Derivative Cap Price Per Share

No definition available.

Name:	gbt_DerivativeCapPricePerShare
Namespace Prefix:	gbt_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- 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.

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

- Definition

The price per share of the conversion feature embedded in the debt instrument.

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Name:	us-gaap_DebtInstrumentConvertibleConversionPrice1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

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Period Type:	duration

- Definition

The number of equity instruments that the holder of the debt instrument would receive if the debt was converted to equity.

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Balance Type:	na
Period Type:	duration

- Definition

Threshold period of specified consecutive trading days within which common stock price to conversion price of convertible debt instrument must exceed threshold percentage for specified number of trading days to trigger conversion feature.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum percentage of common stock price to conversion price of convertible debt instruments to determine eligibility of conversion.

+ References

No definition available.

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Name:	us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Threshold number of specified trading days that common stock price to conversion price of convertible debt instruments must exceed threshold percentage within a specified consecutive trading period to trigger conversion feature.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types: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.

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Balance Type:	na
Period Type:	duration

- Definition

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

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Balance Type:	na
Period Type:	duration

- Definition

Percentage of principal amount of debt redeemed.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value amount of debt instrument that was repurchased.

+ References

No definition available.

+ Details

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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.

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- Definition

Nominal or face amount used to calculate payments on the derivative liability.

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Balance Type:	na
Period Type:	instant

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermDebtFairValue
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Balance Type:	credit
Period Type:	instant

- Definition

The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt.

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- Definition

The cash inflow from the issuance of a long-term debt instrument which can be exchanged for a specified amount of another security, typically the entity's common stock, at the option of the issuer or the holder.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Price of a single share of a number of saleable stocks of a company.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Namespace Prefix:
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Period Type:

- Details

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Period Type:

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Convertible Debt (Additional Information) (Details)	6 Months Ended		12 Months Ended
Convertible Debt (Additional Information) (Details)	Jun. 30, 2022 USD ($) Days $ / shares	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($) $ / shares
Debt Instrument [Line Items]
Debt instrument principal amount	$ 345,000,000.0
Payments Of Debt Issuance Costs	0	$ 49,000
Unamortized debt issuance costs	10,200,000
Long-term debt, gross	$ 250,000,000
One Point Eight Seven Five Percent Convertible Senior Notes Due 2028 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage	2.37%
Debt instrument, fair value	$ 7,200,000
Convertible Debt [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage	1.875%		1.875%
Convertible Debt [Member] \| One Point Eight Seven Five Percent Convertible Senior Notes Due 2028 [Member]
Debt Instrument [Line Items]
Debt instrument principal amount			$ 345,000,000.0
Payments Of Debt Issuance Costs			11,000,000.0
Proceeds from convertible debt			334,000.0
Capped calls transactions	$ 46,800,000		$ 46,800,000
Maturity date			Dec. 15, 2028
Debt instrument convertible conversion ratio			31.4985
Debt instrument repurchase amount	$ 1,000,000
Debt instrument, convertible, conversion price \| $ / shares			$ 31.75
Debt instrument, convertible, threshold percentage of stock price trigger	130.00%
Debt instrument, convertible, threshold trading days \| Days	20
Debt instrument, convertible, threshold consecutive trading days \| Days	30
Debt instrument, redemption price, percentage of principal amount redeemed			100.00%
Derivative cap price per share \| $ / shares	$ 31.7475
Number of shares of common stock underlying notes \| Days	10,866,983
Convertible Debt [Member] \| One Point Eight Seven Five Percent Convertible Senior Notes Due 2028 [Member] \| Call Option [Member]
Debt Instrument [Line Items]
Debt instrument principal amount			$ 45,000,000.0
Share price \| $ / shares	$ 49.80
Non Convertible Debt [Member]
Debt Instrument [Line Items]
Debt instrument principal amount	$ 100,000,000.0