CONSOLIDATED STATEMENT OF CHANGES IN EQUITY (Unaudited) (Parentheticals) - $ / shares shares in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Balance (in shares)	196,142
Vesting/exercising of equity compensation plan (in shares)	103
Shares issued under dividend reinvestment (in shares)	239
Dividend reinvestment and stock purchase plan (in dollars per share)	$ 30.67
Grant of stock as payment of fees (in shares)	2
Grant of stock as payment of fees (in dollars per share)	$ 31.19
Equity shelf program (in shares)	228
Equity shelf program, (in dollars per share)	$ 29.71
Common dividends, (in dollars per share)	$ 0.62
Conversion of OP Units to Common stock (in shares)	47
Conversion of OP Units to Common stock (in dollars per share)	$ 32.30
Redemption of OP Units (in units)	48
Balance (in shares)	196,761	196,142
Balance (in units)	8,814	8,862