Fair Value Measurements - Unobservable Inputs Reconciliation - Assets (Details) - Fair Value, Measurements, Recurring - Level 3 - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 32,031	$ 30,454
Sales and cash collections	(1,249)	(3,634)
Realized gains	(2,497)
Unrealized gains	2,465	2,654
Unrealized losses		(1,109)
Balance at end of period	35,744	28,365
Investments in Associated Companies
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	1,223	1,931
Sales and cash collections	0	0
Realized gains	0
Unrealized gains	0	0
Unrealized losses		(642)
Balance at end of period	1,223	1,289
ModusLink Warrants
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	19	543
Sales and cash collections	0	0
Realized gains	0
Unrealized gains	13	0
Unrealized losses		(467)
Balance at end of period	32	76
Marketable Securities and Other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	30,789	27,980
Sales and cash collections	(1,249)	(3,634)
Realized gains	(2,497)
Unrealized gains	2,452	2,654
Unrealized losses		0
Balance at end of period	$ 34,489	$ 27,000