Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Operating Lease Obligations [Line Items]
Rental expense under operating leases with initial terms exceeding one year	$ 965,000	$ 900,000	$ 805,000
Unused letters of credit, total	$ 233,000

Rental expense for the reporting period incurred under operating leases with initial terms exceeding one year.

No definition available.

Name:	dwsn_OperatingLeaseRentalExpenseInitialTermExceedingOneYear
Namespace Prefix:	dwsn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration