Revision to Prior Year Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
REVENUES
Policy charges and fee income	$ 139,189	$ 129,155
TOTAL REVENUES	222,412	188,712
BENEFITS AND EXPENSES
Policyholders’ benefits	39,478	51,736
Amortization of deferred policy acquisition costs	19,179	26,145
TOTAL BENEFITS AND EXPENSES	150,798	179,469
INCOME (LOSS) FROM OPERATIONS BEFORE INCOME TAXES AND EQUITY IN EARNINGS OF OPERATING JOINT VENTURE	71,614	9,243
Income tax expense (benefit)	(16,880)	(2,699)
INCOME (LOSS) FROM OPERATIONS BEFORE EQUITY IN EARNINGS OF OPERATING JOINT VENTURE	88,494	11,942
Net income (loss)	87,788	11,304
COMPREHENSIVE INCOME (LOSS)	220,289	(103,970)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	87,788	11,304
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	87,788	11,304
Policy charges and fee income	(28,634)	(23,697)
Future policy benefits	437,726	508,412
Reinsurance recoverables	(423,868)	(424,467)
Deferred policy acquisition costs	(74,610)	(45,642)
Income taxes	(16,996)	(2,902)
Other, net	(83,032)	(97,354)
Cash flows from (used in) operating activities	27,984	(7,769)
As previously reported
REVENUES
Policy charges and fee income		125,896
TOTAL REVENUES		185,453
BENEFITS AND EXPENSES
Policyholders’ benefits		48,955
Amortization of deferred policy acquisition costs		26,604
TOTAL BENEFITS AND EXPENSES		177,147
INCOME (LOSS) FROM OPERATIONS BEFORE INCOME TAXES AND EQUITY IN EARNINGS OF OPERATING JOINT VENTURE		8,306
Income tax expense (benefit)		(2,448)
INCOME (LOSS) FROM OPERATIONS BEFORE EQUITY IN EARNINGS OF OPERATING JOINT VENTURE		10,754
Net income (loss)		10,116
COMPREHENSIVE INCOME (LOSS)		(105,158)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		10,116
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)		10,116
Policy charges and fee income		(24,173)
Future policy benefits		511,380
Reinsurance recoverables		(430,215)
Deferred policy acquisition costs		(45,184)
Income taxes		(2,651)
Other, net		(93,619)
Cash flows from (used in) operating activities		(7,769)
Revision
REVENUES
Policy charges and fee income		3,259
TOTAL REVENUES		3,259
BENEFITS AND EXPENSES
Policyholders’ benefits		2,781
Amortization of deferred policy acquisition costs		(459)
TOTAL BENEFITS AND EXPENSES		2,322
INCOME (LOSS) FROM OPERATIONS BEFORE INCOME TAXES AND EQUITY IN EARNINGS OF OPERATING JOINT VENTURE		937
Income tax expense (benefit)		(251)
INCOME (LOSS) FROM OPERATIONS BEFORE EQUITY IN EARNINGS OF OPERATING JOINT VENTURE		1,188
Net income (loss)		1,188
COMPREHENSIVE INCOME (LOSS)		1,188
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		1,188
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)		1,188
Policy charges and fee income		476
Future policy benefits		(2,968)
Reinsurance recoverables		5,748
Deferred policy acquisition costs		(458)
Income taxes		(251)
Other, net		(3,735)
Cash flows from (used in) operating activities		0
Retained Earnings
BENEFITS AND EXPENSES
Net income (loss)	87,788	11,304
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	1,612,435	1,526,310
Net income (loss)	87,788	11,304
Ending Balance	1,699,109	1,515,151
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	87,788	11,304
Retained Earnings | As previously reported
BENEFITS AND EXPENSES
Net income (loss)		10,116
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance		1,511,698
Net income (loss)		10,116
Ending Balance		1,499,351
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)		10,116
Retained Earnings | Revision
BENEFITS AND EXPENSES
Net income (loss)		1,188
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance		14,612
Net income (loss)		1,188
Ending Balance		15,800
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)		1,188
Total Equity
BENEFITS AND EXPENSES
Net income (loss)	87,788	11,304
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	2,733,231	2,835,248
Net income (loss)	87,788	11,304
Total comprehensive income (loss)	220,289	(103,970)
Ending Balance	2,952,402	2,743,175
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 87,788	11,304
Total Equity | As previously reported
BENEFITS AND EXPENSES
Net income (loss)		10,116
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance		2,820,636
Net income (loss)		10,116
Total comprehensive income (loss)		(105,158)
Ending Balance		2,727,375
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)		10,116
Total Equity | Revision
BENEFITS AND EXPENSES
Net income (loss)		1,188
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance		14,612
Net income (loss)		1,188
Total comprehensive income (loss)		1,188
Ending Balance		15,800
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)		$ 1,188