Quarterly Results of Operations (Unaudited) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
QuarterlyFinancialDataAbstract
Total revenues	$ 311,187	$ 308,006	$ 309,786	$ 311,249	$ 286,154	$ 250,028	$ 283,524	$ 290,576	$ 1,240,228	$ 1,110,282	$ 1,279,561
Total benefits and expenses	324,387	197,204	242,370	216,896	72,431	(332,523)	96,720	93,190	980,857	(70,182)	421,868
Income Loss From Continuing Operations Before Income Taxes And Operating Joint Ventures	(13,200)	110,802	67,416	94,353	213,723	582,551	186,804	197,386	259,371	1,180,464	857,693
Net income	$ 19,801	$ 96,037	$ 57,431	$ 77,498	$ 156,738	$ 400,296	$ 143,670	$ 147,388	$ 250,767	$ 848,092	$ 634,059