Realized and Unrealized Investment Gains and Losses (Change in Unrealized Gains (Losses) of Available For Sales Securities) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Realized and Unrealized Investment Gains Losses [Line Items]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, No Previous Impairment			$ 0
Total change in unrealized gains (losses) before income taxes and noncontrolling interests	$ 371,715,000	$ (192,186,000)	72,889,000
Income tax benefit (expense)	(125,315,000)	66,644,000	(23,223,000)
Noncontrolling interests	59,000	38,000	(33,000)
Total change in unrealized gains and losses	246,459,000	(125,504,000)	49,633,000
Debt Securities
Realized and Unrealized Investment Gains Losses [Line Items]
Total change in unrealized gains (losses) before income taxes and noncontrolling interests	(107,094,000)	(144,445,000)	155,765,000
Debt Securities Previously Impaired
Realized and Unrealized Investment Gains Losses [Line Items]
Total change in unrealized gains (losses) before income taxes and noncontrolling interests	451,000	(174,000)	865,000
Equity securities available for sale
Realized and Unrealized Investment Gains Losses [Line Items]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, No Previous Impairment	18,100,000	24,300,000
Total change in unrealized gains (losses) before income taxes and noncontrolling interests	465,727,000	(27,809,000)	(69,016,000)
Investment funds
Realized and Unrealized Investment Gains Losses [Line Items]
Total change in unrealized gains (losses) before income taxes and noncontrolling interests	$ 12,631,000	$ (19,758,000)	$ (14,725,000)