Earnings Per Share, Textuals (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended			3 Months Ended	6 Months Ended		12 Months Ended
	Jul. 18, 2013	Apr. 30, 2013	Jun. 30, 2008	Jun. 30, 2013	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jul. 15, 2013 Warrant Transactions	Jun. 30, 2013 Warrant Transactions
Potential dilutive effect of options and Warrants
Options outstanding to purchase common shares				20,791	20,791		20,791
Average exercise price per share				$ 80.01	$ 80.01		$ 80.01
Potential dilutive effect of options outstanding					0		0
Number of common shares underlying the Warrants outstanding									3,600,000
Average exercise price of common shares underlying Warrants								61.14	61.19
Dividends
Cash dividends paid					$ 11.6	$ 9.8
Cash dividends paid per share				$ 0.30	$ 0.60	$ 0.50
Treasury Stock, Number of Shares and Restriction Disclosures [Abstract]
Stock repurchase program, authorized amount by Board of Directors		75.0	75.0
Common share amount available for additional share repurchase	79.6				81.4		46.9
Repurchase of common stock	28,600				654,277
Weighted-average price per share of common stock repurchased	$ 63.51				$ 61.95
Repurchase of common stock					$ 40.5