Components of net periodic pension cost (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Interest Cost	$ 7,495	$ 7,784	$ 14,990	$ 15,569
Expected return on plan assets	(9,810)	(10,840)	(19,620)	(21,680)
Defined Benefit Plan Amortization Of Net Gains Losses	5,426	2,829	10,852	5,657
Defined Benefit Plan Net Periodic Benefit Cost	3,111	(227)	6,222	(454)
Other Pension Plans Defined Benefit Member
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Interest Cost	393	395	786	790
Expected return on plan assets	(526)	(450)	(1,052)	(901)
Defined Benefit Plan Amortization Of Net Gains Losses	323	148	646	296
Defined Benefit Plan Net Periodic Benefit Cost	$ 190	$ 93	$ 380	$ 185