Employee and Non-Employee Benefit Plans (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	9 Months Ended			3 Months Ended		9 Months Ended			1 Months Ended	9 Months Ended			1 Months Ended	9 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2014 Post Retirement Health Care And Life Benefits [Member]	Sep. 30, 2013 Post Retirement Health Care And Life Benefits [Member]	Sep. 30, 2014 Post Retirement Health Care And Life Benefits [Member]	Sep. 30, 2013 Post Retirement Health Care And Life Benefits [Member]	Sep. 30, 2014 Pension Plan [Member]	Aug. 31, 2014 Employee Equity Incentive Plan [Member]	Sep. 30, 2014 Employee Equity Incentive Plan [Member]	May 30, 2014 Employee Equity Incentive Plan [Member]	May 30, 2014 Employee Stock Purchase Plan [Member]	Jun. 30, 2014 Non-Employee Director Equity Incentive Plan [Member]	Sep. 30, 2014 Non-Employee Director Equity Incentive Plan [Member]	May 30, 2014 Non-Employee Director Equity Incentive Plan [Member]	Sep. 30, 2014 Minimum [Member] Non-Employee Director Equity Incentive Plan [Member]	Sep. 30, 2014 Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Negative plan amendment					$ 919
Prior service cost recognized due to current curtailment					0	0	(52)	0
Other comprehensive income reclassification of defined benefit plan prior service cost and net actuarial loss		(345)	(464)
Other comprehensive income (loss), reclassification of net actuarial loss from accumulated other comprehensive loss into pension benefit income		63	36
Projected cost of plan termination									630
Defined benefit plan, contributions by employer	0
Employer contributions to 401 (k)	$ 26
Share-based compensation arrangement by share-based payment award, equity instruments other than options, nonvested, number (in shares)																		777,747
Common stock, shares authorized (in shares)	40,000,000	40,000,000		40,000,000
Number of shares authorized (in shares)												1,500,000	300,000			300,000
Grants in period (in shares)										12,000				16,360
Award vesting period											3 years				3 years		1 year