Marketable Securities - Details of Marketable Securities (Details) - IronNet [Member] $ in Thousands	Sep. 30, 2021 USD ($)
Marketable Securities [Line Items]
Fair Value	$ 50,828
Basis	69,371
Cumulative Unrealized (Loss) Gain	(18,543)
Private Warrants [Member]
Marketable Securities [Line Items]
Fair Value	20,374
Basis	31,504
Cumulative Unrealized (Loss) Gain	(11,130)
Restricted Common Shares [Member]
Marketable Securities [Line Items]
Fair Value	19,390
Basis	26,501
Cumulative Unrealized (Loss) Gain	(7,111)
PIPE Related Common Shares [Member]
Marketable Securities [Line Items]
Fair Value	4,647
Basis	6,185
Cumulative Unrealized (Loss) Gain	(1,538)
IronNet Securities [Member]
Marketable Securities [Line Items]
Fair Value	44,411
Basis	64,190
Cumulative Unrealized (Loss) Gain	(19,779)
Equity Funds and Other Securities [Member]
Marketable Securities [Line Items]
Fair Value	6,417
Basis	5,181
Cumulative Unrealized (Loss) Gain	$ 1,236