CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
Net of income taxes	$ 0.1	$ 0.0	$ 0.0

The amount represents the other comprehensive income loss pension and net of income taxes.

No definition available.

Name:	gsah_OtherComprehensiveIncomeLossPensionAndNetOfIncomeTaxes
Namespace Prefix:	gsah_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration