Employee Benefit Plans (Employee Savings and Stock Ownership Plan - Shares) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Employee Stock Ownership Plan (ESOP) Disclosures
Employee Stock Ownership Plan (ESOP), Shares Contributed to ESOP (in shares)	16,151	10,735	12,309
Employee Stock Ownership Plan (ESOP), Shares in ESOP (in shares)	93,357	111,145	121,880
Employee Stock Ownership Plan (ESOP), Deferred Shares, Fair Value	$ 4.4	$ 3.3	$ 5.4
Employee Stock Ownership Plan (ESOP), Compensation Expense	0.3	0.3	0.2
Defined Contribution Feature
Employee Stock Ownership Plan (ESOP) Disclosures
Employee Stock Ownership Plan (ESOP), Compensation Expense		$ 1.8