Intangibles (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Intangibles
Gross intangible lease assets	$ 970	$ 984
Intangible assets, accumulated depreciation and amortization	419	380
Gross intangible lease liabilities	155	156
Intangible liabilities, accumulated depreciation and amortization	$ 106	$ 100