XML 14 R50.htm IDEA: XBRL DOCUMENT
v3.20.1

Equity (Detail) | 6 Months Ended |
--- | --- | ---
Mar. 31, 2020 shares | Sep. 30, 2019 shares
Class A Common Stock |  |
Schedule Of Stockholders Equity [Line Items] |  |
Conversion rate | 1 |
Common stock, shares outstanding (in shares) | 32,705,418 | 32,597,736
Class B Common Stock |  |
Schedule Of Stockholders Equity [Line Items] |  |
Conversion of Class B common stock to Class A common stock (in shares) | 107,682 |
Common stock, shares outstanding (in shares) | 19,076,327 | 19,184,009

X
- Definition Conversion Of Common Stock In Connection With Initial Public Offering + References No definition available. + Details
Name: | road_ConversionOfCommonStockInConnectionWithInitialPublicOffering
Namespace Prefix: | road_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Conversion Rate to Reclassify Common Stock to Class B Shares + References No definition available. + Details
Name: | road_ConversionRatetoReclassifyCommonStocktoClassBShares
Namespace Prefix: | road_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | duration

X
- Definition Schedule Of Stockholders Equity [Line Items] + References No definition available. + Details
Name: | road_ScheduleOfStockholdersEquityLineItems
Namespace Prefix: | road_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_CommonStockSharesOutstanding
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassAMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassBMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |