Leases - Narrative (Details) $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Percentage of lease obligations used for office space	98.00%
Lessee, operating lease, lease not yet commenced, amount	$ 46
Lessee, operating lease, lease not yet commenced, term (years)	15 months
Minimum
Lessee, Lease, Description [Line Items]
Lessee, operating lease, term of contract (years)	10 years
Maximum
Lessee, Lease, Description [Line Items]
Lessee, operating lease, term of contract (years)	25 years

Lessee, Operating Lease, Lease Not yet Commenced, Amount

No definition available.

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- Definition

Percentage of Lease Obligations Used for Office Space

+ References

No definition available.

+ Details

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- Definition

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.

+ Details

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Period Type:	duration

- Definition

Term of lessee's operating lease not yet commenced, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980

+ Details

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- Definition

Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980

+ Details

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- Details

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