Borrowings (Credit facility) (Details) (USD $)	12 Months Ended						13 Months Ended			1 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Revolving Credit Facility [Member]	Dec. 31, 2012 Revolving Credit Facility [Member]	Dec. 31, 2011 Revolving Credit Facility [Member] LIBOR [Member]	Apr. 30, 2012 Secured Debt [Member] Equipment Term Loan [Member]	Dec. 31, 2012 Secured Debt [Member] Equipment Term Loan [Member]	Dec. 31, 2012 Secured Debt [Member] Equipment Term Loan [Member] LIBOR [Member]	Jun. 30, 2013 Collateral for Borrowing [Member]
Line of Credit Facility [Line Items]
Revolving line of credit, maximum					$ 15,000,000
Required pledge of equity interests in subsidiary, percent		65.00%
Debt instrument, variable rate						2.25%			2.25%
Debt instrument, interest rate at period end									2.50%
Unused commitment fee, percentage				0.25%
Eligible equipment purchase, percentage							80.00%
Debt instrument, amount borrowed							5,000,000
Restricted cash posted	0	(8,000,000)	0							1,800,000
Debt instrument, term							36 months
Long-term borrowings								3,900,000
Revolving line of credit, current borrowing	$ 0