Fair Value of Assets and Liabilities (Details Textual) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Oct. 03, 2013 Senior Note Due 2017 [Member]	Sep. 30, 2013 Senior Note Due 2017 [Member]	Dec. 31, 2012 Senior Note Due 2017 [Member]	Sep. 30, 2013 6.625% Senior Notes	Dec. 31, 2012 6.625% Senior Notes	Sep. 30, 2013 Senior Notes Due 2023	Mar. 19, 2013 Senior Notes Due 2023	Dec. 31, 2012 Senior Notes Due 2023	Sep. 30, 2013 7.75% Senior Notes	Sep. 30, 2013 Senior Notes 6.625% Senior Notes	Sep. 30, 2013 Senior Notes 7.75% Senior Notes	Oct. 03, 2013 Subsequent Event Senior Notes 7.75% Senior Notes
Debt Instrument [Line Items]
Interest rate	7.75%	7.75%	7.75%	7.75%	6.625%	6.625%	5.125%	5.125%	5.125%	7.75%	6.625%	7.75%
Repurchased amount of aggregate principal													$ 209.1