Stockholders' Equity and Earnings Per Share ("EPS") - Additional Information (Detail) (USD $)	1 Months Ended		3 Months Ended	12 Months Ended			1 Months Ended	12 Months Ended	1 Months Ended	12 Months Ended					12 Months Ended
	Jun. 30, 2010	Nov. 30, 2009	Dec. 31, 2009	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008 Series B Preferred Stock	Dec. 31, 2009 Series B Preferred Stock	Sep. 30, 2010 3.875% Convertible Notes	Dec. 31, 2011 3.875% Convertible Notes	Dec. 31, 2011 3.875% Convertible Notes Hedge and warrant agreement	Dec. 31, 2011 Stockholder Rights Plan	Dec. 31, 2011 Stockholder Rights Plan Lower Limit	Dec. 31, 2011 Stockholder Rights Plan Series A Preferred Stock	Dec. 31, 2010 eProsper	Dec. 31, 2009 eProsper
Stockholders Equity Note [Line Items]
Proceeds from issuance of Series B Preferred Stock							$ 235,000,000
Redemption of outstanding shares of Series B Preferred Stock								235,000
Series B Preferred Stock, liquidation amount per share								$ 1,000
Redemption of preferred stock under the CPP								235,000,000
Dividends payment associated with the repurchase of preferred stock						235,000,000		1,200,000
Dividends paid						12,110,000		12,110,000
Non-cash charge in connection with redemption			11,400,000
Principal value										250,000,000
Debt instrument maturity date										Apr. 15, 2011
Aggregate conversion settlement payment										260,400,000
Payments for settlement of 3.875% Convertible Notes				250,000,000					250,000,000	250,000,000
Value of common stock shares issued										10,400,000
Common stock issued in public offering		7,965,568								187,760
Number of shares called										186,736
Shares of common stock issued, price per share		$ 38.50
Value of stock called										10,300,000
Proceeds from the issuance of common stock under our public equity offering, net of issuance costs		292,107,000				292,107,000
Repurchase of warrant under CPP	6,820,000				6,820,000
Shares of common stock exercisable under warrant, at the time of issuance	708,116
Exercise price of warrant	49.78
Shares of common stock exercisable under warrant	354,058
Repurchase of warrants					(6,820,000)
Percentage of ownership interest																65.00%
Percentage of ownership interest acquired															35.00%
Payment for acquisition of remaining interest in eProsper					1,300,000										1,300,000
Purchase of remaining interest in eProsper															$ 1,800,000
Dividend distribution of rights declared for each outstanding share of common stock												1
Record date for distribution of rights												Nov. 09, 1998
Description of the stock purchase rights plan												The Rights will be exercisable on the tenth (10th) business day (or such later date as is determined by our Board) following the announcement that a person or group (other than the Company, its subsidiaries or their employee benefit plans) has acquired or announces a tender or exchange offer to acquire beneficial ownership of 15 percent or more of the Company's common stock. If a person or group acquires beneficial ownership of 15 percent or more of the Company's common stock, each Right will then be exercisable for shares of common stock having a value equal to two times the exercise price of the Right. Similarly, in the event the Company is acquired in a merger or other business combination transaction or 50 percent or more of our consolidated assets or earning power are sold following such time as a person or group has acquired beneficial ownership of 15 percent or more of the Company's common stock, the rights will be exercisable for shares of the acquirer or its parent having a value equal to two times the exercise price of the Right.
Redemption price of rights												$ 0.001
Redemption date of rights												Jan. 31, 2014
Purchase price of 1/1000th of a share of Series A Participating Preferred Stock														$ 175.00
Right issuable with each new share of common stock														1
Subsidiary or employee benefit plans percentage ownership acquired													15.00%
Price per share of the conversion feature for the hedge and warrant agreement associated with our convertible notes											$ 64.43
Period of warrants ratable expiration beginning July 15, 2011											60 days