Investments and Derivative Instruments Level 4 Concentration of Credit Risk (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Fair Value, Concentration of Risk, Investments	$ 0		$ 0
Concentration Risk, Benchmark Description	greater than 10% of the Company's stockholders' equity	greater than 10% of the Company's stockholders' equity