Common and Preferred Shares (Details 1) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) shares
Series C [Member]
Preferred Shares [Line Items]
Issuance date	Mar. 02, 2015
Securities issued (in shares)	850
Depositary shares issued (in shares)	850,000
Aggregate liquidation preference | $	$ 850
Fixed dividend rate per annum	4.90%
Semi-annual fixed dividend, payment dates	Sep. 15, 2015
Floating dividend rate per annum	3.285%
Quarterly floating dividend payment dates	Beginning June 15, 2020
Fixed to floating rate, conversion date	Mar. 15, 2020
Series B [Member]
Preferred Shares [Line Items]
Issuance date	Nov. 10, 2014
Securities issued (in shares)	750
Depositary shares issued (in shares)	750,000
Aggregate liquidation preference | $	$ 750
Fixed dividend rate per annum	5.20%
Semi-annual fixed dividend, payment dates	May 15, 2015
Floating dividend rate per annum	3.428%
Quarterly floating dividend payment dates	Beginning February 15, 2020
Fixed to floating rate, conversion date	Nov. 15, 2019