Equity (Details 2) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended							1 Months Ended	12 Months Ended	1 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Repurchase of common stock	Dec. 31, 2012 Dividend Paid	Dec. 31, 2011 Dividend Paid	Dec. 31, 2010 Dividend Paid	Jan. 31, 2011 2011 Program	Dec. 31, 2012 2011 Program Repurchase of common stock	Jan. 31, 2013 2013 Program	Feb. 28, 2013 2013 Program Repurchase of common stock	Feb. 15, 2013 2013 Program Repurchase of common stock
Number of shares authorized to be repurchased under the current open-market stock repurchase program								20,000,000		10,000,000
Repurchase of stock program, period								3 years		2 years
Number of shares repurchased under the current open-market stock repurchase program				13,428,389					6,571,611		743,877
Payments for shares repurchased under the current open-market stock repurchase program (in dollars)	$ 380,023	$ 672,191		$ 672,200					$ 380,000		$ 50,290
Remaining number of shares authorized to be repurchased under the current open-market stock repurchase program												9,256,123
Quarter dividend paid, per share (in dollars per share)					$ 0.105	$ 0.015
Dividend paid (in dollars)	70,122	10,282	10,413		70,122	10,282	10,413
Dividends declared	$ 67,677	$ 10,097	$ 10,449