Accumulated Other Comprehensive Income (Changes in AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 2,646
Other comprehensive income (loss), net of tax	(1,244)	$ 414	$ 1,204
Ending balance	(705)	1,421	2,646
Gains and Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(480)	(679)	(679)
Other comprehensive gain before reclassifications	132	70
Other comprehensive income (loss), net of tax	132	70
Ending balance	(348)	(609)	(480)
Unrealized Gains and Losses on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	3,126	1,686	1,686
Other comprehensive gain before reclassifications	(1,308)	450
Reclassification adjustment - gains on equity securities	(2,107)	0
Amounts reclassified from accumulated other comprehensive income	(68)	(106)
Other comprehensive income (loss), net of tax	(3,483)	344
Ending balance	$ (357)	$ 2,030	$ 3,126

Accumulated Other Comprehensive Income (Loss) [Roll Forward]

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Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e637-108580

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-Publisher FASB
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Amount before tax and reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Topic 220
-SubTopic 10
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Amount after tax and reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount, before tax, of reclassification adjustment from accumulated other comprehensive income (loss) for unrealized gain (loss) of investment classified as available-for-sale transferred to equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount before tax of reclassification adjustments of other comprehensive income (loss).

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