Investments in Unconsolidated Affiliates (Symetra) (Details) - USD ($)		3 Months Ended
	Feb. 01, 2016	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Investments in unconsolidated affiliates
Equity in earnings of unconsolidated affiliates, net of tax		$ 0		$ 7,300,000
Unrealized gains (losses) on investments		(230,100,000)		15,200,000
Revenues		427,100,000		391,800,000
Total expenses		415,600,000		391,300,000
Pre-tax (loss) income		11,500,000		500,000
Net income		19,300,000		77,000,000
Trading Securities Unrealized Holding Gain (Loss) on Investments after Tax		(195,700,000)		12,600,000
Sales of common equity securities		$ 767,500,000		59,900,000
Common shares, par value per share (in dollars per share)		$ 1.00	$ 1.00
Net realized and unrealized investment gains		$ 29,500,000		$ 25,000,000
Symetra
Investments in unconsolidated affiliates
Unrealized gains (losses) on investments			$ 258,800,000
Term of amortization (in years)				30 years
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity				$ 165,700,000
Trading Securities Unrealized Holding Gain (Loss) on Investments after Tax			$ 241,100,000
Sales of common equity securities	$ 658,000,000
Common shares, par value per share (in dollars per share)	$ 32.00
Net realized and unrealized investment gains		$ 4,700,000.00
Common Stock | Symetra
Investments in unconsolidated affiliates
Equity in earnings of unconsolidated affiliates, net of tax				7,200,000
Proceeds from Equity Method Investment, Dividends or Distributions				2,200,000
equity in earnings of unconsolidated affiliates | Symetra
Investments in unconsolidated affiliates
After tax amortization through equity in earnings				700,000
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity				35,100,000
Net unrealized gains (losses) of unconsolidated affiliates | Symetra
Investments in unconsolidated affiliates
After tax amortization through equity in net unrealized losses				2,800,000
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity				130,600,000
Expected [Member] | Symetra
Investments in unconsolidated affiliates
Dividends Payable, Amount Per Share		$ 32.00
Amortization of common share basis difference | Common Stock | Symetra
Investments in unconsolidated affiliates
Equity in earnings of unconsolidated affiliates, net of tax		$ 2,015		$ 700,000