Related Party Transactions (Narrative) (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Related Party Transaction [Line Items]
Other long-term investments		$ 238,029,000		$ 238,029,000		$ 182,157,000
Net investment income		115,318,000	$ 33,110,000	233,147,000	$ 104,755,000
Contributed capital				781,125,000	0
Prudential Insurance
Related Party Transaction [Line Items]
Stock option program plan expense		0	0	100,000	100,000
Deferred compensation program expense		200,000	100,000	500,000	400,000
Pension plan expense		300,000	300,000	900,000	1,000,000
Welfare plan expense		400,000	400,000	$ 1,000,000	1,000,000
Defined contribution plan employer matching contribution percent				4.00%
Defined contribution plan, cost recognized		100,000	100,000	$ 400,000	400,000
Affiliated Entity
Related Party Transaction [Line Items]
Accrued interest receivable related to long-term notes receivables		900,000		900,000		100,000
Revenue related to long-tern notes receivable		200,000	300,000	600,000	800,000
Interest expense related to loans payable		20,400,000	0	38,900,000	0
Affiliated Entity | PAIST
Related Party Transaction [Line Items]
Allocated lease expense		100,000	2,000,000	100,000	2,000,000
Allocated sub-lease rental income		0	0	0	0
Affiliated Entity | PAD
Related Party Transaction [Line Items]
Commissions and certain other fees		28,000,000	29,000,000	82,000,000	114,000,000
Affiliated Entity | ASTISI and Prudential Investments
Related Party Transaction [Line Items]
Revenue administrative sharing agreement		29,000,000	37,000,000	84,000,000	143,000,000
Affiliated Entity | PGIM
Related Party Transaction [Line Items]
Net investment income		4,000,000	1,000,000	8,000,000	4,000,000
Prudential Financial Joint Venture
Related Party Transaction [Line Items]
Other long-term investments		100,000,000		100,000,000		45,000,000
Net investment income		3,000,000	$ (1,000,000)	3,000,000	0
Prudential Financial
Related Party Transaction [Line Items]
Line of credit facility, maximum borrowing capacity		$ 2,000,000,000		2,000,000,000
Prudential Financial
Related Party Transaction [Line Items]
Contributed capital				8,421,955,000
Dividends				$ 0	$ 270,000,000	180,000,000
PAI
Related Party Transaction [Line Items]
Contributed capital	$ 8,422,000,000					$ 0