Consolidated Statements of Stockholders' Equity (Parentheticals) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Preferred Stock [Member]
Dividends declared to preferred stockholders per share (in dollars per share)		$ 0.64	$ 0.80
Common Stock [Member]
Dividends declared to common stockholders per share (in dollars per share)	$ 1.75	1.54	1.34
Dividends declared to common stockholders per share (in dollars per share)	$ 1.75	$ 1.54	$ 1.34