Business Combinations (Summary of Preliminary Allocation of Tangible and Identifiable Intangible Assets Acquired and Liabilities Assumed) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017
Preliminary Allocation
Goodwill	$ 129,244		$ 80,216
Data Center Business
Preliminary Allocation
Accounts receivables	33,488	$ 33,488
Inventories	19,934	19,973
Prepaid expenses and other current assets	988	988
Property and equipment	29,160	29,160
Other assets	4,734	4,734
Accounts payable and accrued expenses	(15,737)	(15,850)
Deferred revenue	(33,025)	(33,519)
Total tangible assets acquired and liabilities assumed	39,542	38,974
Identifiable intangible assets	32,200	28,600
Goodwill	12,595	16,763
Total intangible assets acquired	44,795	45,363
Total net assets acquired	84,337	84,337
Change during three months ended March 31, 2018
Adjustments, Inventory	(39)
Adjustments, Accounts payable and accrued expenses	113
Adjustments, Deferred revenue	494
Adjustments, Net tangible assets acquired	568
Adjustments, Identifiable intangible assets	3,600
Adjustments, Goodwill	(4,168)
Adjustments, Total intangible assets acquired	(568)
Campus Fabric Business
Preliminary Allocation
Accounts receivables	18,712	18,295
Inventories	15,545	15,545
Prepaid expenses and other current assets	649	673
Property and equipment	5,406	3,768
Other assets	4,794	5,311
Accounts payable and accrued expenses	(32,314)	(31,919)
Deferred revenue	(8,994)	(10,051)
Other long-term liabilities	(5,205)	(5,205)
Total tangible assets acquired and liabilities assumed	(1,407)	(3,583)
Identifiable intangible assets	42,200	46,900
In-process research and development	2,600	2,500
Goodwill	36,433	34,009
Total intangible assets acquired	81,233	83,409
Total net assets acquired	79,826	$ 79,826
Change during three months ended March 31, 2018
Adjustments, Accounts receivables	417
Adjustments, Prepaid expenses and other current assets	(24)
Adjustments, Property and equipment	1,638
Adjustments, Other assets	(517)
Adjustments, Accounts payable and accrued expenses	(395)
Adjustments, Deferred revenue	1,057
Adjustments, Net tangible assets acquired	2,176
Adjustments, Identifiable intangible assets	(4,700)
Adjustments, In-process research and development	100
Adjustments, Goodwill	2,424
Adjustments, Total intangible assets acquired	$ (2,176)