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

Name:	us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

Subsequent Events (Details) - $ / shares										12 Months Ended
Subsequent Events (Details) - $ / shares	Feb. 21, 2018	Nov. 02, 2017	Aug. 02, 2017	May 05, 2017	Feb. 21, 2017	Nov. 02, 2016	Aug. 03, 2016	May 02, 2016	Feb. 22, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Dividend
Cash dividend declared (in dollars per share)		$ 0.060	$ 0.055	$ 0.055	$ 0.055	$ 0.055	$ 0.055	$ 0.055	$ 0.055	$ 0.225	$ 0.220	$ 0.205
Subsequent Events
Cash Dividend
Cash dividend declared (in dollars per share)	$ 0.06