Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities:
Net income (loss)	$ 52,653	$ (691,148)
(Income) loss from discontinued operations	(16,768)	679,733
Adjustments to reconcile net income (loss) to net cash from operating activities:
Depreciation and amortization	16,137	13,554
Amortization of premiums, discounts and issuance costs	1,838	2,785
Loss on early extinguishment of debt	14,532
Stock-based compensation expense	9,452	13,174
Deferred income taxes	(17,033)	37,896
Other	(1,205)	(855)
Gain on sale of building	(7,280)
Changes in assets and liabilities:
Accounts receivable	(26,005)	29,735
Prepaid expenses and other current assets	40,800	(1,913)
Other long-term assets	(1,859)	1,186
Accounts payable and accrued expenses	(54,453)	(114,543)
Income taxes receivable	(28,165)	(70,487)
Long-term professional liabilities	(715)	17,797
Other liabilities	(10,413)	27,585
Net cash used in operating activities – continuing operations	(28,484)	(55,501)
Net cash (used in) provided by operating activities - discontinued operations	(117)	102,052
Net cash (used in) provided by operating activities	(28,601)	46,551
Cash flows from investing activities:
Acquisition payments, net of cash acquired	(7,207)	(75)
Purchases of investments	(8,355)	(32,335)
Proceeds from maturities or sales of investments	10,745	18,135
Purchases of property and equipment	(18,536)	(16,891)
Proceeds from sale of building	24,728	0
Other	0	476
Net cash provided by (used in) investing activities - continuing operations	1,375	(30,690)
Net cash provided by investing activities-discontinued operations	2,350	9,031
Net cash provided by (used in) investing activities	3,725	(21,659)
Cash flows from financing activities:
Borrowings on credit agreement	0	527,500
Payments on credit agreement	0	(527,500)
Redemption of senior notes, including call premium	(759,848)	0
Payments for credit facility amendment	0	(510)
Payments of contingent consideration liabilities	(189)	0
Payments on finance lease obligations	(1,106)	(186)
Proceeds from issuance of common stock	2,578	4,376
Repurchases of common stock	(2,245)	(3,043)
Net cash (used in) provided from financing activities - continuing operations	(760,810)	637
Net cash used in financing activities-discontinued operations	0	(1,248)
Net cash used in financing activities	(760,810)	(611)
Net (decrease) increase in cash and cash equivalents	(785,686)	24,281
Cash and cash equivalents at beginning of period	1,123,843	107,870
Cash and cash equivalents at end of period	$ 338,157	$ 132,151