Related Party Transactions (Narrative) (Details) $ in Thousands	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Jun. 30, 2017 USD ($) policy	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Apr. 01, 2016 USD ($)
Related Party Transaction [Line Items]
Other long-term investments	$ 347,302				$ 347,302		$ 344,463
Net investment income	91,041		$ 78,619		180,656	$ 184,071
Contributed capital					0	405,321
Prudential Insurance
Related Party Transaction [Line Items]
Contributed capital		$ 5,000	200,000	$ 5,000	5,000	205,000
Dividend			2,593,000		0
Prudential Insurance
Related Party Transaction [Line Items]
Stock option program plan expense	500		400		700	600
Deferred compensation program expense	2,000		2,000		5,000	3,000
Pension plan expense	6,000		6,000		13,000	12,000
Welfare plan expense	7,000		7,000		$ 14,000	14,000
Defined contribution plan, employer matching contribution, percent (up to)					4.00%
Defined contribution plan, cost recognized	3,000		2,000		$ 5,000	5,000
Number of Corporate Owned Life Insurance policies sold | policy					5
Prudential Insurance and Prudential FInancial
Related Party Transaction [Line Items]
Life Insurance, Corporate or Bank Owned, amount	3,600,000				$ 3,600,000		3,367,000
Fees related to Life Insurance, Corporate or Bank Owned, amount	11,000		10,000		23,000	21,000
Maximum amount of mortality risk	3,500				3,500
Prudential Financial
Related Party Transaction [Line Items]
Company's share of corporate expenses	15,000		13,000		$ 32,000	28,000
Number of Corporate Owned Life Insurance policies sold | policy					1
Affiliated Entity
Related Party Transaction [Line Items]
Accrued interested receivable related to long-tern notes receivable	2,000				$ 2,000		1,000
Revenues related to long-term notes receivable	1,000		1,000		3,000	3,000
Line of credit facility, maximum borrowing capacity	2,000,000				2,000,000
Prepaid debt								$ 125,000
Interest expense related to loans payable	400		2,000		600	13,000
Affiliated Entity | PAD
Related Party Transaction [Line Items]
Commissions and fees	160,000		190,000		315,000	364,000
Affiliated Entity | ASTISI and PGIM Investments
Related Party Transaction [Line Items]
Fee income from revenue sharing agreement	80,000		73,000		157,000	142,000
Affiliated Entity | PGIM Investments
Related Party Transaction [Line Items]
Fee income from revenue sharing agreement	4,000		3,000		7,000	6,000
Affiliated Entity | PGIM
Related Party Transaction [Line Items]
Net investment income	4,000		4,000		7,000	$ 9,000
Prudential Financial Joint Ventures
Related Party Transaction [Line Items]
Other long-term investments	109,000				109,000		100,000
Net investment income	$ 2,000		$ 1,000		$ 6,000		$ (3,000)