Consolidated Statements of Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Common dividends, per share amount	$ 0.594	$ 0.875	$ 0.875
Preferred dividends, per share amount	1.375	$ 1.375
Treasury stock retirement (in shares)			107,265
Special cash dividends, per share amount	$ 2.990