Investment Securities, Available-for-Sale (Details Textual) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Investment Securities, Available-for-Sale (Textual) [Abstract]
Investment securities pledged as collateral	$ 1,525,400,000	$ 1,120,047,000
Residential mortgage-backed securities [Member]
Investment Securities, Available-for-Sale (Textual) [Abstract]
Non-guaranteed private label whole loan mortgage-backed securities	$ 46,733,000	$ 49,252,000

The fair value of available-for-sale securities that serve as collateral for borrowings.

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

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 01-6

-Paragraph 13

-Subparagraph i

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6965416&loc=d3e5086-111524

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