Significant Accounting Policies (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014 Entity	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Wholly-owned bankruptcy remote special-purpose corporations	2
Interest expense net of interest income on bank deposits	$ 0.9us-gaap_InterestIncomeExpenseNet	$ 1.2us-gaap_InterestIncomeExpenseNet	$ 1.9us-gaap_InterestIncomeExpenseNet

The net amount of operating interest income (expense).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.10)

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 10

-Article 9

Name:	us-gaap_InterestIncomeExpenseNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration