Quarterly Financial Information (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information (unaudited) [Abstract]
Revenues	$ 139,354	[1]	$ 137,703		$ 138,914		$ 140,970		$ 124,933	[2]	$ 125,049		$ 125,003		$ 126,012		$ 556,942	$ 500,998	$ 452,092
Gross margin	38,970	[1]	42,465		39,195		37,914		38,304	[2]	34,562		34,590		33,105
Income before income taxes	22,843	[1]	30,289		26,800		24,852		20,972	[2]	17,925		19,962		19,208		104,783	78,064	72,919
Income from continuing operations attributable to Tivity Health, Inc.	8,624	[1]	19,886		17,240		15,481		12,125	[2]	4,799		19,962		19,208		61,230	56,091	43,634
Net income (loss) from discontinued operations attributable to Tivity Health, Inc.	(141)	[1]	6,519		(3,673)		(220)		(5,225)	[2]	48,995		(195,558)		(33,417)		2,485	(185,202)	(74,581)
Net income (loss) attributable to Tivity Health, Inc.	$ 8,483	[1]	$ 26,405		$ 13,567		$ 15,261		$ 6,900	[2]	$ 53,794		$ (175,596)		$ (14,209)		$ 63,715	$ (129,111)	$ (30,947)
Earnings (loss) per share attributable to Tivity Health, Inc. - basic [Abstract]
Continuing operations (in dollars per share)	$ 0.22	[1],[3]	$ 0.50	[3]	$ 0.44	[3]	$ 0.40	[3]	$ 0.31	[2],[3]	$ 0.13	[3]	$ 0.55	[3]	$ 0.53	[3]	$ 1.56	$ 1.52	$ 1.22
Discontinued operations (in dollars per share)	0	[1],[3]	0.17	[3]	(0.09)	[3]	(0.01)	[3]	(0.14)	[2],[3]	1.32	[3]	(5.41)	[3]	(0.93)	[3]	0.06	(5.01)	(2.08)
Net income (loss) (dollars per share)	0.21	[1],[3],[4]	0.67	[3],[4]	0.35	[3],[4]	0.39	[3],[4]	0.18	[2],[3],[4]	1.45	[3],[4]	(4.85)	[3],[4]	(0.39)	[3],[4]	1.62	(3.49)	(0.86)
Earnings (loss) per share attributable to Tivity Health, Inc. - diluted [Abstract]
Continuing operations (in dollars per share)	0.20	[1],[3]	0.46	[3]	0.41	[3]	0.38	[3]	0.30	[2],[3]	0.12	[3]	0.54	[3]	0.52	[3]	1.44	1.47	1.18
Discontinued operations (in dollars per share)	0	[1],[3]	0.15	[3]	(0.09)	[3]	(0.01)	[3]	(0.13)	[2],[3]	1.28	[3]	(5.25)	[3]	(0.91)	[3]	0.06	(4.86)	(2.02)
Net income (loss) (dollars per share)	$ 0.20	[1],[3],[4]	$ 0.61	[3],[4]	$ 0.32	[3],[4]	$ 0.38	[3],[4]	$ 0.17	[2],[3],[4]	$ 1.40	[3],[4]	$ (4.72)	[3],[4]	$ (0.39)	[3],[4]	$ 1.50	$ (3.39)	$ (0.84)
Impact of adjustment amount due to decrease in depreciation expense on net income from continuing operations									$ 2,200
Non-cash charge related to both re-measurement of deferred tax assets to lower tax rate and repatriation of foreign earnings	$ 7,400

[1] The Tax Act was signed into law during the fourth quarter of 2017, and we incurred a non-cash charge of $7.4 million during the quarter related to both the re-measurement of our deferred tax assets to the lower tax rate and the requirement to recalculate the impact of repatriation of our foreign earnings, which occurred earlier in the year, under provisions of the new law.

[2] Income from continuing operations for the fourth quarter of 2016 includes the impact of a $2.2 million out of period adjustment to decrease depreciation expense included in continuing operations (with a corresponding increase to depreciation expense included in discontinued operations). This adjustment was recorded after having completed our asset separation analysis and related to the correction of our previous allocation of 2016 depreciation expense between continuing and discontinued operations. The previous interim periods in 2016 were not materially misstated, nor is the correction material to the interim results for the fourth quarter of 2016.

[3] We calculated earnings per share for each of the quarters based on the weighted average number of shares and dilutive securities outstanding for each period. Accordingly, the sum of the quarters may not necessarily be equal to the full year income per share.

[4] Figures may not add due to rounding.