Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets [Abstract]
Fixed maturities, available-for-sale (amortized cost of $9,504,718 in 2020 and $9,448,840 in 2019)	$ 10,123,615	$ 9,970,909
Equity securities (cost of $3,234,028 in 2020 and $3,266,735 in 2019)	5,684,087	7,590,755
Short-term investments, available-for-sale (estimated fair value approximates cost)	250,872	1,196,248
Total Investments	16,058,574	18,757,912
Cash and cash equivalents	3,834,664	3,072,807
Restricted cash and cash equivalents	623,660	427,546
Receivables	2,088,579	1,847,802
Reinsurance recoverables	5,439,942	5,432,712
Deferred policy acquisition costs	630,600	566,042
Prepaid reinsurance premiums	1,260,009	1,415,857
Goodwill	2,309,576	2,308,548
Intangible assets	1,692,248	1,738,474
Other assets	2,110,935	1,906,115
Total Assets	36,048,787	37,473,815
Liabilities and Equity [Abstract]
Unpaid losses and loss adjustment expenses	15,038,812	14,728,676
Life and annuity benefits	975,485	985,729
Unearned premiums	4,190,216	4,057,727
Payables to insurance and reinsurance companies	280,405	406,720
Senior long-term debt and other debt (estimated fair value of $3,587,000 in 2020 and $3,907,000 in 2019)	3,593,954	3,534,183
Other liabilities	2,082,168	2,504,802
Total Liabilities	26,161,040	26,217,837
Redeemable noncontrolling interests	155,417	177,562
Commitments and contingencies
Shareholders' equity:
Common stock	3,419,528	3,404,919
Retained earnings	6,039,474	7,457,176
Accumulated other comprehensive income	261,726	208,772
Total Shareholders' Equity	9,720,728	11,070,867
Noncontrolling interests	11,602	7,549
Total Equity	9,732,330	11,078,416
Total Liabilities and Equity	$ 36,048,787	$ 37,473,815