Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) - USD ($) $ in Thousands | Mar. 31, 2017 | Dec. 31, 2016 |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | $ 3,600,498 | $ 3,548,227 |
Liabilities | 1,690 | 785 |
Notes payable | 371,044 | 320,000 |
Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 636,248 | 684,172 |
Liabilities | 285 | 20 |
Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 2,955,232 | 2,854,987 |
Liabilities | 1,405 | 765 |
Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 9,018 | 9,068 |
Liabilities | 0 | 0 |
Fixed maturity securities [Member] | U.S. Government Bonds and Agencies [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 12,271 | 12,275 |
Fixed maturity securities [Member] | Municipal Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 2,561,428 | 2,449,292 |
Fixed maturity securities [Member] | Mortgage Backed Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 37,847 | 39,777 |
Fixed maturity securities [Member] | Corporate Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 165,761 | 189,688 |
Fixed maturity securities [Member] | Collateralized Loan Obligations [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 89,790 | 86,525 |
Fixed maturity securities [Member] | Other Asset-Backed Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 47,190 | 36,996 |
Fixed maturity securities [Member] | Level 1 [Member] | U.S. Government Bonds and Agencies [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 12,271 | 12,275 |
Fixed maturity securities [Member] | Level 1 [Member] | Municipal Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Fixed maturity securities [Member] | Level 1 [Member] | Mortgage Backed Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Fixed maturity securities [Member] | Level 1 [Member] | Corporate Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Fixed maturity securities [Member] | Level 1 [Member] | Collateralized Loan Obligations [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Fixed maturity securities [Member] | Level 1 [Member] | Other Asset-Backed Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Fixed maturity securities [Member] | Level 2 [Member] | U.S. Government Bonds and Agencies [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Fixed maturity securities [Member] | Level 2 [Member] | Municipal Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 2,561,428 | 2,449,292 |
Fixed maturity securities [Member] | Level 2 [Member] | Mortgage Backed Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 37,847 | 39,777 |
Fixed maturity securities [Member] | Level 2 [Member] | Corporate Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 165,761 | 189,688 |
Fixed maturity securities [Member] | Level 2 [Member] | Collateralized Loan Obligations [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 89,790 | 86,525 |
Fixed maturity securities [Member] | Level 2 [Member] | Other Asset-Backed Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 47,190 | 36,996 |
Fixed maturity securities [Member] | Level 3 [Member] | U.S. Government Bonds and Agencies [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Fixed maturity securities [Member] | Level 3 [Member] | Municipal Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Fixed maturity securities [Member] | Level 3 [Member] | Mortgage Backed Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Fixed maturity securities [Member] | Level 3 [Member] | Corporate Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Fixed maturity securities [Member] | Level 3 [Member] | Collateralized Loan Obligations [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Fixed maturity securities [Member] | Level 3 [Member] | Other Asset-Backed Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Equity Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 383,529 | 316,450 |
Equity Securities [Member] | Nonredeemable Preferred Stock [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 32,959 | 31,809 |
Equity Securities [Member] | Private Equity Funds [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 9,018 | 9,068 |
Equity Securities [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 383,529 | 316,450 |
Equity Securities [Member] | Level 1 [Member] | Nonredeemable Preferred Stock [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Equity Securities [Member] | Level 1 [Member] | Private Equity Funds [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Equity Securities [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Equity Securities [Member] | Level 2 [Member] | Nonredeemable Preferred Stock [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 32,959 | 31,809 |
Equity Securities [Member] | Level 2 [Member] | Private Equity Funds [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Equity Securities [Member] | Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Equity Securities [Member] | Level 3 [Member] | Nonredeemable Preferred Stock [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Equity Securities [Member] | Level 3 [Member] | Private Equity Funds [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 9,018 | 9,068 |
Short-term Investments [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 90,215 | 90,626 |
Short-term Investments [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 69,958 | 70,393 |
Short-term Investments [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 20,257 | 20,233 |
Short-term Investments [Member] | Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Money Market Funds [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 170,490 | 285,054 |
Money Market Funds [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 170,490 | 285,054 |
Money Market Funds [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Money Market Funds [Member] | Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | 0 | 0 |
Total Return Swap [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | | 667 |
Liabilities | 1,405 | 765 |
Total Return Swap [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | | 0 |
Liabilities | 0 | 0 |
Total Return Swap [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | | 667 |
Liabilities | 1,405 | 765 |
Total Return Swap [Member] | Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets | | 0 |
Liabilities | 0 | 0 |
Equity Contract [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities | 285 | 20 |
Equity Contract [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities | 285 | 20 |
Equity Contract [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities | 0 | 0 |
Equity Contract [Member] | Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities | 0 | 0 |
Unsecured debt [Member] | Borrowings [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities | 374,633 | 180,000 |
Notes payable | 371,044 | 180,000 |
Unsecured debt [Member] | Borrowings [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities | 0 | 0 |
Unsecured debt [Member] | Borrowings [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities | 374,633 | 180,000 |
Unsecured debt [Member] | Borrowings [Member] | Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities | 0 | 0 |
Secured Debt [Member] | Borrowings [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities | $ 0 | 140,000 |
Notes payable | | 140,000 |
Secured Debt [Member] | Borrowings [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities | | 0 |
Secured Debt [Member] | Borrowings [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities | | 140,000 |
Secured Debt [Member] | Borrowings [Member] | Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities | | $ 0 |