CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Cash flows from operating activities:
Net income (loss)	$ 6,842	$ (8,323)	$ (844)	$ (16,834)	$ 3,057	$ (28,144)
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense					13,806	11,146
Depreciation					42,021	39,240
Amortization of intangibles					39,349	30,617
Amortization of debt issuance costs and debt discount					3,251	2,076
Deferred income taxes					(2,780)	(11,651)
Restructuring expense, non-cash					0	8,583
Change in fair value of contingent consideration					67	9,364
Other					1,230	614
Changes in assets and liabilities:
Accounts receivable					(23,577)	(1,046)
Prepaid expenses and other current assets					(944)	(6,606)
Income taxes receivable					5,059	1,612
Other assets					(4,196)	(4,686)
Accounts payable and accrued expenses					1,508	(5,444)
Accrued compensation					6,295	8,551
Other current and non-current liabilities					(6,728)	6,695
Deferred revenue					(2,617)	2,094
Payment for acquisition-related contingent consideration					(2,549)	0
Net cash provided by operating activities					72,252	63,015
Cash flows from investing activities:
Maturities of short-term investments					6,964	92,207
Sales of short-term investments					0	161,772
Purchases of property and equipment					(14,022)	(19,943)
Investment in capitalized software					(25,972)	(30,369)
Acquisition, net of cash acquired of $0 and $23,850, respectively					0	(1,082,740)
Net cash used in investing activities					(33,030)	(879,073)
Cash flows from financing activities:
Proceeds from credit facility borrowings, net of discount					0	965,300
Repayment of credit facility borrowings					(7,350)	(236,250)
Payments for debt issuance costs					0	(18,269)
Proceeds from exercise of stock options					3,321	1,628
Finance lease liabilities paid	(596)				(1,769)	(709)
Tax payments for equity award issuances					(2,860)	(1,070)
Payment for acquisition-related contingent consideration					(12,600)	0
Net cash (used in) provided by financing activities					(21,258)	710,630
Increase (Decrease) in cash and cash equivalents					17,964	(105,428)
Cash and cash equivalents, beginning of period		$ 115,591		$ 208,944	115,591	208,944	$ 208,944
Cash and cash equivalents, end of period	$ 133,555		$ 103,516		133,555	103,516	$ 115,591
Supplementary cash flow disclosure:
Income taxes received, net					(5,058)	(3,597)
Interest paid					47,861	27,618
Non-cash transactions:
Operating lease obligations incurred					20,830	0
Finance lease obligations incurred					20	4,602
Accruals for purchases of property, equipment					2,260	7,700
Accruals for investment in capitalized software					2,018	2,450
Acquisition consideration					$ 0	$ 84,156