CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - Unaudited (Parenthetical) - $ / shares	3 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018
Stockholders' Equity Attributable to Parent
Common dividends declared - per share (in dollars per share)	$ 0.75	$ 0.72	$ 0.72	$ 0.72	$ 0.64	$ 0.64
Issuance of shares of common stock, common stock offering, net of expenses	849,751	790,052	232,205	316,102	750,282	179,501
Issuance of shares of common stock, dividend reinvestment plan	441	479	571	0	565	667
Withheld shares of common stock to satisfy tax withholding obligations in connection with the vesting of restricted stock	0	0	28,955	0	0	23,824