Debt - 7.50% Senior Convertible Notes and 7.50% Senior Exchange Convertible Notes due 2016 (Details) - Senior Notes - USD ($)		1 Months Ended
	Jul. 20, 2015	Jul. 31, 2012	Dec. 31, 2016	Feb. 16, 2016	Jun. 23, 2015	Dec. 31, 2014	Feb. 04, 2011
7.50% Senior Convertible Notes due 2016
Debt
Stated interest rate (percent)		7.50%	7.50%	7.50%	7.50%		7.50%
Aggregate principal amount							$ 100,000,000
Debt retired		$ 44,500,000
Face amount of debt repurchased					$ 8,700,000
7.50% Senior Exchange Convertible Notes
Debt
Stated interest rate (percent)	7.50%	7.50%			7.50%	7.50%
Aggregate principal amount		$ 44,500,000
Face amount of debt repurchased					$ 20,500,000
Redemption price as a percentage of principal	100.00%