CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows provided by operating activities:
Net income (loss)	$ (22,618)	$ 27,525	$ (858)	$ (104,671)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	9,330	35,925	36,455	39,259
Provision (benefit) for doubtful accounts		1,131	(733)	9,422
Impairment of intangible assets			183	54,735
Stock-based compensation expense		13,414	13,065	12,930
Deferred income taxes		(3,226)	3,452	26,248
Amortization of right-of-use assets		312
Amortization of debt discounts and issuance costs		1,623	2,837	8,876
Loss on extinguishment of debt	16,998		16,998
Gain on sale and disposal of fixed assets		(1,614)	(2,713)	(2,059)
Changes in operating assets and liabilities (Note U):		(15,932)	9,841	(14,635)
Net cash provided by operating activities		58,846	78,527	30,105
Cash flows used in investing activities
Purchase of property, plant, and equipment		(26,433)	(18,984)	(16,355)
Purchase of therapeutic program equipment leased to third parties under operating leases		(6,672)	(9,835)	(6,000)
Acquisitions, net of cash acquired		(36,585)	(1,978)
Proceeds from company-owned life insurance investment				17,135
Purchase of company-owned life insurance investment		(66)	(598)	(555)
Proceeds from sale of property, plant and equipment		2,598	4,237	4,909
Net cash used in investing activities		(67,158)	(27,158)	(866)
Cash flows (used in ) provided by financing activities
Borrowings under term loan, net of discount			501,467	420
Repayment of term loan		(5,050)	(435,660)	(28,545)
Borrowings under revolving credit agreement			3,000	156,965
Repayments under revolving credit agreement			(8,000)	(151,965)
Payment of employee taxes on stock-based compensation		(4,137)	(2,906)	(1,477)
Payment on seller notes		(3,821)	(2,599)	(5,197)
Payment of financing lease obligations		(474)	(1,207)	(1,210)
Payment of debt issuance costs			(6,757)	(2,863)
Payment of debt extinguishment costs			(8,436)
Proceeds from exercise of options		1,099	64
Net cash (used in) provided by financing activities		(12,383)	38,966	(33,872)
(Decrease) increase in cash, cash equivalents, and restricted cash		(20,695)	90,335	(4,633)
Cash, cash equivalents, and restricted cash, at beginning of period	4,779	95,114	4,779	9,412
Cash, cash equivalents, and restricted cash, at end of period		74,419	95,114	4,779
Reconciliation of Cash, Cash Equivalents, and Restricted Cash:
Cash and cash equivalents, at beginning of period	1,508	95,114	1,508	7,157
Restricted cash, at beginning of period	3,271		3,271	2,255
Cash, cash equivalents, and restricted cash, at beginning of period	$ 4,779	95,114	4,779	9,412
Cash and cash equivalents, at end of period		74,419	95,114	1,508
Restricted cash, at end of period				3,271
Cash, cash equivalents, and restricted cash, at end of period		$ 74,419	$ 95,114	$ 4,779