Intangibles (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Intangibles
Gross intangible lease assets	$ 988	$ 984
Intangible assets, accumulated depreciation and amortization	403	380
Gross intangible lease liabilities	156	156
Intangible liabilities, accumulated depreciation and amortization	$ 103	$ 100