Consolidated statements of cash flows - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2020	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net income (loss)	$ (17,914)	$ 17,884	$ 15,525	$ 33,475
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	7,544	22,843	17,861	14,521
Restructuring (income) loss	22,176	(5,982)	0	0
Stock-based compensation expense	3,683	15,488	16,821	13,474
Amortization of debt issuance costs and discount on debt	190	747	792	810
Deferred income taxes	(3,433)	2,443	(939)	(13,434)
Other, net	242	873	476	1,728
Changes in operating assets and liabilities:
Accounts receivable	4,215	2,504	7,649	(8,001)
Inventories	2,561	(435)	16,338	6,718
Prepaid expenses and other assets	(1,732)	(6,500)	(8,484)	(11,200)
Accounts payable and accrued expenses	(6,021)	5,962	(10,251)	(25,483)
Other liabilities	(3,295)	(11,514)	(206)	(230)
Net cash provided by operating activities	8,216	44,313	55,582	12,378
Cash flows from investing activities:
Acquisition, net of cash acquired	0	(25,923)	0	0
Purchase of property and equipment	(3,400)	(9,422)	(8,872)	(7,544)
Investment in equity securities	0	0	0	(2,875)
Net cash used in investing activities	(3,400)	(35,345)	(8,872)	(10,419)
Cash flows from financing activities:
Proceeds from revolving line of credit	0	0	2,000	25,900
Repayment of revolving line of credit	0	0	(2,000)	(25,900)
Repayment of long-term debt	(2,063)	(9,488)	(8,250)	(8,250)
Debt issuance costs paid	0	0	0	(519)
Repurchase of common stock	0	(7,904)	0	0
Cash received from issuance of common stock	115	1,488	3,176	1,978
Other, net	(199)	(771)	(490)	(404)
Net cash used in financing activities	(2,147)	(16,675)	(5,564)	(7,195)
Net (decrease) increase in cash and cash equivalents	2,669	(7,707)	41,146	(5,236)
Cash and cash equivalents - beginning of period	51,205	53,874	10,059	15,295
Cash and cash equivalents - end of period	53,874	46,167	51,205	10,059
Supplemental disclosure of cash flow information:
Cash paid for interest	1,783	6,302	7,124	8,162
Cash paid for income taxes, net of refunds	6	5,604	4,085	5,673
Cash paid for interest on finance leases	50	179	0	0
Supplemental disclosure of noncash investing and financing activities:
Property and equipment acquired under finance leases	0	0	2,098	10
Property and equipment purchases included in accounts payable and accrued expenses	3,080	1,132	1,838	1,143
Vesting of shares related to early exercise of common stock options	$ 0	$ 0	$ 0	$ 4,074