Shareholders' Equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended				1 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Jul. 31, 2013	Apr. 30, 2013	Jan. 31, 2013 2013 Stock Repurchase Program	Sep. 30, 2013 2013 Stock Repurchase Program
Number of shares authorized to be repurchased under the current open-market stock repurchase program							10,000,000
Repurchase of stock program, period							2 years
Number of shares repurchased under the current open-market stock repurchase program								3,956,615
Payments for shares repurchased under the current open-market stock repurchase program (in dollars)			$ 296,975	$ 229,442				$ 296,975
Quarterly dividend approved by Board prior to payment, per share (in dollars per share)					$ 0.20	$ 0.105
Dividend paid (in dollars)	16,716	16,885	33,472	36,385
Dividends declared	$ 31,629	$ 16,964	$ 65,101	$ 50,905