Capital Stock - Issuances of Common Stock (Details) (USD $)	12 Months Ended		3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Mar. 31, 2014	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014
Stock Issued During Period Shares New Issues	13,352,147	2,360,000
Stock Issued During Period, Value, New Issues	$ 171,295,000	$ 35,400,000
Initial Public Offering [Member]
Share Price			$ 15
Stock Issued During Period Shares New Issues			2,360,000
Stock Issued During Period, Value, New Issues			35,400,000
January 2014 Follow On Offering [Member]
Share Price				$ 12.5
Stock Issued During Period Shares New Issues				2,070,000
Stock Issued During Period, Value, New Issues				24,174,000
March 2014 Follow On Offering [Member]
Share Price				$ 12.55
Stock Issued During Period Shares New Issues				3,680,000
Stock Issued During Period, Value, New Issues				43,989,000
At the Market Offering Program [Member]
Share Price	$ 13.87				$ 13.87	$ 13.99	$ 13.14
Stock Issued During Period Shares New Issues					3,675,207	3,389,441	537,499
Stock Issued During Period, Value, New Issues					49,846,000	46,372,000	6,914,000
Value of Common Stock Available to be issued under At The Money Program	$ 4,500,000				$ 4,500,000