Acquisition of Tokio Millennium Re (Fair Value of Net Assets Acquired and Liabilities Assumed) (Details) - TMR $ in Thousands	Mar. 22, 2019 USD ($) state
Business Acquisition [Line Items]
Excess purchase price over the fair value of net assets acquired assigned to goodwill	$ 13,094
Acquired finite-lived intangibles, weighted average amortization period	10 years 6 months
Value of business acquired, amortization period	2 years
Value of business acquired	$ 287,600
Deferred tax liability related to the estimated fair value of the intangible assets recorded	2,281
Deferred tax liability related to other adjustments	2,606
Insurance licenses
Business Acquisition [Line Items]
Identifiable indefinite lived intangible assets (insurance licenses)	$ 6,800
Number of states, ability to write reinsurance | state	50