Stockholders' Equity and Earnings Per Share ("EPS") - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended				0 Months Ended	12 Months Ended		9 Months Ended	12 Months Ended				12 Months Ended
	Jun. 30, 2010	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010	Apr. 15, 2011 3.875% Convertible Notes	Dec. 31, 2012 3.875% Convertible Notes	Mar. 31, 2011 3.875% Convertible Notes	Sep. 30, 2011 3.875% Convertible Notes Hedge and warrant agreement	Dec. 31, 2012 3.875% Convertible Notes Hedge and warrant agreement	Dec. 31, 2012 Stockholder Rights Plan	Dec. 31, 2012 Stockholder Rights Plan Lower Limit	Dec. 31, 2012 Stockholder Rights Plan Series A Preferred Stock	Dec. 31, 2010 eProsper	Dec. 31, 2009 eProsper
Stockholders Equity Note [Line Items]
Repurchase of warrant under CPP	$ 6,800,000	$ 0		$ 0	$ 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					6,800,000
Percentage of ownership interest															65.00%
Percentage of ownership interest acquired														35.00%
Payment for acquisition of remaining interest in eProsper		0		0	1,300,000									1,300,000
Purchase of remaining interest in eProsper														1,800,000
Record date for distribution of rights											Nov. 09, 1998
Right issuable with each new share of common stock													1
Purchase price of 1/1000th of a share of Series A Participating Preferred Stock													$ 175.00
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.
Subsidiary or employee benefit plans percentage ownership acquired												15.00%
Redemption date of rights											Jan. 31, 2014
Redemption price of rights											$ 0.001
Period of warrants ratable expiration beginning July 15, 2011									60 days	60 days
Price per share of the conversion feature for the hedge and warrant agreement associated with our convertible notes									$ 64.43	$ 64.43
Principal value		0	[1]				250,000,000	250,000,000
Debt instrument maturity date						Apr. 15, 2011	Apr. 15, 2011
Aggregate conversion settlement payment						260,000,000	260,000,000
Payments for settlement of 3.875% Convertible Notes		0		250,000,000	0	250,000,000	250,000,000
Value of common stock shares issued						10,000,000	10,000,000
Common stock issued in public offering						187,760	187,760
Number of shares called						186,736	186,736
Value of stock called						$ 10,000,000				$ 10,000,000

[1] Represents long-term notes payable related to one of our debt fund investments. The last payment related to the notes was made in April 2012.