Balance Sheet Offsetting (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Reverse repurchase agreements
Gross Amount Recognized	$ 700,455,000	$ 700,149,000
Gross amount Offset	(500,153,000)	(500,041,000)
Net Amount Presented in the Balance Sheet	200,302,000	200,108,000
Gross Amounts Not Offset in the Balance Sheet, Securities Collateral	(200,000,000)	(200,000,000)
Net Amount	302,000	108,000
Repurchase agreements
Gross Amount Recognized	500,153,000	500,041,000
Gross Amount Offset	(500,153,000)	(500,041,000)
Derivatives not designated as hedging instruments \| Swap
Financial instruments that are eligible for offset
Principal amount of collateral swap agreement	500,000,000
Financial assets
Fair Value of Securities Pledged as Collateral	540,700,000
Financial liabilities
Fair Value of Securities Received as Collateral	528,000,000
Derivatives not designated as hedging instruments \| Master netting arrangements and similar agreements
Financial assets
Gross Amount Recognized	15,560,000	7,669,000
Gross Amount Offset	(443,000)	(1,562,000)
Net Amount Presented in the Balance Sheet	15,117,000	6,107,000
Gross Amounts Not Offset in the Balance Sheet, Cash Collateral	(1,891,000)
Net Amount	13,226,000	6,107,000
Financial liabilities
Gross Amount Recognized	76,669,000	51,125,000
Gross Amount Offset	(443,000)	(1,562,000)
Net Amount Presented in the Balance Sheet	76,226,000	49,563,000
Gross Amounts Not Offset in the Balance Sheet, Securities Collateral	(21,068,000)	(14,654,000)
Gross Amounts Not Offset in the Balance Sheet, Cash Collateral	(41,638,000)	(28,046,000)
Net Amount	13,520,000	6,863,000
Derivatives designated and not designated as hedging instruments \| Master netting arrangements and similar agreements
Financial assets
Gross Amount Recognized	716,015,000	707,818,000
Gross Amount Offset	(500,596,000)	(501,603,000)
Net Amount Presented in the Balance Sheet	215,419,000	206,215,000
Gross Amounts Not Offset in the Balance Sheet, Securities Collateral	(200,000,000)	(200,000,000)
Gross Amount Not Offset in the Balance Sheet, Cash Collateral	(1,891,000)
Net Amount	13,528,000	6,215,000
Financial Liabilities
Gross Amount Recognized	576,822,000	551,166,000
Gross Amount Offset	(500,596,000)	(501,603,000)
Net Amount Presented in the Balance Sheet	76,226,000	49,563,000
Gross Amounts Not Offset in the Balance Sheet, Securities Collateral	(21,068,000)	(14,654,000)
Gross Amounts Not Offset in the Balance Sheet, Cash Collateral	(41,638,000)	(28,046,000)
Net Amount	$ 13,520,000	$ 6,863,000

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- Details

Name:	us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseAbstract
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Period Type:	duration

- Definition

Amount of asset associated with funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price.

+ References

+ Details

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Period Type:	instant

- Definition

Fair value of securities pledged as collateral against securities sold under agreement to repurchase.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Amount, before effects of master netting arrangements, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

+ References

+ Details

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- Details

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