Capital Stock Transactions (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 28, 2013	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Capital Stock Repurchase Plan Transactions [Abstract]
Shares repurchased		280,701	199,900	280,701	199,900
Weighted average price per share		$ 65.72	$ 55.72	$ 65.72	$ 55.72
Stock Repurchase Program, Authorized Amount	$ 100
Stock Repurchase Program, Remaining Authorized Repurchase Amount				$ 96.3