Schedule I Condensed Financial Information Parent - Long-term debt instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Aug. 05, 2014	Mar. 29, 2010	Mar. 07, 2003
Long-term debt	$ 448,936	$ 525,082
Debt instrument, interest rate, stated percentage				8.125%
Notes8125 Percent Due2018 [Member]
Long-term debt	0	80,213
Debt instrument, unamortized discount and deferred costs	$ 0	$ 1,406
Debt instrument, interest rate, stated percentage	8.125%	8.125%		8.125%
Seven Point Five Percentage Election Two Notes Due Two Thousand Twenty One [Member]
Long-term debt	$ 295	$ 293
Debt instrument, unamortized discount and deferred costs	6	8
Debt instrument, interest rate, stated percentage			7.50%
Notes750 Percent Due2024 [Member]
Long-term debt	390	390
Debt instrument, interest rate, stated percentage					7.50%
Parent Company [Member]
Long-term debt	685	80,896
Parent Company [Member] | Notes8125 Percent Due2018 [Member]
Long-term debt	0	80,213
Debt instrument, interest rate, stated percentage				8.125%
Parent Company [Member] | Seven Point Five Percentage Election Two Notes Due Two Thousand Twenty One [Member]
Long-term debt	$ 295	$ 293
Debt instrument, interest rate, stated percentage	7.50%	7.50%
Parent Company [Member] | Notes750 Percent Due2024 [Member]
Long-term debt	$ 390	$ 390
Debt instrument, interest rate, stated percentage	7.50%	7.50%			7.50%