Securities Securities - Premium Amortization and Discount Accretion Included in Income on Securities (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Investments, Debt and Equity Securities [Abstract]
Premium amortization	$ (21,354)	$ (17,471)	$ (62,192)	$ (48,862)
Discount accretion	2,519	1,865	7,846	4,897
Net (premium amortization) discount accretion	$ (18,835)	$ (15,606)	$ (54,346)	$ (43,965)

Amount of accretion of purchase discount on nonoperating securities.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.8)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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Amount of amortization of purchase premium on nonoperating securities.

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Amount of accretion (amortization) of purchase discount (premium) on nonoperating securities.

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