Allocation of Purchase Price (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Business Acquisition [Line Items]
Goodwill	$ 361,792	$ 349,272	$ 352,778
ZTEC Instruments, Inc.
Business Acquisition [Line Items]
Goodwill	12,520
Intangible assets	4,870
Cash, cash equivalents and short term marketable securities	79
Other current assets	1,612
Non-current assets	1,757
Accounts payable and current liabilities	(1,811)
Long-term deferred tax liabilities	(1,719)
Total purchase price	17,308
Litepoint Corporation
Business Acquisition [Line Items]
Goodwill	349,272
Intangible assets	310,500
Cash, cash equivalents and short term marketable securities	61,250
Other current assets	75,615
Non-current assets	5,838
Accounts payable and current liabilities	(37,177)
Long-term deferred tax liabilities	(115,463)
Other long-term liabilities	(3,788)
Total purchase price	$ 646,047