Derivative Instruments - Narrative (Details) (USD $)			3 Months Ended	9 Months Ended
Sep. 30, 2013 Contracts	Dec. 31, 2012	Sep. 30, 2012 Deposit liabilities	Sep. 30, 2012 Deposit liabilities
Derivative [Line Items]
Derivatives Number of Instruments Held	1
Fair Value Hedge Cumulative Reduction To Expense			$ 0	$ 4,900,000
Collateral posted to counterparty	$ 113,426,000	$ 12,130,000
Deficiency guarantee government backing percent	69.00%

Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 13

-URI http://asc.fasb.org/extlink&oid=28370219&loc=SL20226016-175313

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (d)(2)

-URI http://asc.fasb.org/extlink&oid=20225523&loc=SL20225862-175312

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=d3e41678-113959

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