Summary of Significant Accounting Policies Other Information (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease assets	$ 95,911		$ 0
Net investment income	1,957	$ 454
Investment Income, Nonoperating	1,615	$ 321
Total operating lease liabilities	$ 107,487		$ 0

Amount after accretion (amortization) of discount (premium), and investment expense, of interest income and dividend income on nonoperating securities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.9)
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 220
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 220
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-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

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The aggregate amount of income from investments (for example, dividends) not considered a component of the entity's core operations.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Present value of lessee's discounted obligation for lease payments from operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
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Amount of lessee's right to use underlying asset under operating lease.

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-Name Accounting Standards Codification
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-SubTopic 20
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