Fair Value of Financial Instruments - Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	$ 1,779,298	$ 1,812,510
Trading securities	$ 5,358	7,711
Fair value assumptions, percentage of securities assessed by third-party pricing service	95.00%
Fair Value, Recurring Measurements [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Trading securities	$ 5,358	7,711
Assets, fair value disclosure, recurring	3,848,555	4,260,524
Liabilities, fair value disclosure, recurring	2,063,899	2,440,303
Fair Value, Recurring Measurements [Member] \| Level 1 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure, recurring	43,487	49,273
Fair Value, Recurring Measurements [Member] \| Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Trading securities	5,358	7,711
Assets, fair value disclosure, recurring	3,804,285	4,210,086
Liabilities, fair value disclosure, recurring	2,063,899	2,440,303
Fair Value, Recurring Measurements [Member] \| Level 3 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure, recurring	783	1,165
Fair Value, Recurring Measurements [Member] \| U.S. Government and Agencies [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	20,659	15,647
Fair Value, Recurring Measurements [Member] \| U.S. Government and Agencies [Member] \| Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	20,659	15,647
Fair Value, Recurring Measurements [Member] \| Foreign Government [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	120,216	122,497
Fair Value, Recurring Measurements [Member] \| Foreign Government [Member] \| Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	120,216	122,497
Fair Value, Recurring Measurements [Member] \| States and Political Subdivisions [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	40,565	40,694
Fair Value, Recurring Measurements [Member] \| States and Political Subdivisions [Member] \| Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	40,565	40,694
Fair Value, Recurring Measurements [Member] \| Corporates [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	1,301,762	1,315,868
Fair Value, Recurring Measurements [Member] \| Corporates [Member] \| Level 1 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	2,146	2,104
Fair Value, Recurring Measurements [Member] \| Corporates [Member] \| Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	1,299,613	1,313,534
Fair Value, Recurring Measurements [Member] \| Corporates [Member] \| Level 3 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	3	230
Fair Value, Recurring Measurements [Member] \| Asset-backed Securities [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	248,257	264,414
Fair Value, Recurring Measurements [Member] \| Asset-backed Securities [Member] \| Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	247,525	263,527
Fair Value, Recurring Measurements [Member] \| Asset-backed Securities [Member] \| Level 3 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	732	887
Fair Value, Recurring Measurements [Member] \| Fixed-maturity Securities [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	1,731,459	1,759,120
Fair Value, Recurring Measurements [Member] \| Fixed-maturity Securities [Member] \| Level 1 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	2,146	2,104
Fair Value, Recurring Measurements [Member] \| Fixed-maturity Securities [Member] \| Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	1,728,578	1,755,899
Fair Value, Recurring Measurements [Member] \| Fixed-maturity Securities [Member] \| Level 3 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	735	1,117
Fair Value, Recurring Measurements [Member] \| Equity Securities [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	47,839	53,390
Fair Value, Recurring Measurements [Member] \| Equity Securities [Member] \| Level 1 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	41,341	47,169
Fair Value, Recurring Measurements [Member] \| Equity Securities [Member] \| Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	6,450	6,173
Fair Value, Recurring Measurements [Member] \| Equity Securities [Member] \| Level 3 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, fair value	48	48
Fair Value, Recurring Measurements [Member] \| Separate Accounts Assets, Fair Value Disclosure [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Separate accounts assets	2,063,899	2,440,303
Fair Value, Recurring Measurements [Member] \| Separate Accounts Assets, Fair Value Disclosure [Member] \| Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Separate accounts assets	2,063,899	2,440,303
Fair Value, Recurring Measurements [Member] \| Separate Accounts Liabilities [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Separate account liabilities	2,063,899	2,440,303
Fair Value, Recurring Measurements [Member] \| Separate Accounts Liabilities [Member] \| Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Separate account liabilities	$ 2,063,899	$ 2,440,303

Fair value assumptions percentage of securities assessed by third party pricing service.

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- Definition

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value on a recurring basis by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

+ References

No definition available.

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Aggregation of the liabilities reported on the balance sheet measured at fair value on a recurring basis by the entity.

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- Definition

Fair value portion of liability related to investment contracts for example, but not limited to, guaranteed investment contract or annuities.

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- Definition

Fair value portion of other assets.

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Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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