Stock-Based Compensation (Performance Shares Activity) (Details) (Performance Shares [Member], USD $)	9 Months Ended
	Sep. 30, 2014
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target performance share awards granted	23,685
Fair value per award (1)	$ 80.91	[1]
Number of shares that would be issued based on current performance levels	23,685
Unamortized expense, based on current performance levels	$ 1,545,000

[1] Represents the closing market price of Morningstar's stock on March 14, 2014, which is the last closing price prior to the grant date.