Shareholders' Equity (Narrative) (Details) (USD $)	1 Months Ended	12 Months Ended
	May 31, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Class of Stock [Line Items]
Repurchase of common stock	4,300,000	7,583,471	7,468,869
Common stock price per share	$ 35.00
Proceeds from issuance of common stock	$ 143,300,000	$ 0	$ 0	$ 143,325,000
Reduction to retained earnings	42,800,000
Treasury stock historical value	$ 186,100,000