Common Stock (Details Textual) - USD ($)		3 Months Ended	6 Months Ended
	May. 06, 2015	Jun. 30, 2015	Jun. 30, 2015	Jun. 30, 2014	Mar. 27, 2015
Class of Stock [Line Items]
Stock Issued During Period, Value, New Issues			$ 13,607,940
Proceeds From Issuance Of Common Stock			$ 13,607,946	$ (14,529)
ATM Program [Member]
Class of Stock [Line Items]
Proceeds From Issuance Of Common Stock		$ 86,100,000
Common stock average price		$ 30.59	$ 30.59
Common Stock [Member]
Class of Stock [Line Items]
Registration Payment Arrangement, Maximum Potential Consideration					$ 500,000,000
Common Stock [Member] | ATM Program [Member]
Class of Stock [Line Items]
Stock Issued During Period, Value, New Issues		$ 454,514
Proceeds From Issuance Of Common Stock		$ 13,900,000
Value Of Equity Instruments To Be Issued	$ 100,000,000