Consolidated financial statements	3 Months Ended
Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Consolidated financial statements	Consolidated financial statements The consolidated balance sheet as of March 31, 2018, the consolidated statements of comprehensive income for the quarters ended March 31, 2018 and 2017, the consolidated statement of shareholders’ equity for the quarter ended March 31, 2018, and the consolidated statements of cash flows for the quarters ended March 31, 2018 and 2017 are unaudited. The consolidated balance sheet as of December 31, 2017 was derived from audited consolidated financial statements, but does not include all disclosures required by generally accepted accounting principles (GAAP) in the United States of America. In the opinion of management, all adjustments necessary for a fair statement of the consolidated financial statements are included. Adjustments consist only of normal recurring items, except for any discussed in the notes below. Interim results are not necessarily indicative of results for a full year. The consolidated financial statements and notes are presented in accordance with instructions for Form 10-Q and do not contain certain information included in our annual consolidated financial statements and notes. The consolidated financial statements and notes appearing in this report should be read in conjunction with the consolidated audited financial statements and related notes included in our Annual Report on Form 10-K for the year ended December 31, 2017 (the “2017 Form 10-K”).

Consolidated financial statements

3 Months Ended

Mar. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

The consolidated balance sheet as of March 31, 2018, the consolidated statements of comprehensive income for the quarters ended March 31, 2018 and 2017, the consolidated statement of shareholders’ equity for the quarter ended March 31, 2018, and the consolidated statements of cash flows for the quarters ended March 31, 2018 and 2017 are unaudited. The consolidated balance sheet as of December 31, 2017 was derived from audited consolidated financial statements, but does not include all disclosures required by generally accepted accounting principles (GAAP) in the United States of America. In the opinion of management, all adjustments necessary for a fair statement of the consolidated financial statements are included. Adjustments consist only of normal recurring items, except for any discussed in the notes below. Interim results are not necessarily indicative of results for a full year. The consolidated financial statements and notes are presented in accordance with instructions for Form 10-Q and do not contain certain information included in our annual consolidated financial statements and notes. The consolidated financial statements and notes appearing in this report should be read in conjunction with the consolidated audited financial statements and related notes included in our Annual Report on Form 10-K for the year ended December 31, 2017 (the “2017 Form 10-K”).