CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Unaudited) (Parenthetical) - $ / shares	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Statement of Stockholders' Equity [Abstract]
Dividends declared (in dollars per share)	$ 0.27	$ 0.25	$ 0.79	$ 0.75	$ 1.00