Amkor Technology (AMKR) 10-Q 31 Oct 19 2019 Q3 Quarterly report Financial data

Cover

Cover - shares	9 Months Ended
	Sep. 30, 2019	Oct. 25, 2019
Cover page.
Entity Incorporation, State or Country Code	DE
Title of 12(b) Security	Common Stock, $0.001 par value
Entity Address, Address Line One	2045 East Innovation Circle
Entity File Number	000-29472
Document Quarterly Report	true
Document Transition Report	false
Entity Registrant Name	AMKOR TECHNOLOGY, INC.
Entity Central Index Key	0001047127
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2019
Document Fiscal Period Focus	Q3
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		239,783,075
Entity Address, City or Town	Tempe
Entity Address, State or Province	AZ
Entity Address, Postal Zip Code	85284
City Area Code	480
Local Phone Number	821-5000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Trading Symbol	AMKR
Security Exchange Name	NASDAQ
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Entity Shell Company	false
Entity Tax Identification Number	23-1722724
Amendment Flag	false

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Net sales	$ 1,083,917	$ 1,144,192	$ 2,874,186	$ 3,235,195
Cost of sales	901,677	943,485	2,447,731	2,707,000
Gross profit	182,240	200,707	426,455	528,195
Selling, general and administrative	70,458	70,463	206,803	225,886
Research and development	32,927	37,541	104,867	119,546
Total operating expenses	103,385	108,004	311,670	345,432
Operating income	78,855	92,703	114,785	182,763
Interest expense	16,988	19,770	54,914	60,908
Other (income) expense, net	(1,760)	1,315	641	(6,254)
Total other expense, net	15,228	21,085	55,555	54,654
Income before taxes	63,627	71,618	59,230	128,109
Income tax expense	9,141	14,326	36,418	27,438
Net income	54,486	57,292	22,812	100,671
Net income attributable to non-controlling interests	(416)	(630)	(1,071)	(1,874)
Net income attributable to Amkor	$ 54,070	$ 56,662	$ 21,741	$ 98,797
Net income attributable to Amkor per common share:
Basic (in dollars per share)	$ 0.23	$ 0.24	$ 0.09	$ 0.41
Diluted (in dollars per share)	$ 0.23	$ 0.24	$ 0.09	$ 0.41
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Basic (in shares)	239,586	239,370	239,503	239,312
Diluted (in shares)	239,937	239,766	239,858	239,783

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 54,486	$ 57,292	$ 22,812	$ 100,671
Other comprehensive income (loss), net of tax:
Adjustments to unrealized components of defined benefit pension plans	(125)	(45)	(314)	(126)
Foreign currency translation	51	(6,611)	3,745	(2,664)
Total other comprehensive income (loss)	(74)	(6,656)	3,431	(2,790)
Comprehensive income	54,412	50,636	26,243	97,881
Comprehensive income attributable to non-controlling interests	416	630	1,071	1,874
Comprehensive income attributable to Amkor	$ 53,996	$ 50,006	$ 25,172	$ 96,007

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 598,753	$ 681,569
Restricted cash	2,590	2,589
Accounts receivable, net of allowances	803,104	724,456
Inventories	216,663	230,589
Other current assets	41,891	32,005
Total current assets	1,663,001	1,671,208
Property, plant and equipment, net	2,466,067	2,650,448
Operating lease right of use asset	141,467	0
Goodwill	26,104	25,720
Restricted cash	2,874	3,893
Other assets	106,417	144,178
Total assets	4,405,930	4,495,447
Current liabilities:
Short-term borrowings and current portion of long-term debt	102,952	114,579
Trade accounts payable	477,900	530,398
Capital expenditures payable	157,527	255,237
Accrued expenses	253,876	258,209
Total current liabilities	992,255	1,158,423
Long-term debt	1,195,005	1,217,732
Pension and severance obligations	178,530	184,321
Long-term operating lease liability	85,094	0
Other non-current liabilities	67,426	79,071
Total liabilities	2,518,310	2,639,547
Commitments and contingencies (Note 15)
Stockholders’ equity:
Preferred stock, $0.001 par value, 10,000 shares authorized, designated Series A, none issued	0	0
Common stock, $0.001 par value, 500,000 shares authorized; 285,607 and 285,352 shares issued; and 239,624 and 239,385 shares outstanding in 2019 and 2018, respectively	286	285
Additional paid-in capital	1,915,481	1,909,425
Retained earnings	134,930	113,189
Accumulated other comprehensive income (loss)	27,243	23,812
Treasury stock, at cost, 45,983 and 45,967 shares, in 2019 and 2018, respectively	(216,301)	(216,171)
Total Amkor stockholders’ equity	1,861,639	1,830,540
Non-controlling interests in subsidiaries	25,981	25,360
Total equity	1,887,620	1,855,900
Total liabilities and equity	$ 4,405,930	$ 4,495,447

Consolidated Balance Sheets (_2

Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
Stockholders’ equity:
Preferred stock designated Series A, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock designated Series A, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock designated Series A, shares issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	285,607,000	285,352,000
Common stock, shares outstanding (in shares)	239,624,000	239,385,000
Treasury stock (in shares)	45,983,000	45,967,000

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Total Amkor Stockholders' Equity	Common Stock	Additional Paid- In Capital	Retained Earnings (Accumulated Deficit)	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Noncontrolling Interest in Subsidiaries
Balance at beginning of period, shares at Dec. 31, 2017			285,129
Balance at beginning of period, shares at Dec. 31, 2017							(45,945)
Balance at beginning of period at Dec. 31, 2017	$ 1,719,709	$ 1,696,276	$ 285	$ 1,903,357	$ (13,903)	$ 22,519	$ (215,982)	$ 23,433
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	100,671	98,797			98,797			1,874
Other comprehensive income (loss)	(2,790)	(2,790)				(2,790)
Treasury stock acquired through surrender of shares for tax withholding, shares							(16)
Treasury stock acquired through surrender of shares for tax withholding	(153)	(153)					$ (153)
Issuance of stock through share-based compensation plans, shares			206
Issuance of stock through share-based compensation plans	1,023	1,023		1,023
Share-based compensation	3,791	3,791		3,791
Subsidiary dividends to noncontrolling interests	(410)							(410)
Balance at end of period, shares at Sep. 30, 2018			285,335
Balance at end of period, shares at Sep. 30, 2018							(45,961)
Balance at end of period at Sep. 30, 2018	1,821,841	1,796,944	$ 285	1,908,171	84,894	19,729	$ (216,135)	24,897
Balance at beginning of period, shares at Jun. 30, 2018			285,322
Balance at beginning of period, shares at Jun. 30, 2018							(45,956)
Balance at beginning of period at Jun. 30, 2018	1,770,158	1,745,751	$ 285	1,906,936	28,232	26,385	$ (216,087)	24,407
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	57,292	56,662			56,662			630
Other comprehensive income (loss)	(6,656)	(6,656)				(6,656)
Treasury stock acquired through surrender of shares for tax withholding, shares							(5)
Treasury stock acquired through surrender of shares for tax withholding	(48)	(48)					$ (48)
Issuance of stock through share-based compensation plans, shares			13
Issuance of stock through share-based compensation plans				0
Share-based compensation	1,235	1,235		1,235
Subsidiary dividends to noncontrolling interests	(140)							(140)
Balance at end of period, shares at Sep. 30, 2018			285,335
Balance at end of period, shares at Sep. 30, 2018							(45,961)
Balance at end of period at Sep. 30, 2018	$ 1,821,841	1,796,944	$ 285	1,908,171	84,894	19,729	$ (216,135)	24,897
Balance at beginning of period, shares at Dec. 31, 2018	285,352		285,352
Balance at beginning of period, shares at Dec. 31, 2018	(45,967)						(45,967)
Balance at beginning of period at Dec. 31, 2018	$ 1,855,900	1,830,540	$ 285	1,909,425	113,189	23,812	$ (216,171)	25,360
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	22,812	21,741			21,741			1,071
Other comprehensive income (loss)	3,431	3,431				3,431
Treasury stock acquired through surrender of shares for tax withholding, shares							(16)
Treasury stock acquired through surrender of shares for tax withholding	(130)	(130)					$ (130)
Issuance of stock through share-based compensation plans, shares			255
Issuance of stock through share-based compensation plans	871	871	$ 1	870
Share-based compensation	5,186	5,186		5,186
Subsidiary dividends to noncontrolling interests	$ (450)							(450)
Balance at end of period, shares at Sep. 30, 2019	285,607		285,607
Balance at end of period, shares at Sep. 30, 2019	(45,983)						(45,983)
Balance at end of period at Sep. 30, 2019	$ 1,887,620	1,861,639	$ 286	1,915,481	134,930	27,243	$ (216,301)	25,981
Balance at beginning of period, shares at Jun. 30, 2019			285,510
Balance at beginning of period, shares at Jun. 30, 2019							(45,978)
Balance at beginning of period at Jun. 30, 2019	1,831,176	1,805,311	$ 285	1,913,103	80,860	27,317	$ (216,254)	25,865
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	54,486	54,070			54,070			416
Other comprehensive income (loss)	(74)	(74)				(74)
Treasury stock acquired through surrender of shares for tax withholding, shares							(5)
Treasury stock acquired through surrender of shares for tax withholding	(47)	(47)					$ (47)
Issuance of stock through share-based compensation plans, shares			97
Issuance of stock through share-based compensation plans	435	435	$ 1	434
Share-based compensation	1,944	1,944		1,944
Subsidiary dividends to noncontrolling interests	$ (300)							(300)
Balance at end of period, shares at Sep. 30, 2019	285,607		285,607
Balance at end of period, shares at Sep. 30, 2019	(45,983)						(45,983)
Balance at end of period at Sep. 30, 2019	$ 1,887,620	$ 1,861,639	$ 286	$ 1,915,481	$ 134,930	$ 27,243	$ (216,301)	$ 25,981

Condensed Consolidated Statemen

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net income	$ 22,812	$ 100,671
Depreciation and amortization	398,013	429,181
Other operating activities and non-cash items	51,533	(2,006)
Changes in assets and liabilities	(189,026)	(100,628)
Net cash provided by operating activities	283,332	427,218
Cash flows from investing activities:
Payments for property, plant and equipment	(328,497)	(478,036)
Proceeds from sale of property, plant and equipment	8,495	1,606
Proceeds from insurance recovery for property, plant and equipment	1,538	0
Other investing activities	(353)	3,160
Net cash used in investing activities	(318,817)	(473,270)
Cash flows from financing activities:
Proceeds from revolving credit facilities	172,700	0
Payments of revolving credit facilities	(92,700)	(75,000)
Proceeds from short-term debt	51,434	23,341
Payments of short-term debt	(42,067)	(35,125)
Proceeds from issuance of long-term debt	714,375	372,226
Payments of long-term debt	(847,155)	(279,697)
Payments of finance lease obligations	(4,358)	(2,669)
Other financing activities	(1,963)	(2,482)
Net cash provided by (used in) financing activities	(49,734)	594
Effect of exchange rate fluctuations on cash, cash equivalents and restricted cash	1,385	(3,273)
Net decrease in cash, cash equivalents and restricted cash	(83,834)	(48,731)
Cash, cash equivalents and restricted cash, beginning of period	688,051	602,851
Cash, cash equivalents and restricted cash, end of period	604,217	554,120
Non-cash investing and financing activities:
Property, plant and equipment included in capital expenditures payable	157,959	254,244
Right of use assets acquired through finance lease liabilities	7,628	13,272
Right of use assets acquired through operating lease liabilities	$ 42,217	$ 0

Interim Financial Statements

Interim Financial Statements	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Interim Financial Statements	Interim Financial Statements Basis of Presentation. The Consolidated Financial Statements and related disclosures as of September 30, 2019, and for the three and nine months ended September 30, 2019 and 2018, are unaudited, pursuant to the rules and regulations of the United States Securities and Exchange Commission (“SEC”). The December 31, 2018 Consolidated Balance Sheet data was derived from audited financial statements but does not include all disclosures required by accounting principles generally accepted in the United States of America (“U.S.”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) have been condensed or omitted pursuant to such rules and regulations. In our opinion, these financial statements include all adjustments (consisting only of normal recurring adjustments) necessary for the fair statement of the results for the interim periods. These financial statements should be read in conjunction with the financial statements included in our Annual Report for the year ended December 31, 2018, filed on Form 10-K with the SEC on February 22, 2019. The results of operations for the three and nine months ended September 30, 2019 are not necessarily indicative of the results to be expected for the full year. Unless the context otherwise requires, all references to “Amkor,” “we,” “us,” “our” or the “company” are to Amkor Technology, Inc. and our subsidiaries. Use of Estimates. The Consolidated Financial Statements have been prepared in conformity with U.S. GAAP, using management’s best estimates and judgments where appropriate. These estimates and judgments affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements. The estimates and judgments will also affect the reported amounts for certain revenues and expenses during the reporting period. Actual results could differ materially from these estimates and judgments. Goodwill. The balance of goodwill in our Consolidated Balance Sheets reflects adjustments for foreign currency translation. Unbilled Receivables . Total unbilled receivables as of September 30, 2019 and December 31, 2018 were $109.7 million and $89.3 million, respectively.

New Accounting Standards

New Accounting Standards	9 Months Ended
	Sep. 30, 2019
Accounting Changes and Error Corrections [Abstract]
New Accounting Standards	New Accounting Standards Recently Adopted Standards In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) , which was subsequently amended and clarified. Topic 842 requires a dual approach for lease accounting under which a lessee would account for leases as finance leases or operating leases. The standard also requires the lessee to recognize a right-of-use asset and a corresponding lease liability for both finance leases and operating leases. For finance leases, the lessee recognizes interest expense and amortization of the right-of-use asset, and for operating leases, the lessee recognizes a straight-line lease expense. The standard permits the use of two alternative transition approaches, either with application in all comparative periods presented or with application beginning with the effective date without restating comparative period financial statements. Effective January 1, 2019, we adopted the requirements of Topic 842 using the modified transition approach without restating the comparative period financial statements. The new standard resulted in increases in our operating lease right of use asset, accrued expenses and long-term operating lease liability account balances to record our operating leases on our Consolidated Balance Sheet. The new standard also resulted in additional disclosures for our operating and finance leases (Note 10). In accordance with Topic 842, we applied practical expedients permitted under the transition guidance, which allowed us to not: • Reassess whether any existing contracts are or contain a lease, • Reassess the lease classification for any existing contracts, • Reassess initial direct costs for any existing leases, and • Separate non-lease components from lease components and instead to account for them as a single lease component for all asset classes.

Net Sales by Product Group and

Net Sales by Product Group and End Market	9 Months Ended
	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Net Sales by Product Group and End Market	Net Sales by Product Group and End Market Net sales by product group consist of the following: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (In thousands) Advanced products (1) $ 588,975 $ 582,165 $ 1,444,059 $ 1,554,158 Mainstream products (2) 494,942 562,027 1,430,127 1,681,037 Total net sales $ 1,083,917 $ 1,144,192 $ 2,874,186 $ 3,235,195 (1) Advanced products include flip chip and wafer-level processing and related test services. (2) Mainstream products include wirebond packaging and related test services. Net sales by end market consist of the following: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Communications (handheld devices, smartphones, tablets) 41 % 47 % 39 % 44 % Automotive, industrial and other (driver assist, infotainment, performance, safety) 26 % 25 % 28 % 26 % Computing (datacenter, infrastructure, PC/laptop, storage) 15 % 17 % 17 % 18 % Consumer (connected home, set-top boxes, televisions, visual imaging, wearables) 18 % 11 % 16 % 12 % Total net sales 100 % 100 % 100 % 100 %

Other Income and Expense

Other Income and Expense	9 Months Ended
	Sep. 30, 2019
Other Income and Expenses [Abstract]
Other Income and Expense	Other Income and Expense Other income and expense consists of the following: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (In thousands) Interest income $ (1,269) $ (941) $ (4,931) $ (2,884) Foreign currency (gain) loss, net (174) 1,352 (1,581) (1,045) Loss on debt retirement 179 1,149 8,535 1,167 Other (496) (245) (1,382) (3,492) Other (income) expense, net $ (1,760) $ 1,315 $ 641 $ (6,254)

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income tax expense of $36.4 million for the nine months ended September 30, 2019 reflects income taxes, foreign withholding taxes and minimum taxes. Income tax expense for the nine months ended September 30, 2019 also includes an $11.8 million discrete tax expense primarily for the recognition of a valuation allowance for certain deferred tax assets. We monitor on an ongoing basis our ability to utilize our deferred tax assets and whether there is a need for a related valuation allowance. In evaluating our ability to recover our deferred tax assets in the jurisdictions from which they arise, we consider all available positive and negative evidence, including scheduled reversals of deferred tax liabilities, projected future taxable income, tax-planning strategies and results of recent operations. Based on current projections of future taxable income in foreign jurisdictions, certain foreign deferred tax assets are not expected to be realized, including certain tax credit carryforwards that are expected to expire unused. We maintain a valuation allowance on a portion of our U.S. net deferred tax assets for deferred interest expense carryforwards, net operating loss carryforwards and foreign tax credit carryforwards that are expected to expire unused. Such valuation allowances are released as the related tax benefits are realized or when sufficient evidence exists to conclude that it is more likely than not that the deferred tax assets will be realized. Unrecognized tax benefits represent reserves for potential tax deficiencies or reductions in tax benefits that could result from federal, state or foreign tax audits. Gross unrecognized tax benefits decreased from $25.3 million at December 31, 2018 to $20.4 million as of September 30, 2019, primarily related to the effective settlement of an examination. All of our unrecognized tax benefits would reduce our effective tax rate, if recognized. Our unrecognized tax benefits are subject to change for effective settlement of examinations, changes in the recognition threshold of tax positions, the expiration of statutes of limitations and other factors.

Earnings Per Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share Basic earnings per share (“EPS”) is computed by dividing net income attributable to Amkor common stockholders by the weighted-average number of common shares outstanding during the period. The weighted-average number of common shares outstanding is reduced for treasury stock. Diluted EPS is computed based on the weighted-average number of common shares outstanding plus the effect of dilutive potential common shares outstanding during the period. Dilutive potential common shares include outstanding stock options and unvested restricted shares. The following table summarizes the computation of basic and diluted EPS: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (In thousands, Net income attributable to Amkor common stockholders $ 54,070 $ 56,662 $ 21,741 $ 98,797 Weighted-average number of common shares outstanding — basic 239,586 239,370 239,503 239,312 Effect of dilutive securities: Stock options and restricted share awards 351 396 355 471 Weighted-average number of common shares outstanding — diluted 239,937 239,766 239,858 239,783 Net income attributable to Amkor per common share: Basic $ 0.23 $ 0.24 $ 0.09 $ 0.41 Diluted 0.23 0.24 0.09 0.41 The following table summarizes the potential shares of common stock that were excluded from diluted EPS because the effect of including these potential shares was anti-dilutive: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (In thousands) Stock options and restricted share awards 6,347 3,656 6,487 3,544

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 30, 2019
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Changes in accumulated other comprehensive income (loss), net of tax, consist of the following: Defined Benefit Pension Foreign Currency Translation Total (In thousands) Accumulated other comprehensive income (loss) at December 31, 2018 $ 2,659 $ 21,153 $ 23,812 Other comprehensive income (loss) before reclassifications — 3,745 3,745 Amounts reclassified from accumulated other comprehensive income (loss) (314) — (314) Other comprehensive income (loss) (314) 3,745 3,431 Accumulated other comprehensive income (loss) at September 30, 2019 $ 2,345 $ 24,898 $ 27,243 Defined Benefit Pension Foreign Currency Translation Total (In thousands) Accumulated other comprehensive income (loss) at December 31, 2017 $ 6,303 $ 16,216 $ 22,519 Other comprehensive income (loss) before reclassifications — (2,664) (2,664) Amounts reclassified from accumulated other comprehensive income (loss) (126) — (126) Other comprehensive income (loss) (126) (2,664) (2,790) Accumulated other comprehensive income (loss) at September 30, 2018 $ 6,177 $ 13,552 $ 19,729 Amounts reclassified out of accumulated other comprehensive income (loss) are included as a component of net periodic pension cost (Note 13).

Factoring of Accounts Receivabl

Factoring of Accounts Receivable	9 Months Ended
	Sep. 30, 2019
Factoring of Accounts Receivable [Abstract]
Factoring of Accounts Receivable	Factoring of Accounts Receivable For certain accounts receivable, we use non-recourse factoring arrangements with third-party financial institutions to manage our working capital and cash flows. Under this program, we sell receivables to a financial institution for cash at a discount to the face amount. As part of the factoring arrangements, we perform certain collection and administrative functions for the receivables sold. For the three and nine months ended September 30, 2019, we sold receivables totaling $175.4 million and $480.2 million, net of discounts and fees of $1.1 million and $3.3 million, respectively. For the three and nine months ended September 30, 2018, we sold receivables totaling $193.6 million and $622.2 million, net of discounts and fees of $1.6 million and $5.4 million, respectively.

Property, Plant and Equipment

Property, Plant and Equipment	9 Months Ended
	Sep. 30, 2019
Property, Plant and Equipment [Abstract]
Property, Plant And Equipment	Property, Plant and Equipment Property, plant and equipment consist of the following: September 30, 2019 December 31, 2018 (In thousands) Land $ 219,928 $ 222,884 Land use rights (1) — 26,845 Buildings and improvements 1,571,315 1,523,065 Machinery and equipment 5,298,866 5,196,930 Finance lease assets 31,096 25,874 Software and computer equipment 219,463 213,440 Furniture, fixtures and other equipment 19,644 17,204 Construction in progress 11,330 44,381 Total property, plant and equipment 7,371,642 7,270,623 Accumulated depreciation and amortization (4,905,575) (4,620,175) Total property, plant and equipment, net $ 2,466,067 $ 2,650,448 (1) Effective January 1, 2019, and in connection with the adoption of Topic 842, land use rights were reclassified to operating lease right of use asset within our Consolidated Balance Sheet. The following table summarizes our depreciation expense: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (In thousands) Depreciation expense $ 128,846 $ 143,334 $ 396,984 $ 427,836

Leases

Leases	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Leases	Leases We lease certain machinery and equipment, office space and manufacturing facilities. Leases with an initial term of 12 months or less are not recorded on the balance sheet, and we recognize lease expense for these leases on a straight-line basis over the lease term. We account for lease components (e.g., fixed payments including rent, real estate taxes and insurance costs) combined with the non-lease components (e.g., common-area maintenance costs). We use our incremental borrowing rate based on the information available at the lease commencement date to determine the lease liability. Our leases have remaining lease terms ranging from less than one year to 86 years. For purposes of calculating our lease liabilities, our lease terms include options to extend or terminate the lease when it is reasonably certain that we will exercise those options. Certain leases also include options to purchase the leased property. The components of lease expense were as follows: For the Three Months Ended September 30, 2019 For the Nine Months Ended September 30, 2019 (In thousands) Operating lease cost $ 11,664 $ 29,389 Finance lease cost Amortization of leased assets 1,417 3,628 Interest on lease liabilities 254 666 Total finance lease cost 1,671 4,294 Short-term lease cost 2,050 6,411 Variable lease cost 1,428 4,557 Net lease cost $ 16,813 $ 44,651 Rent expense was $9.3 million and $33.4 million for three and nine months ended September 30, 2018, respectively. Other information related to leases was as follows: For the Nine Months Ended September 30, 2019 Supplemental Cash Flows Information (in thousands) Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 28,254 Operating cash flows for finance leases 652 Financing cash flows for finance leases 4,358 Weighted Average Remaining Lease Term (Years) Operating leases 4.4 Finance leases 3.9 Weighted Average Discount Rate Operating leases 4.2 % Finance leases 4.6 % Maturities of lease liabilities were as follows: September 30, 2019 December 31, 2018 Operating Leases Finance Leases Operating Leases Finance Leases (In thousands) 2019 - Remaining $ 11,464 $ 2,317 $ 32,461 $ 6,430 2020 41,204 8,320 24,630 4,555 2021 31,232 7,248 17,676 4,748 2022 17,405 2,014 10,942 936 2023 9,818 941 9,008 936 Thereafter 26,842 3,757 26,070 3,807 Total future minimum lease payments 137,965 24,597 $ 120,787 $ 21,412 Less: Imputed interest (13,736) (2,366) Total $ 124,229 $ 22,231
Leases	Leases We lease certain machinery and equipment, office space and manufacturing facilities. Leases with an initial term of 12 months or less are not recorded on the balance sheet, and we recognize lease expense for these leases on a straight-line basis over the lease term. We account for lease components (e.g., fixed payments including rent, real estate taxes and insurance costs) combined with the non-lease components (e.g., common-area maintenance costs). We use our incremental borrowing rate based on the information available at the lease commencement date to determine the lease liability. Our leases have remaining lease terms ranging from less than one year to 86 years. For purposes of calculating our lease liabilities, our lease terms include options to extend or terminate the lease when it is reasonably certain that we will exercise those options. Certain leases also include options to purchase the leased property. The components of lease expense were as follows: For the Three Months Ended September 30, 2019 For the Nine Months Ended September 30, 2019 (In thousands) Operating lease cost $ 11,664 $ 29,389 Finance lease cost Amortization of leased assets 1,417 3,628 Interest on lease liabilities 254 666 Total finance lease cost 1,671 4,294 Short-term lease cost 2,050 6,411 Variable lease cost 1,428 4,557 Net lease cost $ 16,813 $ 44,651 Rent expense was $9.3 million and $33.4 million for three and nine months ended September 30, 2018, respectively. Other information related to leases was as follows: For the Nine Months Ended September 30, 2019 Supplemental Cash Flows Information (in thousands) Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 28,254 Operating cash flows for finance leases 652 Financing cash flows for finance leases 4,358 Weighted Average Remaining Lease Term (Years) Operating leases 4.4 Finance leases 3.9 Weighted Average Discount Rate Operating leases 4.2 % Finance leases 4.6 % Maturities of lease liabilities were as follows: September 30, 2019 December 31, 2018 Operating Leases Finance Leases Operating Leases Finance Leases (In thousands) 2019 - Remaining $ 11,464 $ 2,317 $ 32,461 $ 6,430 2020 41,204 8,320 24,630 4,555 2021 31,232 7,248 17,676 4,748 2022 17,405 2,014 10,942 936 2023 9,818 941 9,008 936 Thereafter 26,842 3,757 26,070 3,807 Total future minimum lease payments 137,965 24,597 $ 120,787 $ 21,412 Less: Imputed interest (13,736) (2,366) Total $ 124,229 $ 22,231

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2019
Payables and Accruals [Abstract]
Accrued Expenses	Accrued Expenses Accrued expenses consist of the following: September 30, 2019 December 31, 2018 (In thousands) Payroll and benefits $ 108,167 $ 124,943 Short-term operating lease liability 39,135 — Deferred revenue and customer advances 16,104 16,736 Income taxes payable 14,845 38,567 Accrued severance plan obligations 12,667 13,179 Accrued interest 2,959 10,302 Other accrued expenses 59,999 54,482 Total accrued expenses $ 253,876 $ 258,209

Debt

Debt	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Debt	Debt Following is a summary of short-term borrowings and long-term debt: September 30, 2019 December 31, 2018 (In thousands) Debt of Amkor Technology, Inc.: Senior notes: 6.375% Senior notes, due October 2022 (1) $ — $ 524,971 6.625% Senior notes, due September 2027 (1) 525,000 — Debt of subsidiaries: Amkor Technology Korea, Inc.: $30 million revolving credit facility, LIBOR plus the applicable bank rate, due October 2019 (2) — — Term loan, fixed rate at 3.70%, due May 2020 (3) (5) — 120,000 Term loan, fund floating rate plus 1.60%, due June 2020 (4) (5) (6) 24,000 125,000 Term loan, applicable bank rate plus 2.03%, due July 2022 (5) 40,000 — Term loan, applicable bank rate plus 2.03%, due September 2022 (5) 60,000 — Term loan, LIBOR plus 2.56%, due December 2023 200,000 200,000 Term loan, applicable bank rate plus 1.98%, due December 2028 (6) 66,000 24,000 J-Devices Corporation: Short-term term loans, variable rate (7) 17,737 8,232 Term loan, fixed rate at 0.86%, due June 2022 25,444 31,908 Term loan, fixed rate at 0.60%, due July 2022 5,551 6,838 Term loan, fixed rate at 1.30%, due July 2023 192,450 225,180 Amkor Assembly & Test (Shanghai) Co., Ltd.: Term loan, LIBOR plus 1.80%, due December 2019 (8) — 48,000 Term loan, LIBOR plus 1.60%, due March 2022 (8) 29,500 — Term loan, LIBOR Plus 1.40%, due March 2022 (8) 19,750 — Other: $250 million senior secured revolving credit facility, LIBOR plus 1.25%-1.75%, due July 2023 (Singapore) (9) 80,000 — Revolving credit facility, TAIFX plus the applicable bank rate, due November 2020 (Taiwan) (10) 20,000 20,000 1,305,432 1,334,129 Less: Unamortized premium, discount and deferred debt costs, net (7,475) (1,818) Less: Short-term borrowings and current portion of long-term debt (102,952) (114,579) Long-term debt $ 1,195,005 $ 1,217,732 (1) In April 2019, we redeemed the outstanding $525 million aggregate principal amount of our 6.375% Senior Notes due 2022 (“2022 Notes”). In accordance with the terms of the indenture governing the 2022 Notes, the redemption price was 101.594% of the principal amount of the 2022 Notes plus accrued and unpaid interest. We recorded an $8.4 million loss on extinguishment related to the call premium paid and other debt related costs associated with the 2022 Notes. The redemption of the 2022 Notes was funded with net proceeds from our issuance of $525 million of 6.625% Senior Notes due September 2027 (“2027 Notes”) in March 2019, together with cash on hand. The 2027 Notes were issued at a discount of 99.5% or $2.6 million, and are senior unsecured obligations. Interest is payable semiannually on March 15 and September 15 of each year, commencing September 15, 2019. We incurred $3.6 million of debt issuance costs associated with the 2027 Notes. (2) In October 2018, we entered into a revolving credit facility agreement with availability of $30.0 million. Principal is payable at maturity in October 2019. Interest is payable monthly in arrears, at LIBOR plus the applicable bank rate. As of September 30, 2019, $30.0 million was available to be drawn. In October 2019, we renewed this revolver with a new maturity date of October 2020. (3) In May 2017, we entered into a $120.0 million term loan agreement due May 2020 with a fixed interest rate of 3.7%. During the nine months ended September 30, 2019, we repaid all $120.0 million of the outstanding balance of this term loan. (4) In May 2015, we entered into a term loan agreement pursuant to which we may borrow up to $150.0 million for capital expenditures. Principal is payable at maturity in June 2020. Interest is payable quarterly in arrears, at the bank's fund floating rate plus 1.60% (4.18% as of September 30, 2019). During the nine months ended September 30, 2019, we repaid $101.0 million of the outstanding balance of this term loan. (5) In July 2019, we entered into an agreement pursuant to which we may borrow up to $180.0 million for purchases of materials through two term loans. Principal is payable at maturity and interest is payable quarterly in arrears, at the applicable bank rate plus 2.03%. We borrowed $40.0 million under the first term loan in July 2019 to repay the remaining $40.0 million outstanding balance for the term loan due May 2020. This new term loan bears interest at a fixed rate of 3.80% and has a maturity date of July 2022. We borrowed $60.0 million under the second term loan in September 2019 to repay part of the term loan due June 2020. The $60.0 million borrowing under the second term loan bears interest at a fixed rate of 3.59% and has a maturity date of September 2022. As of September 30, 2019, $80.0 million was available to be drawn under the second term loan. (6) In December 2018, we entered into a term loan agreement pursuant to which we may borrow up to $90.0 million for capital expenditures. During the nine months ended September 30, 2019, we borrowed $42.0 million of this term loan and used the proceeds to repay part of the term loan due June 2020. Principal of this term loan is payable in semiannual installments beginning June 2022 and ending at maturity in December 2028. Interest is payable quarterly in arrears, at the applicable bank rate plus 1.98% (the weighted average interest rate was 4.50% as of September 30, 2019). As of September 30, 2019, $24.0 million was available to be drawn. (7) We entered into various short-term term loans which mature semiannually. Principal and interest are payable in monthly installments. Interest as of September 30, 2019 is at TIBOR plus 0.10% to 0.27% (weighted average of 0.23% as of September 30, 2019). As of September 30, 2019, $6.0 million was available to be drawn. (8) In December 2016, we entered into a $50.0 million term loan agreement. Principal is payable in semiannual installments of $0.5 million, with the remaining balance due at maturity in December 2019. Interest is payable quarterly at a floating rate of LIBOR plus 1.80%. During the nine months ended September 30, 2019, we repaid the entire $48.0 million outstanding balance of this term loan using the proceeds from our term loans due March 2022. In March 2019, we entered into a $30.0 million term loan agreement due March 2022. We borrowed $30.0 million under this term loan and repaid part of the term loan due December 2019. Principal is payable in semiannual installments of $0.5 million, with the remaining balance due at maturity. Interest is payable quarterly at a floating rate of LIBOR plus 1.60% (3.80% as of September 30, 2019). In April 2019, we entered into a term loan agreement with availability of $20.0 million due March 2022. We borrowed $20.0 million under this term loan and repaid part of the term loan due December 2019. Principal is payable in semiannual installments of $0.5 million, with the remaining balance due at maturity. Interest is payable quarterly at a floating rate of LIBOR plus 1.40% (3.53% as of September 30, 2019). (9) In July 2018, we entered into a $250.0 million senior secured revolving credit facility, which is guaranteed by Amkor Technology, Inc. The availability for our revolving credit facility is based on the amount of eligible accounts receivable. Principal is payable at maturity. Interest is payable monthly at LIBOR plus 1.25% to 1.75% (3.36% as of September 30, 2019). We borrowed $80 million in September 2019, which was repaid in October 2019. As of September 30, 2019, $151.0 million was available to be drawn. (10) In November 2015, we entered into a $39.0 million revolving credit facility. Principal is payable at maturity. Interest is payable monthly at TAIFX plus the applicable bank rate (3.31% as of September 30, 2019). As of September 30, 2019, $19.0 million was available to be drawn. Certain of our foreign debt is collateralized by the land, buildings, equipment and accounts receivable in the respective locations. The carrying value of the collateral exceeds the carrying amount of the debt. The debt of Amkor Technology, Inc. is structurally subordinated in right of payment to all existing and future debt and other liabilities of our subsidiaries. From time to time, Amkor Technology, Inc. also guarantees certain debt of our subsidiaries. The agreements governing our indebtedness contain affirmative and negative covenants which restrict our ability to pay dividends and could restrict our operations. We have never paid a dividend to our stockholders, and we do not have any present plans for doing so. We were in compliance with all debt covenants at September 30, 2019.

Pension Plans

Pension Plans	9 Months Ended
	Sep. 30, 2019
Retirement Benefits [Abstract]
Pension Plans	Pension Plans Foreign Defined Benefit Pension Plans Our subsidiaries in Japan, Korea, Malaysia, the Philippines and Taiwan sponsor defined benefit pension plans. Charges to expense are based upon actuarial analyses. The components of net periodic pension cost for these defined benefit pension plans are as follows: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (In thousands) Service cost $ 7,747 $ 8,124 $ 23,513 $ 24,839 Interest cost 1,297 1,199 3,926 3,668 Expected return on plan assets (1,585) (1,390) (4,798) (4,249) Recognized actuarial gain (94) (36) (282) (113) Net periodic pension cost $ 7,365 $ 7,897 $ 22,359 $ 24,145 The components of net periodic pension cost other than the service cost component are included in other (income) expense, net in our Consolidated Statements of Income. Defined Contribution Pension Plans We sponsor defined contribution pension plans in Korea, Malaysia, Taiwan and the U.S. The following table summarizes our defined contribution expense: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (In thousands) Defined contribution expense $ 2,952 $ 2,595 $ 10,708 $ 9,608

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The accounting framework for determining fair value includes a hierarchy for ranking the quality and reliability of the information used to measure fair value, which enables the reader of the financial statements to assess the inputs used to develop those measurements. The fair value hierarchy consists of three tiers as follows: Level 1, defined as quoted market prices in active markets for identical assets or liabilities; Level 2, defined as inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, model-based valuation techniques for which all significant assumptions are observable in the market or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and Level 3, defined as unobservable inputs that are not corroborated by market data. The fair values of cash, accounts receivable, trade accounts payable, capital expenditures payable, and certain other current assets and accrued expenses approximate carrying values because of their short-term nature. The carrying value of certain other non-current assets and liabilities approximates fair value. Our assets and liabilities recorded at fair value on a recurring basis include cash equivalent money market funds and restricted cash money market funds. We also review goodwill for impairment annually during the fourth quarter of each year. Cash equivalent money market funds and restricted cash money market funds are invested in U.S. money market funds and various U.S. and foreign bank operating and time deposit accounts, which are due on demand or carry a maturity date of less than three months when purchased. No restrictions have been imposed on us regarding withdrawal of balances with respect to our cash equivalents as a result of liquidity or other credit market issues affecting the money market funds we invest in or the counterparty financial institutions holding our deposits. Money market funds are valued using quoted market prices in active markets for identical assets. Recurring fair value measurements consist of the following: September 30, 2019 December 31, 2018 (In thousands) Cash equivalent money market funds (Level 1) $ 57,904 $ 74,407 Restricted cash money market funds (Level 1) 2,590 2,589 We also measure certain assets and liabilities, including property, plant and equipment and goodwill, at fair value on a nonrecurring basis. We measure the fair value of our debt for disclosure purposes. The following table presents the fair value of financial instruments that are not recorded at fair value on a recurring basis: September 30, 2019 December 31, 2018 Fair Carrying Fair Carrying (In thousands) Senior notes (Level 1) $ 573,636 $ 519,069 $ 526,131 $ 524,978 Revolving credit facilities and term loans (Level 2) 784,644 778,888 803,867 807,333 Total debt $ 1,358,280 $ 1,297,957 $ 1,329,998 $ 1,332,311 The estimated fair value of our senior notes is based primarily on quoted market prices reported on or near the respective balance sheet dates. The estimated fair value of our revolving credit facilities and term loans is calculated using a discounted cash flow analysis, which utilizes market-based assumptions including forward interest rates adjusted for credit risk.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies We generally warrant that our services will be performed in a professional and workmanlike manner and in compliance with our customers’ specifications. We accrue costs for known warranty issues. Historically, our warranty costs have been immaterial. Legal Proceedings We are involved in claims and legal proceedings and may become involved in other legal matters arising in the ordinary course of our business. We evaluate these claims and legal matters on a case-by-case basis to make a determination as to the impact, if any, on our business, liquidity, results of operations, financial condition or cash flows. Although the outcome of these matters is uncertain, we believe that the ultimate outcome of these claims and proceedings, individually and in the aggregate, will not have a material adverse impact to us. Our evaluation of the potential impact of these claims and legal proceedings on our business, liquidity, results of operations, financial condition or cash flows could change in the future. In accordance with the accounting guidance for loss contingencies, including legal proceedings, lawsuits, pending claims and other legal matters, we accrue for a loss contingency when we conclude that the likelihood of a loss is probable and the amount of the loss can be reasonably estimated. We adjust our accruals from time to time as we receive additional information, but the loss we incur may be significantly greater than or less than the amount we have accrued. We disclose loss contingencies if we believe they are material and there is at least a reasonable possibility that a loss has been incurred. Attorney fees related to legal matters are expensed as incurred.

Interim Financial Statements (P

Interim Financial Statements (Policies)	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation. The Consolidated Financial Statements and related disclosures as of September 30, 2019, and for the three and nine months ended September 30, 2019 and 2018, are unaudited, pursuant to the rules and regulations of the United States Securities and Exchange Commission (“SEC”). The December 31, 2018 Consolidated Balance Sheet data was derived from audited financial statements but does not include all disclosures required by accounting principles generally accepted in the United States of America (“U.S.”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) have been condensed or omitted pursuant to such rules and regulations. In our opinion, these financial statements include all adjustments (consisting only of normal recurring adjustments) necessary for the fair statement of the results for the interim periods. These financial statements should be read in conjunction with the financial statements included in our Annual Report for the year ended December 31, 2018, filed on Form 10-K with the SEC on February 22, 2019. The results of operations for the three and nine months ended September 30, 2019 are not necessarily indicative of the results to be expected for the full year. Unless the context otherwise requires, all references to “Amkor,” “we,” “us,” “our” or the “company” are to Amkor Technology, Inc. and our subsidiaries.
Use of Estimates	Use of Estimates. The Consolidated Financial Statements have been prepared in conformity with U.S. GAAP, using management’s best estimates and judgments where appropriate. These estimates and judgments affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements. The estimates and judgments will also affect the reported amounts for certain revenues and expenses during the reporting period. Actual results could differ materially from these estimates and judgments.
Goodwill	Goodwill. The balance of goodwill in our Consolidated Balance Sheets reflects adjustments for foreign currency translation.
Unbilled Receivables	Unbilled Receivables . Total unbilled receivables as of September 30, 2019 and December 31, 2018 were $109.7 million and $89.3 million, respectively.
Recently Adopted Standards	Recently Adopted Standards In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) , which was subsequently amended and clarified. Topic 842 requires a dual approach for lease accounting under which a lessee would account for leases as finance leases or operating leases. The standard also requires the lessee to recognize a right-of-use asset and a corresponding lease liability for both finance leases and operating leases. For finance leases, the lessee recognizes interest expense and amortization of the right-of-use asset, and for operating leases, the lessee recognizes a straight-line lease expense. The standard permits the use of two alternative transition approaches, either with application in all comparative periods presented or with application beginning with the effective date without restating comparative period financial statements. Effective January 1, 2019, we adopted the requirements of Topic 842 using the modified transition approach without restating the comparative period financial statements. The new standard resulted in increases in our operating lease right of use asset, accrued expenses and long-term operating lease liability account balances to record our operating leases on our Consolidated Balance Sheet. The new standard also resulted in additional disclosures for our operating and finance leases (Note 10). In accordance with Topic 842, we applied practical expedients permitted under the transition guidance, which allowed us to not: • Reassess whether any existing contracts are or contain a lease, • Reassess the lease classification for any existing contracts, • Reassess initial direct costs for any existing leases, and • Separate non-lease components from lease components and instead to account for them as a single lease component for all asset classes.
Income Taxes	We monitor on an ongoing basis our ability to utilize our deferred tax assets and whether there is a need for a related valuation allowance. In evaluating our ability to recover our deferred tax assets in the jurisdictions from which they arise, we consider all available positive and negative evidence, including scheduled reversals of deferred tax liabilities, projected future taxable income, tax-planning strategies and results of recent operations. Based on current projections of future taxable income in foreign jurisdictions, certain foreign deferred tax assets are not expected to be realized, including certain tax credit carryforwards that are expected to expire unused. We maintain a valuation allowance on a portion of our U.S. net deferred tax assets for deferred interest expense carryforwards, net operating loss carryforwards and foreign tax credit carryforwards that are expected to expire unused. Such valuation allowances are released as the related tax benefits are realized or when sufficient evidence exists to conclude that it is more likely than not that the deferred tax assets will be realized.
Commitments and Contingencies	In accordance with the accounting guidance for loss contingencies, including legal proceedings, lawsuits, pending claims and other legal matters, we accrue for a loss contingency when we conclude that the likelihood of a loss is probable and the amount of the loss can be reasonably estimated. We adjust our accruals from time to time as we receive additional information, but the loss we incur may be significantly greater than or less than the amount we have accrued. We disclose loss contingencies if we believe they are material and there is at least a reasonable possibility that a loss has been incurred. Attorney fees related to legal matters are expensed as incurred.

Net Sales by Product Group an_2

Net Sales by Product Group and End Market (Tables)	9 Months Ended
	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Net sales by product group and end market	Net sales by product group consist of the following: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (In thousands) Advanced products (1) $ 588,975 $ 582,165 $ 1,444,059 $ 1,554,158 Mainstream products (2) 494,942 562,027 1,430,127 1,681,037 Total net sales $ 1,083,917 $ 1,144,192 $ 2,874,186 $ 3,235,195 (1) Advanced products include flip chip and wafer-level processing and related test services. (2) Mainstream products include wirebond packaging and related test services. Net sales by end market consist of the following: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Communications (handheld devices, smartphones, tablets) 41 % 47 % 39 % 44 % Automotive, industrial and other (driver assist, infotainment, performance, safety) 26 % 25 % 28 % 26 % Computing (datacenter, infrastructure, PC/laptop, storage) 15 % 17 % 17 % 18 % Consumer (connected home, set-top boxes, televisions, visual imaging, wearables) 18 % 11 % 16 % 12 % Total net sales 100 % 100 % 100 % 100 %

Other Income and Expense (Table

Other Income and Expense (Tables)	9 Months Ended
	Sep. 30, 2019
Other Income and Expenses [Abstract]
Schedule of other income and expense	Other income and expense consists of the following: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (In thousands) Interest income $ (1,269) $ (941) $ (4,931) $ (2,884) Foreign currency (gain) loss, net (174) 1,352 (1,581) (1,045) Loss on debt retirement 179 1,149 8,535 1,167 Other (496) (245) (1,382) (3,492) Other (income) expense, net $ (1,760) $ 1,315 $ 641 $ (6,254)

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Computation of basic and diluted earnings per share	The following table summarizes the computation of basic and diluted EPS: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (In thousands, Net income attributable to Amkor common stockholders $ 54,070 $ 56,662 $ 21,741 $ 98,797 Weighted-average number of common shares outstanding — basic 239,586 239,370 239,503 239,312 Effect of dilutive securities: Stock options and restricted share awards 351 396 355 471 Weighted-average number of common shares outstanding — diluted 239,937 239,766 239,858 239,783 Net income attributable to Amkor per common share: Basic $ 0.23 $ 0.24 $ 0.09 $ 0.41 Diluted 0.23 0.24 0.09 0.41
Summary of potential shares of common stock excluded from diluted earnings per share	The following table summarizes the potential shares of common stock that were excluded from diluted EPS because the effect of including these potential shares was anti-dilutive: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (In thousands) Stock options and restricted share awards 6,347 3,656 6,487 3,544

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2019
Equity [Abstract]
Changes in accumulated other comprehensive income (loss), net of tax	Changes in accumulated other comprehensive income (loss), net of tax, consist of the following: Defined Benefit Pension Foreign Currency Translation Total (In thousands) Accumulated other comprehensive income (loss) at December 31, 2018 $ 2,659 $ 21,153 $ 23,812 Other comprehensive income (loss) before reclassifications — 3,745 3,745 Amounts reclassified from accumulated other comprehensive income (loss) (314) — (314) Other comprehensive income (loss) (314) 3,745 3,431 Accumulated other comprehensive income (loss) at September 30, 2019 $ 2,345 $ 24,898 $ 27,243 Defined Benefit Pension Foreign Currency Translation Total (In thousands) Accumulated other comprehensive income (loss) at December 31, 2017 $ 6,303 $ 16,216 $ 22,519 Other comprehensive income (loss) before reclassifications — (2,664) (2,664) Amounts reclassified from accumulated other comprehensive income (loss) (126) — (126) Other comprehensive income (loss) (126) (2,664) (2,790) Accumulated other comprehensive income (loss) at September 30, 2018 $ 6,177 $ 13,552 $ 19,729

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	9 Months Ended
	Sep. 30, 2019
Property, Plant and Equipment [Abstract]
Summary of property, plant and equipment and depreciation expense	Property, plant and equipment consist of the following: September 30, 2019 December 31, 2018 (In thousands) Land $ 219,928 $ 222,884 Land use rights (1) — 26,845 Buildings and improvements 1,571,315 1,523,065 Machinery and equipment 5,298,866 5,196,930 Finance lease assets 31,096 25,874 Software and computer equipment 219,463 213,440 Furniture, fixtures and other equipment 19,644 17,204 Construction in progress 11,330 44,381 Total property, plant and equipment 7,371,642 7,270,623 Accumulated depreciation and amortization (4,905,575) (4,620,175) Total property, plant and equipment, net $ 2,466,067 $ 2,650,448 (1) Effective January 1, 2019, and in connection with the adoption of Topic 842, land use rights were reclassified to operating lease right of use asset within our Consolidated Balance Sheet. The following table summarizes our depreciation expense: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (In thousands) Depreciation expense $ 128,846 $ 143,334 $ 396,984 $ 427,836

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Components of Lease Expense	The components of lease expense were as follows: For the Three Months Ended September 30, 2019 For the Nine Months Ended September 30, 2019 (In thousands) Operating lease cost $ 11,664 $ 29,389 Finance lease cost Amortization of leased assets 1,417 3,628 Interest on lease liabilities 254 666 Total finance lease cost 1,671 4,294 Short-term lease cost 2,050 6,411 Variable lease cost 1,428 4,557 Net lease cost $ 16,813 $ 44,651 Rent expense was $9.3 million and $33.4 million for three and nine months ended September 30, 2018, respectively. Other information related to leases was as follows: For the Nine Months Ended September 30, 2019 Supplemental Cash Flows Information (in thousands) Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 28,254 Operating cash flows for finance leases 652 Financing cash flows for finance leases 4,358 Weighted Average Remaining Lease Term (Years) Operating leases 4.4 Finance leases 3.9 Weighted Average Discount Rate Operating leases 4.2 % Finance leases 4.6 %
Maturity of Finance Lease Liabilities	Maturities of lease liabilities were as follows: September 30, 2019 December 31, 2018 Operating Leases Finance Leases Operating Leases Finance Leases (In thousands) 2019 - Remaining $ 11,464 $ 2,317 $ 32,461 $ 6,430 2020 41,204 8,320 24,630 4,555 2021 31,232 7,248 17,676 4,748 2022 17,405 2,014 10,942 936 2023 9,818 941 9,008 936 Thereafter 26,842 3,757 26,070 3,807 Total future minimum lease payments 137,965 24,597 $ 120,787 $ 21,412 Less: Imputed interest (13,736) (2,366) Total $ 124,229 $ 22,231
Maturity of Operating Lease Liabilities	Maturities of lease liabilities were as follows: September 30, 2019 December 31, 2018 Operating Leases Finance Leases Operating Leases Finance Leases (In thousands) 2019 - Remaining $ 11,464 $ 2,317 $ 32,461 $ 6,430 2020 41,204 8,320 24,630 4,555 2021 31,232 7,248 17,676 4,748 2022 17,405 2,014 10,942 936 2023 9,818 941 9,008 936 Thereafter 26,842 3,757 26,070 3,807 Total future minimum lease payments 137,965 24,597 $ 120,787 $ 21,412 Less: Imputed interest (13,736) (2,366) Total $ 124,229 $ 22,231
Future Minimum Lease Payments Under Non-cancellable Leases	Maturities of lease liabilities were as follows: September 30, 2019 December 31, 2018 Operating Leases Finance Leases Operating Leases Finance Leases (In thousands) 2019 - Remaining $ 11,464 $ 2,317 $ 32,461 $ 6,430 2020 41,204 8,320 24,630 4,555 2021 31,232 7,248 17,676 4,748 2022 17,405 2,014 10,942 936 2023 9,818 941 9,008 936 Thereafter 26,842 3,757 26,070 3,807 Total future minimum lease payments 137,965 24,597 $ 120,787 $ 21,412 Less: Imputed interest (13,736) (2,366) Total $ 124,229 $ 22,231
Schedule of Capital Lease Obligations	Maturities of lease liabilities were as follows: September 30, 2019 December 31, 2018 Operating Leases Finance Leases Operating Leases Finance Leases (In thousands) 2019 - Remaining $ 11,464 $ 2,317 $ 32,461 $ 6,430 2020 41,204 8,320 24,630 4,555 2021 31,232 7,248 17,676 4,748 2022 17,405 2,014 10,942 936 2023 9,818 941 9,008 936 Thereafter 26,842 3,757 26,070 3,807 Total future minimum lease payments 137,965 24,597 $ 120,787 $ 21,412 Less: Imputed interest (13,736) (2,366) Total $ 124,229 $ 22,231

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2019
Payables and Accruals [Abstract]
Summary of accrued expenses	Accrued expenses consist of the following: September 30, 2019 December 31, 2018 (In thousands) Payroll and benefits $ 108,167 $ 124,943 Short-term operating lease liability 39,135 — Deferred revenue and customer advances 16,104 16,736 Income taxes payable 14,845 38,567 Accrued severance plan obligations 12,667 13,179 Accrued interest 2,959 10,302 Other accrued expenses 59,999 54,482 Total accrued expenses $ 253,876 $ 258,209

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Summary of short-term borrowings and long-term debt	Following is a summary of short-term borrowings and long-term debt: September 30, 2019 December 31, 2018 (In thousands) Debt of Amkor Technology, Inc.: Senior notes: 6.375% Senior notes, due October 2022 (1) $ — $ 524,971 6.625% Senior notes, due September 2027 (1) 525,000 — Debt of subsidiaries: Amkor Technology Korea, Inc.: $30 million revolving credit facility, LIBOR plus the applicable bank rate, due October 2019 (2) — — Term loan, fixed rate at 3.70%, due May 2020 (3) (5) — 120,000 Term loan, fund floating rate plus 1.60%, due June 2020 (4) (5) (6) 24,000 125,000 Term loan, applicable bank rate plus 2.03%, due July 2022 (5) 40,000 — Term loan, applicable bank rate plus 2.03%, due September 2022 (5) 60,000 — Term loan, LIBOR plus 2.56%, due December 2023 200,000 200,000 Term loan, applicable bank rate plus 1.98%, due December 2028 (6) 66,000 24,000 J-Devices Corporation: Short-term term loans, variable rate (7) 17,737 8,232 Term loan, fixed rate at 0.86%, due June 2022 25,444 31,908 Term loan, fixed rate at 0.60%, due July 2022 5,551 6,838 Term loan, fixed rate at 1.30%, due July 2023 192,450 225,180 Amkor Assembly & Test (Shanghai) Co., Ltd.: Term loan, LIBOR plus 1.80%, due December 2019 (8) — 48,000 Term loan, LIBOR plus 1.60%, due March 2022 (8) 29,500 — Term loan, LIBOR Plus 1.40%, due March 2022 (8) 19,750 — Other: $250 million senior secured revolving credit facility, LIBOR plus 1.25%-1.75%, due July 2023 (Singapore) (9) 80,000 — Revolving credit facility, TAIFX plus the applicable bank rate, due November 2020 (Taiwan) (10) 20,000 20,000 1,305,432 1,334,129 Less: Unamortized premium, discount and deferred debt costs, net (7,475) (1,818) Less: Short-term borrowings and current portion of long-term debt (102,952) (114,579) Long-term debt $ 1,195,005 $ 1,217,732 (1) In April 2019, we redeemed the outstanding $525 million aggregate principal amount of our 6.375% Senior Notes due 2022 (“2022 Notes”). In accordance with the terms of the indenture governing the 2022 Notes, the redemption price was 101.594% of the principal amount of the 2022 Notes plus accrued and unpaid interest. We recorded an $8.4 million loss on extinguishment related to the call premium paid and other debt related costs associated with the 2022 Notes. The redemption of the 2022 Notes was funded with net proceeds from our issuance of $525 million of 6.625% Senior Notes due September 2027 (“2027 Notes”) in March 2019, together with cash on hand. The 2027 Notes were issued at a discount of 99.5% or $2.6 million, and are senior unsecured obligations. Interest is payable semiannually on March 15 and September 15 of each year, commencing September 15, 2019. We incurred $3.6 million of debt issuance costs associated with the 2027 Notes. (2) In October 2018, we entered into a revolving credit facility agreement with availability of $30.0 million. Principal is payable at maturity in October 2019. Interest is payable monthly in arrears, at LIBOR plus the applicable bank rate. As of September 30, 2019, $30.0 million was available to be drawn. In October 2019, we renewed this revolver with a new maturity date of October 2020. (3) In May 2017, we entered into a $120.0 million term loan agreement due May 2020 with a fixed interest rate of 3.7%. During the nine months ended September 30, 2019, we repaid all $120.0 million of the outstanding balance of this term loan. (4) In May 2015, we entered into a term loan agreement pursuant to which we may borrow up to $150.0 million for capital expenditures. Principal is payable at maturity in June 2020. Interest is payable quarterly in arrears, at the bank's fund floating rate plus 1.60% (4.18% as of September 30, 2019). During the nine months ended September 30, 2019, we repaid $101.0 million of the outstanding balance of this term loan. (5) In July 2019, we entered into an agreement pursuant to which we may borrow up to $180.0 million for purchases of materials through two term loans. Principal is payable at maturity and interest is payable quarterly in arrears, at the applicable bank rate plus 2.03%. We borrowed $40.0 million under the first term loan in July 2019 to repay the remaining $40.0 million outstanding balance for the term loan due May 2020. This new term loan bears interest at a fixed rate of 3.80% and has a maturity date of July 2022. We borrowed $60.0 million under the second term loan in September 2019 to repay part of the term loan due June 2020. The $60.0 million borrowing under the second term loan bears interest at a fixed rate of 3.59% and has a maturity date of September 2022. As of September 30, 2019, $80.0 million was available to be drawn under the second term loan. (6) In December 2018, we entered into a term loan agreement pursuant to which we may borrow up to $90.0 million for capital expenditures. During the nine months ended September 30, 2019, we borrowed $42.0 million of this term loan and used the proceeds to repay part of the term loan due June 2020. Principal of this term loan is payable in semiannual installments beginning June 2022 and ending at maturity in December 2028. Interest is payable quarterly in arrears, at the applicable bank rate plus 1.98% (the weighted average interest rate was 4.50% as of September 30, 2019). As of September 30, 2019, $24.0 million was available to be drawn. (7) We entered into various short-term term loans which mature semiannually. Principal and interest are payable in monthly installments. Interest as of September 30, 2019 is at TIBOR plus 0.10% to 0.27% (weighted average of 0.23% as of September 30, 2019). As of September 30, 2019, $6.0 million was available to be drawn. (8) In December 2016, we entered into a $50.0 million term loan agreement. Principal is payable in semiannual installments of $0.5 million, with the remaining balance due at maturity in December 2019. Interest is payable quarterly at a floating rate of LIBOR plus 1.80%. During the nine months ended September 30, 2019, we repaid the entire $48.0 million outstanding balance of this term loan using the proceeds from our term loans due March 2022. In March 2019, we entered into a $30.0 million term loan agreement due March 2022. We borrowed $30.0 million under this term loan and repaid part of the term loan due December 2019. Principal is payable in semiannual installments of $0.5 million, with the remaining balance due at maturity. Interest is payable quarterly at a floating rate of LIBOR plus 1.60% (3.80% as of September 30, 2019). In April 2019, we entered into a term loan agreement with availability of $20.0 million due March 2022. We borrowed $20.0 million under this term loan and repaid part of the term loan due December 2019. Principal is payable in semiannual installments of $0.5 million, with the remaining balance due at maturity. Interest is payable quarterly at a floating rate of LIBOR plus 1.40% (3.53% as of September 30, 2019). (9) In July 2018, we entered into a $250.0 million senior secured revolving credit facility, which is guaranteed by Amkor Technology, Inc. The availability for our revolving credit facility is based on the amount of eligible accounts receivable. Principal is payable at maturity. Interest is payable monthly at LIBOR plus 1.25% to 1.75% (3.36% as of September 30, 2019). We borrowed $80 million in September 2019, which was repaid in October 2019. As of September 30, 2019, $151.0 million was available to be drawn. (10) In November 2015, we entered into a $39.0 million revolving credit facility. Principal is payable at maturity. Interest is payable monthly at TAIFX plus the applicable bank rate (3.31% as of September 30, 2019). As of September 30, 2019, $19.0 million was available to be drawn.

Pension Plans (Tables)

Pension Plans (Tables)	9 Months Ended
	Sep. 30, 2019
Retirement Benefits [Abstract]
Components of net periodic pension cost	The components of net periodic pension cost for these defined benefit pension plans are as follows: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (In thousands) Service cost $ 7,747 $ 8,124 $ 23,513 $ 24,839 Interest cost 1,297 1,199 3,926 3,668 Expected return on plan assets (1,585) (1,390) (4,798) (4,249) Recognized actuarial gain (94) (36) (282) (113) Net periodic pension cost $ 7,365 $ 7,897 $ 22,359 $ 24,145
Summary of defined contribution expense	The following table summarizes our defined contribution expense: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 (In thousands) Defined contribution expense $ 2,952 $ 2,595 $ 10,708 $ 9,608

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Recurring fair value measurements	Recurring fair value measurements consist of the following: September 30, 2019 December 31, 2018 (In thousands) Cash equivalent money market funds (Level 1) $ 57,904 $ 74,407 Restricted cash money market funds (Level 1) 2,590 2,589
Fair value of financial instruments that are not recorded at fair value on recurring basis	The following table presents the fair value of financial instruments that are not recorded at fair value on a recurring basis: September 30, 2019 December 31, 2018 Fair Carrying Fair Carrying (In thousands) Senior notes (Level 1) $ 573,636 $ 519,069 $ 526,131 $ 524,978 Revolving credit facilities and term loans (Level 2) 784,644 778,888 803,867 807,333 Total debt $ 1,358,280 $ 1,297,957 $ 1,329,998 $ 1,332,311

Interim Financial Statements (D

Interim Financial Statements (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Unbilled receivables	$ 109.7	$ 89.3

Net Sales by Product Group an_3

Net Sales by Product Group and End Market - Product Group (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Net sales by product group	$ 1,083,917	$ 1,144,192	$ 2,874,186	$ 3,235,195
Advanced products
Disaggregation of Revenue [Line Items]
Net sales by product group	588,975	582,165	1,444,059	1,554,158
Mainstream products
Disaggregation of Revenue [Line Items]
Net sales by product group	$ 494,942	$ 562,027	$ 1,430,127	$ 1,681,037

Net Sales by Product Group an_4

Net Sales by Product Group and End Market - End Market (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total net sales	100.00%	100.00%	100.00%	100.00%
Revenue from Contract with Customer | End Market | Communications (handheld devices, smartphones, tablets)
Disaggregation of Revenue [Line Items]
Total net sales	41.00%	47.00%	39.00%	44.00%
Revenue from Contract with Customer | End Market | Automotive, industrial and other (driver assist, infotainment, performance, safety)
Disaggregation of Revenue [Line Items]
Total net sales	26.00%	25.00%	28.00%	26.00%
Revenue from Contract with Customer | End Market | Computing (datacenter, infrastructure, PC/laptop, storage)
Disaggregation of Revenue [Line Items]
Total net sales	15.00%	17.00%	17.00%	18.00%
Revenue from Contract with Customer | End Market | Consumer (connected home, set-top boxes, televisions, visual imaging, wearables)
Disaggregation of Revenue [Line Items]
Total net sales	18.00%	11.00%	16.00%	12.00%

Other Income and Expense (Detai

Other Income and Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Other Income and Expenses [Abstract]
Interest income	$ (1,269)	$ (941)	$ (4,931)	$ (2,884)
Foreign currency (gain) loss, net	(174)	1,352	(1,581)	(1,045)
Loss on debt retirement	179	1,149	8,535	1,167
Other	(496)	(245)	(1,382)	(3,492)
Other (income) expense, net	$ (1,760)	$ 1,315	$ 641	$ (6,254)

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income tax expense	$ 9,141	$ 14,326	$ 36,418	$ 27,438
Amount of change in deferred tax assets valuation allowance			11,800
Gross unrecognized tax benefits	$ 20,400		$ 20,400		$ 25,300

Earnings Per Share - Computatio

Earnings Per Share - Computation of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Net income attributable to Amkor common stockholders	$ 54,070	$ 56,662	$ 21,741	$ 98,797
Weighted-average number of common shares outstanding — basic (in shares)	239,586	239,370	239,503	239,312
Effect of dilutive securities:
Stock options and restricted share awards (in shares)	351	396	355	471
Weighted-average number of common shares outstanding - diluted (in shares)	239,937	239,766	239,858	239,783
Net income attributable to Amkor per common share:
Basic (in dollars per share)	$ 0.23	$ 0.24	$ 0.09	$ 0.41
Diluted (in dollars per share)	$ 0.23	$ 0.24	$ 0.09	$ 0.41

Earnings Per Share - Potential

Earnings Per Share - Potential Shares of Common Stock Excluded from Diluted EPS (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Stock options and restricted share awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from diluted EPS (in shares)	6,347	3,656	6,487	3,544

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	$ 1,831,176	$ 1,770,158	$ 1,855,900	$ 1,719,709
Other comprehensive income (loss) before reclassifications			3,745	(2,664)
Amounts reclassified from accumulated other comprehensive income (loss)			(314)	(126)
Total other comprehensive income (loss)	(74)	(6,656)	3,431	(2,790)
Balance at end of period	1,887,620	1,821,841	1,887,620	1,821,841
Defined Benefit Pension
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period			2,659	6,303
Other comprehensive income (loss) before reclassifications			0	0
Amounts reclassified from accumulated other comprehensive income (loss)			(314)	(126)
Total other comprehensive income (loss)			(314)	(126)
Balance at end of period	2,345	6,177	2,345	6,177
Foreign Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period			21,153	16,216
Other comprehensive income (loss) before reclassifications			3,745	(2,664)
Amounts reclassified from accumulated other comprehensive income (loss)			0	0
Total other comprehensive income (loss)			3,745	(2,664)
Balance at end of period	24,898	13,552	24,898	13,552
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	27,317	26,385	23,812	22,519
Total other comprehensive income (loss)	(74)	(6,656)	3,431	(2,790)
Balance at end of period	$ 27,243	$ 19,729	$ 27,243	$ 19,729

Factoring of Accounts Receiva_2

Factoring of Accounts Receivable (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net Factored
Factoring of Accounts Receivable [Line Items]
Accounts receivable sold	$ 175.4	$ 193.6	$ 480.2	$ 622.2
Discounts and Fees
Factoring of Accounts Receivable [Line Items]
Accounts receivable sold	$ 1.1	$ 1.6	$ 3.3	$ 5.4

Property, Plant and Equipment -

Property, Plant and Equipment - Summary of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 7,371,642	$ 7,270,623
Accumulated depreciation and amortization	(4,905,575)	(4,620,175)
Total property, plant and equipment, net	2,466,067	2,650,448
Land
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	219,928	222,884
Land use rights
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	0	26,845
Buildings and improvements
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	1,571,315	1,523,065
Machinery and equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	5,298,866	5,196,930
Finance lease assets
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	31,096	25,874
Software and computer equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	219,463	213,440
Furniture, fixtures and other equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	19,644	17,204
Construction in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 11,330	$ 44,381

Property, Plant and Equipment_2

Property, Plant and Equipment - Summary of Depreciation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 128,846	$ 143,334	$ 396,984	$ 427,836

Leases - Components of Lease Ex

Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 11,664		$ 29,389
Finance lease cost
Amortization of leased assets	1,417		3,628
Interest on lease liabilities	254		666
Total finance lease cost	1,671		4,294
Short-term lease cost	2,050		6,411
Variable lease cost	1,428		4,557
Net lease cost	$ 16,813		44,651
Rent expense		$ 9,300		$ 33,400
Operating cash flows for operating leases			28,254
Operating cash flows for finance leases			652
Financing cash flows for finance leases			$ 4,358	$ 2,669
Operating leases, Weighted average remaining lease term	4 years 4 months 24 days		4 years 4 months 24 days
Finance leases, Weighted average remaining lease term	3 years 10 months 24 days		3 years 10 months 24 days
Operating leases, Weighted average discount rate	4.20%		4.20%
Finance leases, Weighted average discount rate	4.60%		4.60%
Minimum
Lessee, Lease, Description [Line Items]
Remaining lease term			1 year
Maximum
Lessee, Lease, Description [Line Items]
Remaining lease term			86 years

Leases - Future Minimum Lease P

Leases - Future Minimum Lease Payments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Operating Leases
2019 - Remaining	$ 11,464
2020	41,204
2021	31,232
2022	17,405
2023	9,818
Thereafter	26,842
Total future minimum lease payments	137,965
Less: Imputed interest	(13,736)
Total	124,229
2019		$ 32,461
2020		24,630
2021		17,676
2022		10,942
2023		9,008
Thereafter		26,070
Total future minimum lease payments		120,787
Finance Leases
2019 - Remaining	2,317
2020	8,320
2021	7,248
2022	2,014
2023	941
Thereafter	3,757
Total future minimum lease payments	24,597
Less: Imputed interest	(2,366)
Total	22,231
2019		6,430
2020		4,555
2021		4,748
2022		936
2023		936
Thereafter		3,807
Total future minimum lease payments		$ 21,412
Amount of leases not yet commenced	$ 19,800

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Payroll and benefits	$ 108,167	$ 124,943
Short-term operating lease liability	39,135	0
Deferred revenue and customer advances	16,104	16,736
Income taxes payable	14,845	38,567
Accrued severance plan obligations	12,667	13,179
Accrued interest	2,959	10,302
Other accrued expenses	59,999	54,482
Total accrued expenses	$ 253,876	$ 258,209

Debt (Details)

Debt (Details)	1 Months Ended									3 Months Ended		9 Months Ended
	Oct. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jul. 31, 2019USD ($)loan	Apr. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Jul. 31, 2018USD ($)	Dec. 31, 2016USD ($)	May 31, 2015USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Oct. 31, 2018USD ($)	May 30, 2017USD ($)	Mar. 31, 2017USD ($)	Nov. 30, 2015USD ($)
Debt Instrument [Line Items]
Long-term Debt		$ 1,305,432,000				$ 1,334,129,000				$ 1,305,432,000		$ 1,305,432,000
Less: Unamortized premium, discount and deferred debt costs, net		(7,475,000)				(1,818,000)				(7,475,000)		(7,475,000)
Less: Short-term borrowings and current portion of long-term debt		(102,952,000)				(114,579,000)				(102,952,000)		(102,952,000)
Long-term debt		1,195,005,000				1,217,732,000				1,195,005,000		1,195,005,000
Early extinguishment of debt										179,000	$ 1,149,000	8,535,000	$ 1,167,000
Proceeds from issuance of long-term debt												714,375,000	372,226,000
Repayments of long-term debt												92,700,000	75,000,000
Payments of long-term debt												847,155,000	279,697,000
Proceeds from revolving credit facilities												172,700,000	$ 0
Term loan, LIBOR plus 1.80%, due December 2019 | China
Debt Instrument [Line Items]
Short-term borrowings and long-term debt		0				48,000,000				0		0
Face amount of debt																$ 50,000,000
Payments of long-term debt												$ 48,000,000
Semiannual installment payments								$ 500,000
Term loan, LIBOR plus 1.80%, due December 2019 | China | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)								1.80%				1.80%
Term loan, LIBOR plus 1.60%, due March 2022 | China
Debt Instrument [Line Items]
Short-term borrowings and long-term debt		$ 29,500,000				0				$ 29,500,000		$ 29,500,000
Face amount of debt					$ 30,000,000
Proceeds from issuance of long-term debt					30,000,000
Interest rate at period end (as a percent)		3.80%								3.80%		3.80%
Semiannual installment payments					$ 500,000
Term loan, LIBOR plus 1.60%, due March 2022 | China | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)					1.60%							1.60%
Term Loan, LIBOR plus 1.40% due March 2022 | China
Debt Instrument [Line Items]
Short-term borrowings and long-term debt		$ 19,750,000				0				$ 19,750,000		$ 19,750,000
Term Loan, LIBOR plus 1.40% due March 2022 | China | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)												1.40%
Line of Credit | $250 million revolving credit facility, LIBOR plus 1.25%-1.75%, due July 2023 (Singapore) | Revolving Credit Facility
Debt Instrument [Line Items]
Short-term borrowings and long-term debt		$ 80,000,000				0				$ 80,000,000		$ 80,000,000
Credit facility, borrowing capacity							$ 250,000,000
Interest rate at period end (as a percent)		3.36%								3.36%		3.36%
Remaining borrowing capacity		$ 151,000,000								$ 151,000,000		$ 151,000,000
Proceeds from revolving credit facilities		80,000,000
Line of Credit | $250 million revolving credit facility, LIBOR plus 1.25%-1.75%, due July 2023 (Singapore) | Revolving Credit Facility | Subsequent Event
Debt Instrument [Line Items]
Repayments of long-term debt	$ 80,000,000
Line of Credit | $250 million revolving credit facility, LIBOR plus 1.25%-1.75%, due July 2023 (Singapore) | Revolving Credit Facility | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)							1.25%
Line of Credit | $250 million revolving credit facility, LIBOR plus 1.25%-1.75%, due July 2023 (Singapore) | Revolving Credit Facility | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)							1.75%
Line of Credit | $250 million revolving credit facility, LIBOR plus 1.25%-1.75%, due July 2023 (Singapore) | Revolving Credit Facility | Singapore
Debt Instrument [Line Items]
Credit facility, borrowing capacity		250,000,000								250,000,000		$ 250,000,000
Line of Credit | $250 million revolving credit facility, LIBOR plus 1.25%-1.75%, due July 2023 (Singapore) | Revolving Credit Facility | Singapore | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)												1.25%
Line of Credit | $250 million revolving credit facility, LIBOR plus 1.25%-1.75%, due July 2023 (Singapore) | Revolving Credit Facility | Singapore | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)												1.75%
Line of Credit | Revolving credit facility, TAIFX plus a bank-determined spread, due November 2020 (Taiwan) | Revolving Credit Facility | Taiwan
Debt Instrument [Line Items]
Short-term borrowings and long-term debt		$ 20,000,000				20,000,000				$ 20,000,000		$ 20,000,000
Credit facility, borrowing capacity																	$ 39,000,000
Interest rate at period end (as a percent)		3.31%								3.31%		3.31%
Remaining borrowing capacity		$ 19,000,000								$ 19,000,000		$ 19,000,000
Senior Notes | 6.375% Senior notes, due October 2022
Debt Instrument [Line Items]
Short-term borrowings and long-term debt		$ 0				524,971,000				$ 0		$ 0
Stated interest rate (as a percent)		6.375%		6.375%						6.375%		6.375%
Face amount of debt				$ 525,000,000
Debt redemption price				101.594%
Early extinguishment of debt				$ 8,400,000
Senior Notes | 6.625% Senior notes, due September 2027
Debt Instrument [Line Items]
Short-term borrowings and long-term debt		$ 525,000,000				0				$ 525,000,000		$ 525,000,000
Stated interest rate (as a percent)		6.625%			6.625%					6.625%		6.625%
Face amount of debt					$ 525,000,000
Debt issuance costs					$ 3,600,000
Debt discount percentage of par					99.50%
Debt discount					$ 2,600,000
Subsidiary Term Loans | Korea | Applicable Bank Rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)			2.03%
Face amount of debt			$ 40,000,000
Number of term loans | loan			2
Subsidiary Term Loans | $30 million revolving credit facility, LIBOR plus the applicable bank rate, due October 2019 | Korea
Debt Instrument [Line Items]
Short-term borrowings and long-term debt		$ 0				0				$ 0		$ 0
Subsidiary Term Loans | Term loan, fixed rate at 3.70%, due May 2020 | Korea
Debt Instrument [Line Items]
Short-term borrowings and long-term debt		$ 0				120,000,000				$ 0		$ 0
Stated interest rate (as a percent)		3.70%								3.70%		3.70%			3.70%
Face amount of debt															$ 120,000,000
Payments of long-term debt												$ 120,000,000
Subsidiary Term Loans | Term loan, fund floating rate plus 1.60%, due June 2020 | Korea
Debt Instrument [Line Items]
Short-term borrowings and long-term debt		$ 24,000,000				125,000,000				$ 24,000,000		24,000,000
Face amount of debt									$ 150,000,000
Payments of long-term debt												$ 101,000,000
Interest rate at period end (as a percent)		4.18%								4.18%		4.18%
Subsidiary Term Loans | Term loan, fund floating rate plus 1.60%, due June 2020 | Korea | Fund Floating Rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)									1.60%			1.60%
Subsidiary Term Loans | Term loan, applicable bank rate plus 2.02%, due July 2022 | Korea
Debt Instrument [Line Items]
Short-term borrowings and long-term debt		$ 40,000,000				0				$ 40,000,000		$ 40,000,000
Stated interest rate (as a percent)			3.80%
Face amount of debt			$ 40,000,000
Subsidiary Term Loans | Term loan, applicable bank rate plus 2.02%, due July 2022 | Korea | Applicable Bank Rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)												2.03%
Subsidiary Term Loans | Term loan, applicable bank rate plus 2.03%, due September 2022 | Korea
Debt Instrument [Line Items]
Short-term borrowings and long-term debt		$ 60,000,000				0				$ 60,000,000		$ 60,000,000
Stated interest rate (as a percent)		3.59%								3.59%		3.59%
Unused borrowing capacity		$ 80,000,000								$ 80,000,000		$ 80,000,000
Proceeds from issuance of long-term debt		60,000,000
Subsidiary Term Loans | Term loan, applicable bank rate plus 2.03%, due September 2022 | Korea | Applicable Bank Rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)												2.03%
Subsidiary Term Loans | Term loan, LIBOR plus 2.56%, due December 2023 | Korea
Debt Instrument [Line Items]
Short-term borrowings and long-term debt		200,000,000				200,000,000				200,000,000		$ 200,000,000
Subsidiary Term Loans | Term loan, LIBOR plus 2.56%, due December 2023 | Korea | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)												2.56%
Subsidiary Term Loans | Term loan, applicable bank rate plus 1.98%, due December 2028 | Korea
Debt Instrument [Line Items]
Short-term borrowings and long-term debt		66,000,000				$ 24,000,000				66,000,000		$ 66,000,000
Face amount of debt					$ 90,000,000
Unused borrowing capacity		$ 24,000,000								$ 24,000,000		24,000,000
Proceeds from issuance of long-term debt												$ 42,000,000
Interest rate at period end (as a percent)		4.50%								4.50%		4.50%
Subsidiary Term Loans | Term loan, applicable bank rate plus 1.98%, due December 2028 | Korea | Applicable Bank Rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)						1.98%						1.98%
Subsidiary Term Loans | Short-term term loans, variable rate | Japan
Debt Instrument [Line Items]
Short-term borrowings and long-term debt		$ 17,737,000				$ 8,232,000				$ 17,737,000		$ 17,737,000
Unused borrowing capacity		$ 6,000,000								$ 6,000,000		$ 6,000,000
Subsidiary Term Loans | Short-term term loans, variable rate | Japan | Weighted Average
Debt Instrument [Line Items]
Weighted average interest rate (as a percent)		0.23%								0.23%		0.23%
Subsidiary Term Loans | Short-term term loans, variable rate | Japan | TIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)												0.10%
Subsidiary Term Loans | Short-term term loans, variable rate | Japan | TIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)												0.27%
Subsidiary Term Loans | Term loan, fixed rate at 0.86%, due June 2022 | Japan
Debt Instrument [Line Items]
Short-term borrowings and long-term debt		$ 25,444,000				31,908,000				$ 25,444,000		$ 25,444,000
Stated interest rate (as a percent)		0.86%								0.86%		0.86%
Subsidiary Term Loans | Term loan, fixed rate at 0.60%, due July 2022 | Japan
Debt Instrument [Line Items]
Short-term borrowings and long-term debt		$ 5,551,000				6,838,000				$ 5,551,000		$ 5,551,000
Stated interest rate (as a percent)		0.60%								0.60%		0.60%
Subsidiary Term Loans | Term loan, fixed rate at 1.30% Due July 2023 | Japan
Debt Instrument [Line Items]
Short-term borrowings and long-term debt		$ 192,450,000				$ 225,180,000				$ 192,450,000		$ 192,450,000
Stated interest rate (as a percent)		1.30%								1.30%		1.30%
Subsidiary Term Loans | Revolving credit facility due October 2020 | Korea
Debt Instrument [Line Items]
Credit facility, borrowing capacity		$ 30,000,000								$ 30,000,000		$ 30,000,000		$ 30,000,000
Unused borrowing capacity		$ 30,000,000								$ 30,000,000		$ 30,000,000
Subsidiary Term Loans | Amkor Assembly & Test (Shanghai) Co., Ltd. Term Loan | China
Debt Instrument [Line Items]
Face amount of debt				20,000,000
Proceeds from issuance of long-term debt				20,000,000
Interest rate at period end (as a percent)		3.53%								3.53%		3.53%
Semiannual installment payments				$ 500,000
Subsidiary Term Loans | Amkor Assembly & Test (Shanghai) Co., Ltd. Term Loan | China | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)				1.40%

Pension Plans - Components of N

Pension Plans - Components of Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Retirement Benefits [Abstract]
Service cost	$ 7,747	$ 8,124	$ 23,513	$ 24,839
Interest cost	1,297	1,199	3,926	3,668
Expected return on plan assets	(1,585)	(1,390)	(4,798)	(4,249)
Recognized actuarial gain	(94)	(36)	(282)	(113)
Net periodic pension cost	$ 7,365	$ 7,897	$ 22,359	$ 24,145

Pension Plans - Summary of Defi

Pension Plans - Summary of Defined Contribution Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Retirement Benefits [Abstract]
Defined contribution expense	$ 2,952	$ 2,595	$ 10,708	$ 9,608

Fair Value Measurements - Recur

Fair Value Measurements - Recurring Measurements (Details) - Recurring Fair Value Measurements - Level 1 - Money Market Funds - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalent money market funds	$ 57,904	$ 74,407
Restricted cash money market funds	$ 2,590	$ 2,589

Fair Value Measurements - Instr

Fair Value Measurements - Instruments Not Recorded on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total debt	$ 1,358,280	$ 1,329,998
Fair Value | Senior notes | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total debt	573,636	526,131
Fair Value | Revolving credit facilities and term loans | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total debt	784,644	803,867
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total debt	1,297,957	1,332,311
Carrying Value | Senior notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total debt	519,069	524,978
Carrying Value | Revolving credit facilities and term loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total debt	$ 778,888	$ 807,333