Capital Stock - Issuances of Common Stock (Details) - USD ($)	3 Months Ended			12 Months Ended
	Mar. 31, 2016	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2013
Stock Issued During Period Shares New Issues				6,235,017	2,400,000
Stock Issued During Period, Value, New Issues	$ 0		$ (16,175,000)	$ 83,275,000
At the Market Offering Program [Member]
Share Price		$ 13.65	$ 13.66
Stock Issued During Period Shares New Issues		5,024,530	1,210,487
Stock Issued During Period, Value, New Issues		$ 67,100,000	$ 16,175,000
Value of Common Stock Available to be issued under At The Money Program	$ 15,000,000