Investments - Aging of Unrealized Losses on Investments in Fixed Maturities and Equity Securities (Details) (USD $)	12 Months Ended
	Dec. 31, 2012 issuer	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Other Receivables	$ 206,100,000	$ 193,100,000
Less than Twelve Months, Fair Value	343,900,000	1,199,100,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses Accumulated in Investments	(7,600,000)	(76,000,000)
Twelve Months or Longer, Fair Value	54,600,000	119,600,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses Accumulated in Investments	(3,800,000)	(9,900,000)
Available-for-sale-Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Securities that have had Recognized Credit Losses in Earnings, Aggregate Losses	(300,000)	0
Available For Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Securities that have had Recognized Credit Losses in Earnings, Aggregate Losses	0	(300,000)
Fair Value	398,500,000	1,318,700,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses Accumulated in Investments	(11,400,000)	(85,900,000)
Available For Sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses Related to Securities that have Previously Recognized Foregin Currency Impairment	100,000
US Government and Government Agencies and Authorities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	40,800,000	95,800,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses Accumulated in Investments	(200,000)	(10,900,000)
Twelve Months or Longer, Fair Value	0	4,400,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses Accumulated in Investments	0	(800,000)
Fair Value	40,800,000	100,200,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses Accumulated in Investments	(200,000)	(11,700,000)
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	6,300,000	222,900,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses Accumulated in Investments	(100,000)	(20,100,000)
Twelve Months or Longer, Fair Value	300,000	2,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses Accumulated in Investments	0	(100,000)
Fair Value	6,600,000	224,900,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses Accumulated in Investments	(100,000)	(20,200,000)
Corporate Bonds and Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	268,500,000	699,800,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses Accumulated in Investments	(5,200,000)	(39,400,000)
Twelve Months or Longer, Fair Value	38,100,000	103,200,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses Accumulated in Investments	(2,300,000)	(8,300,000)
Fair Value	306,600,000	803,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses Accumulated in Investments	(7,500,000)	(47,700,000)
Investments in Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Other Receivables	0	2,500,000
Less than Twelve Months, Fair Value	315,600,000	1,032,400,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses Accumulated in Investments	(5,500,000)	(70,500,000)
Twelve Months or Longer, Fair Value	40,500,000	110,700,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses Accumulated in Investments	(2,600,000)	(9,200,000)
Fair Value	356,100,000	1,143,100,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses Accumulated in Investments	(8,100,000)	(79,700,000)
Redeemable Preferred Stocks [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses Accumulated in Investments	0
Twelve Months or Longer, Fair Value	400,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses Accumulated in Investments	0
Fair Value	400,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses Accumulated in Investments	0
Mortgage and Asset Backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	0	13,900,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses Accumulated in Investments	0	(100,000)
Twelve Months or Longer, Fair Value	1,700,000	1,100,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses Accumulated in Investments	(300,000)	0
Fair Value	1,700,000	15,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses Accumulated in Investments	(300,000)	(100,000)
Preferred Stocks Finance, Insurance and Real Estate [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	0	22,500,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses Accumulated in Investments	0	(2,500,000)
Twelve Months or Longer, Fair Value	2,400,000	2,500,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses Accumulated in Investments	(100,000)	0
Fair Value	2,400,000	25,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses Accumulated in Investments	(100,000)	(2,500,000)
Preferred Stocks Other Industries [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	2,300,000	4,300,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses Accumulated in Investments	(800,000)	(100,000)
Twelve Months or Longer, Fair Value	3,700,000	700,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses Accumulated in Investments	(100,000)	0
Fair Value	6,000,000	5,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses Accumulated in Investments	(900,000)	(100,000)
Common Stocks Manufacturing [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	6,300,000	5,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses Accumulated in Investments	(400,000)	(100,000)
Twelve Months or Longer, Fair Value	0	200,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses Accumulated in Investments	0	0
Fair Value	6,300,000	5,200,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses Accumulated in Investments	(400,000)	(100,000)
Common Stock Other Industries [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	14,200,000	14,200,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses Accumulated in Investments	(400,000)	(900,000)
Twelve Months or Longer, Fair Value	1,300,000	500,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses Accumulated in Investments	(100,000)	0
Fair Value	15,500,000	14,700,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses Accumulated in Investments	(500,000)	(900,000)
Exchange Traded Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value		67,600,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses Accumulated in Investments		(1,000,000)
Twelve Months or Longer, Fair Value		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses Accumulated in Investments		0
Fair Value		67,600,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses Accumulated in Investments		(1,000,000)
Limited Liability Companies and Limited Partnerships [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	5,500,000	53,100,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses Accumulated in Investments	(500,000)	(900,000)
Twelve Months or Longer, Fair Value	6,700,000	5,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses Accumulated in Investments	(900,000)	(700,000)
Fair Value	12,200,000	58,100,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses Accumulated in Investments	(1,400,000)	(1,600,000)
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	28,300,000	166,700,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses Accumulated in Investments	(2,100,000)	(5,500,000)
Twelve Months or Longer, Fair Value	14,100,000	8,900,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses Accumulated in Investments	(1,200,000)	(700,000)
Fair Value	42,400,000	175,600,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses Accumulated in Investments	(3,300,000)	(6,200,000)
External Credit Rating, Investment Grade [Member] | Investments in Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses Accumulated in Investments	(3,800,000)	(74,200,000)
External Credit Rating, Non Investment Grade [Member] | Investments in Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses Accumulated in Investments	(4,300,000)	(5,500,000)
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Related to Securities that have Previously Recognized Foregin Currency Impairment	$ (100,000)
Number of Issuers of Available for Sales Securities Continuous Unrealized Loss Possition Aggregate Losses Related to Securities that have Previously Recognized Foreign Currency impairment	1
Percentage of Unrealized Loss Postion to Amortized Cost Basis of Available for Sale Security Average	3.00%	5.00%