Debt Outstanding Debt (Details) - USD ($) $ in Millions	6 Months Ended
Jul. 01, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total Borrowings at Par Value	$ 16,873.3	$ 16,701.0
Fair Value Hedge Accounting Adjustments	(40.6)	(49.3)
Unamortized Premium, Net	34.0	52.2
Unamortized Debt Issuance Costs	(70.6)	(76.0)
Total Borrowings at Carrying Value	16,796.1	16,627.9
Less: Short-term Obligations and Current Maturities	1,540.4	1,255.5
Long-term Obligations	$ 15,255.7	15,372.4
Commercial Paper Programs [Member]
Debt Instrument [Line Items]
Effective Interest Rate	0.27%
Total Borrowings at Par Value	$ 1,538.1	953.3
Total Borrowings at Carrying Value	1,538.1	953.3
Term Loan [Member]
Debt Instrument [Line Items]
Total Borrowings at Par Value		825.0
Total Borrowings at Carrying Value		823.3
Senior Notes [Member]
Debt Instrument [Line Items]
Total Borrowings at Carrying Value	$ 15,246.0	14,838.3
Debt Instrument, Call Feature	Each of the notes may be redeemed at a redemption price of 100% of the principal amount plus a specified make-whole premium plus accrued interest.
Senior Notes [Member] \| 1.85% 5-Year Senior Notes, Due 1/15/2018 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	1.85%
Debt Instrument, Term	5 years
Debt Instrument, Maturity Date	Jan. 15, 2018
Total Borrowings at Par Value		500.0
Senior Notes [Member] \| Floating Rate 2-Year Senior Notes Due 8/9/2018 (euro-denominated) [Member]
Debt Instrument [Line Items]
Debt Instrument, Term	2 years
Debt Instrument, Maturity Date	Aug. 09, 2018
Effective Interest Rate	0.12%
Total Borrowings at Par Value	$ 685.6	631.0
Senior Notes [Member] \| 2.15% 3-Year Senior Notes, Due 12/14/2018 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	2.15%
Debt Instrument, Term	3 years
Debt Instrument, Maturity Date	Dec. 14, 2018
Effective Interest Rate	2.35%
Total Borrowings at Par Value	$ 450.0	450.0
Senior Notes [Member] \| 2.40% 5-Year Senior Notes, Due 2/1/2019 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	2.40%
Debt Instrument, Term	5 years
Debt Instrument, Maturity Date	Feb. 01, 2019
Effective Interest Rate	2.59%
Total Borrowings at Par Value	$ 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%
Debt Instrument, Term	10 years
Debt Instrument, Maturity Date	Mar. 01, 2020
Effective Interest Rate	2.97%
Total Borrowings at Par Value	$ 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%
Debt Instrument, Term	10 years
Debt Instrument, Maturity Date	May 01, 2020
Effective Interest Rate	4.23%
Total Borrowings at Par Value	$ 300.0	300.0
Senior Notes [Member] \| 1.50% 5-Year Senior Notes, Due 12/1/2020 (euro-denominated) [Member]
Debt Instrument [Line Items]
Stated Interest Rate	1.50%
Debt Instrument, Term	5 years
Debt Instrument, Maturity Date	Dec. 01, 2020
Effective Interest Rate	1.62%
Total Borrowings at Par Value	$ 485.6	447.0
Senior Notes [Member] \| 5.00% 10-Year Senior Notes, Due 1/15/2021 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	5.00%
Debt Instrument, Term	10 years
Debt Instrument, Maturity Date	Jan. 15, 2021
Effective Interest Rate	3.24%
Total Borrowings at Par Value	$ 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%
Debt Instrument, Term	10 years
Debt Instrument, Maturity Date	Mar. 01, 2021
Effective Interest Rate	4.72%
Total Borrowings at Par Value	$ 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%
Debt Instrument, Term	10 years
Debt Instrument, Maturity Date	Aug. 15, 2021
Effective Interest Rate	4.55%
Total Borrowings at Par Value	$ 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%
Debt Instrument, Term	7 years
Debt Instrument, Maturity Date	Feb. 15, 2022
Effective Interest Rate	3.43%
Total Borrowings at Par Value	$ 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%
Debt Instrument, Term	7 years
Debt Instrument, Maturity Date	Jul. 21, 2022
Effective Interest Rate	2.28%
Total Borrowings at Par Value	$ 571.3	525.9
Senior Notes [Member] \| 3.15% 10-Year Senior Notes, Due 1/15/2023 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	3.15%
Debt Instrument, Term	10 years
Debt Instrument, Maturity Date	Jan. 15, 2023
Effective Interest Rate	3.31%
Total Borrowings at Par Value	$ 800.0	800.0
Senior Notes [Member] \| 3.00% 7-Year Senior Notes, Due 4/15/2023 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	3.00%
Debt Instrument, Term	7 years
Debt Instrument, Maturity Date	Apr. 15, 2023
Effective Interest Rate	4.82%
Total Borrowings at Par Value	$ 1,000.0	1,000.0
Senior Notes [Member] \| 4.15% 10-Year Senior Notes, Due 2/1/2024 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	4.15%
Debt Instrument, Term	10 years
Debt Instrument, Maturity Date	Feb. 01, 2024
Effective Interest Rate	4.16%
Total Borrowings at Par Value	$ 1,000.0	1,000.0
Senior Notes [Member] \| 0.75% 8-Year Senior Notes, Due 9/12/2024 (euro-denominated) [Member]
Debt Instrument [Line Items]
Stated Interest Rate	0.75%
Debt Instrument, Term	8 years
Debt Instrument, Maturity Date	Sep. 12, 2024
Effective Interest Rate	0.94%
Total Borrowings at Par Value	$ 1,142.6	1,051.7
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%
Debt Instrument, Term	10 years
Debt Instrument, Maturity Date	Apr. 15, 2025
Effective Interest Rate	2.09%
Total Borrowings at Par Value	$ 731.3	673.1
Senior Notes [Member] \| 3.65% 10-Year Senior Notes, Due 12/15/2025 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	3.65%
Debt Instrument, Term	10 years
Debt Instrument, Maturity Date	Dec. 15, 2025
Effective Interest Rate	3.77%
Total Borrowings at Par Value	$ 350.0	350.0
Senior Notes [Member] \| 2.95% 10-Year Senior Notes, Due 9/19/2026 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	2.95%
Debt Instrument, Term	10 years
Debt Instrument, Maturity Date	Sep. 19, 2026
Effective Interest Rate	3.19%
Total Borrowings at Par Value	$ 1,200.0	1,200.0
Senior Notes [Member] \| 1.45% 10-Year Senior Notes, Due 3/16/2027 (euro-denominated) [Member]
Debt Instrument [Line Items]
Stated Interest Rate	1.45%
Debt Instrument, Term	10 years
Debt Instrument, Maturity Date	Mar. 16, 2027
Effective Interest Rate	1.66%
Total Borrowings at Par Value	$ 571.3
Senior Notes [Member] \| 1.375% 12-Year Senior Notes, 9/12/2028 (euro-denominated) [Member]
Debt Instrument [Line Items]
Stated Interest Rate	1.375%
Debt Instrument, Term	12 years
Debt Instrument, Maturity Date	Sep. 12, 2028
Effective Interest Rate	1.46%
Total Borrowings at Par Value	$ 685.5	631.0
Senior Notes [Member] \| 5.30% 30-Year Senior Notes, Due 2/1/2044 [Member]
Debt Instrument [Line Items]
Stated Interest Rate	5.30%
Debt Instrument, Term	30 years
Debt Instrument, Maturity Date	Feb. 01, 2044
Effective Interest Rate	5.37%
Total Borrowings at Par Value	$ 400.0	400.0
Other Debt [Member]
Debt Instrument [Line Items]
Total Borrowings at Par Value	12.0	13.0
Total Borrowings at Carrying Value	$ 12.0	$ 13.0

Adjustment to the carrying value of an interest-bearing hedged item resulting from an interest rate fair value hedge.

No definition available.

Name:	tmo_FairValueHedgeAccountingAdjustments
Namespace Prefix:	tmo_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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.

+ References

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=75038535&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, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ 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 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

Reference 3: 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(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ 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

+ 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

Amount, after accumulated amortization, of debt discount (premium).

+ 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=64930785&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=64930785&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=64930739&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=64930785&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=64930785&loc=d3e28555-108399

+ Details

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

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: 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=64930785&loc=d3e28555-108399

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 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

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

+ References

+ Details

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