XML 16 R111.htm IDEA: XBRL DOCUMENT v3.20.1

Net Revenues - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2020
Revenues [Abstract]
Billing cycle period	30 days

X

- Definition

Billing cycle period.

+ References

No definition available.

+ Details

Name:	g_BillingCyclePeriod
Namespace Prefix:	g_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- References

No definition available.

+ Details

Name:	us-gaap_RevenuesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration