Pension and Other Postretirement Benefits - Amounts Recognized in Balance Sheets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Amounts recongized in the balance sheets:
Accrued benefit liability (noncurrent)	$ (105,924)	$ (144,320)
Pension Obligations [Member]
Amounts recongized in the balance sheets:
Prepaid benefit cost	5,797	8,728
Accrued benefit liability (current)	(3,878)	(3,900)
Accrued benefit liability (noncurrent)	(61,975)	(95,550)
Net funded status	(60,056)	(90,722)
Other Postretirement Obligations [Member]
Amounts recongized in the balance sheets:
Prepaid benefit cost
Accrued benefit liability (current)	(2,665)	(3,002)
Accrued benefit liability (noncurrent)	(43,949)	(48,770)
Net funded status	$ (46,614)	$ (51,772)