CONSOLIDATED STATEMENTS OF INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
REVENUES
Premiums earned, affiliated	$ 586,609	$ 566,103	$ 534,105
Other income, affiliated	1,021	1,214	1,784
LOSSES AND EXPENSES
Losses and settlement expenses, affiliated	385,708	368,722	378,263
Amortization of deferred policy acquisition costs, affiliated	106,931	101,090	97,551
Other underwriting expenses, affiliated	69,560	68,305	57,148
Other expense, affiliated	$ 1,860	$ 1,822	$ 1,570