Components of net periodic pension cost (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service credit	$ (950)	$ 0	$ (2,850)	$ 0
Recognized net actuarial losses	2,127	6,168	6,379	18,506
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Interest Cost	7,461	6,966	22,383	20,897
Expected return on plan assets	(11,630)	(10,804)	(34,891)	(32,412)
Defined Benefit Plan Future Amortization Of Gain Loss	2,019	5,363	6,056	16,089
Total net periodic pension cost	(2,150)	1,525	(6,452)	4,574
Other Pension Plans Defined Benefit Member
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Interest Cost	415	373	1,244	1,120
Expected return on plan assets	(606)	(542)	(1,816)	(1,625)
Defined Benefit Plan Future Amortization Of Gain Loss	108	332	323	998
Total net periodic pension cost	$ (83)	$ 163	$ (249)	$ 493