Intangible assets - Components of Franchise Rights and Other Intangible Assets (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Unamortized Intangible Assets	[1]	$ 1,014	$ 1,014
Amortized Intangible Assets, Gross		105,921	100,512
Amortized Intangible Assets, Accumulated Amortization		91,197	89,578
Amortized Intangible Assets, Net		14,724	10,934
Total, Gross		106,935	101,526
Total, Net		15,738	11,948
Capitalized SaaS Licenses
Finite-Lived Intangible Assets [Line Items]
Amortized Intangible Assets, Gross	[2]	5,007	0
Amortized Intangible Assets, Accumulated Amortization	[2]	313	0
Amortized Intangible Assets, Net	[2]	4,694	0
Franchise Rights
Finite-Lived Intangible Assets [Line Items]
Amortized Intangible Assets, Gross	[2]	81,062	81,169
Amortized Intangible Assets, Accumulated Amortization	[2]	80,829	80,685
Amortized Intangible Assets, Net	[2]	233	484
Trademarks
Finite-Lived Intangible Assets [Line Items]
Amortized Intangible Assets, Gross	[3]	12,672	12,004
Amortized Intangible Assets, Accumulated Amortization	[3]	9,261	8,628
Amortized Intangible Assets, Net	[3]	3,411	3,376
Contract Acquisition Costs
Finite-Lived Intangible Assets [Line Items]
Amortized Intangible Assets, Gross	[4]	4,943	5,102
Amortized Intangible Assets, Accumulated Amortization	[4]	670	203
Amortized Intangible Assets, Net	[4]	4,273	4,899
Acquired Lease Rights
Finite-Lived Intangible Assets [Line Items]
Amortized Intangible Assets, Gross	[5]	2,237	2,237
Amortized Intangible Assets, Accumulated Amortization	[5]	124	62
Amortized Intangible Assets, Net	[5]	$ 2,113	$ 2,175
Finite-lived intangible asset, useful life		36 years
Minimum | Capitalized SaaS Licenses
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life		3 years
Minimum | Franchise Rights
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life		5 years
Minimum | Trademarks
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life		8 years
Minimum | Contract Acquisition Costs
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life		5 years
Maximum | Capitalized SaaS Licenses
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life		5 years
Maximum | Franchise Rights
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life		25 years
Maximum | Trademarks
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life		40 years
Maximum | Contract Acquisition Costs
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life		12 years

[1] Acquisition of the Suburban brand. The tradename is expected to generate future cash flows for an indefinite period of time.

[2] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjdkNDMzZWIyZjM0ODQ4NDFiOTZhZDRmMDRmNDU5ZjUyfFRleHRTZWxlY3Rpb246RjhGMDBEQ0Q2NEVENTc1QkRDN0QyMzA3N0I2RTRFNUUM}

[3] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjdkNDMzZWIyZjM0ODQ4NDFiOTZhZDRmMDRmNDU5ZjUyfFRleHRTZWxlY3Rpb246RUZFNDMyQjI1RDIyMzMzNkZBODUyMzA3N0I2RUE2QkEM}

[4] Customer contracts acquired in a business combination. Amortized on a straight-line basis over a period of 5 to 12 years.

[5] Acquired lease rights recognized in conjunction with the acquisition of an office building. The costs are being amortized over the 36 year term of the lease in place.