Employee Benefit Plans Employee Benefits Plan (Fair value of plan assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	$ 453,087	$ 427,131	$ 443,962
Limited partnership interests | Significant unobservable inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	1,316	0	0
Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	453,087	427,131	$ 443,962
Recurring basis | Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	451,344	427,131
Recurring basis | Defined Benefit Pension Plan | Quoted prices in active markets for identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	95,950	2,764
Recurring basis | Defined Benefit Pension Plan | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	176,156	130,713
Recurring basis | Defined Benefit Pension Plan | Significant unobservable inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	1,316	0
Recurring basis | Defined Benefit Pension Plan | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	34,578	94,751
Recurring basis | Defined Benefit Pension Plan | Equity securities | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1		0
Recurring basis | Defined Benefit Pension Plan | Midcap index funds
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	35,330	88,267
Recurring basis | Defined Benefit Pension Plan | Midcap index funds | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1		0
Recurring basis | Defined Benefit Pension Plan | World equity index funds
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	44,235	8,511
Recurring basis | Defined Benefit Pension Plan | World equity index funds | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1		0
Recurring basis | Defined Benefit Pension Plan | U.S. equity market funds
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	45,614	94,471
Recurring basis | Defined Benefit Pension Plan | U.S. equity market funds | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1		0
Recurring basis | Defined Benefit Pension Plan | International equity funds
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	11,143
Recurring basis | Defined Benefit Pension Plan | Total common collective trust funds
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	170,900	286,000
Recurring basis | Defined Benefit Pension Plan | Total common collective trust funds | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1		0
Recurring basis | Defined Benefit Pension Plan | U.S. government direct obligations and U.S. agencies
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	5,672	6,753
Recurring basis | Defined Benefit Pension Plan | U.S. government direct obligations and U.S. agencies | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	5,672	6,753
Recurring basis | Defined Benefit Pension Plan | Obligations of U.S. states and their subdivisions
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	18,670	19,074
Recurring basis | Defined Benefit Pension Plan | Obligations of U.S. states and their subdivisions | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	18,670	19,074
Recurring basis | Defined Benefit Pension Plan | Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	142,418	93,811
Recurring basis | Defined Benefit Pension Plan | Corporate debt securities | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	141,102	93,811
Recurring basis | Defined Benefit Pension Plan | Corporate debt securities | Significant unobservable inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	1,316
Recurring basis | Defined Benefit Pension Plan | Asset-backed securities
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	7,828	8,149
Recurring basis | Defined Benefit Pension Plan | Asset-backed securities | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	7,828	8,149
Recurring basis | Defined Benefit Pension Plan | Commercial mortgage-backed securities
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	2,884	2,926
Recurring basis | Defined Benefit Pension Plan | Commercial mortgage-backed securities | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	2,884	2,926
Recurring basis | Defined Benefit Pension Plan | Total fixed maturity investments
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	177,472	130,713
Recurring basis | Defined Benefit Pension Plan | Total fixed maturity investments | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	176,156	130,713
Recurring basis | Defined Benefit Pension Plan | Total fixed maturity investments | Significant unobservable inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	1,316
Recurring basis | Defined Benefit Pension Plan | Fixed income mutual funds
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	21,321
Recurring basis | Defined Benefit Pension Plan | Fixed income mutual funds | Quoted prices in active markets for identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	21,321
Recurring basis | Defined Benefit Pension Plan | Equity mutual funds
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	11,106
Recurring basis | Defined Benefit Pension Plan | Equity mutual funds | Quoted prices in active markets for identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	11,106
Recurring basis | Defined Benefit Pension Plan | Preferred stock
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	640	280
Recurring basis | Defined Benefit Pension Plan | Preferred stock | Quoted prices in active markets for identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	640	280
Recurring basis | Defined Benefit Pension Plan | Total equity investments
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	33,067
Recurring basis | Defined Benefit Pension Plan | Total equity investments | Quoted prices in active markets for identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	33,067
Recurring basis | Defined Benefit Pension Plan | Limited partnership interests
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	7,022	7,654
Recurring basis | Defined Benefit Pension Plan | Limited partnership interests | Significant unobservable inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1		0
Recurring basis | Defined Benefit Pension Plan | Money market funds
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	62,883	2,484
Recurring basis | Defined Benefit Pension Plan | Money market funds | Quoted prices in active markets for identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	$ 62,883	$ 2,484