issuance costs	$ 749.8		749.5
Unamortized discount	0.2		0.5
2.55% Senior Notes due January 2019 | Quoted Prices in Active Markets for Identical Assets (Level 1)
Long-Term Debt
Total debt, Approximate Fair Value	$ 752.8		$ 758.3
1.55% Senior Notes due September 2017
Long-Term Debt
Stated interest rate (as a percent)			1.55%
Debt carrying amount, net of unamortized discount before deferred debt issuance costs			$ 374.9
Unamortized discount			0.1
1.55% Senior Notes due September 2017 | Quoted Prices in Active Markets for Identical Assets (Level 1)
Long-Term Debt
Total debt, Approximate Fair Value			375.4
3.125% Senior Notes due September 2021
Long-Term Debt
Stated interest rate (as a percent)	3.125%
Debt carrying amount, net of unamortized discount before deferred debt issuance costs	$ 374.8		374.8
Unamortized discount	0.2		0.2
3.125% Senior Notes due September 2021 | Quoted Prices in Active Markets for Identical Assets (Level 1)
Long-Term Debt
Total debt, Approximate Fair Value	$ 381.2		380.4
2.20% Senior Notes due April 2020
Long-Term Debt
Stated interest rate (as a percent)	2.20%	2.20%
Debt carrying amount, net of unamortized discount before deferred debt issuance costs	$ 399.8
Unamortized discount	0.2
2.20% Senior Notes due April 2020 | Quoted Prices in Active Markets for Identical Assets (Level 1)
Long-Term Debt
Total debt, Approximate Fair Value	$ 398
3.20% Senior Notes due April 2024
Long-Term Debt
Stated interest rate (as a percent)	3.20%	3.20%
Debt carrying amount, net of unamortized discount before deferred debt issuance costs	$ 349.6
Unamortized discount	0.4
3.20% Senior Notes due April 2024 | Quoted Prices in Active Markets for Identical Assets (Level 1)
Long-Term Debt
Total debt, Approximate Fair Value	351.9
Notes payable to foreign banks and other debt
Long-Term Debt
Debt carrying amount, net of unamortized discount before deferred debt issuance costs	6.6		5.5
Notes payable to foreign banks and other debt | Quoted Prices in Active Markets for Identical Assets (Level 1)
Long-Term Debt
Total debt, Approximate Fair Value	$ 6.6		$ 5.5

Long-Term Debt, Other (Details)

Long-Term Debt, Other (Details) - USD ($) $ in Millions	Apr. 05, 2017	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2015	Dec. 31, 2016
Long-Term Debt
Repayment of long-term debt			$ 375	$ 217.7
The “Revolving Credit Facility”
Long-Term Debt
Maximum borrowing capacity			2,000
Borrowings under the Revolving Credit Facility			0
Commercial Paper Program
Long-Term Debt
Maximum borrowing capacity			$ 2,000
Average interest rate (as a percent)			1.71%		1.06%
Commercial Paper Program | Maximum
Long-Term Debt
Maturity term			397 days
Senior Notes
Long-Term Debt
Redemption price as a percentage of principal amount			100.00%
1.55% Senior Notes due September 2017
Long-Term Debt
Stated interest rate (as a percent)					1.55%
Repayment of long-term debt		$ 375
2.20% Senior Notes due April 2020
Long-Term Debt
Debt instrument, principal amount	$ 400
Stated interest rate (as a percent)	2.20%		2.20%
Debt instrument, face amount, net of discount (as a percent)	99.922%
Redemption price as a percentage of principal amount	100.00%
3.20% Senior Notes due April 2024
Long-Term Debt
Debt instrument, principal amount	$ 350
Stated interest rate (as a percent)	3.20%		3.20%
Debt instrument, face amount, net of discount (as a percent)	99.888%
Redemption price as a percentage of principal amount	100.00%
2.20% and 3.20% Senior Notes due April, 2020 and 2024, respectively
Long-Term Debt
Debt issuance costs incurred			$ 5.2

Long-Term Debt, Debt Maturity (

Long-Term Debt, Debt Maturity (Details) $ in Millions	Dec. 31, 2017USD ($)
Maturity of the Company's long-term debt over each of the next five years
2,018	$ 1.1
2,019	751
2,020	400.7
2,021	1,551.2
2,022	500.2
Thereafter	351.3
Debt (exclusive of unamortized deferred debt issuance costs)	$ 3,555.5

Long-Term Debt. Letter of Credi

Long-Term Debt. Letter of Credit (Details) - Uncommitted standby letter of credit facility $ in Millions	Dec. 31, 2017USD ($)
Long-Term Debt
Maximum borrowing capacity	$ 30
Letter of credit issued	$ 21.7

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair value of assets and liabilities measured on recurring basis
Accumulated other comprehensive gain (loss) associated with foreign exchange rate forward contracts	$ (0.1)	$ 1.6
Recurring basis
Fair value of assets and liabilities measured on recurring basis
Short-term investments	34.6	138.6
Forward contracts	2.3	8.4
Total	36.9	147
Recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair value of assets and liabilities measured on recurring basis
Short-term investments	34.6	138.6
Total	34.6	138.6
Recurring basis | Significant Observable Inputs (Level 2)
Fair value of assets and liabilities measured on recurring basis
Forward contracts	2.3	8.4
Total	$ 2.3	$ 8.4

Income Taxes, Provision for inc

Income Taxes, Provision for income taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income before income taxes:
United States	$ 153	$ 87.7	$ 134.4
Foreign	1,199.4	1,053.4	918.4
Income before income taxes	1,352.4	1,141.1	1,052.8
Current tax provision:
United States	200	74.6	39.5
Foreign	305.4	263.8	228.1
Provision for income taxes, current	505.4	338.4	267.6
Deferred tax provision (benefit):
United States	51	(32.3)	13.3
Foreign	135.3	2.4	(0.4)
Provision for income taxes, deferred	186.3	(29.9)	12.9
Provision for income taxes	$ 691.7	$ 308.5	$ 280.5

Income Taxes, 2017 Tax Cuts and

Income Taxes, 2017 Tax Cuts and Jobs Act (Details) $ in Millions	Dec. 31, 2017item	Dec. 31, 2017USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
U.S. statutory federal tax rate (as a percent)				35.00%	35.00%	35.00%
Estimated Tax Act Charge		$ 398.5
Estimated Transition Tax		259.4
Provisional charge on unremitted foreign earnings		176.6
Income tax expense (benefit) associated with the remeasurement of net deferred tax liabilities		$ (37.5)
Number of components | item	3
Forecast
U.S. statutory federal tax rate (as a percent)			21.00%
Period for payment of Transition Tax			8 years

Income Taxes, Valuation allowan

Income Taxes, Valuation allowance and tax carryforwards (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income taxes
Valuation allowance, related to the foreign net operating loss carryforwards and U.S. state tax credits	$ 39.6	$ 37.2
Change in the valuation allowance, related to foreign net operating loss and foreign and U.S. state credit carryforwards	2.4	$ 18.7
Foreign
Income taxes
Loss carryforwards	139.6
Operating loss carryforwards to expire or be refunded	98.6
Tax credit carryforwards	2.8
Tax credit carryforwards to expire or be refunded	2.8
U.S. Federal
Income taxes
Loss carryforwards	3.5
Operating loss carryforwards to expire or be refunded	3.5
Tax credit carryforwards	32.7
Tax credit carryforwards to expire or be refunded	32.7
U.S. State
Income taxes
Loss carryforwards	45.9
Operating loss carryforwards to expire or be refunded	45.9
Tax credit carryforwards	12.4
Tax credit carryforwards to expire or be refunded	$ 6.8

Income Taxes, U.S. statutory fe

Income Taxes, U.S. statutory federal tax rate (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Differences between the U.S. statutory federal tax rate and the Company's effective income tax rate
U.S. statutory federal tax rate (as a percent)	35.00%	35.00%	35.00%
State and local taxes (as a percent)	0.20%	0.10%	0.10%
Foreign earnings and dividends taxed at different rates (as a percent)	(9.10%)	(9.70%)	(8.80%)
Valuation allowance (as a percent)	0.10%	0.70%	0.30%
Tax Act - transition tax (as a percent)	19.20%
Tax Act - remeasurement of deferred tax liabilities, net (as a percent)	(2.80%)
Tax Act - change in indefinite reinvestment assertion (as a percent)	13.10%
Excess tax benefits related to stock-based compensation (as a percent)	(4.90%)
Impact of acquisition-related expenses (as a percent)		0.50%	0.10%
Other, net (as a percent)	0.30%	0.40%	(0.10%)
Effective tax rate (as a percent)	51.10%	27.00%	26.60%

Income Taxes, Deferred tax asse

Income Taxes, Deferred tax assets and liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets relating to:
Accrued liabilities and reserves	$ 31.7	$ 36.8
Operating loss and tax credit carry forwards	84.2	58.8
Pensions	27.8	64.7
Inventories	35.1	45.3
Employee benefits	29.8	43.4
Total deferred tax assets	208.6	249
Valuation allowance	(39.6)	(37.2)
Total deferred tax assets, net of valuation allowances	169	211.8
Deferred tax liabilities relating to:
Goodwill	135.5	185.9
Depreciation and amortization	61.8	67.6
Unremitted foreign earnings	176.6
Contingent consideration	4.3	6.6
Total deferred tax liabilities	378.2	260.1
Net deferred tax liability	209.2	48.3
Classification of deferred tax assets and liabilities, as reflected on the Consolidated Balance Sheets:
Deferred tax assets included in Intangibles, net and other long-term assets	32	29.4
Deferred income taxes	241.2	77.7
Net deferred tax liability, long-term	$ 209.2	$ 48.3

Income Taxes, Unrecognized tax

Income Taxes, Unrecognized tax benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes
Gross increases in unrecognized tax benefits related to acquisitions		$ 78.7
Reconciliation of the gross amounts of unrecognized tax benefits excluding interest and penalties
Unrecognized tax benefits as of January 1	$ 106.2	29.8	$ 27.7
Gross increases for tax positions in prior periods	32.7	81.9	0.3
Gross increases for tax positions in current period	2.4	7	2.1
Settlements	(11)	(10.8)
Lapse of statute of limitations	(3)	(1.7)	(0.3)
Unrecognized tax benefits at the end of the period	127.3	106.2	29.8
Estimated interest and penalties included in provision for income taxes	3.7	6.5	1.5
Tax-related interest and penalties liability for unrecognized tax benefits	39.3	35.3	$ 6
Liability for unrecognized tax benefits, including penalties and interest, which if recognized would impact the effective tax rate	130.1	$ 138.7
Unrecognized tax benefits, anticipated adjustment for changing facts and circumstances, over the next twelve month period	$ 38.4

Equity, Stock-based Comp Expens

Equity, Stock-based Comp Expense (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Expense incurred for stock-based compensation plans					$ 49.7	$ 47.6	$ 44.2
Recognized tax benefit related to stock-based compensation					78.3	11.4	11.3
Income tax expense (benefit)					691.7	308.5	280.5
Selling, General and Administrative Expenses
Expense incurred for stock-based compensation plans					49.7	$ 47.6	$ 44.2
Impact of ASU 2016-09
Income tax expense (benefit)	$ (20.8)	$ (16.6)	$ (21.2)	$ (8)	$ (66.6)

Equity, Stock Option and Restri

Equity, Stock Option and Restricted Shares (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
2000 Employee Option Plan
Stock-Based Compensation
Options exercisable period	10 years
2009 Employee Option Plan
Stock-Based Compensation
Number of additional stock options that will be granted (in shares)	0
Options ratable vesting period	5 years
Options exercisable period	10 years
2017 Employee Option Plan
Stock-Based Compensation
Common Stock reserved for issuance	30,000,000
Shares available for the granting of additional stock options	22,991,400
Options ratable vesting period	5 years
Options exercisable period	10 years
2004 Directors Option Plan
Stock-Based Compensation
Options exercisable period	10 years
Stock Options
Stock option activity
Options outstanding at the beginning of the period (in shares)	32,266,391	31,136,475	27,787,920
Options granted (in shares)	7,029,600	7,560,450	6,490,200
Options exercised (in shares)	(5,773,287)	(5,703,254)	(2,718,745)
Options forfeited (in shares)	(300,340)	(727,280)	(422,900)
Options outstanding at the end of the period (in shares)	33,222,364	32,266,391	31,136,475	27,787,920
Vested and non-vested options expected to vest at the end of the period (in shares)	31,214,883
Exercisable at the end of the period (in shares)	13,621,924
Weighted Average Exercise Price
Weighted average exercise price, options outstanding at the beginning of the period (in dollars per share)	$ 44.14	$ 37.62	$ 31.60
Weighted average exercise price, options granted (in dollars per share)	72.98	57.72	57.85
Weighted average exercise price, options exercised (in dollars per share)	31.87	25.80	23.71
Weighted average exercise price, options forfeited (in dollars per share)	55.16	50.17	41.73
Weighted average exercise price, options outstanding at the end of the period (in dollars per share)	52.27	$ 44.14	$ 37.62	$ 31.60
Weighted average exercise price, vested and non-vested options expected to vest (in dollars per share)	51.61
Weighted average exercise price, exercisable (in dollars per share)	$ 39.48
Weighted Average Remaining Contractual Term
Weighted average remaining contractual term of options outstanding	7 years 18 days	7 years 11 days	6 years 11 months 1 day	7 years 1 month 2 days
Weighted average remaining contractual term of options vested options and non-vested expected to vest	6 years 11 months 16 days
Weighted average remaining contractual term of options exercisable	5 years 4 months 24 days
Aggregate Intrinsic Value
Aggregate intrinsic value of options outstanding	$ 1,180.3
Aggregate intrinsic value of options, vested and non-vested options expected to vest	1,129.8
Aggregate intrinsic value of options exercisable	$ 658.2
Status of the Company's non-vested options and changes during the year
Non-vested options at the beginning of the period (in shares)	18,725,570
Options granted (in shares)	7,029,600	7,560,450	6,490,200
Non-vested options, options vested (in shares)	(5,854,390)
Non-vested options, options forfeited (in shares)	(300,340)
Non-vested options at the end of the period (in shares)	19,600,440	18,725,570
Weighted Average Fair Value at Grant Date
Weighted average fair value at the grant date, options outstanding at the beginning of the period (in dollars per share)	$ 7.99
Weighted average fair value at grant date, options granted (in dollars per share)	8.78	$ 7.39	$ 8.47
Weighted average fair value at grant date, options vested (in dollars per share)	7.91
Weighted average fair value at grant date, options forfeited (in dollars per share)	8.10
Weighted average fair value at the grant date, options outstanding at the end of the period (in dollars per share)	$ 8.29	$ 7.99
Fair Value at Grant Date
Total intrinsic value of stock options exercised (in dollars)	$ 268.7	$ 197.2	$ 88.1
Total fair value of stock options vested (in dollars)	46.3	$ 43.1	$ 39.9
Total compensation cost related to non-vested options not yet recognized (in dollars)	$ 120.3
Weighted average expected amortization period	3 years 3 months 18 days
Restricted Shares | 2012 Directors Restricted Stock Plan
Stock-Based Compensation
Shares available for the granting of additional stock options	124,164
Restricted share activity
Restricted shares outstanding at the beginning of the period (in shares)	16,905	17,256	18,340
Restricted shares granted (in shares)	12,905	16,905	17,948
Shares vested and issued (in shares)	(16,905)	(17,256)	(19,032)
Restricted shares outstanding at the end of the period (in shares)	12,905	16,905	17,256	18,340
Fair Value at Grant Date
Fair value at the grant date, restricted shares outstanding at the beginning of the period (in dollars per share)	$ 57.99	$ 57.97	$ 47.72
Fair value of restricted shares vested and issued (in dollar per share)	57.99	57.97	47.98
Fair value of restricted shares granted (in dollars per share)	73.25	57.99	57.85
Fair value at the grant date, restricted shares outstanding at the end of the period (in dollars per share)	$ 73.25	$ 57.99	$ 57.97	$ 47.72
Weighted Average Remaining Amortization Term (in years)	4 months 13 days	4 months 17 days	4 months 21 days	4 months 21 days
Total fair value of restricted share awards vested (in dollars)	$ 1	$ 1	$ 0.9
Total compensation cost related to non-vested restricted shares not yet recognized (in dollars)	$ 0.4
Weighted average expected amortization period	4 months 13 days

Equity, Stock Repurchase (Detai

Equity, Stock Repurchase (Details) - USD ($) shares in Millions, $ in Millions	Jan. 24, 2017	Jan. 31, 2018	Jan. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
2017 Stock Repurchase Program
Shareholders' Equity
Value of shares authorized to be repurchased	$ 1,000
Repurchase of stock program, period	2 years
Number of shares repurchased and retired				8.4
Payments for shares repurchased and retired (in dollars)				$ 618
Number of shares repurchased		1.1
Payments for shares repurchased (in dollars)		$ 105.5
Value of shares remaining that may be repurchased under the stock repurchase program		$ 276.5
2015 Stock Repurchase Program
Shareholders' Equity
Number of shares authorized to be repurchased under the current open-market stock repurchase program			10
Repurchase of stock program, period			2 years
Number of shares repurchased and retired					5.5	4.5
Payments for shares repurchased and retired (in dollars)					$ 325.8	$ 248.9

Equity, Dividends (Details)

Equity, Dividends (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended												12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity
Dividends declared per common share (in dollars per share)	$ 0.19	$ 0.19	$ 0.16	$ 0.16	$ 0.16	$ 0.14	$ 0.14	$ 0.14	$ 0.14	$ 0.14	$ 0.125	$ 0.125	$ 0.7	$ 0.58	$ 0.53
Dividends declared													$ 213.7	$ 178.8	$ 163.7
Dividends paid													$ 205	$ 172.7	$ 159.3

Equity, Accumulated Other Compr

Equity, Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Increase (Decrease) In Accumulated Other Comprehensive Income (Loss)
Balance at beginning of period	$ 3,674.9
Balance at end of period	3,989.8	$ 3,674.9
Accumulated Other Comprehensive Loss
Increase (Decrease) In Accumulated Other Comprehensive Income (Loss)
Balance at beginning of period	(469)	(349.5)	$ (205.8)
Other comprehensive income (loss) before reclassification, net of tax	250.9	(135.8)	(161.9)
Amounts reclassified from Accumulated other comprehensive income (loss) to earnings, net of tax	17.1	16.3	18.2
Balance at end of period	(201)	(469)	(349.5)
Foreign Currency Translation Adjustments
Increase (Decrease) In Accumulated Other Comprehensive Income (Loss)
Balance at beginning of period	(273.5)	(164.9)	(13.4)
Other comprehensive income (loss) before reclassification, net of tax	240.3	(108.6)	(151.5)
Balance at end of period	(33.2)	(273.5)	(164.9)
Foreign currency translation adjustments, tax	0	0	0
Unrealized Gain (Loss) on Cash Flow Hedges
Increase (Decrease) In Accumulated Other Comprehensive Income (Loss)
Balance at beginning of period	(0.1)	(1.7)	(1.3)
Other comprehensive income (loss) before reclassification, net of tax	(0.1)	1.6	(0.4)
Balance at end of period	(0.2)	(0.1)	(1.7)
Unrealized loss on cash flow hedges, tax	0.1	(0.3)	0.1
Defined Benefit Plan Adjustment
Increase (Decrease) In Accumulated Other Comprehensive Income (Loss)
Balance at beginning of period	(195.4)	(182.9)	(191.1)
Other comprehensive income (loss) before reclassification, net of tax	10.7	(28.8)	(10)
Amounts reclassified from Accumulated other comprehensive income (loss) to earnings, net of tax	17.1	16.3	18.2
Balance at end of period	(167.6)	(195.4)	(182.9)
Defined benefit plan, before reclassification, tax	(3.4)	12.3	5.5
Amounts reclassified from Accumulated Other Comprehensive Income (Loss), tax	$ (9.1)	$ (8.9)	$ (10.1)

Earnings Per Share, ASU 2016-09

Earnings Per Share, ASU 2016-09 (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Adoption of ASU 2016-09
Effect of dilutive stock options (in shares)	10.8	6.9	7.4
Impact of ASU 2016-09
Adoption of ASU 2016-09
Effect of dilutive stock options (in shares)	2

Earnings Per Share, Reconciliat

Earnings Per Share, Reconciliation (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share
Net income attributable to Amphenol Corporation shareholders									$ 650.5	$ 822.9	$ 763.5
Basic weighted average common shares outstanding (in shares)									305.7	308.3	309.1
Effect of dilutive stock options (in shares)									10.8	6.9	7.4
Diluted weighted average common shares outstanding (in shares)									316.5	315.2	316.5
Earnings per share attributable to Amphenol Corporation shareholders:
Basic (in dollars per share)	$ (0.34)	$ 0.91	$ 0.82	$ 0.73	$ 0.76	$ 0.73	$ 0.67	$ 0.51	$ 2.13	$ 2.67	$ 2.47
Diluted (in dollars per share)	$ (0.34)	$ 0.88	$ 0.80	$ 0.71	$ 0.75	$ 0.71	$ 0.65	$ 0.50	$ 2.06	$ 2.61	$ 2.41
Anti-dilutive common shares
Anti-dilutive stock options, excluded from the computations of earning per share (in shares)	12.4								1.6	8.5	6.3

Benefit Plans and Other Postr60

Benefit Plans and Other Postretirement Benefits, Benefit obligation and plan assets (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amounts recognized in the balance sheet as of December 31:
Accrued pension and postretirement benefit obligations		$ 272	$ 288.4
Accumulated other comprehensive loss, net		$ (201)	$ (469)
U.S.
Weighted average assumptions used to determine projected benefit obligations:
Rate of compensation increase (as a percent)		3.00%	3.00%
International Plans
Weighted average assumptions used to determine projected benefit obligations:
Rate of compensation increase (as a percent)		1.70%	1.63%
Pension Benefits
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$ 741.7	$ 703.3	$ 635.2
Service cost		9.6	9	$ 9.3
Interest cost		20	20.9	22.8
Acquisitions			47.4
Plan amendments			3.7
Actuarial (gain) loss		18.9	39.6
Foreign exchange translation		26.7	(17.3)
Benefits paid		(36.8)	(35.2)
Projected benefit obligation at end of year		741.7	703.3	635.2
Change in plan assets:
Fair value of plan assets at the beginning of the year	497.9	439.9	392.2
Actual return on plan assets		62.4	31.8
Employer contributions		22.5	22.2	20.9
Acquisitions			36.7
Foreign exchange translation		9.9	(7.8)
Benefits paid		(36.8)	(35.2)
Fair value of plan assets at end of year		497.9	439.9	392.2
Underfunded status at end of year		243.8	263.4
Amounts recognized in the balance sheet as of December 31:
Other accrued expenses		3.1	2.8
Accrued pension and postretirement benefit obligations		240.7	260.6
Accumulated other comprehensive loss, net		(164.4)	(191.8)
Accumulated benefit obligation
Accumulated benefit obligation		731.2	691.1
Pension Benefits | U.S.
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	486.7	469.8	460.8
Service cost		6.7	6.2	6.5
Interest cost		15.3	15.4	17.4
Plan amendments			3.7
Actuarial (gain) loss		21.1	11.6
Benefits paid		(26.2)	(27.9)
Projected benefit obligation at end of year		486.7	469.8	460.8
Change in plan assets:
Fair value of plan assets at the beginning of the year	389.6	342.1	333.2
Actual return on plan assets		57.2	20.4
Employer contributions	80	16.5	16.4
Benefits paid		(26.2)	(27.9)
Fair value of plan assets at end of year		389.6	342.1	333.2
Underfunded status at end of year		97.1	127.7
Amounts recognized in the balance sheet as of December 31:
Accrued pension and postretirement benefit obligations		97.1	127.7
Accumulated other comprehensive loss, net		$ (110.5)	$ (129.3)
Weighted average assumptions used to determine projected benefit obligations:
Benefit obligation discount rate (as a percent)		3.48%	3.93%
Accumulated benefit obligation
Accumulated benefit obligation		$ 484.4	$ 465.8
Pension Benefits | International Plans
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	255	233.5	174.4
Service cost		2.9	2.8	2.8
Interest cost		4.7	5.5	5.4
Acquisitions			47.4
Actuarial (gain) loss		(2.2)	28
Foreign exchange translation		26.7	(17.3)
Benefits paid		(10.6)	(7.3)
Projected benefit obligation at end of year		255	233.5	174.4
Change in plan assets:
Fair value of plan assets at the beginning of the year	108.3	97.8	59
Actual return on plan assets		5.2	11.4
Employer contributions		6	5.8
Acquisitions			36.7
Foreign exchange translation		9.9	(7.8)
Benefits paid		(10.6)	(7.3)
Fair value of plan assets at end of year		108.3	97.8	$ 59
Underfunded status at end of year		146.7	135.7
Amounts recognized in the balance sheet as of December 31:
Other accrued expenses		3.1	2.8
Accrued pension and postretirement benefit obligations		143.6	132.9
Accumulated other comprehensive loss, net		$ (53.9)	$ (62.5)
Weighted average assumptions used to determine projected benefit obligations:
Benefit obligation discount rate (as a percent)		2.21%	2.28%
Accumulated benefit obligation
Accumulated benefit obligation		$ 246.8	$ 225.3
Largest international pension plan | Pension Benefits | Unfunded Plan | International Plans
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$ 93	81.7
Projected benefit obligation at end of year		$ 93	$ 81.7

Benefit Plans and Other Postr61

Benefit Plans and Other Postretirement Benefits, Net pension expense (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
U.S.
Weighted average assumptions used to determine net periodic benefit cost/expense:
Rate of compensation increase (as a percent)		3.00%	3.00%	3.00%
International Plans
Weighted average assumptions used to determine net periodic benefit cost/expense:
Rate of compensation increase (as a percent)		1.63%	1.61%	1.45%
Pension Benefits
Defined Benefit Plan Disclosure
Plan contributions by employer		$ 22.5	$ 22.2	$ 20.9
Components of net pension expense:
Service cost		9.6	9	9.3
Interest cost		20	20.9	22.8
Expected return on plan assets		(30.7)	(30.1)	(29.1)
Amortization of prior service cost		2.7	2.4	2.3
Amortization of net actuarial losses		22.9	22	25.7
Net pension expense		24.5	24.2	31
Pension Benefits | U.S.
Defined Benefit Plan Disclosure
Plan contributions by employer	$ 80	16.5	16.4
Components of net pension expense:
Service cost		6.7	6.2	6.5
Interest cost		15.3	15.4	17.4
Expected return on plan assets		(27.2)	(26.2)	(25.9)
Amortization of prior service cost		2.7	2.4	2.3
Amortization of net actuarial losses		18.3	18.6	21.5
Net pension expense		$ 15.8	$ 16.4	$ 21.8
Weighted average assumptions used to determine net periodic benefit cost/expense:
Discount rate (as a percent)		3.93%	4.11%	3.75%
Expected long-term return on assets (as a percent)		7.75%	7.75%	8.00%
Pension Benefits | International Plans
Defined Benefit Plan Disclosure
Plan contributions by employer		$ 6	$ 5.8
Components of net pension expense:
Service cost		2.9	2.8	$ 2.8
Interest cost		4.7	5.5	5.4
Expected return on plan assets		(3.5)	(3.9)	(3.2)
Amortization of net actuarial losses		4.6	3.4	4.2
Net pension expense		$ 8.7	$ 7.8	$ 9.2
Weighted average assumptions used to determine net periodic benefit cost/expense:
Discount rate (as a percent)		2.28%	2.96%	2.91%
Expected long-term return on assets (as a percent)		3.80%	4.29%	5.47%

Benefit Plans and Other Postr62

Benefit Plans and Other Postretirement Benefits, Weighted-average assumptions (Details) - Pension Benefits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
U.S.
Weighted-average assumptions used to determine benefit obligations
Benefit obligation discount rate (as a percent)	3.48%	3.93%
Increase (decrease) in benefit obligation due to change in discount rate	$ 24
International Plans
Weighted-average assumptions used to determine benefit obligations
Benefit obligation discount rate (as a percent)	2.21%	2.28%

Benefit Plans and Other Postr63

Benefit Plans and Other Postretirement Benefits, Expected long-term rate of return (Details) - Pension Benefits - U.S.	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure
Historical compounded return on plan assets (as a percent)	8.75%
Expected long-term return on assets (as a percent)	7.75%	7.75%	8.00%
Equity securities
Defined Benefit Plan Disclosure
Target allocation (as a percent)	60.00%
Plan asset allocations, assumptions (as a percent)	60.00%
Equity securities | Minimum
Defined Benefit Plan Disclosure
Expected long-term return on assets (as a percent)	8.00%
Equity securities | Maximum
Defined Benefit Plan Disclosure
Expected long-term return on assets (as a percent)	9.00%
Fixed income securities
Defined Benefit Plan Disclosure
Target allocation (as a percent)	40.00%
Plan asset allocations, assumptions (as a percent)	40.00%
Fixed income securities | Minimum
Defined Benefit Plan Disclosure
Expected long-term return on assets (as a percent)	5.00%
Fixed income securities | Maximum
Defined Benefit Plan Disclosure
Expected long-term return on assets (as a percent)	6.00%

Benefit Plans and Other Postr64

Benefit Plans and Other Postretirement Benefits, Fair value measurements of plan assets (Details) - Pension Benefits - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure
Fair value of pension plan assets	$ 497.9	$ 439.9	$ 392.2
U.S. equities — large cap
Defined Benefit Plan Disclosure
Fair value of pension plan assets	141.5	118.8
U.S. equities — small/mid cap and other
Defined Benefit Plan Disclosure
Fair value of pension plan assets	22	25.8
International equities — growth
Defined Benefit Plan Disclosure
Fair value of pension plan assets	35.6	46.5
International equities — other
Defined Benefit Plan Disclosure
Fair value of pension plan assets	95.5	60.6
Alternative investment funds
Defined Benefit Plan Disclosure
Fair value of pension plan assets	12.9	12.6
U.S. fixed income securities — short term
Defined Benefit Plan Disclosure
Fair value of pension plan assets	6.1	6
U.S. fixed income securities — intermediate term
Defined Benefit Plan Disclosure
Fair value of pension plan assets	61.4	58.4
U.S. fixed income securities — high yield
Defined Benefit Plan Disclosure
Fair value of pension plan assets	21.9	22.2
International fixed income securities — other
Defined Benefit Plan Disclosure
Fair value of pension plan assets	47.4	43
Insurance contracts
Defined Benefit Plan Disclosure
Fair value of pension plan assets	37.9	34
Real estate funds
Defined Benefit Plan Disclosure
Fair value of pension plan assets	7
Cash and cash equivalents
Defined Benefit Plan Disclosure
Fair value of pension plan assets	8.7	12
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure
Fair value of pension plan assets	207.1	212.6
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. equities — large cap
Defined Benefit Plan Disclosure
Fair value of pension plan assets	106.6	88.7
Quoted Prices in Active Markets for Identical Assets (Level 1) | International equities — growth
Defined Benefit Plan Disclosure
Fair value of pension plan assets	30.4	46.5
Quoted Prices in Active Markets for Identical Assets (Level 1) | International equities — other
Defined Benefit Plan Disclosure
Fair value of pension plan assets		7
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. fixed income securities — intermediate term
Defined Benefit Plan Disclosure
Fair value of pension plan assets	61.4	58.4
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash and cash equivalents
Defined Benefit Plan Disclosure
Fair value of pension plan assets	8.7	12
Significant Observable Inputs (Level 2)
Defined Benefit Plan Disclosure
Fair value of pension plan assets	172.1	155
Significant Observable Inputs (Level 2) | U.S. equities — large cap
Defined Benefit Plan Disclosure
Fair value of pension plan assets	34.9	30.1
Significant Observable Inputs (Level 2) | U.S. equities — small/mid cap and other
Defined Benefit Plan Disclosure
Fair value of pension plan assets	22	25.8
Significant Observable Inputs (Level 2) | International equities — growth
Defined Benefit Plan Disclosure
Fair value of pension plan assets	5.2
Significant Observable Inputs (Level 2) | International equities — other
Defined Benefit Plan Disclosure
Fair value of pension plan assets	40.7	33.9
Significant Observable Inputs (Level 2) | U.S. fixed income securities — high yield
Defined Benefit Plan Disclosure
Fair value of pension plan assets	21.9	22.2
Significant Observable Inputs (Level 2) | International fixed income securities — other
Defined Benefit Plan Disclosure
Fair value of pension plan assets	47.4	43
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure
Fair value of pension plan assets	44.9	34
Significant Unobservable Inputs (Level 3) | Insurance contracts
Defined Benefit Plan Disclosure
Fair value of pension plan assets	37.9	34
Significant Unobservable Inputs (Level 3) | Real estate funds
Defined Benefit Plan Disclosure
Fair value of pension plan assets	7
Fair Value Measured At Net Asset Value
Defined Benefit Plan Disclosure
Fair value of pension plan assets	73.8	38.3
Fair Value Measured At Net Asset Value | International equities — other
Defined Benefit Plan Disclosure
Fair value of pension plan assets	54.8	19.7
Fair Value Measured At Net Asset Value | Alternative investment funds
Defined Benefit Plan Disclosure
Fair value of pension plan assets	12.9	12.6
Fair Value Measured At Net Asset Value | U.S. fixed income securities — short term
Defined Benefit Plan Disclosure
Fair value of pension plan assets	$ 6.1	$ 6

Benefit Plans and Other Postr65

Benefit Plans and Other Postretirement Benefits, Level 3 plan assets (Details) - Pension Benefits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure
Fair value of plan assets at the beginning of the year	$ 439.9	$ 392.2
Additions due to acquisitions		36.7
Foreign currency translation	9.9	(7.8)
Fair value of plan assets at end of year	497.9	439.9
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure
Fair value of plan assets at the beginning of the year	34
Additions due to acquisitions		34.3
Unrealized gains (losses), net	0.6	2.7
Purchases, sales and settlements, net	5.8	(0.9)
Foreign currency translation	4.5	(2.1)
Fair value of plan assets at end of year	$ 44.9	$ 34

Benefit Plans and Other Postr66

Benefit Plans and Other Postretirement Benefits, Other (Details) - Pension Benefits - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated other comprehensive income (loss), before tax
Net loss		$ 237.7	$ 265.7
Net prior service cost		7.7	10.5
Expected to be amortized from Accumulated other comprehensive loss over next fiscal year
Net loss that will be amortized from Accumulated other comprehensive loss into net periodic benefit cost over the next fiscal year		23.4
Prior service cost that will be amortized from Accumulated other comprehensive loss into net periodic benefit cost over the next fiscal year		2.3
Defined Benefit Plan, Contributions
Plan contributions by employer		22.5	22.2	$ 20.9
Estimated future employer contribution in next fiscal year		90
Expected benefits payments
2,018		32.3
2,019		32.9
2,020		34.2
2,021		37
2,022		38.3
2023-2027		202.3
U.S.
Accumulated other comprehensive income (loss), before tax
Net loss		167.7	194.7
Net prior service cost		7.7	10.5
Defined Benefit Plan, Contributions
Plan contributions by employer	$ 80	16.5	16.4
Expected benefits payments
2,018		24.8
2,019		25.8
2,020		26.9
2,021		27.8
2,022		28.9
2023-2027		151.2
International Plans
Accumulated other comprehensive income (loss), before tax
Net loss		70	71
Defined Benefit Plan, Contributions
Plan contributions by employer		6	5.8
Expected benefits payments
2,018		7.5
2,019		7.1
2,020		7.3
2,021		9.2
2,022		9.4
2023-2027		51.1
Net liability
Net liability for foreign subsidiaries with benefits under local statutory plans		$ 16.6	$ 13.9

Benefit Plans and Other Postr67

Benefit Plans and Other Postretirement Benefits, OPEB benefit obligation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amounts recognized in the balance sheet as of December 31:
Accrued pension and postretirement benefit obligations	$ 272	$ 288.4
Accumulated other comprehensive loss, net	(201)	(469)
Other Postretirement Benefits
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	13.6	13.2
Interest cost	0.4	0.4	$ 0.4
Benefits paid	(0.9)	(0.9)
Actuarial (gain) loss		0.9
Projected benefit obligation at end of year	13.1	13.6	$ 13.2
Amounts recognized in the balance sheet as of December 31:
Other accrued expenses	1.2	1.2
Accrued pension and postretirement benefit obligations	11.9	12.4
Underfunded status at end of year	13.1	13.6
Accumulated other comprehensive loss, net	$ (3.2)	$ (3.6)
Weighted average assumptions used to determine projected benefit obligations:
Benefit obligation discount rate (as a percent)	3.29%	3.65%

Benefit Plans and Other Postr68

Benefit Plans and Other PostretirementBenefits, OPEB benefit expense (Details) - Other Postretirement Benefits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components of net pension expense:
Service cost			$ 0.1
Interest cost	$ 0.4	$ 0.4	0.4
Amortization of net actuarial losses	0.5	0.7	0.3
Net pension expense	$ 0.9	$ 1.1	$ 0.8
Weighted average assumptions used to determine net periodic benefit cost/expense:
Discount rate (as a percent)	3.65%	3.71%	3.50%

Benefit Plans and Other Postr69

Benefit Plans and Other Postretirement Benefits, OPEB other (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Assumed Health Care Cost Trend Rates
Health care cost trend rate assumed for next year (as a percent)	7.75%	8.25%
Health care cost trend rate (as a percent)	4.75%
Other Postretirement Benefits
Accumulated other comprehensive income (loss), before tax
Net loss	$ 5.1	$ 5.7
Net prior service cost	0	0
Net transition asset	0	$ 0
Expected to be amortized from Accumulated other comprehensive loss over next fiscal year
Net loss that will be amortized from Accumulated other comprehensive loss into net periodic benefit cost over the next fiscal year	0.6
Prior service cost that will be amortized from Accumulated other comprehensive loss into net periodic benefit cost over the next fiscal year	0
Net transition asset (obligation) that will be amortized from Accumulated other comprehensive loss into net periodic benefit cost over the next fiscal year	0
Other Postretirement Benefits | Minimum
Expected benefit payments
Benefit payments per year, including amounts to be paid out of Company assets and reflecting future expected services, for the next ten years	1.2
Other Postretirement Benefits | Maximum
Expected benefit payments
Benefit payments per year, including amounts to be paid out of Company assets and reflecting future expected services, for the next ten years	$ 1.5

Benefit Plans and Other Postr70

Benefit Plans and Other Postretirement Benefits, Defined contribution plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Benefit Plans and Other Postretirement Benefits
Contributions to U.S. defined contribution plans by the Company, maximum percentage of eligible compensation	5.00%
Matching contributions to U.S. defined contribution plans by the Company	$ 6.9	$ 5	$ 4.2

Leases (Details)

Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Leases
Rent expense under operating leases	$ 58.5	$ 50.5	$ 41
Minimum lease payments under non-cancelable operating leases
2,018	53.2
2,019	37.3
2,020	23.7
2,021	15.5
2,022	10.2
Beyond 2,022	21.3
Total minimum obligation	$ 161.2

Acquisitions (Details)

Acquisitions (Details) - USD ($) $ in Millions	Jan. 08, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Acquisitions
Purchase price, net of cash acquired		$ 265.5	$ 1,305.1	$ 199.8
FCI Asia Pte Ltd (“FCI”)
Acquisitions
Purchase price, net of cash acquired	$ 1,178.6

Acquisitions, Other (Details)

Acquisitions, Other (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)
Acquisitions
Foreign exchange negative impact on net sales	$ 61.3
Net sales increase compared to prior period, excluding the impact of foreign exchange and acquisitions (as a percent)	2.00%

Acquisitions, Pro Forma Financi

Acquisitions, Pro Forma Financial Information (Details) - FCI Asia Pte Ltd (“FCI”) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Pro forma adjustments
Net sales	$ 6,296.1	$ 6,137.3
Net income attributable to Amphenol Corporation	$ 856.2	$ 799.3
Net income per common share - Diluted	$ 2.72	$ 2.53
Acquisition-related expenses included in reported results, but excluded from proforma amounts
Pro forma adjustments
Net income attributable to Amphenol Corporation	$ 33.1	$ 5.7
Amortization expense related to acquired intangible assets not reflected in historical results, but included in pro forma amounts
Pro forma adjustments
Net income attributable to Amphenol Corporation		(8.8)
Interest income of funds used to fund the acquisition included in historical results, but excluded from pro forma amounts
Pro forma adjustments
Net income attributable to Amphenol Corporation		(11.6)
Other income included in historical results, but excluded from pro forma amounts
Pro forma adjustments
Net income attributable to Amphenol Corporation		$ (4.8)

Acquisitions, Acquisition-relat

Acquisitions, Acquisition-related Expenses (Details) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Jun. 30, 2017	Sep. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Acquisitions
Acquisition-related expenses	$ 4			$ 4	$ 36.6	$ 5.7
Acquisition-related expenses, net of tax	$ 3.7
FCI Asia Pte Ltd (“FCI”)
Acquisitions
Acquisition-related expenses			$ 30.3
Acquisition-related expenses, net of tax			$ 27.3			$ 5.7
Other
Acquisitions
Acquisition-related expenses		$ 6.3
Acquisition-related expenses, net of tax		$ 5.8

Goodwill and Other Intangible76

Goodwill and Other Intangible Assets, Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill.
Goodwill, Beginning Balance	$ 3,678.8	$ 2,692.9
Acquisition-related	233.8	1,031.3
Foreign currency translation	130	(45.4)
Goodwill, Ending Balance	4,042.6	3,678.8
Interconnect Products and Assemblies
Goodwill.
Goodwill, Beginning Balance	3,532.5	2,569.2
Acquisition-related	233.6	1,008.7
Foreign currency translation	130	(45.4)
Goodwill, Ending Balance	3,896.1	3,532.5
Cable Products and Solutions
Goodwill.
Goodwill, Beginning Balance	146.3	123.7
Acquisition-related	0.2	22.6
Goodwill, Ending Balance	$ 146.5	$ 146.3

Goodwill and Other Intangible77

Goodwill and Other Intangible Assets, Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Intangible Assets
Weighted average useful lives of acquired amortizable intangible assets	10 years
Gross Carrying Amount (definite-lived)	$ 539.6	$ 521.8
Intangible assets, gross (excluding goodwill)	725.7	707.9
Accumulated Amortization	284.1	233.5
Net Carrying Amount, (definite-lived)	255.5	288.3
Indefinite-lived trade name intangible asset	186.1	186.1
Net Carrying Amount, intangible assets	$ 441.6	474.4
Customer relationships
Intangible Assets
Weighted average useful lives of acquired amortizable intangible assets	10 years
Gross Carrying Amount (definite-lived)	$ 398.1	381.1
Accumulated Amortization	199.8	159.1
Net Carrying Amount, (definite-lived)	$ 198.3	222
Proprietary technology
Intangible Assets
Weighted average useful lives of acquired amortizable intangible assets	11 years
Gross Carrying Amount (definite-lived)	$ 107.5	106.7
Accumulated Amortization	50.7	40.9
Net Carrying Amount, (definite-lived)	$ 56.8	65.8
Backlog and other
Intangible Assets
Weighted average useful lives of acquired amortizable intangible assets	2 years
Gross Carrying Amount (definite-lived)	$ 34	34
Accumulated Amortization	33.6	33.5
Net Carrying Amount, (definite-lived)	$ 0.4	$ 0.5

Goodwill and Other Intangible78

Goodwill and Other Intangible Assets, Amortization (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangible assets
Amortization expense	$ 48.6	$ 54.6	$ 34.7
Amortization expense estimated for each of the next five fiscal years
2,018	46.5
2,019	42.6
2,020	37.2
2,021	32
2,022	$ 24.2
Backlog
Intangible assets
Amortization expense		$ 8

Reportable Business Segments 79

Reportable Business Segments and International Operations (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2017USD ($)segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Segment reporting information
Number of reportable business segments | segment									2
Net sales	$ 1,943.9	$ 1,840.8	$ 1,666.5	$ 1,560.1	$ 1,651.1	$ 1,635.9	$ 1,548.2	$ 1,451.2	$ 7,011.3	$ 6,286.4	$ 5,568.7
Depreciation and amortization									226.8	217	171.6
Segment operating income	399.4	$ 377.9	$ 336.2	$ 314.1	339.1	$ 326.3	$ 300.3	$ 239.4	1,427.6	1,205.2	1,104.7
Segment assets (excluding goodwill)	5,932.9				4,784.6				5,932.9	4,784.6
Operating Segment
Segment reporting information
Net sales									7,011.3	6,286.4	5,568.7
Depreciation and amortization									221	211.7	165.3
Segment operating income									1,529.4	1,333.1	1,198.6
Segment assets (excluding goodwill)	5,932.9				4,784.6				5,932.9	4,784.6	4,743.9
Capital expenditures									226	190.2	171.6
Operating Segment | Interconnect Products and Assemblies
Segment reporting information
Net sales									6,606.9	5,922.3	5,239.1
Depreciation and amortization									214.7	206.8	162.3
Segment operating income									1,475.2	1,280.3	1,158.3
Segment assets (excluding goodwill)	5,732.6				4,587.5				5,732.6	4,587.5	4,580.4
Capital expenditures									220.4	186.2	167.1
Operating Segment | Cable Products and Solutions
Segment reporting information
Net sales									404.4	364.1	329.6
Depreciation and amortization									6.3	4.9	3
Segment operating income									54.2	52.8	40.3
Segment assets (excluding goodwill)	$ 200.3				$ 197.1				200.3	197.1	163.5
Capital expenditures									5.6	4	4.5
Inter-Segment
Segment reporting information
Net sales									50.4	36.9	28.8
Inter-Segment | Interconnect Products and Assemblies
Segment reporting information
Net sales									9.7	6.9	7.2
Inter-Segment | Cable Products and Solutions
Segment reporting information
Net sales									$ 40.7	$ 30	$ 21.6

Reportable Business Segments 80

Reportable Business Segments and International Operations, Reconciliation of Segment Operating Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of segment operating income to consolidated income before income taxes
Segment operating income	$ 399.4	$ 377.9	$ 336.2	$ 314.1	$ 339.1	$ 326.3	$ 300.3	$ 239.4	$ 1,427.6	$ 1,205.2	$ 1,104.7
Interest expense									(92.3)	(72.6)	(68.3)
Other income, net									17.1	8.5	16.4
Stock-based compensation expense									(49.7)	(47.6)	(44.2)
Acquisition-related expenses			$ (4)						(4)	(36.6)	(5.7)
Other operating expenses									(48.1)	(43.7)	(44)
Income before income taxes									1,352.4	1,141.1	1,052.8
Operating Segment
Reconciliation of segment operating income to consolidated income before income taxes
Segment operating income									$ 1,529.4	$ 1,333.1	$ 1,198.6

Reportable Business Segments 81

Reportable Business Segments and International Operations, Reconciliation of Segment Assets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of segment assets to consolidated total assets
Segment assets excluding goodwill	$ 5,932.9	$ 4,784.6
Goodwill	4,042.6	3,678.8	$ 2,692.9
Other assets	28.4	35.3
Total assets	$ 10,003.9	$ 8,498.7

Reportable Business Segments 82

Reportable Business Segments and International Operations, Geographic information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues and long-lived assets by geographical area
Net sales	$ 1,943.9	$ 1,840.8	$ 1,666.5	$ 1,560.1	$ 1,651.1	$ 1,635.9	$ 1,548.2	$ 1,451.2	$ 7,011.3	$ 6,286.4	$ 5,568.7
Property, plant and equipment, net	816.8				711.4				816.8	711.4	$ 609.5
Net sales | Customer risk | Largest Customer
Concentration risk
Concentration of net sales (as a percent)											11.00%
U.S.
Revenues and long-lived assets by geographical area
Net sales									1,978.4	1,740.7	$ 1,696.3
Property, plant and equipment, net	212.7				209.2				212.7	209.2	214.4
China
Revenues and long-lived assets by geographical area
Net sales									2,067.3	1,865.6	1,675.5
Property, plant and equipment, net	244.7				200.1				244.7	200.1	151.4
Other international locations
Revenues and long-lived assets by geographical area
Net sales									2,965.6	2,680.1	2,196.9
Property, plant and equipment, net	$ 359.4				$ 302.1				$ 359.4	$ 302.1	$ 243.7

Other Income, net (Details)

Other Income, net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Income, net
Agency and commitment fees	$ (3.1)	$ (3)	$ (2)
Interest income	20.2	11.5	18.4
Other income, net	$ 17.1	$ 8.5	$ 16.4

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Millions	Dec. 31, 2017USD ($)
Commitments and Contingencies
Purchase commitments of certain goods and services in 2018	$ 286.9
Purchase commitments of certain goods and service in 2019 and 2020	56.2
Purchase commitments of certain goods and services after 2020	$ 2.5

Selected Quarterly Financial 85

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Selected Quarterly Financial Data (Unaudited)
Net sales	$ 1,943.9	$ 1,840.8	$ 1,666.5	$ 1,560.1	$ 1,651.1	$ 1,635.9	$ 1,548.2	$ 1,451.2	$ 7,011.3	$ 6,286.4	$ 5,568.7
Gross Profit	635.4	606.1	552.6	515.9	546.1	537.3	497.3	459.2	2,309.9	2,040	1,779.5
Operating income	399.4	377.9	336.2	314.1	339.1	326.3	300.3	239.4	1,427.6	1,205.2	1,104.7
Net income (loss)	(100.4)	280.3	253.6	227.3	238.3	227.1	208.7	158.4	660.7	832.6	772.3
Net income (loss) attributable to Amphenol Corporation shareholders	$ (103.4)	$ 277.5	$ 251.5	$ 224.9	$ 235.4	$ 224.3	$ 206.5	$ 156.6	$ 650.5	$ 822.9	$ 763.5
Net income (loss) per common share — Basic (in dollars per share)	$ (0.34)	$ 0.91	$ 0.82	$ 0.73	$ 0.76	$ 0.73	$ 0.67	$ 0.51	$ 2.13	$ 2.67	$ 2.47
Net income (loss) per common share—Diluted (in dollars per share)	$ (0.34)	$ 0.88	$ 0.80	$ 0.71	$ 0.75	$ 0.71	$ 0.65	$ 0.50	$ 2.06	$ 2.61	$ 2.41

Selected Quarterly Financial 86

Selected Quarterly Financial Data (Unaudited), Additional Information (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income tax expense (benefit)									$ 691.7	$ 308.5	$ 280.5
Net income	$ (100.4)	$ 280.3	$ 253.6	$ 227.3	$ 238.3	$ 227.1	$ 208.7	$ 158.4	660.7	832.6	772.3
Net income attributable to Amphenol Corporation shareholders	$ (103.4)	$ 277.5	$ 251.5	$ 224.9	$ 235.4	$ 224.3	$ 206.5	$ 156.6	$ 650.5	$ 822.9	$ 763.5
Net income (loss) per common share—Diluted (in dollars per share)	$ (0.34)	$ 0.88	$ 0.80	$ 0.71	$ 0.75	$ 0.71	$ 0.65	$ 0.50	$ 2.06	$ 2.61	$ 2.41
Operating income	$ 399.4	$ 377.9	$ 336.2	$ 314.1	$ 339.1	$ 326.3	$ 300.3	$ 239.4	$ 1,427.6	$ 1,205.2	$ 1,104.7
Acquisition-related expenses			4						$ 4	$ 36.6	$ 5.7
Acquisition-related expenses, net of tax			3.7
Provisional Tax Act Charge	$ 398.5
Impact on earnings per share related to Tax Cuts and Jobs Act (in dollars per share)	$ (1.26)
Anti-dilutive stock options, excluded from the computations of earning per share (in shares)	12.4								1.6	8.5	6.3
Earnings per share - diluted change (in dollars per share)	$ 0.01
Operating income (loss), aggregate effect			(4)
Net income, aggregate effect	$ (377.7)		17.5
Net income attributable to Amphenol Corporation shareholders, aggregate effect	$ (377.7)		$ 17.5
Earnings per share - diluted, aggregate effect (in dollars per share)	$ (1.20)		$ 0.06
FCI Asia Pte Ltd (“FCI”)
Acquisition-related expenses								30.3
Acquisition-related expenses, net of tax								27.3			$ 5.7
Acquisition-related costs
Net income						(5.8)
Net income attributable to Amphenol Corporation shareholders						$ (5.8)
Net income (loss) per common share—Diluted (in dollars per share)			$ (0.01)			$ (0.02)
Operating income						$ (6.3)
Acquisition-related expenses			$ 4
Acquisition-related expenses, net of tax			3.7
Acquisition-related costs | FCI Asia Pte Ltd (“FCI”)
Net income								(27.3)
Net income attributable to Amphenol Corporation shareholders								$ (27.3)
Net income (loss) per common share—Diluted (in dollars per share)								$ (0.09)
Operating income								$ (30.3)
Impact of ASU 2016-09
Income tax expense (benefit)	$ (20.8)	(16.6)	$ (21.2)	(8)					$ (66.6)
Net income		16.6		8
Net income attributable to Amphenol Corporation shareholders		$ 16.6		$ 8
Net income (loss) per common share—Diluted (in dollars per share)	$ 0.07	$ 0.05	$ 0.07	$ 0.02

SCHEDULE II - VALUATION AND QUA

SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts
Valuation and Qualifying Accounts
Balance at beginning of period	$ 23.6	$ 25.6	$ 20.2
Charged to cost and expenses	1.8	6	3.7
Additions (Deductions)	(2.4)	(8)	1.7
Balance at end of period	23	23.6	25.6
Valuation allowance on deferred tax assets
Valuation and Qualifying Accounts
Balance at beginning of period	37.2	18.5	15.5
Charged to cost and expenses	2.5	4.8	3
Additions (Deductions)	(0.1)	13.9
Balance at end of period	$ 39.6	$ 37.2	$ 18.5