Stock Offerings (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 08, 2011	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014
Stock offering
Number of shares issued		9,283				9,283
SBLF capital received			$ 7,834
Preferred stock, par value (in dollars per share)		$ 1,000				$ 1,000
Series B Preferred Stock
Stock offering
Number of shares issued		400
Dividend rate (as a percent)		6.00%
Period from first, second, third, fourth, and fifth anniversary of original issue date that stock may be convertible		30 days
Conversion price (in dollars per share)		$ 16
Series C Preferred Stock
Stock offering
Number of shares issued		383.4
Dividend rate (as a percent)		6.50%
Period from first, second, third, fourth, and fifth anniversary of original issue date that stock may be convertible		30 days
Conversion price (in dollars per share)		$ 16
Preferred Class A
Stock offering
Dividend rate (as a percent)				1.00%	1.00%
Stock offering (in shares)	8,500
SBLF capital received	$ 8,500
Preferred stock, par value (in dollars per share)	$ 1,000
Preferred Class A | Through 8 March 2016
Stock offering
Dividend rate (as a percent)		1.00%
Preferred Class A | After 8 March 2016
Stock offering
Dividend rate (as a percent)		9.00%