Securities Sold Under Repurchase Agreements (Details) (USD $)	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Securities Sold Under Repurchase Agreements
Average outstanding amount	$ 1,041,186,000	$ 1,276,831,000
Maximum amount outstanding at any month end	1,119,531,000	1,412,744,000
Collateral Securities and Repurchase Borrowing agreements
Collateralized Securities, Book Value of Securities Sold	1,313,637,000	1,418,665,000
Collateralized securities, Fair Value of Securities Sold	1,317,998,000	1,459,837,000
Repurchase Borrowing, Balance of Liability	957,381,000	1,129,679,000
Repurchase Borrowing, Weighted Average Interest Rate (as a percent)	2.91%	2.85%
Overnight agreements
Collateral Securities and Repurchase Borrowing agreements
Collateralized Securities, Book Value of Securities Sold	332,042,000	340,711,000
Collateralized securities, Fair Value of Securities Sold	341,238,000	350,933,000
Repurchase Borrowing, Balance of Liability	209,899,000	263,992,000
Repurchase Borrowing, Weighted Average Interest Rate (as a percent)	0.17%	0.28%
1 to 29 days
Collateral Securities and Repurchase Borrowing agreements
Collateralized Securities, Book Value of Securities Sold	27,954,000	10,378,000
Collateralized securities, Fair Value of Securities Sold	28,288,000	10,910,000
Repurchase Borrowing, Balance of Liability	18,666,000	6,992,000
Repurchase Borrowing, Weighted Average Interest Rate (as a percent)	0.40%	1.10%
30 to 90 days
Collateral Securities and Repurchase Borrowing agreements
Collateralized Securities, Book Value of Securities Sold	8,106,000	33,619,000
Collateralized securities, Fair Value of Securities Sold	8,263,000	35,097,000
Repurchase Borrowing, Balance of Liability	3,295,000	22,078,000
Repurchase Borrowing, Weighted Average Interest Rate (as a percent)	0.43%	1.05%
Over 90 days
Collateral Securities and Repurchase Borrowing agreements
Collateralized Securities, Book Value of Securities Sold	945,535,000	1,033,957,000
Collateralized securities, Fair Value of Securities Sold	940,209,000	1,062,897,000
Repurchase Borrowing, Balance of Liability	$ 725,521,000	$ 836,617,000
Repurchase Borrowing, Weighted Average Interest Rate (as a percent)	3.78%	3.73%

Represents the average amount of securities sold under repurchase agreements during the period.

No definition available.

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- Definition

Represents the maximum balance outstanding at any month end during the period as of the balance sheet date.

+ References

No definition available.

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- Definition

Carrying amount of assets sold under agreements to repurchase when the carrying amount (or market value, if higher than the carrying amount) of securities or other assets sold under repurchase agreements exceeds 10 percent of total assets.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(m)(1)(i)(A)(i))

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-Name Regulation S-X (SX)

-Number 210

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- Definition

Interest rate on the amount to be repaid to the counterparty to the repurchase agreement when the carrying amount (or market value, if higher than the carrying amount) of securities or other assets sold under the repurchase agreement exceeds 10 percent of total assets.

+ References

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

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Market value of assets sold under agreements to repurchase when the carrying amount (or market value, if higher than the carrying amount) of securities or other assets sold under repurchase agreements exceeds 10 percent of total assets.

+ References

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- Definition

Amount, after the effects of master netting arrangements, of funds outstanding borrowed in the form of a security resale agreement between the entity and another party for the purchase and resale of identical or substantially the same securities at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.13(1))

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