Schedule II - Condensed Financial Information of Registrant (Condensed Statements of Operations) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Net investment income	$ 178,284	$ 176,656	$ 177,964	$ 176,839	$ 174,947	$ 169,400	$ 175,176	$ 174,121	$ 709,743	$ 693,644	$ 693,028
Realized investment gains (losses)	1,525	4,459	5,913	(3,907)	20,883	7,283	4,661	5,006	7,990	37,833	25,904
Total revenue	930,594	932,789	950,339	958,216	928,698	877,100	885,795	897,923	3,771,938	3,589,516	3,377,401
General operating expenses									214,690	198,176	201,636
Interest expense									80,461	80,512	77,908
Total benefits and expenses									3,008,812	2,823,523	2,653,619
Operating income (loss) before income taxes and equity in earnings of affiliates	206,429	190,850	192,784	173,063	220,587	188,791	186,380	170,235	763,126	765,993	723,782
Income taxes									234,654	236,669	226,166
Net income	142,817	132,122	133,901	119,632	150,987	130,672	128,988	118,677	528,472	529,324	497,161
Other comprehensive income (loss):
Comprehensive income (loss)									(185,822)	904,683	1,023,985
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net investment income									24,268	22,968	23,542
Realized investment gains (losses)									0	(3,534)	508
Total revenue									24,268	19,434	24,050
General operating expenses									53,255	49,549	30,945
Reimbursements from affiliates									(46,855)	(31,184)	(19,335)
Interest expense									84,273	81,145	75,426
Total benefits and expenses									90,673	99,510	87,036
Operating income (loss) before income taxes and equity in earnings of affiliates									(66,405)	(80,076)	(62,986)
Income taxes									17,390	24,916	14,380
Net operating loss before equity in earnings of affiliates									(49,015)	(55,160)	(48,606)
Equity in earnings of affiliates									577,487	584,484	545,767
Net income									528,472	529,324	497,161
Other comprehensive income (loss):
Attributable to Parent Company									38,557	(31,388)	(5,410)
Attributable to affiliates									(752,851)	406,747	532,234
Comprehensive income (loss)									$ (185,822)	$ 904,683	$ 1,023,985