Business combinations (Narrative) (Details) (Enterasys Networks, Inc., USD $) In Thousands, unless otherwise specified	0 Months Ended
Sep. 30, 2014	Dec. 31, 2013	Oct. 31, 2013
Enterasys Networks, Inc.
Business Acquisition [Line Items]
Purchase price paid in acquisition	$ 180,000	$ 180,000	$ 180,000

The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration