Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Cash flows from operating activities
Net income	$ 88,181	$ 53,158	$ 23,511
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	12,087	11,227	11,645
Amortization of deferred financing costs	144	144	145
Benefit for deferred income taxes	(5,145)	(1,253)	(13,657)
Change in fair value of equity securities	(6,281)	13,238
Change in fair value of derivative instruments	(30)	(2,130)	2,170
Other than temporary impairment of marketable securities			814
Loss (gain) on the sale of investments	1,662	(1,227)	(127)
Stock based compensation	21	357	998
(Gain) loss on disposal of property and equipment	(11)	41	195
Noncash interest expense	29	28	27
Changes in operating assets and liabilities:
Accounts receivable	(93,970)	5,679	2,386
Accounts receivable – related parties	(2,758)	(1,679)	220
Inventory	1,723	4,458	8,339
Income tax receivable	(1,204)	79	13,571
Prepaid expenses	(165)	(107)	34
Accrued interest on marketable securities	(33)	(25)	16
Other assets	239	(317)	(9)
Accounts payable	41,453	1,243	(4,403)
Accounts payable - related parties	(434)	506	(71)
Accrued expenses and other current liabilities	1,087	274	60
Accrued expenses and other current liabilities – related parties	64		(142)
Deferred revenue	1,628	(1,258)	(4,215)
Other noncurrent liabilities	(3,649)	3,177	(2,160)
Net cash provided by operating activities	34,638	85,613	39,347
Cash flows from investing activities
Collateralization of derivative instruments	(111)	1,680	(1,901)
Purchase of marketable securities	(20,131)	(19,664)	(30,959)
Proceeds from the sale of marketable securities	31,419	48,235	23,254
Proceeds from the sale of property and equipment	13	22	4
Capital expenditures	(6,971)	(4,867)	(3,581)
Net cash provided by (used in) investing activities	4,219	25,406	(13,183)
Cash flows from financing activities
Minimum tax withholding on stock options exercised and awards vested		(176)	(121)
Payment of dividends	(10,498)	(10,498)	(110,688)
Net cash used in financing activities	(10,498)	(10,674)	(110,809)
Net change in cash and cash equivalents	28,359	100,345	(84,645)
Cash and cash equivalents at beginning of period	214,972	114,627	199,272
Cash and cash equivalents at end of period	243,331	214,972	114,627
Cash paid for interest
Cash paid for income taxes	2,372	9,182	55
Noncash investing and financing activities:
Noncash capital expenditures	207	420
Noncash operating leases	432
Noncash items incurred for dividends	$ 10,498	$ 10,498	$ 10,498