Preferred Stock (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015	Dec. 31, 2004
Preferred stock
Stock issued (in shares)	237	250
Cumulative dividends (as a percent)	6.50%	6.50%
6.5% Cumulative convertible preferred stock
Preferred stock
Stock issued (in shares)			250
Stated value (in dollars per share)			$ 31,992
Purchase price of stock issued			$ 7,998,000
Sales price of stock issued			$ 31,992
Cumulative dividends (as a percent)			6.50%
Conversion price (in dollars per share)	$ 14.06		$ 15.50
Period after the date of issuance preferred stock can be converted			3 years
Convertible preferred stock converted to common shares	13
Common Stock
Preferred stock
Preferred shares converted to common shares	29,575