Segment and Related Information - Reconciliation of the Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Segment and Related Information
Income (loss) from operations	$ 26,901	$ 17,403	$ 23,103	$ (1,979)	$ 22,771	$ 15,924	$ 20,329	$ 623	$ 65,428	$ 59,647	$ (18,950)
Interest expense, net	8,285	8,954	8,481	8,538	9,046	8,939	7,317	12,263	34,258	37,566	57,688
Loss on extinguishment of debt								16,998		16,998
Non-service defined benefit plan expense	172	173	173	173	176	176	176	176	691	703	736
Income (loss) before income taxes	18,444	8,276	14,449	(10,690)	13,549	6,809	12,836	(28,814)	30,479	4,380	(77,374)
Provision for income taxes	(306)	2,585	4,414	(3,739)	9,086	2,440	(92)	(6,196)	2,954	5,238	27,297
Net income (loss)	18,750	5,691	10,035	(6,951)	4,463	4,369	12,928	(22,618)	27,525	(858)	(104,671)
Consolidated net revenues	300,891	279,638	281,098	236,419	284,853	262,946	266,966	233,995	1,098,046	1,048,760	1,040,769
Consolidated material costs	95,961	$ 92,034	$ 91,399	$ 78,377	90,340	$ 84,805	$ 86,516	$ 76,356	357,771	338,017	329,223
Consolidated purchase of property, plant and equipment									26,433	18,984	16,355
Consolidated purchase of property, plant and equipment and therapeutic program equipment leased to third parties under operating leases									33,105	28,819	22,355
Consolidated assets	842,253				703,010				842,253	703,010		$ 791,132
Corporate & other
Segment and Related Information
Income (loss) from operations									(94,113)	(92,681)	(113,692)
Consolidated purchase of property, plant and equipment and therapeutic program equipment leased to third parties under operating leases									7,963	4,313	6,039
Consolidated assets	183,936				186,588				183,936	186,588
Consolidating adjustments
Segment and Related Information
Consolidated net revenues									(203,496)	(192,096)	(178,768)
Consolidated material costs									(203,496)	(192,096)	(178,768)
Patient Care
Segment and Related Information
Income (loss) from operations									141,576	126,805	122,418
Consolidated net revenues									905,691	857,382	851,973
Consolidated material costs									250,407	234,409	228,091
Consolidated purchase of property, plant and equipment									16,102	12,781	8,163
Consolidated purchase of property, plant and equipment and therapeutic program equipment leased to third parties under operating leases									16,102	12,781	8,163
Consolidated assets	552,644				415,469				552,644	415,469
Patient Care | Operating segments
Segment and Related Information
Consolidated net revenues									905,691	857,382	851,973
Consolidated material costs									274,801	258,201	251,899
Products & Services
Segment and Related Information
Income (loss) from operations									17,965	25,523	(27,676)
Consolidated net revenues									192,355	191,378	188,796
Consolidated material costs									107,364	103,608	101,132
Consolidated purchase of property, plant and equipment									2,368	1,890	2,153
Consolidated purchase of therapeutic program equipment leased to third parties under operating leases									6,672	9,835	6,000
Consolidated assets	$ 105,673				$ 100,953				105,673	100,953
Products & Services | Operating segments
Segment and Related Information
Consolidated net revenues									395,851	383,474	367,564
Consolidated material costs									$ 286,466	$ 271,912	$ 256,092