Commitments and contingencies (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Employment agreements
Commitment to pay severance in event of employment termination without cause	$ 1.6	$ 1.6
Commitment to pay severance in event of employment termination upon change of control	1.9	1.9
Contingent liabilities
Contingent liability	0	0
Fraud related to certain credit card transactions
Contingent liabilities
Cash reserves required to be posted by merchant	$ 0.2

The carrying amount as of the balance sheet date of the combined total of loss contingency liabilities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14326-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 9, 10, 11, 12

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_LossContingencyAccrualAtCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant