Pension Benefits And Other Postretirement Benefits Recognized In the Accompanying Consolidated Balance Sheets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Other noncurrent assets	$ 263	$ 355
Deferred tax asset	26,421	10,972
Total assets	26,684	11,327
Current liabilities	(4,561)	(4,411)
Long-term liabilities	(226,584)	(157,843)
Deferred tax liability	(449)	(269)
Total liabilities	(231,594)	(162,523)
Accumulated other comprehensive income	70,377	32,002
Net amount recognized	(134,533)	(119,194)
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Other noncurrent assets	0	0
Deferred tax asset	1,764	1,247
Total assets	1,764	1,247
Current liabilities	(654)	(977)
Long-term liabilities	(13,564)	(11,240)
Deferred tax liability	0	0
Total liabilities	(14,218)	(12,217)
Accumulated other comprehensive income	2,805	1,984
Net amount recognized	$ (9,649)	$ (8,986)