Equity (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	9 Months Ended	12 Months Ended					3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Dec. 31, 2011 2007 Repurchase Program [Member]	Sep. 30, 2012 2011 Repurchase Program [Member]	Sep. 30, 2012 First ASR Agreement [Member]	Sep. 30, 2012 Second ASR Agreement [Member]	Mar. 31, 2012 Uncollared ASR Agreement [Member]	Dec. 31, 2011 Uncollared ASR Agreement [Member]	Sep. 30, 2012 Capped ASR Agreement [Member]	Dec. 31, 2011 Capped ASR Agreement [Member]
Equity (Textual) [Abstract]
Stock repurchase program number of shares authorized to be repurchased				50,000,000
Maximum number of shares authorized for repurchase under stock repurchase plan as percentage of outstanding common stock				17.00%
Remaining shares available under repurchase program			0	16,900,000
Repurchase of additional shares		$ 500
Repurchase of shares at a per share price					250	250		250		250
Percentage of VWAP of common stock						110.00%
Shares received on initial delivery								5,000,000		5,000,000
Percentage of shares received on initial delivery								20.00%
Shares hold back on initial delivery								$ 50
Additional shares received							800,000		100,000
Additional repurchase program shares received							6,000,000		5,000,000
Interest In Joint Venture Minimum Percentage	20.00%
Business Acquisition, Agreement Terms, Change of Control, Put Option for Minority Interest Ownership, Effective Period	15 days