Fair Value of Financial Instruments - Schedule of Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financial liabilities:
Notes payable, fair value	$ 161,011	$ 155,768
Subordinated amortizing notes
Financial liabilities:
Long-term debt, fair value	1,700	7,478
5 3/4% Senior Notes due April 15, 2019
Financial liabilities:
Long-term debt, fair value	$ 151,875	$ 151,125
Stated interest rate	5.75%	5.75%
8 1/2% Senior Notes due November 15, 2020
Financial liabilities:
Long-term debt, fair value	$ 0	$ 444,125
Stated interest rate	8.50%	8.50%
7% Senior Notes due August 15, 2022
Financial liabilities:
Long-term debt, fair value	$ 362,250	$ 363,125
Stated interest rate	7.00%	7.00%
Five Point Eight Seven Five Percent Senior Notes Due Two Thousand Twenty Five [Member]
Financial liabilities:
Long-term debt, fair value	$ 462,375	$ 0
Stated interest rate	5.875%
Carrying Amount
Financial liabilities:
Notes payable, fair value	$ 161,011	155,768
Carrying Amount | Subordinated amortizing notes
Financial liabilities:
Long-term debt, fair value	1,619	7,225
Carrying Amount | 5 3/4% Senior Notes due April 15, 2019
Financial liabilities:
Long-term debt, fair value	149,226	148,826
Carrying Amount | 8 1/2% Senior Notes due November 15, 2020
Financial liabilities:
Long-term debt, fair value	0	422,817
Carrying Amount | 7% Senior Notes due August 15, 2022
Financial liabilities:
Long-term debt, fair value	346,556	346,014
Carrying Amount | Five Point Eight Seven Five Percent Senior Notes Due Two Thousand Twenty Five [Member]
Financial liabilities:
Long-term debt, fair value	$ 439,221	$ 0