Note Payable (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Debt Disclosure [Line Items]
Number of lines of credit	1	2
Aggregate borrowing capacity	$ 225	$ 225
Accordian feature available amount	50
Note payable	$ 104	$ 104
Line of credit facility, term	5 years
Expiration date of Line of credit	May 31, 2017
Minimum [Member]
Debt Disclosure [Line Items]
Line of credit, interest rate	0.70%
Maximum [Member]
Debt Disclosure [Line Items]
Line of credit, interest rate	2.58%