Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Fixed maturities - available for sale, amortized cost	$ 6,784,594	$ 7,032,749
Short-term investments, cost	458,165	174,155
Other invested assets, cost	$ 929,729	$ 882,647
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	3,000	3,000
Common stock, shares issued	1,000	1,000
Common stock, shares outstanding	1,000	1,000
Accumulated other comprehensive income (loss), deferred income tax expense (benefit)	$ (7,510)	$ (33,506)
Senior Notes 4.868% [Member] | Senior Notes [Member]
Debt instrument, maturity date	Jun. 01, 2044	Jun. 01, 2044
Subordinated Notes 6.6% [Member] | Long Term Subordinated Debt [Member]
Debt instrument, maturity date	May 01, 2067	May 01, 2067