Segment Information - Business Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Total revenue	$ 77,451	$ 191,413	$ 283,235	$ 457,218
Total gross profit	23,601	65,882	99,724	139,503
Supercomputing [Member]
Segment Reporting Information [Line Items]
Total revenue	60,730	156,519	216,125	370,053
Total gross profit	18,322	51,590	74,893	109,639
Storage and Data Management [Member]
Segment Reporting Information [Line Items]
Total revenue	12,330	22,068	50,755	63,736
Total gross profit	3,917	8,908	18,091	21,186
Maintenance and Support [Member]
Segment Reporting Information [Line Items]
Total revenue	26,292	23,106	79,862	68,833
Total gross profit	8,447	9,174	30,530	30,706
Other Segments [Member]
Segment Reporting Information [Line Items]
Total revenue	4,391	12,826	16,355	23,429
Total gross profit	1,362	5,384	6,740	8,678
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenue	(26,292)	(23,106)	(79,862)	(68,833)
Total gross profit	$ (8,447)	$ (9,174)	$ (30,530)	$ (30,706)