Segment and Related Information - Financial Information (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
Segment and Related Information
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
Material costs	95,961	92,034	91,399	78,377	90,340	84,805	86,516	76,356	357,771	338,017	329,223
Personnel expenses	99,430	94,594	91,490	86,711	97,574	90,853	89,554	86,108	372,225	364,089	361,090
Depreciation & amortization	9,019	9,373	8,760	8,773	8,903	8,950	9,272	9,330	35,925	36,455	39,259
Impairment of intangible assets					183					183	54,735
Segment 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)
Purchase of property, plant and equipment									26,433	18,984	16,355
Patient Care
Segment and Related Information
Net revenues									905,691	857,382	851,973
Material costs									250,407	234,409	228,091
Personnel expenses									319,633	312,736	312,695
Other expenses									151,140	140,527	143,598
Depreciation & amortization									18,541	19,113	21,363
Segment income (loss) from operations									141,576	126,805	122,418
Purchase of property, plant and equipment									16,102	12,781	8,163
Patient Care | Operating segments
Segment and Related Information
Net revenues									905,691	857,382	851,973
Material costs									274,801	258,201	251,899
Patient Care | Intersegments
Segment and Related Information
Material costs									24,394	23,792	23,808
Products & Services
Segment and Related Information
Net revenues									192,355	191,378	188,796
Material costs									107,364	103,608	101,132
Personnel expenses									52,592	51,353	48,395
Other expenses									28,178	24,306	25,855
Depreciation & amortization									10,650	10,197	10,163
Impairment of intangible assets										183	54,735
Segment income (loss) from operations									17,965	25,523	(27,676)
Purchase of property, plant and equipment									2,368	1,890	2,153
Purchase of therapeutic program equipment leased to third parties under operating leases									6,672	9,835	6,000
Products & Services | Operating segments
Segment and Related Information
Net revenues									395,851	383,474	367,564
Material costs									286,466	271,912	256,092
Products & Services | Intersegments
Segment and Related Information
Net revenues									203,496	192,096	178,768
Material costs									$ 179,102	$ 168,304	$ 154,960