Income Taxes Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2016	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Examination [Line Items]
Income Tax Examination, Year under Examination			2015	2014	2013	2012	2011	2010
Decrease in Unrecognized Tax Benefits is Reasonably Possible	$ 140		$ 320
Income Taxes Paid		$ 150