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Investments (Narrative) (Details) $ in Thousands | 3 Months Ended |  |
--- | --- | --- | ---
Mar. 31, 2017 USD ($) Affiliate Business Issuer investment_interest Security | Mar. 31, 2016 USD ($) Issuer | Dec. 31, 2016 USD ($) Issuer Security | Dec. 31, 2015 USD ($)
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Number of investment affiliates exceeding shareholder's equity ten percent threshold limit | Affiliate | 0 |  |  |
Threshold limit of investments based on shareholders' equity | 10.00% |  |  |
Securities on deposit with state insurance departments | $ 46,400 |  |  |
Business owned life insurance cost | 33,000 |  |  |
Investment in unconsolidated subsidiaries | 330,479 |  | $ 340,906 |
Investments in LPs/LLCs fair value | $ 199,696 |  | 204,719 |
Number of LPs / LLCs with investment ownership percent over 25% | Business | 3 |  |  |
Equity in earnings, losses from affordable housing projects | $ (3,300) | $ (5,200) |  |
Affordable housing tax credits | 4,600 | 4,600 |  |
Losses from historic tax credit investments | (400) | (200) |  |
Tax credits recognized related to historic tax credit investments | 1,800 | 2,600 |  |
Net impairment losses recognized in earnings | 171 | 9,666 |  |
Portion of noncredit OTTI losses recognized in OCI | 248 | 1,068 |  |
Credit-related other-than-temporary impairment recognized in earnings | $ 1,329 | 6,559 | 1,158 | $ 5,751
Tax Credit Partnerships Almost 100% Ownership [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Number of tax credit partnerships almost 100% ownership percentage | investment_interest | 2 |  |  |
Investment in unconsolidated subsidiaries | $ 38,300 |  | 40,200 |
Tax Credit Partnerships Less Than 20% Ownership [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Investment in unconsolidated subsidiaries | 60,700 |  | 62,100 |
Other Limited Partnerships and Limited Liability Company, Not Considered Investment Funds [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Investment in unconsolidated subsidiaries | $ 20,700 |  | 22,400 |
Other Limited Partnerships and Limited Liability Company, Greater Than 25% Ownership [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Equity method investment ownership percentage | 25.00% |  |  |
Investment in unconsolidated subsidiaries | $ 20,800 |  | 18,500 |
Other Limited Partnerships and Limited Liability Company Less than 25% Ownership [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Investment in unconsolidated subsidiaries | $ 199,600 |  | $ 208,600 |
Maximum [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Period for federal home loan bank stock liquidation process | 5 years |  |  |
Maximum [Member] | Tax Credit Partnerships Almost 100% Ownership [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Equity method investment ownership percentage | 100.00% |  |  |
Maximum [Member] | Tax Credit Partnerships Less Than 20% Ownership [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Equity method investment ownership percentage | 20.00% |  |  |
Fixed maturities [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Required FAL Deposit | $ 96,700 |  |  |
Short-term investments [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Required FAL Deposit | $ 1,000 |  |  |
Non Government-Backed [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Number of debt securities in unrealized loss position | Security | 587 |  | 703 |
Debt securities in unrealized loss position as percentage of total debt securities held | 23.20% |  | 27.20% |
Number of issuers in unrealized loss position | Issuer | 397 |  | 456 |
Single greatest unrealized loss position | $ 500 |  | $ 500 |
Second greatest unrealized loss position | 400 |  | 500 |
Corporate debt [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Portion of noncredit OTTI losses recognized in OCI | 248 | $ 1,068 |  |
Credit-related other-than-temporary impairment recognized in earnings |  |  | $ 5,500 |
Debt securities, number of issuers | Issuer |  | 10 |  |
Corporate bonds [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Net impairment losses recognized in earnings |  | $ 6,500 |  |
Portion of noncredit OTTI losses recognized in OCI |  | 900 |  |
Other investments [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Net impairment losses recognized in earnings |  | $ 3,100 |  |
Revolving Credit Facility [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Securities pledged as collateral | $ 246,500 |  |  |

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