Derivative Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 item	Dec. 31, 2011
Derivative Financial Instruments [Abstract]
Interest rate swaps designated as cash flow hedges, notional amount	$ 10	$ 20
Fair values of effective portion of hedges reflected in Other Comprehensive Income	(1.06)	(1.41)
Number of interest rate derivative positions	2
Interest rate derivatives, combined notional amount	$ 28.63	$ 29.60