Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income		$ 231,092	$ 190,455	$ 317,369
Components of other comprehensive income (loss)
Unrealized holding gains (losses), net, arising on available-for-sale fixed maturity investments		20,295	(643,880)	586,458
Unrealized holding gains (losses), net, arising on cash flow hedges		44,776	31,061	20,137
Reclassification adjustment for (gains) losses, net, realized in net income		74,271	52,597	56,159
Net unrealized gains (losses) related to investments		(9,200)	(665,416)	550,436
Future policy benefits, DAC and VOBA adjustments		10,983	65,245	(58,760)
Employee benefit plan adjustment		1,966	31,586	(95,886)
Other, net		12,949	96,831	(154,646)
Other comprehensive income (loss) before income taxes		3,749	(568,585)	395,790
Income tax expense (benefit) related to items of other comprehensive income		1,312	(199,005)	138,526
Net current period other comprehensive income (loss)	[1]	2,437	(369,580)	257,264
Total comprehensive income (loss)		$ 233,529	$ (179,125)	$ 574,633

[1] Other comprehensive income (loss) includes the non-credit component of impaired losses on fixed maturities available-for-sale, net of future policy benefits, DAC and VOBA adjustments and income taxes, in the amounts of $(6,520), $(6,596), and $177 for the years ended December 31, 2016, 2015, and 2014, respectively.