Postretirement Benefits - Schedule of Amounts Recognized in Accumulated Other Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Pension and Other Postretirement Benefits Recognized in Accumulated Other Comprehensive Income (Loss) [Line Items]
Net amounts recognized at year end	$ (97,467)	$ (168,129)	$ (119,863)	$ (105,903)
Pension Benefits [Member]
Schedule of Pension and Other Postretirement Benefits Recognized in Accumulated Other Comprehensive Income (Loss) [Line Items]
Net loss (gain)	90,878	156,567
Prior service cost	5,476	7,752
Transition obligation	0	0
Net amounts recognized at year end	$ 96,354	$ 164,319