Debt - Private Placement Shelf Agreement (Details) - Senior Notes - USD ($) $ in Thousands	Sep. 22, 2016	Sep. 22, 2014
Prudential Private Placement Shelf Agreement
Debt Instrument [Line Items]
Debt Instrument, Term		12 years
MetLife Private Placement Shelf Agreement
Debt Instrument [Line Items]
Debt Instrument, Term	12 years
Maximum | Prudential Private Placement Shelf Agreement
Debt Instrument [Line Items]
Agreement face amount		$ 100,000
Maximum | MetLife Private Placement Shelf Agreement
Debt Instrument [Line Items]
Agreement face amount	$ 100,000