Capital Stock - Issuances of Common Stock (Details) (USD $)	9 Months Ended		3 Months Ended			1 Months Ended	3 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Mar. 31, 2013 Initial Public Offering [Member]	Mar. 31, 2014 January 2014 Follow On Offering [Member]	Mar. 31, 2014 March 2014 Follow On Offering [Member]	Oct. 31, 2014 At the Market Offering Program [Member]	Sep. 30, 2014 At the Market Offering Program [Member]	Jun. 30, 2014 At the Market Offering Program [Member]	Oct. 28, 2014 At the Market Offering Program [Member]
Share Price			$ 15	$ 12.5	$ 12.55		$ 13.99	$ 13.14	$ 13.9
Stock Issued During Period Shares New Issues		2,360,000	2,360,000	2,070,000	3,680,000	52,532	3,389,441	537,499
Stock Issued During Period, Value, New Issues	$ 121,448,984		$ 35,400,000	$ 24,174,000	$ 43,989,000	$ 716,000	$ 46,372,000	$ 6,914,000
Value of Common Stock Available to be issued under At The Money Program							$ 55,500,000