Contingencies - Additional Information (Detail) $ in Thousands		1 Months Ended
	Aug. 15, 2017	Dec. 31, 2017 USD ($)
US Attorney Prescription Drug Investigation
Other Commitments [Line Items]
Litigation Settlement, Amount Awarded to Other Party		$ 63,700
Stockholder Derivative Litigation
Other Commitments [Line Items]
Loss Contingency Number of Previously Disclosed Lawsuits Consolidated Into One	3
Incremental Cash Portion | US Attorney Prescription Drug Investigation
Other Commitments [Line Items]
Litigation Settlement, Amount Awarded to Other Party		41,500
Cash Paid For Portion Previously Refunded | US Attorney Prescription Drug Investigation
Other Commitments [Line Items]
Litigation Settlement, Amount Awarded to Other Party		$ 22,200