Equity Method Investments - Summarized Balance Sheets (Details) - USG Boral Building Products - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Current assets	$ 392	$ 438
Non-current assets	964	981
Current liabilities	232	255
Long-term debt	10	10
Other non-current liabilities	22	12
Shareholders' equity	1,092	1,142
Current portion of long-term debt	15	16
Shareholders' equity related to non-controlling interests	$ 64	$ 66