Fair Value of Assets and Liabilities (Details Textual) - Senior Notes - USD ($)	Sep. 30, 2016	Apr. 18, 2016	Dec. 31, 2015	Feb. 10, 2011
5.875% Senior Notes, Due 2024
Debt Instrument [Line Items]
Interest rate	5.875%		5.875%
5.125% Senior Notes
Debt Instrument [Line Items]
Interest rate	5.125%		5.125%
5.875% Senior Notes, due 2022
Debt Instrument [Line Items]
Interest rate	5.875%		5.875%
6.00% Senior Notes
Debt Instrument [Line Items]
Interest rate	6.00%		6.00%
Face amount		$ 350,000,000
6.625% Senior Notes
Debt Instrument [Line Items]
Interest rate	6.625%		6.625%
Face amount				$ 300,000,000