Securities Securities - Premium Amortization and Discount Accretion Included in Income on Securities (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Investments, Debt and Equity Securities [Abstract]
Premium amortization	$ (22,762)	$ (21,354)	$ (67,321)	$ (62,192)
Discount accretion	2,497	2,519	8,250	7,846
Net (premium amortization) discount accretion	$ (20,265)	$ (18,835)	$ (59,071)	$ (54,346)

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=63488584&loc=d3e20235-122688

+ Details

Name:	us-gaap_InvestmentIncomeAmortizationOfDiscount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of amortization of purchase premium on nonoperating securities.

+ References

+ Details

Name:	us-gaap_InvestmentIncomeAmortizationOfPremium
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

+ Details

Name:	us-gaap_InvestmentIncomeNetAmortizationOfDiscountAndPremium
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration