Related Party Transactions (Affiliated Asset Transfers) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Related Party Transaction [Line Items]
Realized investment gains (losses)	$ (1,547)	$ 39,584	$ 8,117	$ (61,301)
Affiliated Entity | Prudential Insurance February 2019 Sale
Related Party Transaction [Line Items]
Fair Value	4,995		4,995
Book Value	5,000		5,000
APIC, Net of Tax Increase/(Decrease)	(4)		(4)
Realized investment gains (losses)			0
Affiliated Entity | PALAC April 2019 Sale
Related Party Transaction [Line Items]
Fair Value	14,525		14,525
Book Value	13,466		13,466
APIC, Net of Tax Increase/(Decrease)	0		0
Realized investment gains (losses)			1,059
Affiliated Entity | Term Re September 2019 Sale
Related Party Transaction [Line Items]
Fair Value	9,178		9,178
Book Value	8,135		8,135
APIC, Net of Tax Increase/(Decrease)	0		0
Realized investment gains (losses)			1,043
Affiliated Entity | PURC September 2019 Sale
Related Party Transaction [Line Items]
Fair Value	8,399		8,399
Book Value	7,455		7,455
APIC, Net of Tax Increase/(Decrease)	0		0
Realized investment gains (losses)			944
Affiliated Entity | PARU September 2019 Sale
Related Party Transaction [Line Items]
Fair Value	31,466		31,466
Book Value	28,146		28,146
APIC, Net of Tax Increase/(Decrease)	0		0
Realized investment gains (losses)			3,320
Affiliated Entity | Prudential Insurance September 2019 - Sale
Related Party Transaction [Line Items]
Fair Value	10,702		10,702
Book Value	9,254		9,254
APIC, Net of Tax Increase/(Decrease)	1,144		1,144
Realized investment gains (losses)			0
Affiliated Entity | PURC December 2019 Sale
Related Party Transaction [Line Items]
Fair Value	7,767		7,767
Book Value	6,002		6,002
APIC, Net of Tax Increase/(Decrease)	0		0
Realized investment gains (losses)			1,765
Affiliated Entity | PAR Term December 2019 Sale
Related Party Transaction [Line Items]
Fair Value	27,330		27,330
Book Value	24,739		24,739
APIC, Net of Tax Increase/(Decrease)	0		0
Realized investment gains (losses)			2,591
Affiliated Entity | PURC December 2019 Sale
Related Party Transaction [Line Items]
Fair Value	93,830		93,830
Book Value	75,586		75,586
APIC, Net of Tax Increase/(Decrease)	0		0
Realized investment gains (losses)			18,244
Affiliated Entity | PURC December 2019 Sale
Related Party Transaction [Line Items]
Fair Value	78,884		78,884
Book Value	68,645		68,645
APIC, Net of Tax Increase/(Decrease)	0		0
Realized investment gains (losses)			10,239
Affiliated Entity | Prudential Insurance December 2019 Purchase
Related Party Transaction [Line Items]
Fair Value	9,000		9,000
Book Value	9,000		9,000
APIC, Net of Tax Increase/(Decrease)	0		0
Realized investment gains (losses)			0
Affiliated Entity | Prudential Insurance March 2020 - Purchase
Related Party Transaction [Line Items]
Fair Value	1,390		1,390
Book Value	1,390		1,390
APIC, Net of Tax Increase/(Decrease)	0		0
Realized investment gains (losses)			0
Affiliated Entity | Prudential Insurance April 2020 - Purchase
Related Party Transaction [Line Items]
Fair Value	61,953		61,953
Book Value	59,659		59,659
APIC, Net of Tax Increase/(Decrease)	(1,812)		(1,812)
Realized investment gains (losses)			0
Affiliated Entity | Prudential Insurance April 2020 - Purchase
Related Party Transaction [Line Items]
Fair Value	3,485		3,485
Book Value	3,320		3,320
APIC, Net of Tax Increase/(Decrease)	(130)		(130)
Realized investment gains (losses)			0
Affiliated Entity | GA BV LLC July 2020 - Transfer Out
Related Party Transaction [Line Items]
Fair Value	1,914		1,914
Book Value	1,914		1,914
APIC, Net of Tax Increase/(Decrease)	$ 0		0
Realized investment gains (losses)			$ 0