Fair Value Measurement (Detail) - (Table) number in Thousands	3 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)
Assets:
Foreign Currency Contract, Asset, Fair Value Disclosure			$ (783,000)	$ (191,000)
Proceeds from Collection of Notes Receivable			221,000	249,000	$ 466,000
Liabilities:
Business Combination, Contingent Consideration, Liability			20,617,000	0		$ 10,000,000	$ 20,617,000
Business Acquisition, Contingent Consideration, Actual Cash Payment	$ 2,741,000	$ 3,482,000	4,618,000
Repayment of Notes Receivable from Related Parties			409,000	409,000	409,000
Increase (Decrease) in Accrued Interest Receivable, Net			54,000	63,000	71,000
business combinations contingent liability payment			7,359,000	16,402,000	6,270,000
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability			(11,206,000)	(425,000)	(5,576,000)
Fair Value [Member]
Assets:
Cash Equivalents			58,436,000	3,309,000
Current marketable securities – available for sale			64,027,000	39,495,000
Long-term marketable securities – available for sale			29,523,000	70,559,000
Total assets			151,986,000	113,554,000
Liabilities:
Business Combination, Contingent Consideration, Liability			10,000,000	7,948,000	$ 24,775,000
Total liabilities			10,783,000	7,948,000
Fair Value [Member] | Forward Contracts [Member]
Liabilities:
Foreign Currency Contracts, Liability, Fair Value Disclosure			783,000
Fair Value, Inputs, Level 1 [Member]
Assets:
Cash Equivalents			58,436,000	3,309,000
Current marketable securities – available for sale			64,027,000	39,495,000
Long-term marketable securities – available for sale			29,523,000	70,559,000
Total assets			151,986,000	113,363,000
Liabilities:
Business Combination, Contingent Consideration, Liability			0	0
Total liabilities			0	0
Fair Value, Inputs, Level 2 [Member]
Assets:
Cash Equivalents			0	0
Current marketable securities – available for sale			0	0
Long-term marketable securities – available for sale			0	0
Total assets			0	191,000
Liabilities:
Business Combination, Contingent Consideration, Liability			0	0
Total liabilities			783,000	0
Fair Value, Inputs, Level 3 [Member]
Assets:
Cash Equivalents			0	0
Current marketable securities – available for sale			0	0
Long-term marketable securities – available for sale			0	0
Total assets			0	0
Liabilities:
Business Combination, Contingent Consideration, Liability			10,000,000	7,948,000
Total liabilities			$ 10,000,000	$ 7,948,000
Contingent Consideration Type [Domain]
Foreign Currency Exchange Rate, Translation			0	0