Shareholders' Equity - Schedule of Preferred Shares Outstanding (Details) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($) $ / shares shares
Series C Preferred Stock, Depository Share
Class of Stock [Line Items]
Depositary shares issued (shares) | shares	20,000,000
Liquidation preference per share (USD per share)	$ 25
Series C Preferred Stock
Class of Stock [Line Items]
Ownership Interest per Depositary Share	0.025%
Liquidation preference per share (USD per share)	$ 100,000
Proceeds from issuance of preferred stock, net | $	$ 488
Series D Preferred Stock, Depository Share
Class of Stock [Line Items]
Depositary shares issued (shares) | shares	30,000,000
Liquidation preference per share (USD per share)	$ 25
Series D Preferred Stock
Class of Stock [Line Items]
Ownership Interest per Depositary Share	0.025%
Liquidation preference per share (USD per share)	$ 100,000
Proceeds from issuance of preferred stock, net | $	$ 742
Series E Preferred Stock, Depository Share
Class of Stock [Line Items]
Depositary shares issued (shares) | shares	30,000,000
Liquidation preference per share (USD per share)	$ 25
Series E Preferred Stock
Class of Stock [Line Items]
Ownership Interest per Depositary Share	0.025%
Liquidation preference per share (USD per share)	$ 100,000
Proceeds from issuance of preferred stock, net | $	$ 728
Series F Preferred Stock, Depository Share
Class of Stock [Line Items]
Depositary shares issued (shares) | shares	750,000
Liquidation preference per share (USD per share)	$ 1,000
Series F Preferred Stock
Class of Stock [Line Items]
Ownership Interest per Depositary Share	1.00%
Liquidation preference per share (USD per share)	$ 100,000
Proceeds from issuance of preferred stock, net | $	$ 742
Series G Preferred Stock, Depository Share
Class of Stock [Line Items]
Depositary shares issued (shares) | shares	20,000,000
Liquidation preference per share (USD per share)	$ 25
Series G Preferred Stock
Class of Stock [Line Items]
Ownership Interest per Depositary Share	0.025%
Liquidation preference per share (USD per share)	$ 100,000
Proceeds from issuance of preferred stock, net | $	$ 493