Equity (Details 2) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	280,000,000	280,000,000		280,000,000
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000		50,000,000
Common stock shares issued in connection with stock options exercised (in shares)		128,192
Common stock issued through the dividend reinvestment plan (in shares)		1,689	1,608
Number of shares of stock grants withheld (in shares)		53,214	39,800
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares)		5,671
Stock Issued During Period, Shares, Share-based Compensation, Forfeited (in shares)		407	4,293
Continuous Equity Program CEP IV [Member]
Class of Stock [Line Items]
Maximum value of shares of common stock that can be sold (in dollars)	$ 1,000,000,000	$ 1,000,000,000
Common stock shares issued	0	0
Maximum [Member] | Continuous Equity Program CEP IV [Member]
Class of Stock [Line Items]
Percentage of compensation received by sales agent		2.00%
Restricted Stock and Restricted Stock Converted From Performance Shares [Member]
Class of Stock [Line Items]
Restricted stock granted (in shares)		196,491	157,779
Deferred Compensation, Share-based Payments [Member] | Non Employee Director [Member]
Class of Stock [Line Items]
Restricted stock granted (in shares)		44,327	46,589