Adoption of New Accounting Standards (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net investment income	$ 193,213	$ 189,588	$ 579,632	$ 567,569
Total revenue	998,759	974,488	3,054,985	2,989,695
Income before income taxes	216,744	197,051	585,564	588,400
Income taxes	(71,358)	(64,639)	(191,420)	(192,209)
Net income	$ 145,386	132,412	$ 394,144	396,191
As previously reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net investment income		182,101		545,978
Total revenue		967,001		2,968,104
Income before income taxes		189,564		566,809
Income taxes		(57,152)		(170,618)
Net income		132,412		396,191
Adjustments [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net investment income		7,487		21,591
Total revenue		7,487		21,591
Income before income taxes		7,487		21,591
Income taxes		(7,487)		(21,591)
Net income		$ 0		$ 0