Units Outstanding (Details)	6 Months Ended
Jun. 30, 2018 shares
Units Outstanding
Outstanding as of December 31, 2017 (in units)	96,461,989
Options exercised (in units)	488,513
Units issued (in units)	2,471,307
Units retired (in units)	(1,392,989)
Outstanding as of June 30, 2018 (in units)	98,028,820

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

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- Definition

Number of share instruments newly issued under a share-based compensation plan.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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- Definition

Number of shares issued which are neither cancelled nor held in the treasury.

+ References

No definition available.

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- Definition

Total number of shares issued during the period, including shares forfeited, as a result of Restricted Stock Awards.

+ References

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-Publisher FASB
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- Definition

Number of shares that have been repurchased and retired during the period.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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