Investments (Other Invested Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Other Invested Assets [Line Items]
Other invested assets	$ 429,558	$ 377,429
LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	370,437	286,490
Company’s investment in separate accounts
Other Invested Assets [Line Items]
Other invested assets	46,573	40,126
Derivative Instruments
Other Invested Assets [Line Items]
Other invested assets	12,548	50,813
Equity Method | LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	295,529	216,586
Equity Method | Private equity | LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	189,095	149,164
Equity Method | Hedge funds | LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	64,002	57,171
Equity Method | Real estate-related | LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	42,432	10,251
Fair Value | LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	74,908	69,904
Fair Value | Private equity | LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	62,639	60,118
Fair Value | Hedge funds | LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	562	762
Fair Value | Real estate-related | LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	$ 11,707	$ 9,024