Summary of significant accounting policies (Tables)

9 Months Ended

Sep. 30, 2017

Accounting Policies [Abstract]

Estimated Useful Lives of Intangible Assets Acquired

Intangible assets acquired individually or with a group of other assets or in a business combination and developed internally are carried at cost less accumulated amortization based on their estimated useful lives as follows:

Customer-related intangible assets	1-14 years
Marketing-related intangible assets	1-10 years
Technology-related intangible assets	2-8 years
Other intangible assets	2-9 years