Consolidated Financial Statements - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Accounting Policies [Abstract]
Proceeds from termination of life insurance contracts	$ 793,000	$ 5,327,000
Capitalized interest		4,900,000
Increase (decrease) in retirement liabilities			(10,600,000)
Increase (decrease) in deferred income taxes (non-current)			(3,500,000)
Increase (decrease) in other current liabilities			7,200,000
Increase (decrease) in deferred income taxes (current)			$ 100,000