Earnings Per Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share [Abstract]
Income from continuing operations	$ (11)	$ 24	$ 92	$ 51
Less: Net income attributable to noncontrolling interest	1	0	1	0
Income (loss) from continuing operations attributable to USG	(12)	24	91	51
Loss from discontinued operations, net of tax	0	(1)	(1)	(1)
Net income (loss) attributable to USG	(12)	23	90	50
Effect of dilutive securities - RSUs, MSUs, performance shares and stock options	0	0	0	0
Effect of dilutive securities - 10% convertible senior notes	0	0	2	0
Effect of dilutive securities - Deferred compensation program for non-employee directors	0	0	0	0
Income (loss) available to shareholders	$ (12)	$ 23	$ 92	$ 50
Average common shares	144,646,284	108,608,086	140,944,207	108,486,583
Dilutive RSUs, MSUs, performance shares and stock options	0	2,400,000	2,500,000	2,600,000
Common shares issuable upon conversion of our 10% convertible senior notes	0	0	3,500,000	0
Deferred shares associated with a deferred compensation program for non-employee directors	0	0	200,000	0
Average diluted common shares	144,646,284	111,008,421	147,087,399	111,052,333
Income (loss) from continuing operations per average common share	$ (0.09)	$ 0.23	$ 0.65	$ 0.48
Loss from discontinued operations per average common share	$ 0.00	$ (0.01)	$ (0.01)	$ (0.01)
Earnings (loss) per average common share	$ (0.09)	$ 0.22	$ 0.64	$ 0.47
Income (loss) from continuing operations per average dilutive share	$ (0.09)	$ 0.22	$ 0.63	$ 0.47
Loss from discontinued operations	$ 0.00	$ (0.01)	$ (0.01)	$ (0.01)
Earnings (loss) per average diluted common share	$ (0.09)	$ 0.21	$ 0.62	$ 0.46