Subsequent Events (Details) (USD $)	3 Months Ended		12 Months Ended	1 Months Ended	3 Months Ended	1 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Apr. 22, 2014 Subsequent Event	Mar. 31, 2014 Convertible Notes	Apr. 22, 2014 Convertible Notes Subsequent Event	Mar. 31, 2014 Call Options	Apr. 22, 2014 Call Options Subsequent Event	Mar. 31, 2014 Warrants	Mar. 31, 2013 Warrants	Apr. 22, 2014 Warrants Subsequent Event
Subsequent Events (Textuals) [Abstract]
Cash dividend declared per common share				$ 0.35
Cash dividends declared				$ 6,400,000
Conversion rate of common stock shares per $1,000 of principal amount					20.8234	20.8549
Principal amount in conversion feature					1,000	1,000
Conversion price per share of note					$ 48.02	$ 47.95
Exercise price per share of Call Options							$ 48.02	$ 47.95
Exercise price per share of Warrants									60.98	61.25	60.89
Repurchase of common stock, shares	184,400	259,596
Weighted-average price per share of common stock repurchased	$ 69.07	$ 62.62
Common share amount available for additional share repurchase	$ 104,900,000		$ 117,600,000