Other Investments - Additional Information (Detail) (USD $)	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
FHLB stock totaled	$ 32,479,000		$ 39,796,000
Maximum percentage of stock to be purchased	5.00%	5.00%
Repurchases of stock	$ 7,300,000	$ 7,000,000

The net cash outflow or inflow of federal home loan bank stock during the period. Federal Home Loan Bank (or Federal Reserve Bank) stock is an equity interest in a Federal Home Loan Bank (or Federal Reserve Bank).

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 16

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 17

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_PaymentsForProceedsFromFederalHomeLoanBankStock
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration