Stock Option Plan - Summary of Stock Options Outstanding and Exercisable by Exercise Price (Details) - $ / shares	6 Months Ended
Jun. 30, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options Outstanding, Number Outstanding	1,052,936
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	7 years 1 month 6 days
Options Outstanding, Weighted-Average Exercise Price	$ 2.08	$ 2.01
Options Vested and Exercisable, Number Exercisable	493,137
Options Vested and Exercisable, Weighted-Average Exercise Price	$ 1.86
Exercise Price 0.16
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise Price	$ 0.16
Options Outstanding, Number Outstanding	64,950
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	4 years 7 months 6 days
Options Outstanding, Weighted-Average Exercise Price	$ 0.16
Options Vested and Exercisable, Number Exercisable	64,950
Options Vested and Exercisable, Weighted-Average Exercise Price	$ 0.16
Exercise Price 0.37
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise Price	$ 0.37
Options Outstanding, Number Outstanding	153,338
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	5 years 10 months 24 days
Options Outstanding, Weighted-Average Exercise Price	$ 0.37
Options Vested and Exercisable, Number Exercisable	70,663
Options Vested and Exercisable, Weighted-Average Exercise Price	$ 0.37
Exercise Price 0.97
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise Price	$ 0.97
Options Outstanding, Number Outstanding	144,001
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	6 years 8 months 12 days
Options Outstanding, Weighted-Average Exercise Price	$ 0.97
Options Vested and Exercisable, Number Exercisable	73,952
Options Vested and Exercisable, Weighted-Average Exercise Price	$ 0.97
Exercise Price 2.51
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise Price	$ 2.51
Options Outstanding, Number Outstanding	177,695
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	7 years 2 months 12 days
Options Outstanding, Weighted-Average Exercise Price	$ 2.51
Options Vested and Exercisable, Number Exercisable	80,860
Options Vested and Exercisable, Weighted-Average Exercise Price	$ 2.51
Exercise Price 2.89
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise Price	$ 2.89
Options Outstanding, Number Outstanding	49,000
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	7 years 8 months 12 days
Options Outstanding, Weighted-Average Exercise Price	$ 2.89
Options Vested and Exercisable, Number Exercisable	19,500
Options Vested and Exercisable, Weighted-Average Exercise Price	$ 2.89
Exercise Price 2.93
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise Price	$ 2.93
Options Outstanding, Number Outstanding	333,752
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	7 years 10 months 24 days
Options Outstanding, Weighted-Average Exercise Price	$ 2.93
Options Vested and Exercisable, Number Exercisable	139,097
Options Vested and Exercisable, Weighted-Average Exercise Price	$ 2.93
Exercise Price 3.18
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise Price	$ 3.18
Options Outstanding, Number Outstanding	130,200
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	8 years 1 month 6 days
Options Outstanding, Weighted-Average Exercise Price	$ 3.18
Options Vested and Exercisable, Number Exercisable	44,115
Options Vested and Exercisable, Weighted-Average Exercise Price	$ 3.18

Share based compensation shares authorized under stock option plans exercise price.

No definition available.

Name:	ck0001556898_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePrice
Namespace Prefix:	ck0001556898_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

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

- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of fully vested and expected to vest exercisable options that may be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (e)(2)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (e)(2)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Weighted average remaining contractual term of outstanding stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (e)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=ck0001556898_ExercisePriceZeroPointOneSixMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=ck0001556898_ExercisePriceZeroPointThreeSevenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=ck0001556898_ExercisePriceZeroPointNineSevenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=ck0001556898_ExercisePriceTwoPointFiveOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=ck0001556898_ExercisePriceTwoPointEightNineMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=ck0001556898_ExercisePriceTwoPointNineThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=ck0001556898_ExercisePriceThreePointOneEightMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: