Pension and Other Postretirement Benefits - Benefits Expected to be Paid in Subsequent Years from Our Pension and Other Postretirement as Well as Medicare Subsidy Receipts (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013
Medicare Subsidy Receipts [Member]
Pension And Other Employee Benefit Plans [Line Items]
2014	$ 91
2015	85
2016	78
2017	71
2018	64
2019-2023	225
Total	614
Pension Benefits [Member]
Pension And Other Employee Benefit Plans [Line Items]
2014	15,505
2015	15,752
2016	17,239
2017	17,273
2018	16,796
2019-2023	90,585
Total	173,150
Other Benefits [Member]
Pension And Other Employee Benefit Plans [Line Items]
2014	2,823
2015	2,840
2016	2,779
2017	2,701
2018	2,653
2019-2023	12,890
Total	$ 26,686