Related Party Transactions (Narrative) (Details) - USD ($)		3 Months Ended						9 Months Ended		12 Months Ended
		Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Related Party Transaction [Line Items]
Investment expense		$ 3,883,000				$ 3,783,000		$ 11,226,000	$ 11,431,000
commissions and fees		550,592,000				555,907,000		1,653,225,000	1,646,310,000
Other invested assets	[1]	254,050,000			$ 335,811,000			254,050,000		$ 335,811,000
Net investment income		103,164,000				107,953,000		300,035,000	314,310,000
Fee income from revenue sharing agreement		93,320,000				102,713,000		291,460,000	307,384,000
Contributed capital		0								0
Prudential Insurance
Related Party Transaction [Line Items]
Stock option program plan expense		0				0		100,000	0
Deferred compensation program expense		200,000				200,000		500,000	600,000
Pension plan expense		400,000				300,000		1,000,000	1,000,000
Welfare plan expense		500,000				400,000		$ 2,000,000	1,000,000
Defined contribution plan employer matching contribution percent								4.00%
Defined contribution plan, cost recognized		200,000				100,000		$ 500,000	400,000
Affiliated Entity
Related Party Transaction [Line Items]
Accrued interest receivable related to long-term notes receivables		500,000			200,000			500,000		200,000
Revenue related to long-term notes receivable		100,000				200,000		300,000	500,000
Interest expense related to loans payable		14,000,000				19,000,000		44,000,000	48,000,000
Affiliated Entity | PAIST
Related Party Transaction [Line Items]
Allocated sub-lease rental income		0				0		0	0
Allocated lease expense		0				0		0	0
Affiliated Entity | PAD
Related Party Transaction [Line Items]
commissions and fees		32,000,000				27,000,000		91,000,000	81,000,000
Affiliated Entity | ASTISI and PGIM Investments
Related Party Transaction [Line Items]
Fee income from revenue sharing agreement		26,000,000				28,000,000		80,000,000	83,000,000
Affiliated Entity | PGIM
Related Party Transaction [Line Items]
Investment expense		3,000,000				3,000,000		9,000,000	9,000,000
Prudential Financial Joint Venture
Related Party Transaction [Line Items]
Other invested assets		160,000,000			111,000,000			160,000,000		$ 111,000,000
Net investment income		2,000,000				2,000,000		4,000,000	7,000,000
Prudential Financial
Related Party Transaction [Line Items]
Company's share of corporate expenses (benefits)		4,000,000				(2,000,000)		12,000,000	$ 10,000,000
Line of credit facility, maximum borrowing capacity		9,000,000,000						$ 9,000,000,000
PAI
Related Party Transaction [Line Items]
Return of capital		$ 250,000,000	$ 250,000,000	$ 300,000,000	$ 650,000,000	$ 200,000,000	$ 100,000,000

[1] (1)Prior period amounts have been reclassified to conform to current period presentation. See "Adoption of ASU 2016-01" in Note 2 for details.