Shareholders' Equity (Details) (USD $)	1 Months Ended			12 Months Ended			12 Months Ended	1 Months Ended	12 Months Ended	1 Months Ended		12 Months Ended		1 Months Ended	12 Months Ended
	Oct. 31, 2008 designee	Jul. 31, 2008	Jun. 30, 2007	Dec. 31, 2011 demandregistration	Dec. 31, 2010	Jul. 03, 2008	Dec. 31, 2011 Minimum	Oct. 31, 2008 Maximum	Dec. 31, 2011 Maximum D	Jun. 30, 2011 Common Stock	Jun. 30, 2010 Common Stock	Dec. 31, 2011 Common Stock	Dec. 31, 2010 Common Stock	Oct. 31, 2008 Preferred Stock	Dec. 31, 2011 Preferred Stock D	Dec. 31, 2010 Preferred Stock	Dec. 31, 2011 Preferred Stock Minimum	Dec. 31, 2011 Preferred Stock Maximum
Stockholders' Equity
Amount of common stock authorized to repurchase										$ 300,000,000	$ 300,000,000
Number of shares of common stock repurchased												2,981,406	1,526,400
Amount for which shares of stock are repurchased				105,206,000	35,858,000							105,200,000	35,900,000
Average price paid per share of common stock repurchased												$ 35.29	$ 23.49
Preferred equity investment
Consideration that the shareholders would have received under merger agreement before termination (in dollars per share)			$ 67.00
Total consideration from the termination of the Merger Agreement		1,475,000,000
Non-refundable cash termination fee from the termination of the Merger Agreement		225,000,000
Investment in preferred equity from the termination of the Merger Agreement						1,250,000,000
Issuance of preferred stock (in shares)														12,500
Repurchase of Preferred Stock (in shares)																225
Repurchase value of preferred stock					11,200,000											11,200,000
Threshold for consideration per share from change in control or other significant transactions to allow voting rights with common stock on an as-converted basis																		$ 45
Premium on stock repurchase for which the approval of holders of a majority of the Investment shares is required (as a percent)																		20.00%
Aggregate liquidation preference															1,230,000,000
Threshold of the consideration per share paid to the holders of the Common Stock in the event of a change-in-control transaction which would require consideration for holders of preferred stock																	$ 67
Threshold of the consideration per share paid to the holders of the common stock in the event of a change-in-control transaction which would require consideration for holders of preferred stock																		$ 45
Number of consecutive trading days considered for measurement of average trading price (in days)															20
Average trading price of the Common Stock (in dollars per share)																	$ 67	$ 45
Redemption price of the Investment															$ 1,040,000,000
Number of shares of a common stock issuance necessary to redeem all shares of preferred stock												27,300,000
Percentage of common stock acquired which would restrict voting rights							20.00%
Period to accord voting rights to holders of securities in excess of twenty percent (in days)									90
Required investment ownership percentage by Fortress and its affiliates, in which a Purchaser Designee should be appointed if requirement is not met								66.67%
Number of Purchaser Designees that Fortress and the Company would appoint until Fortress and its affiliates own less than two-thirds of the shares of the Investment issued to them	1
Beneficial ownership of the Common Stock by the purchasers (as a percent)									2.50%
Number of demand registrations that the purchasers and any permitted transferees of Registrable Securities are entitled to				4
Beneficial ownership by investment holders which entitles them to preemptive rights under the Investor Rights Agreement (as a percent)							66.67%