Condensed Consolidated Balance Sheets (Parenthetical) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Debt securities, available-for sale, allowance for expected credit losses	$ 1,085,000	$ 0
Debt securities, available-for-sale	4,549,133,000	4,476,358,000
Short-term investments	510,800,000	67,353,000
Other investments	282,866,000	311,287,000
Cash and cash equivalents	188,282,000	135,942,000
Restricted cash and cash equivalents	63,061,000	28,521,000
Accrued investment income	26,135,000	30,927,000
Premiums and other receivables, net	1,598,316,000	1,428,948,000
Premiums and other receivables, allowance for expected credit losses	37,163,000	24,067,000
Deferred acquisition costs	284,963,000	263,523,000
Reinsurance recoverable, net	1,286,852,000	1,394,308,000
Reinsurance recoverable, allowance for expected credit losses	810,000	0
Prepaid reinsurance premiums	458,960,000	575,747,000
Premises and equipment, net	382,696,000	403,827,000
Intangible assets, net	345,974,000	365,823,000
Prepaid and other assets	66,890,000	94,642,000
Unpaid loss and loss adjustment expense reserves	2,897,465,000	2,886,414,000
Unearned premiums and other revenue	2,337,469,000	2,312,241,000
Reinsurance payable	402,428,000	562,844,000
Accounts payable and accrued expenses	420,144,000	315,366,000
Other liabilities	$ 401,749,000	$ 376,169,000
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred Stock, Shares Issued (in shares)	2,565,120	2,565,120
Preferred stock, shares outstanding (in shares)	2,565,120	2,565,120
Aggregate liquidation preference	$ 450,000,000	$ 450,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, Shares Authorized	150,000,000	150,000,000
Common Stock, Issued (in shares)	113,934,259	113,368,811
Common Stock, Outstanding (in shares)	113,475,176	113,368,811
Treasury Stock, Common, Shares	459,083	0
Reciprocal Exchanges
Debt securities, available-for sale, allowance for expected credit losses	$ 150,000
Debt securities, available-for-sale	300,124,000	$ 324,249,000
Short-term investments	30,952,000	5,245,000
Cash and cash equivalents	416,000	959,000
Restricted cash and cash equivalents	325,000	24,000
Accrued investment income	1,397,000	2,001,000
Premiums and other receivables, net	70,076,000	55,859,000
Premiums and other receivables, allowance for expected credit losses	844,000	541,000
Deferred acquisition costs	18,507,000	23,307,000
Reinsurance recoverable, net	125,095,000	119,125,000
Reinsurance recoverable, allowance for expected credit losses	173,000
Prepaid reinsurance premiums	105,597,000	105,894,000
Premises and equipment, net	0	241,000
Intangible assets, net	3,090,000	3,225,000
Prepaid and other assets	4,312,000	3,521,000
Unpaid loss and loss adjustment expense reserves	208,496,000	205,786,000
Unearned premiums and other revenue	219,582,000	252,553,000
Reinsurance payable	51,711,000	35,689,000
Accounts payable and accrued expenses	7,604,000	8,497,000
Other liabilities	44,004,000	30,803,000
Related Parties
Other investments	231,593,000	238,841,000
Accrued investment income	$ 1,210,000	$ 2,391,000