Fair Value Measurement (Quantitative Information Regarding Level 3 Valuations) (Details) $ in Thousands	Mar. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)
Assets:
Estimated Fair Value	$ 3,663,483	$ 3,582,207
Other investments	223,317	226,269
Level 3
Assets:
Equity investments	4,817	5,506
Other investments	$ 1,021	500
Level 3 | Comparability Adjustment | Discounted Cash Flows | Minimum
Assets:
Equity securities measured at fair value	0
Other investments, measurement input	0
Level 3 | Comparability Adjustment | Discounted Cash Flows | Maximum
Assets:
Equity securities measured at fair value	0.10
Other investments, measurement input	0.10
Level 3 | Comparability Adjustment | Discounted Cash Flows | Weighted Average
Assets:
Equity securities measured at fair value	0.05
Other investments, measurement input	0.05
Corporate debt, limited observable inputs | Level 3
Assets:
Estimated Fair Value	$ 68,947	81,062
Corporate debt, limited observable inputs | Level 3 | Comparability Adjustment | Market Comparable Securities | Minimum
Assets:
Assets measured at fair value	0
Corporate debt, limited observable inputs | Level 3 | Comparability Adjustment | Market Comparable Securities | Maximum
Assets:
Assets measured at fair value	0.05
Corporate debt, limited observable inputs | Level 3 | Comparability Adjustment | Market Comparable Securities | Weighted Average
Assets:
Assets measured at fair value	0.025
Corporate debt, limited observable inputs | Level 3 | Comparability Adjustment | Discounted Cash Flows | Minimum
Assets:
Assets measured at fair value	0
Corporate debt, limited observable inputs | Level 3 | Comparability Adjustment | Discounted Cash Flows | Maximum
Assets:
Assets measured at fair value	0.05
Corporate debt, limited observable inputs | Level 3 | Comparability Adjustment | Discounted Cash Flows | Weighted Average
Assets:
Assets measured at fair value	0.025
Residential mortgage-backed, other commercial mortgage-backed and other asset-backed securities | Level 3
Assets:
Estimated Fair Value	$ 4,573	$ 3,774
Residential mortgage-backed, other commercial mortgage-backed and other asset-backed securities | Level 3 | Comparability Adjustment | Market Comparable Securities | Minimum
Assets:
Assets measured at fair value	0
Residential mortgage-backed, other commercial mortgage-backed and other asset-backed securities | Level 3 | Comparability Adjustment | Market Comparable Securities | Maximum
Assets:
Assets measured at fair value	0.05
Residential mortgage-backed, other commercial mortgage-backed and other asset-backed securities | Level 3 | Comparability Adjustment | Market Comparable Securities | Weighted Average
Assets:
Assets measured at fair value	0.025
Residential mortgage-backed, other commercial mortgage-backed and other asset-backed securities | Level 3 | Comparability Adjustment | Discounted Cash Flows | Minimum
Assets:
Assets measured at fair value	0
Residential mortgage-backed, other commercial mortgage-backed and other asset-backed securities | Level 3 | Comparability Adjustment | Discounted Cash Flows | Maximum
Assets:
Assets measured at fair value	0.05
Residential mortgage-backed, other commercial mortgage-backed and other asset-backed securities | Level 3 | Comparability Adjustment | Discounted Cash Flows | Weighted Average
Assets:
Assets measured at fair value	0.025