Employee and Non-Employee Benefit Plans (Detail) - Net Periodic Benefit Cost (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Post Retirement Health Care and Life Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 28	$ 33
Interest cost	47	43
Amortization of prior service cost	(155)	(167)
Amortization of net actuarial loss	0	8
Total post-retirement benefit cost / (income)	(80)	(83)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	22	21
Expected return on plan assets	(26)	(29)
Amortization of net actuarial loss	5	17
Total post-retirement benefit cost / (income)	$ 1	$ 9