Financial Instruments, Fair Value Measurements and Credit Risk - Gains Recognized in the Statement of Operations (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value Disclosures [Abstract]
Trading securities loss	$ 6,326us-gaap_TradingGainsLosses	$ 0us-gaap_TradingGainsLosses	$ 0us-gaap_TradingGainsLosses
Foreign currency derivatives gain (loss)	(1,604)	0	0
Gain (Loss) on Investments and Derivative Instruments, Net, Pretax	$ (4,722)	$ 0	$ 0

Amount of gain (loss) resulting from the difference between the acquisition price and the selling price or fair value of trading assets and trading liabilities, conducted separately from customer trading activities. Includes, but is not limited to, changes in fair value of trading assets and trading liabilities.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 940

-SubTopic 320

-Section 45

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=29643736&loc=d3e42567-110969

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.13(e))

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

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 940

-SubTopic 320

-Section 35

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=29643654&loc=d3e42454-110968

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