Operations and Significant Accounting Policies - Concentraion of Credit Risk (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Customer Information [Line Items]
Major Customer, Percent of Total Revenue	12.00%	12.30%	12.60%
Large Power Customer [Member]
Customer Information [Line Items]
Number of Customers	9
Large Power Customers, Accounts Receivable	$ 14.2	$ 13.7