Earnings Per Share, Textuals (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Potential dilutive effect of options and Warrants
Options outstanding to purchase common shares	20,791		20,791
Average exercise price per share	$ 80.01		$ 80.01
Potential dilutive effect of options outstanding	0	0
Dividends
Cash dividends paid	$ 6.4	$ 5.9
Cash dividends paid per share	$ 0.35	$ 0.30
Treasury Stock, Number of Shares and Restriction Disclosures [Abstract]
Common share amount available for additional share repurchase	104.9		117.6
Repurchase of common stock, shares	184,400	259,596
Weighted-average price per share of common stock repurchased	$ 69.07	$ 62.62
Repurchase of common stock	$ 12.7	$ 16.2
Warrant Transactions
Potential dilutive effect of options and Warrants
Number of common shares underlying the Warrants outstanding	3,600,000	3,600,000
Average exercise price of common shares underlying Warrants	60.98	61.25

Exercise price per share or per unit of warrants or rights outstanding.

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