XML 67 R30.htm IDEA: XBRL DOCUMENT
v3.19.1

Cash and Cash Equivalents, Restricted Cash and Restricted Cash - Asbestos Cash and Cash Equivalents, Restricted Cash and Restricted Cash - Asbestos (Tables) | 12 Months Ended
--- | ---
Mar. 31, 2019
Cash and Cash Equivalents, Restricted Cash and Restricted Cash - Asbestos [Abstract] |
Cash and Cash Equivalents, Restricted Cash and Restricted Cash - Asbestos [Table Text Block] | The following table provides a reconciliation of Cash and cash equivalents, Restricted cash and Restricted cash - Asbestos reported within the consolidated balance sheets that sum to the total of the same such amounts shown in the consolidated statements of cash flows:
| 31 March
(Millions of US dollars) | 2019 |  | 2018
Cash and cash equivalents | $ | 78.7 |  |  | $ | 281.6 |
Restricted cash | 5.1 |  |  | 5.0 |
Restricted cash - Asbestos | 39.8 |  |  | 26.6 |
Total cash and cash equivalents, restricted cash and restricted cash - Asbestos | $ | 123.6 |  |  | $ | 313.2 |

X
- Definition Cash and Cash Equivalents, Restricted Cash and Restricted Cash - Asbestos [Abstract] + References No definition available. + Details
Name: | jhx_CashandCashEquivalentsRestrictedCashandRestrictedCashAsbestosAbstract
Namespace Prefix: | jhx_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Cash and Cash Equivalents, Restricted Cash and Restricted Cash - Asbestos [Table Text Block] + References No definition available. + Details
Name: | jhx_CashandCashEquivalentsRestrictedCashandRestrictedCashAsbestosTableTextBlock
Namespace Prefix: | jhx_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration