Condensed Statements of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net earnings	$ 460,664	$ 562,195	$ 680,132
Adjustments to reconcile net earnings to net cash provided by (used in) operating activities:
Depreciation and amortization	160,469	163,062	178,949
Net realized capital (gains) losses	(63,205)	(213,897)	(247,058)
Other than temporary impairment losses	45,165	133,868	36,294
Net adjustments	332,263	(236,217)	(307,353)
Net cash (used in) provided by operating activities	792,927	325,978	372,779
Cash flows from investing activities
Purchases of equity securities	(2,093,644)	(3,496,203)	(1,521,201)
Sales of debt securities	4,895,282	6,377,573	5,558,948
Maturities and redemptions of debt securities	1,512,879	1,653,606	1,437,988
Sales of equity securities	2,067,095	3,172,826	1,043,181
Net (purchase) sale in short-term investments	(442,784)	326,765	624,209
Purchases of property and equipment	(24,005)	(27,258)	(43,681)
Other, net	(29,861)	(26,820)	(257,090)
Net cash provided by (used in) investing activities	(672,727)	171,658	51,035
Cash flows from financing activities
Proceeds from issuance of senior notes			297,942
Debt issue costs paid			(3,625)
Treasury stock acquisitions	(68,320)	(243,814)	(300,478)
Other, net	50,906	2,033	22,674
Net cash provided by (used in) financing activities	(17,414)	(608,783)	(302,075)
Effect of exchange rate changes on cash	16,038	(18,845)	(14,795)
Net (decrease) increase in cash	118,824	(129,992)	106,944
Cash at beginning of period	475,267	605,259	498,315
Cash at end of period	594,091	475,267	605,259
Cash paid during the period for:
Interest paid	80,817	102,146	100,977
Income taxes paid (refunds received)	83,023	59,699	335,050
Parent Company
Cash flows from operating activities
Net earnings	460,664	562,195	680,132
Adjustments to reconcile net earnings to net cash provided by (used in) operating activities:
Equity in undistributed net (earnings) losses of consolidated subsidiaries	(524,201)	(628,747)	(722,445)
Depreciation and amortization	2,035	1,949	1,845
Net realized capital (gains) losses	10,674	9,088	(14,349)
Other than temporary impairment losses		2,388
Increase (decrease) in other liabilities and taxes payable	14,677	38,065	22,654
Net adjustments	(496,815)	(577,257)	(712,295)
Net cash (used in) provided by operating activities	(36,151)	(15,062)	(32,163)
Cash flows from investing activities
Purchases of equity securities	(132,129)	(440,143)	(226,418)
Sales of debt securities		39,548
Maturities and redemptions of debt securities	73	89	121
Sales of equity securities	166,634	256,502	216,951
Net (purchase) sale in short-term investments	(152,375)	69,808	(74,842)
Purchases of property and equipment	(5,779)	(4)	(158)
Other, net	(37,600)	259	383
Net cash provided by (used in) investing activities	(161,176)	(73,941)	(83,963)
Cash flows from financing activities
Proceeds from issuance of senior notes			297,942
Debt issue costs paid			(3,625)
Treasury stock acquisitions	(68,320)	(243,814)	(300,478)
Capital contributions to consolidated subsidiaries	(163,732)	(175,635)	(453,551)
Distributions from consolidated subsidiaries	434,900	497,283	566,723
Other, net	(1,859)	3,111	2,294
Net cash provided by (used in) financing activities	200,989	80,945	109,305
Effect of exchange rate changes on cash	0	0	0
Net (decrease) increase in cash	3,662	(8,058)	(6,821)
Cash at beginning of period	2,477	10,535	17,356
Cash at end of period	6,139	2,477	10,535
Cash paid during the period for:
Interest paid	51,375	51,620	36,675
Income taxes paid (refunds received)	$ 37,220	$ (8,523)	$ 221,309