Summary of Components of Net Periodic Benefit Cost and Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Defined benefit pension plans
Net periodic benefit cost:
Service cost	$ 13,285		$ 13,610		$ 12,441
Interest cost	29,530		28,433		27,934
Expected return on plan assets	(31,270)		(25,714)		(24,581)
Amortization of prior service (credit) cost	(502)		1,776		2,453
Recognized actuarial loss (gain)	19,020		19,492		13,499
Settlement loss	3,534
Net periodic benefit cost	33,597		37,597		31,746
Other changes in plan assets and benefit obligations recognized in other comprehensive income:
Net actuarial loss (gain)	27,144		62,687		482
Prior service (credit) cost	(11,789)		2		(675)
Amortization of prior service credit (cost)	501		(1,776)		(2,453)
Total recognized in other comprehensive income	15,856	[1]	60,913	[1]	(2,646)	[1]
Total recognized in net periodic benefit cost and other comprehensive income	49,453		98,510		29,100
Postretirement benefit plans
Net periodic benefit cost:
Service cost	79		73		76
Interest cost	1,411		1,576		1,820
Recognized actuarial loss (gain)	117		(48)		52
Net periodic benefit cost	1,607		1,601		1,948
Other changes in plan assets and benefit obligations recognized in other comprehensive income:
Net actuarial loss (gain)	4,755		(1,249)		(9,502)
Total recognized in other comprehensive income	4,755	[1]	(1,249)	[1]	(9,502)	[1]
Total recognized in net periodic benefit cost and other comprehensive income	$ 6,362		$ 352		$ (7,554)

[1] Amounts exclude related tax (benefit) expense of $(2.3) million, $(21.6) million, and $4.4 million, during 2012, 2011, and 2010, respectively, which are also included in other comprehensive income.