Securities Purchased under Resale Agreements and Sold under Repurchase Agreements (Repurchase Agreements) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Amount of securities sold under repurchase agreements
Gross repurchase agreements	$ 450,000	$ 450,000
Maturities in 2019	0
Maturities in 2020	0
Maturities in 2021	0
Maturities in 2022	150,000
Maturities in 2023	300,000
Maturities thereafter	$ 0
Weighted average interest rates (as a percent)	4.46%	3.48%	2.97%

Assets Purchased Under Agreements to Repurchase, Interest Rate

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- Definition

Securities Sold Under Agreements To Repurchase Maturing in Year Five

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- Definition

Securities Sold Under Agreements To Repurchase Maturing in Year Four

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- Definition

Securities Sold Under Agreements To Repurchase Maturing in Year One

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- Definition

Securities Sold Under Agreements To Repurchase Maturing in Year Three

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- Definition

Securities Sold Under Agreements To Repurchase Maturing in Year Two

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- Definition

Securities Sold under Agreements to Repurchase Year Six And Thereafter

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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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226000-175313

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