Fair Value Measurements Financial assets measured at fair value on a recurring basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Cash And Cash Equivalent
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	$ 1,000
Marketable Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	800
Cash, including short-term deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	72,602	[1]	68,265	[1]
Cash, including short-term deposits | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	72,602	[1]	68,265	[1]
Cash, including short-term deposits | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	0	[1]	0	[1]
Cash, including short-term deposits | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	0	[1]	0	[1]
Cash, including short-term deposits | Cash And Cash Equivalent
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets			68,200
Cash, including short-term deposits | Marketable Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets			100
Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	20,783	[2]	11,820	[2]
Mutual funds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	20,783	[2]	11,820	[2]
Mutual funds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	0	[2]	0	[2]
Mutual funds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	0	[2]	0	[2]
United States Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	50,379	[2]	99,477	[2]
United States Government Securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	50,379	[2]	99,477	[2]
United States Government Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	0	[2]	0	[2]
United States Government Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	0	[2]	0	[2]
Corporate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	74,559	[2]	20,117	[2]
Corporate securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	68,624	[2]	20,117	[2]
Corporate securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	0	[2]	0	[2]
Corporate securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	5,935	[2]	0	[2]
Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	1,799	[3]	22,291	[4]
Commercial Paper | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	0	[3]	0	[4]
Commercial Paper | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	1,799	[3]	22,291	[4]
Commercial Paper | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	0	[3]	0	[4]
Commercial Paper | Cash And Cash Equivalent
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets			3,400	[2]
Commercial Paper | Marketable Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets			18,900	[2]
Corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	31,965	[2]	48,714	[2]
Corporate obligations | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	0	[2]	0	[2]
Corporate obligations | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	14,535	[2]	46,931	[2]
Corporate obligations | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	17,430	[2]	1,783	[2]
Investments in Certain Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	844	[5]	1,021	[6]
Investments in Certain Funds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	0	[5]	0	[6]
Investments in Certain Funds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	0	[5]	0	[6]
Investments in Certain Funds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	844	[5]	1,021	[6]
Financial Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	252,931		271,705
Financial Assets | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	212,388		199,679
Financial Assets | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	16,334		69,222
Financial Assets | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets	24,209		2,804
Acquisition-related Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities			(475)	[7]
Acquisition-related Contingent Consideration | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities			0	[7]
Acquisition-related Contingent Consideration | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities			0	[7]
Acquisition-related Contingent Consideration | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities			$ (475)

[1] Reported within "Cash and cash equivalents."

[2] Reported within “Marketable securities.”

[3] $1.0 million reported within "Cash and cash equivalents" and $0.8 million reported within "Marketable securities."

[4] $3.4 million reported within "Cash and cash equivalents" and $18.9 million reported within "Marketable securities."

[5] Reported within "Other investments."

[6] Reported within "Other investments"

[7] Reported within “Accrued expenses”.