Consolidated Statements of Changes in Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash dividends declared on common shares, per share (in dollars per share)	$ 0.38	$ 0.33	$ 0.290
Series A Preferred Stock [Member]
Cash dividends declared on Preferred Stock (in dollars per share)	1.9375	7.75	$ 7.75
Series C Preferred Stock [Member]
Cash dividends declared on Preferred Stock (in dollars per share)	0.539063	0.539063
Series D Preferred Stock [Member]
Cash dividends declared on Preferred Stock (in dollars per share)	50.00	$ 13.33
Series E Preferred Stock [Member]
Cash dividends declared on Preferred Stock (in dollars per share)	$ 1.544012