Subsequent Events (Details) - Subsequent Event [Member] - Dividend Declared Q1-2018 [Member]	Feb. 09, 2018 $ / shares
Subsequent Event [Abstract]
Dividend payable, date declared	Feb. 09, 2018
Dividend payable, date to be paid	Mar. 09, 2018
Dividend payable, date of record	Feb. 23, 2018
Class A [Member]
Subsequent Event [Abstract]
Dividend payable (in dollars per share)	$ 0.28
Class B [Member]
Subsequent Event [Abstract]
Dividend payable (in dollars per share)	$ 0.28

Date the declared dividend will be paid, in CCYY-MM-DD format.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586

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- Definition

The per share amount of a dividend declared, but not paid, as of the financial reporting date.

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- Definition

Date the dividend to be paid was declared, in CCYY-MM-DD format.

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- Definition

Date the holder must own the stock to be entitled to the dividend, in CCYY-MM-DD format.

+ References

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