Securities In An Unrealized Loss Position Non-Investment Grade Fixed Maturity Securities (Details)	Jun. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	$ 3,656,084,000	$ 2,895,204,000
Available For Sale Equity Securities Gross Unrealized Gains	12,022,000	20,314,000
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	95,535,000	69,142,000
Preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	36,242,000	49,774,000
Available For Sale Equity Securities Gross Unrealized Gains	12,022,000	8,385,000
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	4,283,000	4,165,000
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	47,359,000	15,929,000
Available For Sale Equity Securities Gross Unrealized Gains	0	11,929,000
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	10,669,000	5,453,000
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	434,899,000	388,661,000
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	10,607,000	9,501,000
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	1,829,576,000	1,800,866,000
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	33,428,000	24,781,000
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	982,360,000	308,878,000
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	16,061,000	4,020,000
Foreign government
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	179,755,000	161,496,000
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	$ 16,932,000	$ 18,065,000
Noninvestment Grade Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities	8
Noninvestment Grade Investments at Loss Less than 5 Million [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities	20
Aggregate fair value of securities in a continuous unrealized loss position	$ 114,366,000
Gross Unrealized Loss	$ 4,091,000
Noninvestment Grade Investments at Loss Less than 5 Million [Member] | Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Number of Securities	7
Aggregate fair value of securities in a continuous unrealized loss position	$ 24,150,000
Gross Unrealized Loss	$ 1,605,000
Noninvestment Grade Investments at Loss Less than 5 Million [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities	13
Aggregate fair value of securities in a continuous unrealized loss position	$ 90,216,000
Gross Unrealized Loss	2,486,000
Preferred stocks | Noninvestment Grade Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	3,600,000
Available For Sale Equity Securities Gross Unrealized Gains	$ 1,200,000