Debt (Details)		3 Months Ended		3 Months Ended		3 Months Ended
	Mar. 31, 2014 USD ($)	Mar. 31, 2014 Wells Fargo [Member] USD ($)	Dec. 31, 2013 Wells Fargo [Member] USD ($)	Mar. 31, 2014 Wells Fargo [Member] Minimum [Member]	Mar. 31, 2014 Wells Fargo [Member] Maximum [Member]	Mar. 31, 2014 Osborn [Member] USD ($)	Mar. 31, 2014 Osborn [Member] ZAR
Line of Credit Facility [Line Items]
Amount of credit facility		$ 100,000,000				$ 7,055,000	75,000,000
Sub-limit for letters of credit		25,000,000
Original terms of credit facility		100,000,000
Borrowings outstanding		2,104,000	0			0
Letters of credit outstanding	7,677,000	5,989,000
Line of credit, additional borrowing capacity		91,907,000
Term of credit facility		5 years
Maturity date		Apr. 30, 2017
Interest rate description		daily one month LIBOR rate plus a 0.75% marginor 0.91%.
Additional rate over base, percentage (in hundredths)				0.75%
Unused facility fee as a percentage of line of credit (in hundredths)		0.175%
Performance guarantees						821,000
Available credit under the facility						$ 6,234,000
Basis spread on variable rate (in hundredths)						(0.25%)	(0.25%)
Interest rate at period end (in hundredths)					0.91%	8.75%	8.75%