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Fair Value Measurements Fair Value Measurements - Liabilities Not Measured at Fair Value (Details) - USD ($) $ in Thousands | Sep. 30, 2016 | Aug. 31, 2016 | Feb. 29, 2016 | Dec. 31, 2015 | Sep. 30, 2015
--- | --- | --- | --- | --- | ---
5% Convertible Senior Notes due 2017 |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Stated interest rate (in hundredths) | 5.00% |  |  | 5.00% | 5.00%
2% Convertible Senior Notes due 2020 |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Stated interest rate (in hundredths) | 2.00% |  |  | 2.00% | 2.00%
Senior Notes | 5.75% Senior Notes |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Stated interest rate (in hundredths) | 5.75% | 5.75% |  | 5.75% |
Convertible Junior Subordinated Debentures, interest at 9% per annum, due April 2063 |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Stated interest rate (in hundredths) | 9.00% |  | 9.00% | 9.00% | 9.00%
Carrying Value |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
FHLB Advance | $ 155,000 |  |  |  |
5% Notes | 144,629 |  |  | $ 331,546 |
2% Notes | 204,444 |  |  | 490,755 |
5.75% Notes | 417,087 |  |  |  |
9% Debentures | 256,872 |  |  | 389,522 |
Total long-term debt | 1,178,032 |  |  | 1,211,823 |
Fair Value | Significant Other Observable Inputs (Level 2) |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
FHLB Advance | 159,302 |  |  |  |
5% Notes | 148,904 |  |  | 345,616 |
2% Notes | 261,530 |  |  | 701,955 |
5.75% Notes | 442,531 |  |  |  |
9% Debentures | 318,077 |  |  | 455,067 |
Total long-term debt | $ 1,330,344 |  |  | $ 1,502,638 |

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