Condensed Consolidated Statements of Equity (Parenthetical) - $ / shares	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Statement of Stockholders' Equity [Abstract]
Common dividends (in usd per share)	$ 0.185	$ 0.185	$ 0.185	$ 0.17	$ 0.555	$ 0.51	$ 0.68