Business combinations (Estimated Purchase Price) (Details) (USD $)	0 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Oct. 31, 2013	Jun. 30, 2014	Sep. 30, 2014
Business Acquisition [Line Items]
Goodwill	$ 70,877,000			$ 70,877,000	$ 70,877,000
Enterasys Networks, Inc.
Business Acquisition [Line Items]
Cash	7,397,000	4,969,000			7,397,000
Receivables	23,271,000	25,699,000			23,271,000
Inventory	33,662,000	33,662,000			33,662,000
Other current assets	7,374,000	8,888,000			7,374,000
Property and equipment	21,293,000	23,122,000			21,293,000
Identifiable intangible assets	108,900,000	108,900,000			108,900,000
In-process research and development	3,000,000	3,000,000			3,000,000
Deferred tax assets	9,000	9,000			9,000
Other assets	7,343,000	7,343,000			7,343,000
Goodwill	70,877,000	57,922,000			70,877,000
Current liabilities	(81,535,000)	(75,394,000)			(81,535,000)
Other long-term liabilities	(14,194,000)	(13,151,000)			(14,194,000)
Total purchase price allocation	187,397,000	184,969,000			187,397,000
Less: Cash acquired from acquisition	(7,397,000)	(4,969,000)
Total purchase price consideration, net of cash acquired	180,000,000	180,000,000	180,000,000
Change during the period, Cash					2,428,000	[1]
Change during the period, Receivables				(2,428,000)	(2,428,000)	[1]
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Other Current Assets				(1,514,000)	(1,514,000)	[2]
Change during the period, Property and equipment					(1,829,000)	[3]
Change during period, Identifiable intangible assets					0	[4]
Change during the period, Goodwill					12,955,000
Change during the period, Current Liabilities					(6,141,000)	[3],[5],[6]
Change during the period, Other long-term liabilities					(1,043,000)	[3]
Change during the period, Total purchase price allocation					2,428,000
Change during the period, Cash acquired from acquisition					(2,428,000)	[1]
Goodwill, increase (decrease)				2,400,000
Increase (decrease) in current liabilities for litigation and statutory tax assessments				5,400,000
Increase (decrease) for accrued liabilities				500,000
Enterasys Networks, Inc. | Order backlog
Business Acquisition [Line Items]
Finite-lived intangible asset useful lives		1 year 6 months	1 year
Enterasys Networks, Inc. | Goodwill [Member]
Business Acquisition [Line Items]
Change during the period, Property and equipment				3,000,000
Enterasys Networks, Inc. | Property, Plant and Equipment [Member]
Business Acquisition [Line Items]
Change during the period, Property and equipment				1,200,000
Enterasys Networks, Inc. | Other Current Liabilities [Member]
Business Acquisition [Line Items]
Change during the period, Property and equipment				200,000
Enterasys Networks, Inc. | Other Noncurrent Liabilities [Member]
Business Acquisition [Line Items]
Change during the period, Property and equipment				$ 1,000,000

[1] The Company finalized the working capital adjustment during the nine months ended September 30, 2014, which led to a decrease of $2.4 million in receivables and a corresponding increase in cash. As a result of this adjustment, the total cash acquired from the acquisition also increased by the same amount. The net effect of this adjustment is an increase in goodwill of $2.4 million.

[2] The Company obtained new information regarding the existence of prepaids as of the acquisition date which led to a decrease in the fair value of current assets of $1.5 million, and a corresponding increase in goodwill. The change in the amortization of prepaids due to the change in fair value of current assets was immaterial.

[3] The Company updated its preliminary estimate of the fair value of property and equipment which led to a decrease of $3.0 million in property and equipment with a corresponding increase in goodwill. The Company also updated the fair values of the asset retirement obligations and the related asset retirement assets which led to an increase in the fair value of property and equipment of $1.2 million and a corresponding increase in current liabilities and other long-term liabilities of $0.2 million and $1.0 million, respectively. The decrease in depreciation expense due to the change in fair value of property and equipment was immaterial.

[4] During the nine months ended September 30, 2014, there were no changes to the fair value of the identifiable intangible assets acquired. However, the Company revised the estimated useful life of Order backlog from 1.5 years to 1 year.

[5] The Company obtained new information regarding the existence of accrued liabilities as of the acquisition date which led to a net increase in the fair value of accrued liabilities by $0.5 million with a corresponding increase in goodwill.

[6] The Company obtained new information regarding accruals for litigation and statutory tax assessment as of the acquisition date which led to an increase in the fair value of current liabilities of $5.4 million and a corresponding increase in goodwill.