Related Party Transactions (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016
Related Party Transaction [Line Items]
Investment expense	$ 3,798			$ 1,386
Other long-term investments	251,188	$ 551,931
Net investment income	102,249			33,010
Prudential Insurance
Related Party Transaction [Line Items]
Stock option program plan expense	0			0
Deferred compensation program expense	300			100
Pension plan expense	300			300
Welfare plan expense	$ 400			400
Defined contribution plan employer matching contribution percent	4.00%
Defined contribution plan, cost recognized	$ 100			100
Affiliated Entity
Related Party Transaction [Line Items]
Accrued interest receivable related to long-term notes receivables	300	100
Revenue related to long-tern notes receivable	100			200
Interest expense related to loans payable	13,000			0
Affiliated Entity | PAIST
Related Party Transaction [Line Items]
Allocated lease expense	0			0
Allocated sub-lease rental income	0			0
Affiliated Entity | PAD
Related Party Transaction [Line Items]
Commissions and certain other fees	27,000			27,000
Affiliated Entity | ASTISI and Prudential Investments
Related Party Transaction [Line Items]
Fee income from revenue sharing agreement	27,000			25,000
Affiliated Entity | PGIM
Related Party Transaction [Line Items]
Investment expense	3,000			1,000
Prudential Financial Joint Venture
Related Party Transaction [Line Items]
Other long-term investments	106,000	102,000
Net investment income	3,000			(1,000)
Prudential Financial
Related Party Transaction [Line Items]
Company's share of corporate expenses	4,000			$ 3,000
Line of credit facility, maximum borrowing capacity	9,000,000
Prudential Financial
Related Party Transaction [Line Items]
Dividends	0	$ 1,140,000
PAI
Related Party Transaction [Line Items]
Contributed capital	$ 0		$ 8,422,000