Equity Transactions (Tables)

12 Months Ended

Dec. 31, 2016

Equity [Abstract]

Schedule of Sale of Common Stock [Table Text Block]

Sales of common stock under our At the Market sales program activity during 2016 and 2015 are as follows:

Quarter Ended	Common Stock Issued	Weighted Average Sales Price		Net Proceeds (in Millions)
December 31, 2016	19,498	$	75.90	$	1.5
September 30, 2016	620,828	$	76.81	$	47.1
June 30, 2016	485,000	$	71.86	$	34.4
September 30, 2015	608,100	$	68.00	$	40.8
June 30, 2015	26,200	$	65.15	$	1.7
March 31, 2015	342,011	$	63.94	$	21.5

Schedule of Conversions of Stock [Table Text Block]

Below is the activity of conversions during 2016 and 2015:

		Year Ended December 31, 2016		Year Ended December 31, 2015
Series	Conversion Rate	Units/Shares	Common Stock	Units/Shares	Common Stock
Common OP unit	1	104,106	104,106	99,851	99,851
Series A-1 preferred OP unit	2.439	20,691	50,458	41,116	100,277
Series A-4 preferred OP unit	0.4444	120,906	53,733	114,414	50,848
Series A-4 preferred stock	0.4444	385,242	171,218	231,093	102,708
Series C preferred OP unit	1.11	7,043	7,815	—	—