Commitments and Loss Contingency - Additional Information (Detail)	9 Months Ended
Sep. 30, 2012
Minimum [Member]
Long-term Purchase Commitment [Line Items]
Term of agreements with third party vendors	One year
Maximum [Member]
Long-term Purchase Commitment [Line Items]
Term of agreements with third party vendors	Five year

Specifies the time period covered by the arrangement.

No definition available.

Name:	us-gaap_LongTermPurchaseCommitmentTimePeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration