Subsequent Events (unaudited)	12 Months Ended
Dec. 31, 2013
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events (Unaudited) On January 9, 2014, AFG reached a definitive agreement to acquire Summit Holdings Southeast, Inc. and its related companies (“Summit”), from Liberty Mutual using cash on hand at the parent company. Under the terms of the agreement, AFG will pay an estimated $250 million at closing, subject to adjustment through the closing date primarily for changes in Summit’s GAAP tangible book value. Including an anticipated capital contribution at closing, AFG’s total capital investment in the Summit business will be approximately $400 million. Summit is based in Lakeland, Florida and is a leading provider of workers’ compensation solutions in the southeastern United States, with net written premiums expected to be in excess of $500 million in 2013. Following the transaction, Summit will continue to operate under the Summit brand as a member of AFG’s Great American Insurance Group. The transaction is expected to close in the first or second quarter of 2014, following customary regulatory approvals. On February 5, 2014, Great American Insurance Company (“GAI”) commenced a tender offer to acquire all of the outstanding shares of National Interstate Corporation common stock not currently owned by GAI for $30.00 per share in cash (as adjusted on February 17). The tender offer and withdrawal rights are scheduled to expire on March 6, 2014, unless the offer is extended or earlier terminated in accordance with the terms of the offer and the applicable Securities and Exchange Commission rules and regulations. GAI intends to pay for any shares acquired in the tender offer with cash on hand. If the tender offer is completed, and following the tender offer, GAI owns at least 90% of the outstanding shares of National Interstate on a fully diluted basis, AFG and GAI intend to cause a second step, short-form, merger of National Interstate into GAI or an affiliate of GAI.

Subsequent Events (Unaudited)

On January 9, 2014, AFG reached a definitive agreement to acquire Summit Holdings Southeast, Inc. and its related companies (“Summit”), from Liberty Mutual using cash on hand at the parent company. Under the terms of the agreement, AFG will pay an estimated $250 million at closing, subject to adjustment through the closing date primarily for changes in Summit’s GAAP tangible book value. Including an anticipated capital contribution at closing, AFG’s total capital investment in the Summit business will be approximately $400 million. Summit is based in Lakeland, Florida and is a leading provider of workers’ compensation solutions in the southeastern United States, with net written premiums expected to be in excess of $500 million in 2013. Following the transaction, Summit will continue to operate under the Summit brand as a member of AFG’s Great American Insurance Group. The transaction is expected to close in the first or second quarter of 2014, following customary regulatory approvals.

On February 5, 2014, Great American Insurance Company (“GAI”) commenced a tender offer to acquire all of the outstanding shares of National Interstate Corporation common stock not currently owned by GAI for $30.00 per share in cash (as adjusted on February 17). The tender offer and withdrawal rights are scheduled to expire on March 6, 2014, unless the offer is extended or earlier terminated in accordance with the terms of the offer and the applicable Securities and Exchange Commission rules and regulations. GAI intends to pay for any shares acquired in the tender offer with cash on hand. If the tender offer is completed, and following the tender offer, GAI owns at least 90% of the outstanding shares of National Interstate on a fully diluted basis, AFG and GAI intend to cause a second step, short-form, merger of National Interstate into GAI or an affiliate of GAI.