Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 30,753	$ 29,106
Adjustments to reconcile net income to net cash provided by operating activities:
Asset impairment		612
Depreciation and amortization expense	4,002	2,639
Bad debt expense	13,719	12,862
Compensation expense related to share-based awards	3,753	3,212
Deferred income taxes	4,767	9,468
Changes in operating assets and liabilities	(12,286)	(13,131)
Net cash provided by operating activities	44,708	44,768
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of available-for-sale investments	(126,009)	(111,753)
Sales of available-for-sale investments	64,408	52,893
Purchases of property and equipment	(1,042)	(1,015)
Business acquisition		(34,065)
Net cash used in investing activities	(62,643)	(93,940)
CASH FLOWS FROM FINANCING ACTIVITIES:
Issuance of common stock	314	413
Purchase of treasury stock		(17,309)
Payments of employee tax associated with stock compensation	(2,032)	(687)
Net cash used in financing activities	(1,718)	(17,583)
NET DECREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(19,653)	(66,755)
CASH, CASH EQUIVALENTS AND RESTRICTED CASH, beginning of the period	109,684	108,687
CASH, CASH EQUIVALENTS AND RESTRICTED CASH, end of the period	$ 90,031	41,932
Supplemental non-cash disclosure:
Amounts placed in escrow during the period to secure indemnification obligations from business acquisition		$ 4,000