Investments - Other Investments (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule Of Investments [Abstract]
Investment in other companies	$ 49,767	$ 51,351

Amount of Equity in net profit and loss for the period. Give totals for each group. If operations of any controlled companies are different in character from those of the company, group such affiliates (1) within divisions and (2) by type of activities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 320

-Section S99

-Paragraph 6

-Subparagraph (SX 210.12-14)

-URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611322-123010

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 14

-Paragraph 2,6

-Article 12

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 14

-Paragraph Column C

-Article 12

Name:	us-gaap_InvestmentsInAndAdvancesToAffiliatesAmountOfEquity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant