Aggregate dividends paid 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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- Definition

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

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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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Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

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Subsequent Events (Narrative) (Details) - $ / shares			3 Months Ended								12 Months Ended
Subsequent Events (Narrative) (Details) - $ / shares	Feb. 20, 2018	Jan. 05, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Subsequent Event [Line Items]
Dividend paid to common stockholders			$ 0.39	$ 0.39	$ 0.39	$ 0.36	$ 0.36	$ 0.36	$ 0.36	$ 0.32	$ 1.53	$ 1.40
Dividends payable, date of record				Jun. 16, 2017	Mar. 16, 2017	Dec. 16, 2016	Sep. 20, 2016	Jun. 17, 2016	Mar. 18, 2016	Dec. 17, 2015	Sep. 22, 2017
Dividends payable, date payable				Jul. 06, 2017	Apr. 05, 2017	Jan. 05, 2017	Oct. 05, 2016	Jul. 06, 2016	Apr. 05, 2016	Jan. 06, 2016	Oct. 05, 2017
Subsequent Event
Subsequent Event [Line Items]
Dividend paid to common stockholders		$ 0.39
Cash dividend payable per common share	$ 0.41
Dividends payable, date declared	Feb. 20, 2018
Dividends payable, date of record	Mar. 22, 2018	Dec. 05, 2017
Dividends payable, date payable	Apr. 05, 2018	Jan. 05, 2018