Investments (Net Unrealized Gains Losses on Investments by Asset Class) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Gain (Loss) on Securities [Line Items]
Net unrealized gains (losses) on investments	$ 198,692	$ 116,039
Fixed maturities | Available-for-sale | OTTI
Gain (Loss) on Securities [Line Items]
Net unrealized gains (losses) on investments		51
Fixed maturities | Available-for-sale | All Other
Gain (Loss) on Securities [Line Items]
Net unrealized gains (losses) on investments		112,249
Fixed maturities | Available-for-sale | With an allowance
Gain (Loss) on Securities [Line Items]
Net unrealized gains (losses) on investments	0
Fixed maturities | Available-for-sale | Without an allowance
Gain (Loss) on Securities [Line Items]
Net unrealized gains (losses) on investments	184,549
Derivatives designated as cash flow hedges
Gain (Loss) on Securities [Line Items]
Net unrealized gains (losses) on investments	13,596	3,193
Affiliated notes
Gain (Loss) on Securities [Line Items]
Net unrealized gains (losses) on investments	508	480
Other investments
Gain (Loss) on Securities [Line Items]
Net unrealized gains (losses) on investments	$ 39	$ 66