Fair Value of Financial Instruments - Rollforward of Balance Sheet Amounts Within Level 3 Valuation Hierarchy (Details) - Recurring - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Other liabilities
Assets measured on recurring basis, unobservable input reconciliation, calculation [Roll Forward]
Fair value, beginning of period	$ 0	$ 0
Total realized gains included in income	0	0
Changes in unrealized gains/losses included in other comprehensive income for assets and liabilities still held at March 31	0	0
Purchases	0	0
Issuances	0	0
Settlements	0	0
Transfers out of Level 3	0	0
Fair value, end of period	0	0
Total realized gains included in income related to financial assets and liabilities still on the consolidated balance sheet at March 31	0	0
Other assets
Assets measured on recurring basis, unobservable input reconciliation, calculation [Roll Forward]
Fair value, beginning of period	28,874	10,478
Total realized gains included in income	512	197
Changes in unrealized gains/losses included in other comprehensive income for assets and liabilities still held at March 31	0	0
Purchases	870	120
Issuances	0	0
Settlements	(468)	(303)
Transfers out of Level 3	0	0
Fair value, end of period	29,788	10,492
Total realized gains included in income related to financial assets and liabilities still on the consolidated balance sheet at March 31	512	197
Available-for-sale Securities [Member]
Assets measured on recurring basis, unobservable input reconciliation, calculation [Roll Forward]
Fair value, beginning of period	17,029	0
Total realized gains included in income	31	0
Changes in unrealized gains/losses included in other comprehensive income for assets and liabilities still held at March 31	(666)	0
Purchases	0	0
Issuances	0	0
Settlements	(1,168)	0
Transfers out of Level 3	0	0
Fair value, end of period	15,226	0
Total realized gains included in income related to financial assets and liabilities still on the consolidated balance sheet at March 31	$ 31	$ 0

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

Amount of gain (loss) recognized in other comprehensive income (loss) for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

Amount of issuances of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
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-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Topic 820
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-Section 50
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-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

Amount of settlements of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
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-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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