Unaudited Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 26,253	$ 9,463
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization expense	4,685	7,786
Bad debt expense	13,679	15,112
Compensation expense related to share-based awards	2,698	2,326
Deferred income taxes	6,641	8,744
Changes in operating assets and liabilities	(39,202)	(77,677)
Net cash provided by (used in) operating activities	14,754	(34,246)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of available-for-sale investments	(101,043)	(145,088)
Sales of available-for-sale investments	106,139	169,480
Purchases of property and equipment	(2,737)	(2,146)
Net cash provided by investing activities	2,359	22,246
CASH FLOWS FROM FINANCING ACTIVITIES:
Issuance of common stock	1,170	2,459
Payments of employee tax associated with stock compensation	(3,218)	(1,101)
Net cash (used in) provided by financing activities	(2,048)	1,358
EFFECT OF FOREIGN CURRENCY EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS:		33
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	15,065	(10,609)
CASH AND CASH EQUIVALENTS, beginning of the period	18,899	50,882
CASH AND CASH EQUIVALENTS, end of the period	$ 33,964	$ 40,273