Income Taxes - Components of Comprehensive Provision for Income Taxes Allocation (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Comprehensive provision (benefit) for income taxes allocable to:
Net income (loss)	$ (125,000)	$ (8,024,000)	$ 845,000	$ (20,682,000)
Other comprehensive income (loss):
Marketable securities	(12,400,000)	(11,900,000)	(57,500,000)	6,400,000
Currency translation	(400,000)	(600,000)	(700,000)	(2,300,000)
Total	(12,700,000)	(19,000,000)	(57,000,000)	(16,000,000)
Defined Benefit Pension Plans
Other comprehensive income (loss):
Defined benefit plans	300,000	300,000	600,000	700,000
OPEB
Other comprehensive income (loss):
Defined benefit plans	$ (100,000)		$ (200,000)	$ (100,000)