Equity Method Investments - Balance Sheet (Details) - USG Boral Building Products - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Current assets	$ 438	$ 389
Non-current assets	981	903
Current liabilities	255	211
Long-term debt	10	37
Other non-current liabilities	12	17
Shareholders' equity	1,142	1,027
Current portion of long-term debt	16	15
Shareholders' equity related to non-controlling interests	$ 66	$ 50