Accumulated Other Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Income or Loss (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				12 Months Ended
	Mar. 31, 2013		Mar. 31, 2012		Dec. 31, 2012		Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ (57,808)		$ (62,802)		$ (62,802)
Other comprehensive income before reclassifications	(9,407)		6,226
Amounts reclassified from accumulated other comprehensive income	1,037		2,635
Net current-period other comprehensive income			8,861		(8,370)
Ending balance	(66,178)		(53,941)		(57,808)
AOCI, Pension and other postretirement benefit plans, tax	21,813		20,799		22,371		20,799
AOCI, Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Tax	126		0		127		0
AOCI, Available-for-sale Securities Adjustment, Tax			1,555
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			(1,168)	[1]	(1,168)	[1]
Other comprehensive income before reclassifications			0	[1]
Amounts reclassified from accumulated other comprehensive income			1,168	[1]
Net current-period other comprehensive income			1,168	[1]
Ending balance			0	[1]
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(235)	[2]	(270)	[3]	(270)	[3]
Other comprehensive income before reclassifications	(9)	[2]	255	[3]
Amounts reclassified from accumulated other comprehensive income	0	[2]	0	[3]
Net current-period other comprehensive income	(9)	[2]	255	[3]
Ending balance	(244)	[2]	(15)	[3]
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(70,158)	[4]	(67,239)	[5]	(67,239)	[5]
Other comprehensive income before reclassifications	0	[4]	0	[5]
Amounts reclassified from accumulated other comprehensive income	1,037	[4]	1,467	[5]
Net current-period other comprehensive income	1,037	[4]	1,467	[5]
Ending balance	(69,121)	[4]	(65,772)	[5]
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	12,585		5,875		5,875
Other comprehensive income before reclassifications	(9,398)		5,971
Amounts reclassified from accumulated other comprehensive income	0		0
Net current-period other comprehensive income	(9,398)		5,971
Ending balance	$ 3,187		$ 11,846

[1] Net of taxes of $1,555 for the period ended December 31, 2011.

[2] Net of taxes of $126 and $127 for the periods ended March 31, 2013 and December 31, 2012, respectively.

[3] Net of taxes of $0 and $0 for the periods ended March 31, 2012 and December 31, 2011.

[4] Net of taxes of $21,813 and $22,371 for the periods ended March 31, 2013 and December 31, 2012, respectively.

[5] Net of taxes of $20,799 and $20,799 for the periods ended March 31, 2012 and December 31, 2011.