Related Party Transactions (Narrative) (Details) - USD ($)		3 Months Ended					6 Months Ended		12 Months Ended
		Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Related Party Transaction [Line Items]
Investment expense		$ 3,549,000				$ 3,850,000	$ 7,343,000	$ 7,648,000
commissions and fees		547,343,000				553,097,000	1,102,633,000	1,090,403,000
Other invested assets	[1]	211,819,000		$ 335,811,000			211,819,000		$ 335,811,000
Net investment income		100,160,000				104,108,000	196,871,000	206,357,000
Fee income from revenue sharing agreement		98,603,000				105,869,000	198,140,000	204,671,000
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		100,000				200,000	300,000	400,000
Pension plan expense		500,000				300,000	900,000	700,000
Welfare plan expense		500,000				400,000	$ 1,100,000	900,000
Defined contribution plan employer matching contribution percent							4.00%
Defined contribution plan, cost recognized		200,000				100,000	$ 400,000	300,000
Affiliated Entity
Related Party Transaction [Line Items]
Accrued interest receivable related to long-term notes receivables		400,000		200,000			400,000		200,000
Revenue related to long-term notes receivable		100,000				200,000	200,000	400,000
Interest expense related to loans payable		15,000,000				16,000,000	30,000,000	29,000,000
Affiliated Entity | PAIST
Related Party Transaction [Line Items]
Allocated sub-lease rental income							0	0
Allocated lease expense							0	0
Affiliated Entity | PAD
Related Party Transaction [Line Items]
commissions and fees		29,000,000				27,000,000	59,000,000	54,000,000
Affiliated Entity | ASTISI and PGIM Investments
Related Party Transaction [Line Items]
Fee income from revenue sharing agreement		27,000,000				28,000,000	54,000,000	55,000,000
Affiliated Entity | PGIM
Related Party Transaction [Line Items]
Investment expense		3,000,000				3,000,000	6,000,000	6,000,000
Prudential Financial Joint Venture
Related Party Transaction [Line Items]
Other invested assets		129,000,000		111,000,000			129,000,000		$ 111,000,000
Net investment income		2,000,000				2,000,000	2,000,000	5,000,000
Prudential Financial
Related Party Transaction [Line Items]
Company's share of corporate expenses (benefits)		4,000,000				9,000,000	8,000,000	$ 13,000,000
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	$ 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.