Recent Adopted Accounting Pronouncements - Additional Information (Detail)	12 Months Ended
Dec. 31, 2012
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Minimum likely hood for more-likely-than-not threshold	50.00%

Minimum likely hood for more likely than not threshold.

No definition available.

Name:	gale_MinimumLikelyHoodForMoreLikelyThanNotThreshold
Namespace Prefix:	gale_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration