Related Party Transactions (Debt Agreements) (Details) - Affiliated Entity - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	$ 1,384,000
Prudential Financial Loan issued 12/15/2011
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	11,000
Interest Rates	3.61%
Prudential Financial Loan issued 12/16/2011
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	11,000
Interest Rates	3.61%
Prudential Financial Loan issued 11/15/2013
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	9,000
Interest Rates	2.24%
Prudential Financial Loan issued 11/15/2013
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	23,000
Interest Rates	3.19%
Prudential Insurance Loan issued 12/6/2013
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	120,000
Interest Rates	2.60%
Prudential Insurance Loan issued 12/6/2013
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	130,000
Interest Rates	4.39%
Prudential Insurance Loan issued 12/6/2013
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	250,000
Interest Rates	3.64%
Prudential Insurance Loan issued 9/25/2014
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	30,000
Interest Rates	1.89%
Prudential Insurance Loan issued 9/25/2014
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	40,000
Interest Rates	3.95%
Prudential Insurance Loan issued 9/25/2014
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	20,000
Interest Rates	2.80%
Prudential Insurance Loan issued 9/25/2014
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	50,000
Interest Rates	3.95%
Prudential Insurance Loan issued 9/25/2014
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	50,000
Interest Rates	2.80%
Prudential Insurance Loan issued 9/25/2014
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	100,000
Interest Rates	3.47%
Prudential Insurance Loan issued 9/25/2014
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	100,000
Interest Rates	3.95%
Prudential Financial Loan issued 12/15/2014
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	5,000
Interest Rates	2.57%
Prudential Financial Loan issued 12/15/2014
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	23,000
Interest Rates	3.14%
Prudential Financial Loan issued 6/15/2015
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	66,000
Interest Rates	3.52%
Prudential Financial Loan issued 6/15/2015
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	6,000
Interest Rates	2.86%
Prudential Financial Loan issued 9/21/2015
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	158,000
Prudential Financial Loan issued 9/21/2015
Related Party Transaction [Line Items]
Short-term and Long-term debt	0	132,000
Prudential Financial Loan issued 9/21/2015
Related Party Transaction [Line Items]
Short-term and Long-term debt	0	26,000
Prudential Financial Loan issued 12/16/2015
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	5,000
Interest Rates	2.85%
Prudential Financial Loan issued 12/16/2015
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	1,000
Interest Rates	2.85%
Prudential Financial Loan issued 12/16/2015
Related Party Transaction [Line Items]
Short-term and Long-term debt	$ 0	$ 18,000
Interest Rates	3.37%
Minimum | Prudential Financial Loan issued 9/21/2015
Related Party Transaction [Line Items]
Interest Rates	1.09%
Minimum | Prudential Financial Loan issued 9/21/2015
Related Party Transaction [Line Items]
Interest Rates	1.40%
Minimum | Prudential Financial Loan issued 9/21/2015
Related Party Transaction [Line Items]
Interest Rates	1.40%
Maximum | Prudential Financial Loan issued 9/21/2015
Related Party Transaction [Line Items]
Interest Rates	1.63%
Maximum | Prudential Financial Loan issued 9/21/2015
Related Party Transaction [Line Items]
Interest Rates	1.93%
Maximum | Prudential Financial Loan issued 9/21/2015
Related Party Transaction [Line Items]
Interest Rates	1.93%