Sales by Channel (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Net Revenue	$ 72,161,000	$ 74,732,000	$ 145,525,000	$ 153,965,000
Medifast Direct
Segment Reporting Information [Line Items]
Net Revenue	13,675,000	15,201,000	28,117,000	32,344,000
Take Shape For Life
Segment Reporting Information [Line Items]
Net Revenue	52,258,000	54,053,000	104,360,000	111,019,000
Medifast Weight Control Centers- Franchise
Segment Reporting Information [Line Items]
Net Revenue	4,672,000	3,821,000	9,337,000	7,409,000
Medifast Wholesale
Segment Reporting Information [Line Items]
Net Revenue	$ 1,556,000	$ 1,657,000	$ 3,711,000	$ 3,193,000