Notes Payable (Details) - USD ($)		1 Months Ended	12 Months Ended
	Jun. 23, 2015	Jul. 31, 2012	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jun. 17, 2015	Sep. 30, 2014	Aug. 31, 2014	Apr. 07, 2014	Dec. 31, 2012	Feb. 04, 2011
Debt Instrument [Line Items]
Outstanding debt			$ 326,723,000	$ 299,956,000
Stated interest rate (percent)	6.00%
Interest Paid	$ 1,500,000
Repayments of Notes Payable			53,163,000	5,446,000	$ 0
Minimum cash and cash equivalents			46,898,000	180,334,000	144,727,000					$ 79,815,000
Repurchase Right [Abstract]
Interest payments			24,000,000	7,600,000	$ 7,900,000
Maturities of notes payable:
2016			46,793,000
2017			0
2018			0
2019			200,000,000
2020			79,930,000
Thereafter			0
Total			326,723,000
Line of Credit [Member]
Debt Instrument [Line Items]
Line Of Credit Facility, Maximum Borrowing Capacity, Swing Line									$ 0
Line of Credit Facility, Amount Outstanding							$ 0
Maturities of notes payable:
Line of Credit Facility, Maximum Borrowing Capacity			105,000,000
Line Of Credit Facility, Conditional Maximum Borrowing Capacity			0						0
Corporate 7.50 Senior Convertible Notes [Member]
Debt Instrument [Line Items]
Face amount of debt instrument											$ 100,000,000
Stated interest rate (percent)		7.50%									7.50%
Repurchase Right [Abstract]
Extinguishment of Debt, Amount		$ 44,500,000
7.50% Senior Exchange Convertible Notes Member [Member]
Debt Instrument [Line Items]
Face amount of debt instrument				44,500,000
Stated interest rate (percent)		7.50%
7.50% Senior Exchange Convertible Notes [Member] | Senior Exchange Convertible Debt [Member]
Debt Instrument [Line Items]
Outstanding debt			$ 0	44,475,000
Stated interest rate (percent)		7.50%
Debt Instrument, Repurchased Face Amount	15,400,000
Repurchase amount of debt instrument	20,500,000
Corporate 7.50 Senior Convertible Notes [Member]
Debt Instrument [Line Items]
Stated interest rate (percent)			7.50%
Corporate 7.50 Senior Convertible Notes [Member] | Senior Convertible Debt [Member]
Debt Instrument [Line Items]
Outstanding debt			$ 46,793,000	55,481,000
Stated interest rate (percent)											7.50%
Repurchase amount of debt instrument	8,700,000
Eight Point Five Percent Senior Notes Due Twenty Nineteen [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Outstanding debt			200,000,000	200,000,000
Face amount of debt instrument							$ 0
Stated interest rate (percent)							8.50%
6.00% Senior Convertible Notes Due 2020 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Outstanding debt			79,930,000	0
Face amount of debt instrument	$ 80,000,000
Stated interest rate (percent)	6.00%
Proceeds from Notes Payable	$ 64,500,000
Repurchase amount of debt instrument	$ 30,700,000
Senior Credit Facility [Member] | Senior Exchange Convertible Debt [Member]
Maturities of notes payable:
2016			46,800,000
Senior Credit Facility [Member] | Line of Credit [Member]
Debt Instrument [Line Items]
Outstanding debt			$ 0	$ 0
JPMorgan Chase Bank, N.A. [Member] | Line of Credit [Member]
Maturities of notes payable:
Line of Credit Facility, Maximum Borrowing Capacity									$ 0
Citibank N.A. [Member] | Line of Credit [Member]
Maturities of notes payable:
Line of Credit Facility, Maximum Borrowing Capacity								$ 0
TPG Aviator, L.P. [Member]
Debt Instrument [Line Items]
Equity Method Investment, Ownership Percentage						44.00%