Employee and Non-Employee Benefit Plans (Detail) - Net Periodic Benefit Cost (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Post Retirement Health Care And Life Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 14	$ 32	$ 58	$ 96
Interest cost	34	41	116	123
Amortization of prior service cost	(66)	(162)	(305)	(485)
Amortization of net actuarial loss	7	7	12	21
Prior service cost recognized due to current curtailment	0	0	(52)	0
Total post-retirement benefit cost / (income)	(11)	(82)	(171)	(245)
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	22	21	66	62
Expected return on plan assets	(26)	(29)	(78)	(86)
Amortization of net actuarial loss	5	17	15	50
Total post-retirement benefit cost / (income)	$ 1	$ 9	$ 3	$ 26