Date of loan agreement payable.

No definition available.

Name:	cdna_DateOfLoanAgreementPayable
Namespace Prefix:	cdna_
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Balance Type:	na
Period Type:	duration

- Definition

Debentures prepayment date.

+ References

No definition available.

+ Details

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Balance Type:	na
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- Definition

Debt instrument pre payment premium percentage.

+ References

No definition available.

+ Details

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- Definition

Debt possible redemption amount.

+ References

No definition available.

+ Details

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- Definition

Extinguishment of compound derivative liability related to debt conversion.

+ References

No definition available.

+ Details

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- Definition

Extinguishment of unamortized debt discount related to debt conversion.

+ References

No definition available.

+ Details

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- Definition

Interest payable noncurrent.

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No definition available.

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- Definition

Line of credit facility covenant payment amount.

+ References

No definition available.

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Period Type:	duration

- Definition

Line of credit facility integral multiples.

+ References

No definition available.

+ Details

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Balance Type:	credit
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- Definition

Loss on conversion of debt to shares of common stock.

+ References

No definition available.

+ Details

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Period Type:	duration

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Percentage of lowest volume weighed average price of common stock on redemption.

+ References

No definition available.

+ Details

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- Definition

Percentage of prior trading days volume weighed average price of common stock on redemption.

+ References

No definition available.

+ Details

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- Definition

Principle amount of loan agreement.

+ References

No definition available.

+ Details

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- Definition

Adjustment to additional paid in capital resulting from the recognition of convertible debt instruments as two separate components - a debt component and an equity component. This bifurcation may result in a basis difference associated with the liability component that represents a temporary difference for purposes of applying accounting for income taxes. The initial recognition of deferred taxes for the tax effect of that temporary difference is as an adjustment to additional paid in capital.

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- Definition

The number of shares issued in exchange for the original debt being converted in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or payments in the period.

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The name of the original debt issue that has been converted in a noncash (or part noncash) transaction during the accounting period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

No definition available.

+ Details

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The amount of the original debt being converted in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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Period Type:	duration

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

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Period Type:	instant

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The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

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

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The average effective interest rate during the reporting period.

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

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

+ References

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Date the debt instrument was issued, in CCYY-MM-DD format.

+ References

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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

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

+ References

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Period Type:	duration

- Definition

Amount of the required periodic payments including both interest and principal payments.

+ References

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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

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Amount of the required periodic payments applied to interest.

+ References

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Period Type:	duration

- Definition

Amount of the required periodic payments applied to principal.

+ References

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Period Type:	duration

- Definition

Description of debt redemption features under terms of the debt agreement.

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Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

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Period Type:	duration

- Definition

Amount of unamortized debt discount (premium) and debt issuance costs.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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Amount of cash paid for interest. Includes, but is not limited to, payment to settle zero-coupon bond attributable to accreted interest of debt discount and debt instrument with insignificant coupon interest rate in relation to effective interest rate of borrowing attributable to accreted interest of debt discount.

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-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3536-108585

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Period Type:	duration

- Definition

Carrying value as of the balance sheet date of [accrued] interest payable on all forms of debt, including trade payables, that has been incurred and is unpaid. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Amount of interest payable on debt, including, but not limited to, trade payables.

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Period Type:	instant

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Period Type:	instant

- Definition

The maximum amount of borrowing capacity under a line of credit that is available as of the balance sheet date for a specific purpose other than for financing goods acquired for inventory or imminent delivery to a customer.

+ References

No definition available.

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Date the credit facility first became available, in CCYY-MM-DD format.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The cash inflow from additional borrowings, net of cash paid to third parties in connection with debt origination.

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No definition available.

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The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

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No definition available.

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Amount of cash restricted as to withdrawal or usage, classified as noncurrent. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.

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Per share or per unit amount of equity securities issued.

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No definition available.

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Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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- Definition

Number of shares issued during the period as a result of the conversion of convertible securities.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Section S99
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Section 50
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Name Accounting Standards Codification
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-Section S99
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Debt - Additional Information (Detail)																	1 Months Ended		2 Months Ended	3 Months Ended		12 Months Ended
Debt - Additional Information (Detail)	Apr. 17, 2018 USD ($)	Mar. 01, 2018	Feb. 28, 2018 USD ($)	Feb. 28, 2018 SEK (kr)	Oct. 10, 2017 $ / shares shares	Oct. 05, 2017 USD ($) $ / shares shares	Jul. 01, 2017 USD ($) $ / shares shares	Jul. 01, 2017 SEK (kr) shares	Mar. 15, 2017 USD ($) $ / shares shares	Mar. 07, 2016 USD ($)	Dec. 29, 2015 USD ($)	Jun. 18, 2015 USD ($)	Feb. 25, 2015 USD ($)	Feb. 25, 2015 SEK (kr)	Jun. 28, 2013 USD ($)	Jun. 25, 2013 USD ($)	Oct. 31, 2017 USD ($)	Oct. 31, 2017 SEK (kr)	Mar. 31, 2018 USD ($)	Mar. 31, 2018 USD ($) shares	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($) shares	Apr. 13, 2018	Mar. 31, 2018 SEK (kr)	Dec. 31, 2017 SEK (kr)	Jul. 03, 2017 $ / shares	Aug. 04, 2016 USD ($)	Aug. 04, 2016 SEK (kr)	Mar. 07, 2016 SEK (kr)	Dec. 29, 2015 SEK (kr)	Jun. 18, 2015 SEK (kr)	Feb. 25, 2015 SEK (kr)	Jun. 28, 2013 SEK (kr)	Jun. 25, 2013 SEK (kr)
Debt Instrument [Line Items]
Unamortized debt discount and issuance costs																			$ 0	$ 0		$ 4,600,000
Total accrued interest on debt																			300,000	300,000		300,000
Current portion of accrued interest																			26,000	26,000		81,000
Current portion of long-term debt																			461,000	461,000		15,721,000
Proceeds from debt, net of issuance costs																				0	$ 24,002,000
Loss on debt extinguishment																				2,806,000	$ 0
Principal outstanding amount																			9,729,000	$ 9,729,000		18,338,000
Allenex [Member]
Debt Instrument [Line Items]
Shares issued upon conversion \| shares							1,022,544	1,022,544
Conversion into common stock per share price \| $ / shares							$ 1.12
S S P Primers Aktieboulag [Member] \| Allenex [Member]
Debt Instrument [Line Items]
Debt instrument maturity date			Feb. 26, 2018	Feb. 26, 2018
Term loan facility amount outstanding																						1,200,000			kr 10,000,000
Loan agreement initiation date													Feb. 25, 2015	Feb. 25, 2015
Principle amount of loan agreement													$ 1,700,000																			kr 14,000,000
Accrued interest paid			$ 100,000	kr 650,000
Payable on February 25, 2016 [Member] \| S S P Primers Aktieboulag [Member] \| Allenex [Member]
Debt Instrument [Line Items]
Loan agreement, periodic payment													$ 500,000	kr 4,000,000
Date of loan agreement payable													Mar. 07, 2016	Mar. 07, 2016
JGB Debt [Member]
Debt Instrument [Line Items]
Unamortized debt discount and issuance costs									$ 6,968,000
Current portion of long-term debt																						$ 7,743,000
Aggregate principal amount									27,780,000
Proceeds from debt, net of issuance costs									24,000,000
Pay-off of term debt									11,200,000
Minimum cash requirement									$ 9,400,000
Debt instrument maturity date									Feb. 28, 2020
Interest rate									9.50%
Debentures convertible into common stock \| shares									6,092,105											6,161,331
Conversion price per share \| $ / shares					$ 4.33	$ 4.34			$ 4.56																	$ 4.40
Debt conversion description									Additionally, after September 1, 2017, upon the satisfaction of certain conditions, including the volume weighted average price of the Company’s common stock exceeding 250% of the Conversion Price for twenty consecutive trading days, the Company could have required that the Debentures be converted into shares of the Company’s common stock, subject to certain limitations.
Debt, possible redemption amount after March 1, 2018									$ 937,500
Debt redemption description									Commencing on March 1, 2018, each of the holders of the Debentures had the right, at its option, to require the Company to redeem up to $937,500 of the outstanding principal amount of its Debenture per month. The Company was required to promptly, but in any event no more than one trading day after the holder delivers a redemption notice to the Company, pay the applicable redemption amount in cash or, at the Company’s election and subject to certain conditions, in shares of the Company’s common stock. If the Company elected to pay the redemption amount in shares of the Company’s common stock, then the shares would have been delivered based on a price equal to the lowest of (a) 88% of the average of the three lowest volume weighted average prices of the Company’s common stock over the prior 20 trading days, (b) 88% of the prior trading day’s volume weighted average price, or (c) the Conversion Price.
Percentage of average three lowest volume weighted average prices of common stock if elected to pay in shares									88.00%
Percentage of prior trading day's volume weighted average price if elected to pay in shares									88.00%
Shares issued upon conversion \| shares							1,022,544	1,022,544												6,415,039		6,415,039
Conversion into common stock per share price \| $ / shares							$ 1.12
Debentures convertible into common stock, outstanding principal amount																			$ 26,700,000
Debentures prepayment date		Apr. 13, 2018
Term loan facility amount outstanding																						$ 26,500,000
Amount recognized to additional paid in capital																				$ 38,800,000
Extinguishment of unamortized debt discount																				2,700,000
Extinguishment of compound derivative liability																				12,100,000
Principal outstanding amount																						14,168,000
JGB Debt [Member] \| FastPartner AB [Member] \| Allenex [Member]
Debt Instrument [Line Items]
Debt instrument interest rate							8.00%	8.00%
JGB Debt [Member] \| Mohammed Al Amoudi [Member] \| Allenex [Member]
Debt Instrument [Line Items]
Debt instrument interest rate							6.00%	6.00%
JGB Debt [Member] \| Other Income (Expense) [Member]
Debt Instrument [Line Items]
Loss on debt extinguishment																				$ 2,800,000
JGB Debt [Member] \| Common Stock [Member]
Debt Instrument [Line Items]
Debentures convertible into common stock \| shares						288,022
Conversion into common stock per share price \| $ / shares						$ 4.34
Common stock shares issued \| shares					651,240	288,022														6,161,331
Debentures convertible into common stock, outstanding principal amount						$ 1,250,000														$ 6,000
JGB Debt [Member] \| If Debentures are Prepaid on or Prior to March 1, 2018 [Member]
Debt Instrument [Line Items]
Prepayment premium percentage on principal amount																			15.00%	15.00%				15.00%
JGB Debt [Member] \| If the Debentures are Prepaid After March 1, 2018 but Prior to March 1, 2019 [Member]
Debt Instrument [Line Items]
Prepayment premium percentage on principal amount																			8.00%	8.00%				8.00%
JGB Debt [Member] \| If the Debentures are Prepaid on or After March 1, 2019 [Member]
Debt Instrument [Line Items]
Prepayment premium percentage on principal amount																			5.00%	5.00%				5.00%
JGB Debt [Member] \| If Debenture is accelerated prior to March 1, 2018 [Member]
Debt Instrument [Line Items]
Percentage of debt principal and interest outstanding repayment									115.00%
JGB Debt [Member] \| If Debenture is accelerated after March 1, 2018 but prior to March 1, 2019 [Member]
Debt Instrument [Line Items]
Percentage of debt principal and interest outstanding repayment									108.00%
JGB Debt [Member] \| If Debenture is accelerated after March 1, 2019 [Member]
Debt Instrument [Line Items]
Percentage of debt principal and interest outstanding repayment									105.00%
Subordinated Promissory Note [Member] \| FastPartner AB [Member] \| Allenex [Member]
Debt Instrument [Line Items]
Aggregate principal amount										$ 500,000	$ 200,000				$ 1,100,000														kr 4,000,000	kr 2,000,000			kr 9,400,000
Debt instrument maturity date							Mar. 31, 2019	Mar. 31, 2019
Interest rate										10.00%	10.00%				10.00%														10.00%	10.00%			10.00%
Issuance date										Mar. 07, 2016	Dec. 29, 2015				Jun. 28, 2013
Debt instrument repayment of principal amount outstanding							$ 1,900,000	kr 15,400,000
Debt instrument accrued interest							$ 500,000
Debt instrument interest rate							10.00%	10.00%
Principal outstanding amount																			$ 2,400,000	$ 2,400,000		2,400,000		kr 19,757,000	19,757,000
Subordinated Promissory Note [Member] \| Mohammed Al Amoudi [Member] \| Allenex [Member]
Debt Instrument [Line Items]
Aggregate principal amount															$ 1,200,000																		kr 10,600,000
Debt instrument maturity date							Mar. 31, 2019	Mar. 31, 2019
Interest rate															10.00%																		10.00%
Issuance date															Jun. 28, 2013
Debt instrument repayment of principal amount outstanding							$ 1,300,000	kr 10,600,000
Debt instrument accrued interest							$ 500,000
Debt instrument interest rate							10.00%	10.00%
Principal outstanding amount																			1,700,000	1,700,000		1,700,000		14,575,000	kr 14,575,000
Subsequent Event [Member] \| JGB Debt [Member]
Debt Instrument [Line Items]
Prepayment premium percentage on principal amount																							8.00%
Perceptive Term Loan [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Aggregate principal amount	$ 15,000,000
Danske Bank Credit Facility [Member]
Debt Instrument [Line Items]
Current portion of long-term debt																			461,000	461,000		6,763,000
Term Loan Facility [Member] \| Allenex [Member]
Debt Instrument [Line Items]
Term loan facility amount outstanding																			5,600,000	$ 5,600,000				47,000,000
Term Loan Facility [Member] \| Danske Bank A S [Member]
Debt Instrument [Line Items]
Conditional principal repayment amount																	$ 700,000	kr 6,000,000
Term Loan Facility [Member] \| Danske Bank A S [Member] \| Allenex [Member]
Debt Instrument [Line Items]
Aggregate principal amount																$ 8,800,000																		kr 71,000,000
Loan agreement initiation date																Jun. 25, 2013
Term loan facility available for utilization advances																$ 600,000																		5,000,000
Term loan facility integral multiples																$ 100,000																		kr 1,000,000
Interest rate basis spread																3.00%
Interest rate, description																				The interest rate applicable to each advance was the percentage rate per annum calculated as the aggregate of (i) Stockholm Interbank Offered Rate (“STIBOR”) (as defined in the Term Loan Facility) and (ii) the Margin (as described in the Term Loan Facility) at 3% conditional on the fulfillment of certain criteria.
Term Loan Facility [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Debt instrument maturity date	Apr. 17, 2023
Interest rate	9.00%
Interest rate basis spread	1.50%
Interest rate, description	The Term Loan accrues interest per annum at 9.00% (the “Applicable Margin”) plus the greater of the one-month LIBOR or 1.5%.
Short Term Credit Facility [Member] \| Danske Bank A S [Member] \| Allenex [Member]
Debt Instrument [Line Items]
Aggregate principal amount												$ 1,000,000															$ 1,200,000	kr 10,000,000			kr 8,000,000
Debt instrument maturity date												Jun. 30, 2018
Loan agreement initiation date												Jun. 18, 2015
Short term credit facility																			500,000	$ 500,000				kr 3,850,000
Accrued and Other Liabilities [Member]
Debt Instrument [Line Items]
Current portion of accrued interest																						100,000
Other Liabilities Long Term [Member]
Debt Instrument [Line Items]
Long-term portion of accrued interest																			$ 300,000	$ 300,000		$ 200,000