Benefit Plans - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	1 Months Ended		3 Months Ended
	Nov. 30, 2011	Sep. 30, 2011	Dec. 31, 2012	Dec. 31, 2011	Sep. 30, 2012
Defined Benefit Plan Disclosure [Line Items]
Description of plan amendment for the defined benefit plan			Effective January 1, 2013, all plan participants' benefits in the U.S. defined benefit traditional pension plan, which provided benefits to participants based upon a final average pay formula, were converted to a defined benefit cash balance pension plan.
Net pension cost					$ 40,200
Defined pension plan discount rate	5.10%	4.90%
Expected change in net benefit cost due to change in discount rate					5,300
Expected change in net benefit cost due to change in plan assets					6,200
Net pension cost for negative prior service cost					28,700
Postemployment benefit costs			$ 11,694	$ 8,995