Income Taxes - Components of Comprehensive Provision for Income Taxes Allocation (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Comprehensive provision (benefit) for income taxes allocable to:
Net income	$ 970,000	$ (12,658,000)
Other comprehensive income (loss):
Marketable securities	(45,200,000)	18,300,000
Currency translation	(300,000)	(2,900,000)
Total	(44,300,000)	3,000,000
Defined Benefit Pension Plans
Other comprehensive income (loss):
Defined benefit plans	300,000	400,000
OPEB
Other comprehensive income (loss):
Defined benefit plans	$ (100,000)	$ (100,000)