Investments Contractual maturies (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Available-for-sale Securities, Amortized Cost Basis	$ 0.4	$ 0.3
Available-for-sale Securities, Fair Value Disclosure	5.8
Within one year from the balance sheet date [Member]
Available-for-sale Securities, Amortized Cost Basis	0.0
Available-for-sale Securities, Fair Value Disclosure	0.0
more than one year from balance sheet date [Member]
Available-for-sale Securities, Amortized Cost Basis	0.4
Available-for-sale Securities, Fair Value Disclosure	$ 5.8

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26610-111562

Name:	us-gaap_AvailableForSaleSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant