Consolidated Statements of Stockholders' Equity (unaudited) (Parenthetical) - $ / shares	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Consolidated Statements of Stockholders' Equity (unaudited) [Abstract]
Cash dividends - per share (in dollars per share)	$ 0.48	$ 0.23
Net issuance of shares to employee benefit plans and other stock plans (in shares)	72,844	184,651

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

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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Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant