CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fixed Maturity Securities [Abstract]
Available-for-sale at fair value (amortized cost of $35,281,412 and $30,211,787)	$ 38,150,820	$ 32,093,625
Mortgage loans on real estate (net of allowances of $9,384 and $7,685)	4,400,533	3,775,522
Policy loans	1,357,624	1,427,602
Funds withheld at interest	6,083,388	5,875,919
Short-term investments	93,304	76,710
Other invested assets	1,605,484	1,591,940
Total investments	51,691,153	44,841,318
Cash and cash equivalents	1,303,524	1,200,718
Accrued investment income	392,721	347,173
Premiums receivable and other reinsurance balances	2,338,481	1,930,755
Reinsurance ceded receivables	782,027	683,972
Deferred policy acquisition costs	3,239,824	3,338,605
Other assets	767,088	755,338
Total assets	60,514,818	53,097,879
Liabilities and Stockholders’ Equity
Future policy benefits	22,363,241	19,581,573
Interest-sensitive contract liabilities	16,227,642	14,029,354
Other policy claims and benefits	4,992,074	4,263,026
Other reinsurance balances	488,739	388,989
Deferred income taxes	2,198,309	2,770,640
Other liabilities	1,102,975	1,041,880
Long-term debt	2,788,365	3,088,635
Collateral finance and securitization notes	783,938	840,700
Total liabilities	50,945,283	46,004,797
Commitments and contingent liabilities (See Note 12)
Stockholders Equity:
Preferred stock (par value $.01 per share; 10,000,000 shares authorized; no shares issued or outstanding)	0	0
Common stock (par value $.01 per share; 140,000,000 shares authorized; shares issued: 79,137,758 at December 31, 2017 and 2016)	791	791
Additional paid-in-capital	1,870,906	1,848,611
Retained earnings	6,736,265	5,199,130
Treasury stock, at cost - 14,685,663 and 14,835,256 shares	(1,102,058)	(1,094,779)
Accumulated other comprehensive income	2,063,631	1,139,329
Total stockholders’ equity	9,569,535	7,093,082
Total liabilities and stockholders’ equity	$ 60,514,818	$ 53,097,879