Related Party Transactions (Debt Agreements) (Details) - Affiliated Entity - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 1,004,750	$ 1,000
Prudential Insurance Loan Issued 4/20/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 28,102	0
Interest Rate	1.89%
Prudential Insurance Loan Issued 4/20/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 18,734	0
Interest Rate	2.60%
Prudential Insurance Loan Issued 4/20/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 25,000	0
Interest Rate	2.60%
Prudential Insurance Loan Issued 4/20/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 46,835	0
Interest Rate	2.80%
Prudential Insurance Loan Issued 4/20/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 18,734	0
Interest Rate	2.80%
Prudential Insurance Loan Issued 4/20/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 37,468	0
Interest Rate	3.64%
Prudential Insurance Loan Issued 4/20/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 93,671	0
Interest Rate	3.64%
Prudential Insurance Loan Issued 4/20/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 103,038	0
Interest Rate	3.64%
Prudential Insurance Loan Issued 4/20/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 93,671	0
Interest Rate	3.47%
Prudential Insurance Loan Issued 4/20/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 93,671	0
Interest Rate	4.39%
Prudential Insurance Loan Issued 4/20/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 28,102	0
Interest Rate	4.39%
Prudential Insurance Loan Issued 4/20/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 37,468	0
Interest Rate	3.95%
Prudential Insurance Loan Issued 4/20/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 93,671	0
Interest Rate	3.95%
Prudential Insurance Loan Issued 4/20/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 46,835	0
Interest Rate	3.95%
Prudential Insurance Loan Issued 6/28/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 30,000	0
Interest Rate	2.08%
Prudential Insurance Loan Issued 6/28/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 50,000	0
Interest Rate	3.87%
Prudential Insurance Loan Issued 6/28/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 25,000	0
Interest Rate	3.49%
Prudential Insurance Loan Issued 6/28/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 26,000	0
Interest Rate	2.59%
Prudential Insurance Loan Issued 6/28/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 25,000	0
Interest Rate	2.08%
Prudential Insurance Loan Issued 6/28/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 20,000	0
Interest Rate	2.08%
Prudential Insurance Loan Issued 6/28/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 25,000	0
Interest Rate	3.49%
Prudential Retirement Insurance & Annuity Issued 6/28/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 34,000	0
Interest Rate	3.09%
Prudential Funding Loan Issued 9/27/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 1,500	0
Interest Rate	0.56%
Prudential Funding Loan Issued 9/30/2016
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 3,250	0
Interest Rate	0.56%
Prudential Funding Loan Issued 12/30/2015
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	$ 1,000
Interest Rate	5.05%