Note 16 - Reportable Segments - Reconciliation of Reportable Segment Net Income (Loss) to Consolidated Net Income (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Net income (loss) attributable to Corning Incorporated		$ 599	$ (96)
Gain on foreign currency hedges related to translated earnings		272	68
Research, development, and engineering expenses		(222)	(261)
Amortization of intangibles		(32)	(26)
Interest expense, net		(77)	(64)
Income tax (provision) benefit		226	(12)
Cumulative adjustment related to customer contract	[1]		105
Severance charges			(77)
Operating Segments [Member]
Net income (loss) attributable to Corning Incorporated	[2]	513	236
Research, development, and engineering expenses	[3]	(187)	(209)
Income tax (provision) benefit	[4]	(136)	(62)
Operating Segments [Member] | Reportable Segments [Member]
Net income (loss) attributable to Corning Incorporated		537	305
Operating Segments [Member] | Nonreportable Segments [Member]
Net income (loss) attributable to Corning Incorporated	[5]	(24)	(69)
Segment Reconciling Items [Member]
Impact of foreign currency movements not included in segment net income (loss)		6	(19)
Gain on foreign currency hedges related to translated earnings		272	58
Translation gain (loss) on Japanese yen-denominated debt		118	(14)
Research, development, and engineering expenses		(34)	(39)
Amortization of intangibles		(32)	(26)
Interest expense, net		(74)	(58)
Income tax (provision) benefit		(90)	74
Cumulative adjustment related to customer contract	[6]		(105)
Severance charges	[7]		(77)
Capacity realignment and other charges and credits	[7]		(148)
Other corporate items		$ (80)	$ 22

[1] Amount represents the negative impact of a cumulative adjustment to reduce revenue in the amount of $105 million recorded during the first quarter of 2020. The adjustment was associated with a previously recorded commercial benefit asset, reflected as a prepayment, to a customer with a long-term supply agreement that exited its production of LCD panels.

[2] Many of Corning's administrative and staff functions are performed on a centralized basis. Where practicable, Corning charges these expenses to segments based upon the extent to which each business uses a centralized function. Other staff functions, such as corporate finance, human resources and legal, are allocated to segments, primarily as a percentage of sales. Expenses that are not allocated to the segments are included in the reconciliation of reportable segment net income (loss) to consolidated net income (loss).

[3] Research, development and engineering expenses include direct project spending that is identifiable to a segment.

[4] Income tax (provision) benefit reflects a tax rate of 21%.

[5] The Company obtained a controlling interest in HSG during the third quarter of 2020 and has consolidated results in “All Other” as of September 9, 2020.

[6] Amount represents the negative impact of a cumulative adjustment to reduce revenue in the amount of $105 million recorded during the first quarter of 2020. The adjustment was associated with a previously recorded commercial benefit asset, reflected as a prepayment, to a customer with a long-term supply agreement that is exiting its production of LCD panels. Refer to Note 4 (Revenue) to the consolidated financial statements for additional information.

[7] Refer to Note 2 (Restructuring, Impairment and Other Charges and Credits) to the consolidated financial statements for additional information on restructuring activities and impairment.