Basis of Presentation (Narrative) (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2020 USD ($) segment	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of reportable segments (in segments) | segment		5
Premium receivable, allowance for credit loss		$ 6,197		$ 1,590
Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment adoption of ASU	[1]		$ 4,076
Accounting Standards Update 2020-04
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Percent of investments with exposure to LIBOR		6.00%
Investments with exposure to LIBOR		$ 185,000
Investments with exposure to LIBOR, issued in 2020 or 2019				25.00%
Retained Earnings | Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment adoption of ASU	[1]		$ 4,076

[1] See Note 1 for discussion of accounting guidance adopted during the period.