Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income (loss)	$ 85,083	$ 72,845	$ (27,052)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	39,551	34,545	15,061
Amortization of debt issuance costs and discounts	7,199	6,263	3,746
Amortization of unfavorable lease liability	(431)	(431)	(72)
Equity-based compensation	2,021	7,502	942
Loss (gain) on disposal or impairment of long-lived assets, net	2,355	(2,097)	1,804
Gain on legal settlement	(14,101)	0	0
Loss on debt extinguishment	11,876	16,102	23,414
Tax receivable agreement expense	3,733	119,911	0
Deferred income taxes	6,882	(149,891)	14,089
Interest on contingent consideration obligation	1,124	1,041	964
Provision for doubtful accounts	24,212	23,578	9,509
Income from equity investments, net of distributions received	(846)	(543)	(713)
Changes in operating assets and liabilities, net of acquisitions and divestitures:
Accounts receivable	(60,622)	(48,783)	(20,161)
Other operating assets and liabilities	17,203	4,439	418
Net cash provided by operating activities	125,239	84,481	21,949
Cash flows from investing activities:
Purchases of property and equipment, net	(39,109)	(33,439)	(7,736)
Payments for acquisitions, net of cash acquired	(146,405)	(112,596)	(263,280)
Proceeds from divestitures	765	11,193	0
Net cash used in investing activities	(184,749)	(134,842)	(271,016)
Cash flows from financing activities:
Proceeds from initial public offering, net of offering costs	0	250,979	0
Principal payments on long-term debt	(473,437)	(328,329)	(1,009,874)
Borrowings of long-term debt	650,707	196,366	1,477,288
Payments of debt issuance costs	(14,296)	0	(7,496)
Penalty on prepayment of debt	(4,900)	0	0
Payment of premium of debt extinguishment	0	(7,305)	(17,840)
Distributions to non-controlling interest holders	(65,778)	(69,720)	(35,182)
Distribution to owners	0	0	(93,000)
Payments related to ownership transactions with consolidated affiliates	(20,096)	(12,175)	278
Repurchase of units	0	0	(3,143)
Financing lease obligation	(924)	3,558	(70)
Net cash provided by financing activities	71,276	33,374	310,961
Net (decrease) increase in cash and cash equivalents	11,766	(16,987)	61,894
Cash and cash equivalents at beginning of period	57,933	74,920	13,026
Cash and cash equivalents at end of period	69,699	57,933	74,920
Non-cash transactions:
Notes payable issued in connection with an acquisition	325	7,430	0
Interest paid, net of interest income received	7,866	5,443	3,252
Cash payments:
Interest paid, net of interest income received	79,262	96,799	50,377
Cash paid for income taxes	$ 661	$ 1,093	$ 676