Allowance for Credit Losses - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Credit Loss [Abstract]
Accounts receivable, allowance for credit loss, incremental increase (decrease) due to COVID	$ 0.0	$ 3.1

Accounts Receivable, Allowance For Credit Loss, Incremental Increase (Decrease) Due To COVID-19

No definition available.

Name:	dxm_AccountsReceivableAllowanceForCreditLossIncrementalIncreaseDecreaseDueToCOVID19
Namespace Prefix:	dxm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration