Summary of Significant Accounting Policies - Investment in Unconsolidated Investees (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) Item	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
INVESTMENT IN UNCONSOLIDATED INVESTEES:
Investment amount	$ 128,382	$ 103,836
Investee earnings recorded in income	20,233	20,960	$ 16,056
Reinsurance assumed	29,129	25,047	48,303
Net premiums earned	865,747	839,111	791,366
Undistributed earnings from equity method investees included in retained earnings	106,000
Dividends received	4,675	13,200	9,900
Investments in Unconsolidated Investees
INVESTMENT IN UNCONSOLIDATED INVESTEES:
Investee earnings recorded in income	$ 70,400	77,300	50,200
Maui Jim Inc.
INVESTMENT IN UNCONSOLIDATED INVESTEES:
Equity ownership interest (as a percent)	40.00%
Investment amount	$ 90,900	79,600
Investee earnings recorded in income	$ 10,400	13,600	12,500
Dividends received		13,200
Prime Holdings Insurance Services, Inc. (Prime)
INVESTMENT IN UNCONSOLIDATED INVESTEES:
Equity ownership interest (as a percent)	23.00%
Investment amount	$ 32,700	24,200
Investee earnings recorded in income	$ 10,800	7,400	3,600
Number of insurance carriers Company writes through | Item	2
Reinsurance assumed	$ 15,700	13,100	41,100
Net premiums earned	14,300	$ 28,700	$ 34,200
Dividends received	$ 4,700