Employee and Non-Employee Benefit Plans (Detail) - Net Periodic Benefit Cost (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Post Retirement Health Care And Life Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 16	$ 31	$ 44	$ 64
Interest cost	35	39	81	82
Amortization of prior service cost	(84)	(156)	(239)	(323)
Amortization of net actuarial loss	5	6	5	14
Prior service cost recognized due to current curtailment	(52)	0	(52)	0
Total post-retirement benefit cost / (income)	(80)	(80)	(161)	(163)
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	22	21	44	42
Expected return on plan assets	(26)	(28)	(52)	(57)
Amortization of net actuarial loss	5	16	10	33
Total post-retirement benefit cost / (income)	$ 1	$ 9	$ 2	$ 18