Aggregate dividends declared during the period for each share of common stock outstanding.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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

+ References

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

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

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Subsequent events (Details) - $ / shares			3 Months Ended		6 Months Ended
Subsequent events (Details) - $ / shares	Jan. 16, 2018	Oct. 17, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Subsequent Event [Line Items]
Common stock, dividends declared (in dollars per share)			$ 0.0975	$ 0.0950	$ 0.1950	$ 0.1900
2018 Annual Dividend [Member]
Subsequent Event [Line Items]
Common stock, dividends declared (in dollars per share)		$ 0.39
Subsequent Event [Member] \| 2018 Annual Dividend [Member]
Subsequent Event [Line Items]
Common stock, dividends declared (in dollars per share)	$ 0.39
Subsequent Event [Member] \| 2018 Q2 Dividend [Member]
Subsequent Event [Line Items]
Dividends payable, date declared	Jan. 16, 2018
Common stock, dividends declared (in dollars per share)	$ 0.0975
Dividends payable, date of record	Feb. 15, 2018
Dividends payable, date paid	Feb. 28, 2018