Selected Quarterly Data (Schedule Of Selected Quarterly Data) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2010		Sep. 30, 2010		Jun. 30, 2010		Mar. 31, 2010		Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Premium and policy charges	$ 653,542		$ 650,525		$ 672,350		$ 679,901		$ 653,418		$ 657,827		$ 669,569		$ 670,944		$ 2,656,318		$ 2,651,758		$ 2,610,105
Net investment income	174,786		173,491		173,104		171,647		166,304		172,337		170,612		167,111		693,028		676,364		632,540
Realized investment gains (losses)	4,755		12,600		31,272		(22,723)		27,036		8,045		(5,002)		7,261		25,924		42,190		13,879
Total revenue	833,554		837,241		877,334		829,272		847,171		838,888		835,895		845,678		3,377,401		3,367,632		3,115,073
Policy benefits	435,681		438,774		454,694		464,127		436,419		433,514		454,177		468,934		1,793,276		1,793,044		1,753,329
Amortization of acquisition costs	105,437		104,804		106,752		107,788		100,392		104,045		104,851		109,602		424,781		418,890		415,986
Pretax Income from continuing operations	182,504		198,822		218,528		155,812		215,480		208,313		180,720		174,054		755,666		778,567		577,076
Income from continuing operations	126,357		136,911		148,940		106,132		148,955		138,097		119,848		115,393		518,340		522,293		386,052
Income from discontinued operations	0		144		0		(599)		5,853		(23,566)		6,201		6,283		(455)		(5,229)		18,901
Net income	126,357		137,055		148,940		105,533		154,808		114,531		126,049		121,676		517,885		517,064	[1]	404,953
Continuing operations	$ 1.25	[2]	$ 1.31	[2]	$ 1.34	[2]	$ 0.91	[2]	$ 1.24	[2]	$ 1.14	[2]	$ 0.97	[2]	$ 0.93	[2]	$ 4.79	[3]	$ 4.28	[3]	$ 3.10	[3]
Discontinued operations	$ 0.00	[2]	$ 0.00	[2]	$ 0.00	[2]	$ (0.01)	[2]	$ 0.05	[2]	$ (0.19)	[2]	$ 0.05	[2]	$ 0.05	[2]	$ (0.01)	[3]	$ (0.04)	[3]	$ 0.15	[3]
Total basic net income per share	$ 1.25	[2]	$ 1.31	[2]	$ 1.34	[2]	$ 0.90	[2]	$ 1.29	[2]	$ 0.95	[2]	$ 1.02	[2]	$ 0.98	[2]	$ 4.78	[3]	$ 4.24	[3]	$ 3.25	[3]
Continuing operations	$ 1.23	[2]	$ 1.30	[2]	$ 1.32	[2]	$ 0.89	[2]	$ 1.23	[2]	$ 1.13	[2]	$ 0.97	[2]	$ 0.92	[2]	$ 4.72	[3]	$ 4.24	[3]	$ 3.10	[3]
Discontinued operations	$ 0.00	[2]	$ 0.00	[2]	$ 0.00	[2]	$ 0.00	[2]	$ 0.05	[2]	$ (0.19)	[2]	$ 0.05	[2]	$ 0.05	[2]	$ 0.00	[3]	$ (0.04)	[3]	$ 0.15	[3]
Total diluted net income per share	$ 1.23	[2]	$ 1.30	[2]	$ 1.32	[2]	$ 0.89	[2]	$ 1.28	[2]	$ 0.94	[2]	$ 1.02	[2]	$ 0.97	[2]	$ 4.72	[3]	$ 4.20	[3]	$ 3.25	[3]
Parent Company [Member]
Net investment income																	23,542		26,031		17,374
Realized investment gains (losses)																	508		(1,646)		(1)
Total revenue																	24,050		24,385		17,373
Pretax Income from continuing operations																	(62,986)		(58,749)		(66,460)
Net income																	$ 517,885		$ 517,064		$ 404,953

[1] During 2011, management changed the definition of total segment profits before tax to exclude the amortization of low-income housing interests, which management views as a tax expense. Accordingly, the 2010 total segment profits before tax and applicable tax amount have been updated for comparison purposes.

[2] Basic and diluted net income per share by quarter may not add to per share income on a year-to-date basis due to share weighting and rounding.

[3] Per share amounts have been retroactively adjusted for stock split described in Note 1.