Acquisition (Detail) $ in Thousands		3 Months Ended	12 Months Ended
	Oct. 06, 2017 USD ($) payment	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) payment
Business Acquisition [Line Items]
Goodwill		$ 337,032	$ 337,028
Secured debt	$ 245,000	143,187	245,000
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, Low		256,000
Triage Business [Member]
Business Acquisition [Line Items]
Cash consideration—Triage Business	399,798
Goodwill	245,531
Secured debt	245,000
Contingent consideration—BNP Business	19,700
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High		280,000
Deferred consideration - BNP Business			220,600
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability		19,700	19,700
Consideration A [Member] | Triage Business [Member]
Business Acquisition [Line Items]
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, Low	$ 16,000
Contingent consideration—BNP Business		$ 24,000	$ 24,000
Number of installment payments | payment	5
Amount of installment payment	$ 8,000
Consideration B [Member] | Triage Business [Member]
Business Acquisition [Line Items]
Number of installment payments | payment			6
Amount of installment payment			$ 40,000
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High			$ 240,000
Consideration C [Member] | Triage Business [Member]
Business Acquisition [Line Items]
Inventory related adjustment	$ 205