CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CONSOLIDATED STATEMENTS OF OPERATIONS [Abstract]
Revenues	$ 556,942	$ 500,998	$ 452,092
Cost of services (exclusive of depreciation and amortization of $2,802, $3,468, and $5,440, respectively, included below)	395,605	357,120	318,060
Selling, general and administrative expenses	34,361	39,478	35,546
Depreciation and amortization	3,357	4,085	6,869
Restructuring and related charges	3,223	4,933	702
Operating income	120,396	95,382	90,915
Interest expense	15,613	17,318	17,996
Income before income taxes	104,783	78,064	72,919
Income tax expense	43,553	21,973	29,285
Income from continuing operations	61,230	56,091	43,634
Income (loss) from discontinued operations, net of income tax	2,485	(184,706)	(74,952)
Net income (loss)	63,715	(128,615)	(31,318)
Less: net income (loss) attributable to non-controlling interest	0	496	(371)
Net income (loss) attributable to Tivity Health, Inc.	$ 63,715	$ (129,111)	$ (30,947)
Earnings (loss) per share attributable to Tivity Health, Inc. - basic:
Continuing operations (in dollars per share)	$ 1.56	$ 1.52	$ 1.22
Discontinued operations (in dollars per share)	0.06	(5.01)	(2.08)
Net income (loss) (in dollars per share)	1.62	(3.49)	(0.86)
Earnings (loss) per share attributable to Tivity Health, Inc. - diluted:
Continuing operations (in dollars per share)	1.44	1.47	1.18
Discontinued operations (in dollars per share)	0.06	(4.86)	(2.02)
Net income (loss) (in dollars per share)	$ 1.50	$ (3.39)	$ (0.84)
Comprehensive income (loss)	$ 68,217	$ (128,878)	$ (33,509)
Weighted average common shares and equivalents:
Basic (in shares)	39,357	36,999	35,832
Diluted (in shares)	42,547	38,075	36,854