Employee Benefit Plans - Changes in Plan Assets (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Changes in plan assets
Fair value of plan assets at end of year	$ 1,595,679,000	$ 1,470,030,000
Pension Benefits [Member]
Changes in plan assets
Fair value of plan assets at beginning of year	1,470,030,000	1,439,711,000
Actual return on plan assets	168,491,000	31,528,000
Exchange rate changes	4,498,000	(3,598,000)
Employer contributions	16,465,000	58,481,000
Plan participants' contributions	3,962,000	3,887,000
Benefits paid	(67,767,000)	(59,979,000)
Fair value of plan assets at end of year	1,595,679,000	1,470,030,000
Other Postretirement Benefits [Member]
Changes in plan assets
Fair value of plan assets at beginning of year
Actual return on plan assets
Exchange rate changes
Employer contributions	2,038,000	1,914,000
Plan participants' contributions	3,074,000	3,412,000
Benefits paid	(5,112,000)	(5,326,000)
Fair value of plan assets at end of year