Equity (Details 2) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Class of Stock [Line Items]
Common stock, shares authorized	280,000,000	280,000,000		280,000,000
Preferred stock, shares authorized	50,000,000	50,000,000		50,000,000
Common stock shares issued in connection with stock options exercised		116,428
Common stock issued through the dividend reinvestment plan (in shares)		1,041	1,028
Number of shares of stock grants withheld		53,011	36,104
Stock Issued During Period, Shares, Employee Stock Purchase Plans		5,671
Stock Issued During Period, Shares, Share-based Compensation, Forfeited		12	2,011
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
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		196,059	157,779
Deferred Compensation, Share-based Payments [Member] | Non Employee Director [Member]
Class of Stock [Line Items]
Restricted stock granted		44,327	46,589