Unconditional Purchase Obligations (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Unconditional Purchase Obligations (Excluding Capital Stock Redemptions) [Abstract]
Unconditional purchase obligations, beginning of year	$ 4,000,000	$ 5,000,000	$ 2,900,000
Future expenditures under purchase obligations, 2013	3,300,000
Future expenditures under purchase obligations, 2014	200,000
Future expenditures under purchase obligations, 2015	$ 30,000