Stock-based Compensation (Schedule of Share-based Goods and Nonemployee Services Transaction) (Details) (Non-Employee Director)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Restricted Stock
Share-based Goods and Nonemployee Services Transaction [Line Items]
Number of units the plan allows for each non-employee director to receive an annual award	800
Number of months each offering period lasts beginning on January 1 and July 1 each year (in months)	6 months
Mandatory director retirement age	72 years
Years of service on the Board	4 years
Percentage of annual restriction lapse	25.00%
Number of shares reserved for non-employee issuance (in shares)	200,000
Number of shares issued to non-employee directors, inception to date (in shares)	145,600
Number of shares issued to non-employee directors during the period (in shares)		7,200	8,000
Restricted Stock Units (RSUs)
Share-based Goods and Nonemployee Services Transaction [Line Items]
Number of units the plan allows for each non-employee director to receive an annual award	800
Number of shares issued to non-employee directors during the period (in shares)	8,000
Number of shares of restricted stock issued to non-employee directors (in shares)	44,720
Minimum | Restricted Stock
Share-based Goods and Nonemployee Services Transaction [Line Items]
Annual installment period	5 years
Maximum | Restricted Stock
Share-based Goods and Nonemployee Services Transaction [Line Items]
Annual installment period	10 years