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Description of business	12 Months Ended
Description of business	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of business	Description of business Kinsale Capital Group, Inc., an insurance holding company, is a Delaware corporation that was formed in 2009 and conducts its operations through its wholly-owned subsidiaries. Kinsale Capital Group Inc. writes excess and surplus lines insurance on a non-admitted basis principally through its insurance subsidiary, Kinsale Insurance Company ("Kinsale Insurance"), which is authorized to write business in 50 states, the District of Columbia, the Commonwealth of Puerto Rico and the U.S. Virgin Islands. Kinsale Capital Group, Inc. also markets certain products through its subsidiary, Aspera Insurance Services, Inc. ("Aspera"), an insurance broker.