Consolidated Statement of Changes in Stockholders' Equity (Parenthetical) - $ / shares	9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Options exercised (shares)	12,200	700
Options exercised (shares)	200	200
Cash dividends declared (per share)	$ 0.14	$ 0.14
Series C Preferred Stock [Member]
Preferred stock, dividend rate	6.00%	6.00%	6.00%
Series D Preferred Stock [Member]
Preferred stock, dividend rate	4.50%	4.50%	4.50%
Series F Preferred Stock [Member]
Preferred stock, dividend rate	6.00%