Investments Held in Rabbi Trust - Components of Investment Income (Losses), Included in Other Income (Expense) in Accompanying Consolidated Statements of Operations (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investments Debt And Equity Securities [Abstract]
Gross realized gains from sale of trading securities	$ 160	$ 163	$ 201
Gross realized (losses) from sale of trading securities	(10)	(1)	(20)
Dividend and interest income	279	129	69
Net unrealized holding gains (losses)	568	312	(383)
Net investment income (losses)	$ 997	$ 603	$ (133)