Borrowings (Repurchase Agreements) (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Borrowing Balance	$ 488,043	$ 328,748
Securities Sold under Agreements to Repurchase [Member]
Debt Instrument [Line Items]
Borrowing Balance	$ 377,808	$ 192,500
Weighted Average Coupon	2.31%
Securities Sold under Agreements to Repurchase [Member] \| Due Date: 10 02 2018 [Member]
Debt Instrument [Line Items]
Borrowing Balance	$ 39,989
Weighted Average Coupon	2.30%
Settlement Date	Sep. 18, 2018
Investment Repurchase Agreement, Repurchase Date	Oct. 02, 2018
Securities Sold under Agreements to Repurchase [Member] \| Due date: 10 10 2018 [Member]
Debt Instrument [Line Items]
Borrowing Balance	$ 32,525
Weighted Average Coupon	2.19%
Settlement Date	Sep. 10, 2018
Investment Repurchase Agreement, Repurchase Date	Oct. 10, 2018
Securities Sold under Agreements to Repurchase [Member] \| Due date 10 15 2018 [Member]
Debt Instrument [Line Items]
Borrowing Balance	$ 12,000
Weighted Average Coupon	2.40%
Settlement Date	Sep. 25, 2018
Investment Repurchase Agreement, Repurchase Date	Oct. 15, 2018
Securities Sold under Agreements to Repurchase [Member] \| Due date 10 25 2018 [Member]
Debt Instrument [Line Items]
Borrowing Balance	$ 53,294
Weighted Average Coupon	2.45%
Settlement Date	Sep. 24, 2018
Investment Repurchase Agreement, Repurchase Date	Oct. 25, 2018
Securities Sold under Agreements to Repurchase [Member] \| Due date 07 06 2020 [Member]
Debt Instrument [Line Items]
Borrowing Balance	$ 50,000
Weighted Average Coupon	2.86%
Settlement Date	Jul. 06, 2018
Investment Repurchase Agreement, Repurchase Date	Jul. 06, 2020
Securities Sold under Agreements to Repurchase [Member] \| Due date: 09 03 2019 [Member]
Debt Instrument [Line Items]
Borrowing Balance	$ 50,000
Weighted Average Coupon	1.72%
Settlement Date	Mar. 02, 2017
Investment Repurchase Agreement, Repurchase Date	Sep. 03, 2019
Securities Sold under Agreements to Repurchase [Member] \| Due Date: 3/2/2020 [Member]
Debt Instrument [Line Items]
Borrowing Balance	$ 60,000
Weighted Average Coupon	1.85%
Settlement Date	Mar. 02, 2017
Investment Repurchase Agreement, Repurchase Date	Mar. 02, 2020
Securities Sold under Agreements to Repurchase [Member] \| Due Date: 3/15/2020 [Member]
Debt Instrument [Line Items]
Borrowing Balance	$ 50,000
Weighted Average Coupon	2.61%
Settlement Date	Mar. 15, 2018
Investment Repurchase Agreement, Repurchase Date	Mar. 15, 2020
Securities Sold under Agreements to Repurchase [Member] \| Due Date: 3/23/2020 [Member]
Debt Instrument [Line Items]
Borrowing Balance	$ 30,000
Weighted Average Coupon	2.70%
Settlement Date	Mar. 23, 2018
Investment Repurchase Agreement, Repurchase Date	Mar. 23, 2020

Date the repurchase agreement was made.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 12
-Footnote 2

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Date the repurchase will be made.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 12
-Footnote 2

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Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13,16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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