Schedule II - Valuation and Qualifying Accounts (Details) - Valuation and Qualifying Accounts (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Valuation and Qualifying Accounts [Abstract]
Deferred tax asset valuation allowance, beginning balance	$ 65,272	$ 60,041	$ 54,788
Additions charged to costs and expenses	6,667	5,231	5,253
Deferred tax asset valuation allowance, ending balance	$ 71,939	$ 65,272	$ 60,041

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32537-109319

Name:	us-gaap_DeferredTaxAssetsValuationAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant