Fair Value Measurement - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Oct. 06, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	$ 36,086	$ 36,086
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, Low	256,000	256,000
Debt Issuance Costs Incurred During Noncash or Partial Noncash Transaction			$ 0	$ 0
Accretion of interest on deferred consideration	2,608		0	0
Total liabilities at fair value	247,459	247,459	5,175
Cash equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	36,086	36,086	133,540
Contingent consideration
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total liabilities at fair value	24,301	24,301	5,175
Deferred consideration
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total liabilities at fair value	223,158	223,158	0
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value			133,540
Total liabilities at fair value	0	0	0
Level 1 [Member] | Cash equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	36,086	36,086	133,540
Level 1 [Member] | Contingent consideration
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total liabilities at fair value	0	0	0
Level 1 [Member] | Deferred consideration
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total liabilities at fair value	0	0	0
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	0	0	0
Total liabilities at fair value	223,158	223,158	0
Level 2 [Member] | Cash equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	0	0	0
Level 2 [Member] | Contingent consideration
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total liabilities at fair value	0	0	0
Level 2 [Member] | Deferred consideration
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total liabilities at fair value	223,158	223,158	0
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		80	500	$ 100
Total assets at fair value	0	0	0
Total liabilities at fair value	24,301	24,301	5,175
Level 3 [Member] | Cash equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	0	0	0
Level 3 [Member] | Contingent consideration
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total liabilities at fair value	24,301	24,301	5,175
Level 3 [Member] | Deferred consideration
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total liabilities at fair value	0	0	0
Triage Business
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	280,000	280,000
Contingent consideration—BNP Business					$ 19,700
Debt Issuance Costs Incurred During Noncash or Partial Noncash Transaction		220,550
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability		19,700
Bio Helix
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Contingent consideration—BNP Business	$ 4,600	$ 4,600	$ 5,200