Employee Benefit Plans - Components of Net Periodic Benefit Cost (Credit) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pension Plans [Member]
Components of Net Benefit Cost (Credit):
Service cost	$ 223	$ 314
Interest cost	7,531	6,753
Expected return on plan assets	(8,079)	(6,797)
Amortization of:
Prior service cost	733	706
Net actuarial loss	1,111	914
Net benefit cost	1,519	1,890
Medical Plan [Member]
Components of Net Benefit Cost (Credit):
Service cost	12	10
Interest cost	53	47
Expected return on plan assets
Amortization of:
Prior service cost
Net actuarial loss	(23)
Net benefit cost	$ 42	$ 57