Accrued Severance Benefits - Additional Information (Detail)	Dec. 31, 2014	Dec. 31, 2013
Compensation and Retirement Disclosure [Abstract]
Percentage of employees eligible for severance benefits	98.00%
Percentage of severance benefits fund	0.80%	0.90%

Plan assets of a defined benefit plan, as a percentage of projected benefit obligation.

No definition available.

Name:	us-gaap_DefinedBenefitPlanFundedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant