Benefits Expected to Be Paid from Pension and Other Postretirement Benefit Plans, Which Reflect Future Years of Services and Medicare Subsidy Expected to Be Received (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
2014	$ 30,138
2015	31,690
2016	33,299
2017	34,969
2018	36,663
2019 — 2023	203,677
Defined Benefit Plan, Expected Future Benefit Payments, Total	370,436
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
2014	3,291
2015	3,194
2016	2,827
2017	2,838
2018	2,726
2019 — 2023	12,436
Defined Benefit Plan, Expected Future Benefit Payments, Total	$ 27,312