Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Liabilities:
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net	$ 0	$ 0	$ 0
Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net, non current	0	$ 0	$ 0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets:
Money market instruments	2,334,000
Corporate bonds	0
Treasury bills	0
Asset-backed securities	0
Agency bonds	0
Municipal bonds	0
Cash flow hedge forward contracts	0
Economic hedge forward contracts	0
Liabilities:
Economic hedge forward contracts	0
Significant Other Observable Inputs (Level 2) [Member]
Assets:
Money market instruments	0
Corporate bonds	311,140,000
Treasury bills	159,455,000
Asset-backed securities	96,560,000
Euro liquidity funds	46,499,000
Sovereign bonds	30,883,000
Agency bonds	13,242,000
Municipal bonds	7,750,000
Cash flow hedge forward contracts	43,000
Economic hedge forward contracts	1,000
Liabilities:
Economic hedge forward contracts	(11,000)
Fair Value, Inputs, Level 3 [Member]
Liabilities:
Contingent consideration liabilities	$ (4,173,000)