Shareholders' Equity (Details) (USD $)	0 Months Ended	3 Months Ended			1 Months Ended
	Mar. 19, 2014	Mar. 31, 2014	Mar. 31, 2014 Common Stock	Mar. 31, 2013 Common Stock	May 07, 2014 Subsequent Event [Member] Common Stock
Class of Stock [Line Items]
Share repurchase authorized amount			$ 400,000,000
Share repurchase program, number of shares repurchased during period			1,400,000	1,900,000	3,000,000
Common share repurchase, amount repurchased		$ 35,000,000	$ 35,000,000	$ 39,000,000	$ 75,000,000
Common share repurchase, average price per share			$ 25.92	$ 20.46	$ 25.19
Stock sold by affiliates, number of shares	4,000,000
Stock sold by affiliates, percentage of outstanding shares of the Company		6.00%