The amount of cash paid for interest during the period.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 29

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 25

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3536-108585

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

Note Payable (Details) (NXT Loan, USD $)	3 Months Ended		6 Months Ended
Note Payable (Details) (NXT Loan, USD $)	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 17, 2010
Debt Instrument [Line Items]
Maximum borrowing capacity of loan					$ 30,000,000
Remaining borrowing capacity for loan	10,000,000		10,000,000
Cash paid for interest expense	$ 0	$ 155,000	$ 0	$ 508,000
Maximum
Debt Instrument [Line Items]
Interest rate on loan (percent)	7.25%		7.25%
One-Month London Interbank Offered Rate \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate loan (percent)	3.75%		3.75%