Number of shares issued during the period as a result of a spin-off.

No definition available.

Name:	mghl_StockIssuedDuringPeriodSharesSpinOff
Namespace Prefix:	mghl_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Subsequent Events (FY) (Details) - Associated Capital Group [Member] - shares	Mar. 16, 2020	Mar. 14, 2020
Stock Transaction [Abstract]
Shares to be distributed to shareholders in spin-off (in shares)	50,000,000
Subsequent Event [Member]
Stock Transaction [Abstract]
Shares to be distributed to shareholders in spin-off (in shares)		50,000,000