Stock Based Compensation Plans (Employee Stock Purchase Plan - Summary) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Employee Stock Purchase Plan - Shares Issued	157,856	167,260	183,892
Minimum [Member]
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Employee Stock Purchase Plan - Purchase Price Per Share	84.6	69.27	58.05
Maximum [Member]
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Employee Stock Purchase Plan - Purchase Price Per Share	86.67	73.7	55.39