Income Taxes (Unrecognized Tax Benefits, Narrative) (Details) $ in Millions	3 Months Ended
Mar. 31, 2018 USD ($)
Income Tax Disclosure [Abstract]
Decrease in unrecognized tax benefits from settlement with taxing authorities	$ 2.4

Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319

Name:	us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration