Debt Outstanding Debt (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 26, 2015	Sep. 26, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Principal Outstanding	$ 13,171.3	$ 13,171.3	$ 14,422.5
Fair Value Hedge Accounting Adjustments	26.9	26.9	(0.5)
Unamortized Premium, Net	113.7	113.7	142.0
Debt Obligations - Carrying Value	13,311.9	13,311.9	14,564.0
Less: Short-term obligations and current maturities of long-term obligations	3,034.0	3,034.0	2,212.4
Long-term Obligations	$ 10,277.9	10,277.9	12,351.6
Losses on Extinguishment of Debt		$ 6.0
Commercial Paper [Member]
Debt Instrument [Line Items]
Effective Interest Rate	1.01%	1.01%
Principal Outstanding	$ 727.6	$ 727.6	0.0
Debt Obligations - Carrying Value	727.6	727.6	0.0
Term Loan
Debt Instrument [Line Items]
Principal Outstanding	0.0	0.0	1,275.0
Debt Obligations - Carrying Value	0.0	0.0	1,275.0
Losses on Extinguishment of Debt	3.0
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Obligations - Carrying Value	$ 12,566.9	$ 12,566.9	13,265.8
Debt Instrument, Call Feature		Each of the notes may be redeemed at any time at a redemption price of 100% of the principal amount plus a specified make-whole premium plus accrued interest
Senior Notes [Member] \| 4.40% 5-Year Senior Notes, Due 3/1/2015 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	4.40%	4.40%
Debt Instrument, Term		5 years
Debt Instrument, Maturity Date		Mar. 01, 2015
Principal Outstanding	$ 0.0	$ 0.0	500.0
Senior Notes [Member] \| 3.20% 5-Year Senior Notes, Due 5/1/2015 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	3.20%	3.20%
Debt Instrument, Term		5 years
Debt Instrument, Maturity Date		May 01, 2015
Principal Outstanding	$ 0.0	$ 0.0	450.0
Senior Notes [Member] \| 5.00% 10-Year Senior Notes, Due 6/1/2015 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	5.00%	5.00%
Debt Instrument, Term		10 years
Debt Instrument, Maturity Date		Jun. 01, 2015
Principal Outstanding	$ 0.0	$ 0.0	250.0
Losses on Extinguishment of Debt		$ 3.0
Senior Notes [Member] \| 3.50% 5-Year Senior Notes, Due 1/15/2016 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	3.50%	3.50%
Debt Instrument, Term		5 years
Debt Instrument, Maturity Date		Jan. 15, 2016
Effective Interest Rate	1.06%	1.06%
Principal Outstanding	$ 400.0	$ 400.0	400.0
Senior Notes [Member] \| 3.20% 5-Year Senior Notes, Due 3/1/2016 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	3.20%	3.20%
Debt Instrument, Term		5 years
Debt Instrument, Maturity Date		Mar. 01, 2016
Effective Interest Rate	3.21%	3.21%
Principal Outstanding	$ 900.0	$ 900.0	900.0
Senior Notes [Member] \| 2.25% 5-Year Senior Notes, Due 8/15/2016 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	2.25%	2.25%
Debt Instrument, Term		5 years
Debt Instrument, Maturity Date		Aug. 15, 2016
Effective Interest Rate	2.29%	2.29%
Principal Outstanding	$ 1,000.0	$ 1,000.0	1,000.0
Senior Notes [Member] \| 1.30% 3-Year Senior Notes, Due 2/1/2017 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	1.30%	1.30%
Debt Instrument, Term		3 years
Debt Instrument, Maturity Date		Feb. 01, 2017
Effective Interest Rate	0.70%	0.70%
Principal Outstanding	$ 900.0	$ 900.0	900.0
Senior Notes [Member] \| 1.85% 5-Year Senior Notes, Due 1/15/2018 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	1.85%	1.85%
Debt Instrument, Term		5 years
Debt Instrument, Maturity Date		Jan. 15, 2018
Effective Interest Rate	1.85%	1.85%
Principal Outstanding	$ 500.0	$ 500.0	500.0
Senior Notes [Member] \| 2.40% 5-Year Senior Notes, Due 2/1/2019 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	2.40%	2.40%
Debt Instrument, Term		5 years
Debt Instrument, Maturity Date		Feb. 01, 2019
Effective Interest Rate	2.44%	2.44%
Principal Outstanding	$ 900.0	$ 900.0	900.0
Senior Notes [Member] \| 6.00% 10-Year Senior Notes, Due 3/1/2020 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	6.00%	6.00%
Debt Instrument, Term		10 years
Debt Instrument, Maturity Date		Mar. 01, 2020
Effective Interest Rate	2.98%	2.98%
Principal Outstanding	$ 750.0	$ 750.0	750.0
Senior Notes [Member] \| 4.70% 10-Year Senior Notes, Due 5/1/2020 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	4.70%	4.70%
Debt Instrument, Term		10 years
Debt Instrument, Maturity Date		May 01, 2020
Effective Interest Rate	3.03%	3.03%
Principal Outstanding	$ 300.0	$ 300.0	300.0
Senior Notes [Member] \| 5.00% 10-Year Senior Notes, Due 1/15/2021 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	5.00%	5.00%
Debt Instrument, Term		10 years
Debt Instrument, Maturity Date		Jan. 15, 2021
Effective Interest Rate	3.25%	3.25%
Principal Outstanding	$ 400.0	$ 400.0	400.0
Senior Notes [Member] \| 4.50% 10-Year Senior Notes, Due 3/1/2021 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	4.50%	4.50%
Debt Instrument, Term		10 years
Debt Instrument, Maturity Date		Mar. 01, 2021
Effective Interest Rate	2.93%	2.93%
Principal Outstanding	$ 1,000.0	$ 1,000.0	1,000.0
Senior Notes [Member] \| 3.60% 10-Year Senior Notes, Due 8/15/2021 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	3.60%	3.60%
Debt Instrument, Term		10 years
Debt Instrument, Maturity Date		Aug. 15, 2021
Effective Interest Rate	2.63%	2.63%
Principal Outstanding	$ 1,100.0	$ 1,100.0	1,100.0
Senior Notes [Member] \| 3.30% 7-Year Senior Notes, Due 2/15/2022 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	3.30%	3.30%
Debt Instrument, Term		7 years
Debt Instrument, Maturity Date		Feb. 15, 2022
Effective Interest Rate	3.30%	3.30%
Principal Outstanding	$ 800.0	$ 800.0	800.0
Senior Notes [Member] \| 2.15% 7-Year Senior Notes, Due 7/21/2022 (euro denominated) [Member]
Debt Instrument [Line Items]
Stated Interest Rate	2.15%	2.15%
Debt Instrument, Term		7 years
Debt Instrument, Maturity Date		Jul. 21, 2022
Effective Interest Rate	2.18%	2.18%
Principal Outstanding	$ 559.8	$ 559.8	0.0
Senior Notes [Member] \| 3.15% 10-Year Senior Notes, Due 1/15/2023 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	3.15%	3.15%
Debt Instrument, Term		10 years
Debt Instrument, Maturity Date		Jan. 15, 2023
Effective Interest Rate	3.21%	3.21%
Principal Outstanding	$ 800.0	$ 800.0	800.0
Senior Notes [Member] \| 4.15% 10-Year Senior Notes, Due 2/1/2024 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	4.15%	4.15%
Debt Instrument, Term		10 years
Debt Instrument, Maturity Date		Feb. 01, 2024
Effective Interest Rate	4.07%	4.07%
Principal Outstanding	$ 1,000.0	$ 1,000.0	1,000.0
Senior Notes [Member] \| 2.00% 10-Year Senior Notes, Due 4/15/2025 (euro denominated) [Member]
Debt Instrument [Line Items]
Stated Interest Rate	2.00%	2.00%
Debt Instrument, Term		10 years
Debt Instrument, Maturity Date		Apr. 15, 2025
Effective Interest Rate	2.03%	2.03%
Principal Outstanding	$ 716.5	$ 716.5	774.3
Senior Notes [Member] \| 5.30% 30-Year Senior Notes, Due 2/1/2044 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	5.30%	5.30%
Debt Instrument, Term		30 years
Debt Instrument, Maturity Date		Feb. 01, 2044
Effective Interest Rate	5.30%	5.30%
Principal Outstanding	$ 400.0	$ 400.0	400.0
Other Debt [Member]
Debt Instrument [Line Items]
Principal Outstanding	17.4	17.4	23.2
Debt Obligations - Carrying Value	$ 17.4	$ 17.4	$ 23.2

Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.13,16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

Name:	us-gaap_DebtAndCapitalLeaseObligations
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of short-term debt and current maturity of long-term debt and capital lease obligations due within one year or the normal operating cycle, if longer.

+ References

+ Details

Name:	us-gaap_DebtCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Description of a feature that permits the issuer of the debt to repay or convert it before the stated maturity date (early retirement date). The description may include such items as the call price, the period that the issuer can call the debt, including the earliest call date, and other significant terms of the call feature, which may include the debt holders' ability to convert the debt to equity if the call option is exercised and contingent events that trigger the issuer's ability to call the debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

-Section 50

-Paragraph 3

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(5))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentCallFeature
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of long-term debt before deduction of unamortized discount or premium. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, with initial maturities beyond one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

+ Details

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of debt discount (net of debt premium) that was originally recognized at the issuance of the instrument that has yet to be amortized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28567-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 1A

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28555-108399

+ Details

Name:	us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount as of the balance sheet date of the unamortized adjustment to the carrying value of an interest-bearing hedged item made under an effective fair value hedge that is amortized upon discontinuation of the fair value hedge.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 25

-Section 35

-Paragraph 9

-URI http://asc.fasb.org/extlink&oid=56949341&loc=d3e75592-113984

+ Details

Name:	us-gaap_DeferredGainLossOnDiscontinuationOfFairValueHedge
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 50

-Section 40

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12317-112629

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 50

-Section 40

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12355-112629

+ Details

Name:	us-gaap_GainsLossesOnExtinguishmentOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of long-term debt and capital lease obligation due after one year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 6

-Section H

+ Details

Name:	us-gaap_LongTermDebtAndCapitalLeaseObligations
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_CommercialPaperMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_UnsecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes440Due2015Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes320Due2015Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes5Due2015Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes350Due2016Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes320Due2016Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes225Due2016Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes130Due2017Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes185Due2018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes240Due2019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes600Due2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes470Due2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes500Due2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes450Due2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes360Due2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes330Due2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes215Due2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes315Due2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes415Due2024Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes200Due2025Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmo_SeniorNotes530Due2044Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=tmo_OtherDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: