Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net (loss) income	$ (302,269)	$ 15,188	$ 25,020
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	97,112	66,566	50,045
Goodwill impairments	224,966
Impairments of definite-lived intangible assets	82,678		4,804
Share-based compensation expense	18,172	7,281	5,412
Net provision for doubtful accounts	8,660	9,424	9,534
Amortization of debt issuance costs	4,733	2,655	1,176
Change in fair value of contingent consideration	3,364	3,675	(8,922)
Contingent consideration payments	(4,239)		(4,174)
Deferred income tax (benefit) expense	(11,847)	(10,795)	8,779
Equity loss and impairment of non-consolidated entities	329		4,659
Other	(73)	1	2
Changes in operating assets and liabilities, net of business acquisitions:
Accounts receivable	(2,333)	7,735	(15,128)
Inventories	(3,932)	13,813	(44,342)
Accounts payable	(80,412)	23,088	(5,906)
Rebates payable	(5,479)	1,238
Other assets and liabilities	5,612	(4,615)	367
Net cash provided by operating activities	35,042	135,254	31,326
Cash flows from investing activities:
Payments to acquire businesses, net of cash acquired	(13,070)	(3,505)	(12,595)
Expenditures for property and equipment	(1,139)	(623,067)	(67,156)
Expenditures for capitalized software for internal use	(10,474)	(6,652)	(6,217)
Capital investments in and loans to non-consolidated entities		(100)
Net proceeds from sales of property and equipment	13,448	5	1
Net cash used in investing activities	(11,235)	(633,319)	(85,967)
Cash flows from financing activities:
Net (payments) borrowings from line of credit	(11,950)	148,995	39,255
Proceeds from long-term debt		575,000
Payments on long-term debt	(85,500)	(136,000)	(6,000)
Payments of debt issuance costs	(891)	(21,507)	(28)
Proceeds from issuance of stock upon stock option exercises	4,098	7,875	4,448
Contingent consideration payments	(4,330)		(2,681)
Net cash (used in) provided by financing activities	(98,573)	574,363	34,994
Net (decrease) increase in cash and equivalents	(74,766)	76,298	(19,647)
Cash and equivalents at beginning of year	84,251	7,953	27,600
Cash and equivalents at end of year	9,485	84,251	7,953
Supplemental disclosures of cash flow information:
Cash paid for interest	37,851	7,327	5,273
Cash paid for income taxes	$ 3,520	$ 5,876	$ 728