Dividends - Cash Dividends per Common Share (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Equity [Abstract]
Dividends declared (in dollars per share)	$ 0.19000	$ 0.18500	$ 0.56625	$ 0.55125