Income Taxes (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Net purchases of T&L Bonds	$ 61,860	$ 59,739	$ 51,673
T&L Bonds held as of end of year	$ 181,272	$ 119,412