Stockholders' Equity - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Class of Stock [Line Items]
Common stock, shares authorized	1,125,000,000.000	1,125,000,000.000
Common stock, par value (in dollars per share)	$ 0.20	$ 0.20
Common stock shares outstanding (in shares)	426,000,000
Common shares unissued but encumbered (in shares)	52,000,000
Common stock dividends	$ 0	$ 0	$ 0
Separation adjustments related to Spin-Off of Navient Corporation		$ 0
Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock shares outstanding (in shares)	3,300,000	3,300,000
Preferred stock dividend rate	6.97%
Preferred stock dividend rate (in dollars per share)	$ 3.485
Preferred stock liquidation preference (in dollars per share)	$ 50
Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock shares outstanding (in shares)	4,000,000	4,000,000
Preferred stock liquidation preference (in dollars per share)	$ 100
Common Stock
Class of Stock [Line Items]
Share price (in dollars per share)	$ 6.52
Three Month LIBOR | Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock dividend rate	1.70%
Additional Paid-in Capital
Class of Stock [Line Items]
Separation adjustments related to Spin-Off of Navient Corporation	$ 1,660,000	$ 1,062,519,000