Fair Value of Financial Instruments - Rollforward of Balance Sheet Amounts Within Level 3 Valuation Hierarchy (Details) - Recurring - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Other assets
Assets measured on recurring basis, unobservable input reconciliation, calculation [Roll Forward]
Fair value, beginning of period	$ 29,788	$ 10,492	$ 28,874	$ 10,478
Total realized gains included in income	2,265	240	2,777	437
Changes in unrealized gains/losses included in other comprehensive income for assets and liabilities still held at June 30	0	0	0	0
Acquired	0	17,062	0	17,062
Purchases	3,948	649	4,818	769
Issuances	0	0	0	0
Settlements	(257)	(593)	(725)	(896)
Transfers out of Level 3	(12,166)	0	(12,166)	0
Fair value, end of period	23,578	27,850	23,578	27,850
Total realized gains included in income related to financial assets and liabilities still on the consolidated balance sheet at June 30	2,265	240	2,777	437
Available-for-sale Securities
Assets measured on recurring basis, unobservable input reconciliation, calculation [Roll Forward]
Fair value, beginning of period	15,226	0	17,029	0
Total realized gains included in income	30	0	60	0
Changes in unrealized gains/losses included in other comprehensive income for assets and liabilities still held at June 30	34	0	(631)	0
Acquired	0	0	0	0
Purchases	0	0	0	0
Issuances	0	0	0	0
Settlements	0	0	(1,168)	0
Transfers out of Level 3	0	0		0
Fair value, end of period	15,290	0	15,290	0
Total realized gains included in income related to financial assets and liabilities still on the consolidated balance sheet at June 30	$ 30	$ 0	$ 60	$ 0

Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Acquisitions

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- Definition

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

+ References

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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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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.

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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.

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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.

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- Definition

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

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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.

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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.

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