Income Taxes - Valuation Allowances and Unrecognized Tax Benefits (Details) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($)
Income Taxes
Amount of decrease in valuation allowance	$ 5.0
Decrease in unrecognized tax benefits, expiration of statute of limitations	$ 2.1

Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319

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