Fair Value of Assets and Liabilities (Details Textual) - Senior Notes	Mar. 31, 2016	Dec. 31, 2015
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%
6.625% Senior Notes
Debt Instrument [Line Items]
Interest rate	6.625%	6.625%