Fair value measurements (Fair value hierarchy) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	$ 5,576,341	$ 5,510,331
Short-term investments, at fair value	2,481,406	1,941,635
Other investments, at fair value	394,695	336,856
Total investments	8,452,442	7,788,822
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments	8,452,442	7,788,822
Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments	2,460,412	1,926,944
Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments	5,319,901	5,307,479
Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments	314,431	245,837
Managed investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	5,419,950	5,323,952
Short-term investments, at fair value	197,803	237,369
Other investments, at fair value	394,695	336,856
Total investments	6,012,448	5,898,177
Managed investments | U.S. government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	837,546	937,202
Managed investments | Non-US government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	248,390	237,968
Managed investments | U.S. states, municipalities and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	283,361	301,289
Managed investments | Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	657,876	610,582
Managed investments | Non-Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	20,615	26,920
Managed investments | U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	1,526,677	1,489,951
Managed investments | Non-U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	431,632	446,570
Managed investments | Bank loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	587,537	576,211
Managed investments | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	485,519	437,124
Managed investments | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	340,797	260,135
Managed investments | Fund of hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	959	1,417
Managed investments | Hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	18,056	20,980
Managed investments | Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	83,670	63,771
Managed investments | Fixed income investment funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	233,437	188,721
Managed investments | Overseas deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	53,246	54,484
Managed investments | Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	5,327	7,483
Managed investments | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	5,419,950	5,323,952
Short-term investments, at fair value	197,803	237,369
Other investments, at fair value	394,695	336,856
Total investments	6,012,448	5,898,177
Managed investments | Recurring | U.S. government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	837,546	937,202
Managed investments | Recurring | Non-US government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	248,390	237,968
Managed investments | Recurring | U.S. states, municipalities and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	283,361	301,289
Managed investments | Recurring | Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	657,876	610,582
Managed investments | Recurring | Non-Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	20,615	26,920
Managed investments | Recurring | U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	1,526,677	1,489,951
Managed investments | Recurring | Non-U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	431,632	446,570
Managed investments | Recurring | Bank loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	587,537	576,211
Managed investments | Recurring | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	485,519	437,124
Managed investments | Recurring | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	340,797	260,135
Managed investments | Recurring | Fund of hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	959	1,417
Managed investments | Recurring | Hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	18,056	20,980
Managed investments | Recurring | Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	83,670	63,771
Managed investments | Recurring | Fixed income investment funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	233,437	188,721
Managed investments | Recurring | Overseas deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	53,246	54,484
Managed investments | Recurring | Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	5,327	7,483
Managed investments | Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Short-term investments, at fair value	176,809	222,678
Other investments, at fair value	0	0
Total investments	176,809	222,678
Managed investments | Recurring | Level 1 | U.S. government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Managed investments | Recurring | Level 1 | Non-US government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Managed investments | Recurring | Level 1 | U.S. states, municipalities and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Managed investments | Recurring | Level 1 | Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Managed investments | Recurring | Level 1 | Non-Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Managed investments | Recurring | Level 1 | U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Managed investments | Recurring | Level 1 | Non-U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Managed investments | Recurring | Level 1 | Bank loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Managed investments | Recurring | Level 1 | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Managed investments | Recurring | Level 1 | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Managed investments | Recurring | Level 1 | Fund of hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	0	0
Managed investments | Recurring | Level 1 | Hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	0	0
Managed investments | Recurring | Level 1 | Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	0	0
Managed investments | Recurring | Level 1 | Fixed income investment funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	0	0
Managed investments | Recurring | Level 1 | Overseas deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	0	0
Managed investments | Recurring | Level 1 | Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	0	0
Managed investments | Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	5,143,554	5,091,615
Short-term investments, at fair value	20,994	14,691
Other investments, at fair value	36,997	28,294
Total investments	5,201,545	5,134,600
Managed investments | Recurring | Level 2 | U.S. government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	837,546	937,202
Managed investments | Recurring | Level 2 | Non-US government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	248,390	237,968
Managed investments | Recurring | Level 2 | U.S. states, municipalities and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	283,361	301,289
Managed investments | Recurring | Level 2 | Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	657,876	610,582
Managed investments | Recurring | Level 2 | Non-Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	20,615	26,920
Managed investments | Recurring | Level 2 | U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	1,526,677	1,489,951
Managed investments | Recurring | Level 2 | Non-U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	431,632	446,570
Managed investments | Recurring | Level 2 | Bank loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	335,037	343,874
Managed investments | Recurring | Level 2 | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	461,623	437,124
Managed investments | Recurring | Level 2 | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	340,797	260,135
Managed investments | Recurring | Level 2 | Fund of hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	0	0
Managed investments | Recurring | Level 2 | Hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	0	0
Managed investments | Recurring | Level 2 | Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	0	0
Managed investments | Recurring | Level 2 | Fixed income investment funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	31,670	20,811
Managed investments | Recurring | Level 2 | Overseas deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	0	0
Managed investments | Recurring | Level 2 | Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	5,327	7,483
Managed investments | Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	276,396	232,337
Short-term investments, at fair value	0	0
Other investments, at fair value	0	0
Total investments	276,396	232,337
Managed investments | Recurring | Level 3 | U.S. government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Managed investments | Recurring | Level 3 | Non-US government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Managed investments | Recurring | Level 3 | U.S. states, municipalities and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Managed investments | Recurring | Level 3 | Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Managed investments | Recurring | Level 3 | Non-Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Managed investments | Recurring | Level 3 | U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Managed investments | Recurring | Level 3 | Non-U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Managed investments | Recurring | Level 3 | Bank loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	252,500	232,337
Managed investments | Recurring | Level 3 | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	23,896	0
Managed investments | Recurring | Level 3 | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Managed investments | Recurring | Level 3 | Fund of hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	0	0
Managed investments | Recurring | Level 3 | Hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	0	0
Managed investments | Recurring | Level 3 | Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	0	0
Managed investments | Recurring | Level 3 | Fixed income investment funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	0	0
Managed investments | Recurring | Level 3 | Overseas deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	0	0
Managed investments | Recurring | Level 3 | Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	0	0
Non-managed investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	156,391	186,379
Short-term investments, at fair value	2,283,603	1,704,266
Total investments	2,439,994	1,890,645
Non-managed investments | Catastrophe bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	156,391	186,379
Non-managed investments | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, at fair value	2,283,603	1,704,266
Total investments	2,439,994	1,890,645
Non-managed investments | Recurring | Catastrophe bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	156,391	186,379
Non-managed investments | Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, at fair value	2,283,603	1,704,266
Total investments	2,283,603	1,704,266
Non-managed investments | Recurring | Level 1 | Catastrophe bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Non-managed investments | Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, at fair value	0	0
Total investments	118,356	172,879
Non-managed investments | Recurring | Level 2 | Catastrophe bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	118,356	172,879
Non-managed investments | Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, at fair value	0	0
Total investments	38,035	13,500
Non-managed investments | Recurring | Level 3 | Catastrophe bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	38,035	13,500
Fair value based on NAV practical expedient | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments	357,698	308,562
Fair value based on NAV practical expedient | Managed investments | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Short-term investments, at fair value	0	0
Other investments, at fair value	357,698	308,562
Total investments	357,698	308,562
Fair value based on NAV practical expedient | Managed investments | Recurring | U.S. government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Fair value based on NAV practical expedient | Managed investments | Recurring | Non-US government and government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Fair value based on NAV practical expedient | Managed investments | Recurring | U.S. states, municipalities and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Fair value based on NAV practical expedient | Managed investments | Recurring | Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Fair value based on NAV practical expedient | Managed investments | Recurring | Non-Agency residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Fair value based on NAV practical expedient | Managed investments | Recurring | U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Fair value based on NAV practical expedient | Managed investments | Recurring | Non-U.S. corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Fair value based on NAV practical expedient | Managed investments | Recurring | Bank loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Fair value based on NAV practical expedient | Managed investments | Recurring | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Fair value based on NAV practical expedient | Managed investments | Recurring | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	0	0
Fair value based on NAV practical expedient | Managed investments | Recurring | Fund of hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	959	1,417
Fair value based on NAV practical expedient | Managed investments | Recurring | Hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	18,056	20,980
Fair value based on NAV practical expedient | Managed investments | Recurring | Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	83,670	63,771
Fair value based on NAV practical expedient | Managed investments | Recurring | Fixed income investment funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	201,767	167,910
Fair value based on NAV practical expedient | Managed investments | Recurring | Overseas deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	53,246	54,484
Fair value based on NAV practical expedient | Managed investments | Recurring | Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	0	0
Fair value based on NAV practical expedient | Non-managed investments | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, at fair value	0	0
Total investments	0	0
Fair value based on NAV practical expedient | Non-managed investments | Recurring | Catastrophe bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	$ 0	$ 0