Common Stock (Details)	1 Months Ended			12 Months Ended
	Aug. 31, 2012 agreement	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Sales Agency Agreement [Member]	Dec. 31, 2012 Sales Agency Agreement [Member]	Dec. 31, 2011 Sales Agency Agreement [Member]	Aug. 31, 2012 Sales Agency Agreement [Member]
Class of Stock [Line Items]
Number of sales agency agreements	2
Common stock, shares authorized		200,000,000	200,000,000				2,726,390
Remaining authorized repurchase amount				1,795,199
Shares issued under sales agency agreement				0	931,191	807,000
Preferred stock, shares authorized		10,000,000
Preferred stock, shares outstanding		0	0