Convertible Debt and Notes Payable (Details)			3 Months Ended		6 Months Ended		40 Months Ended
		Oct. 10, 2014 USD ($)	Jun. 30, 2016 USD ($) letters_of_credit	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) letters_of_credit	Jun. 30, 2015 USD ($)	Jan. 31, 2014 USD ($)	Jan. 31, 2016	Dec. 31, 2015 USD ($)	Mar. 10, 2014 USD ($) $ / shares
Debt and Capital Lease Obligations [Line Items]
Interest Expense, Lessee, Assets under Capital Lease			$ 100,000	$ 100,000
Components of short-term borrowings and other debt
Convertible debt	[1]		126,138,000		$ 126,138,000				$ 122,401,000
Revolver			25,000,000		25,000,000				5,000,000
Capital lease obligations			2,250,000		2,250,000				2,734,000
Debt, Long-term and Short-term, Combined Amount			230,890,000		230,890,000				190,966,000
Debt Instrument, Face Amount			61,040,000		61,040,000				60,831,000
Amortization of debt discount					3,366,000	$ 3,081,000
Other Notes Payable			16,462,000		16,462,000				0
Capital Lease Obligations Incurred							$ 7,600,000
Capital Leases, Income Statement, Interest Expense			100,000	100,000	100,000	100,000
Future minimum lease payments for capital lease obligations
2016			469,000		469,000
2017			938,000		938,000
2018			938,000		938,000
2019			78,000		78,000
2020			0		0
Thereafter			0		0
Subtotal			2,423,000		2,423,000
Less: Amount representing interest	[2]		(173,000)		(173,000)
Capital lease obligations			$ 2,250,000		$ 2,250,000				2,734,000
Number of Letters of Credit | letters_of_credit			9		9
Restricted Cash and Cash Equivalents			$ 13,772,000		$ 13,772,000				10,085,000
Revolving Credit Facility
Components of short-term borrowings and other debt
Revolver			25,000,000		25,000,000
Letter of credit, borrowing capacity			25,000,000		$ 25,000,000
Line of Credit Facility, Commitment Fee Percentage					3.00%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage					0.38%
Interest Expense, Debt			$ 200,000		$ 400,000
Minimum
Components of short-term borrowings and other debt
Capital Lease Obligation, Initial Term					48 months
Capital leases, interest rate			0.60%		0.60%
Maximum
Components of short-term borrowings and other debt
Capital Lease Obligation, Initial Term					60 months
Capital leases, interest rate			6.03%		6.03%
Cash Convertible Note Economic Hedge And Warrant Transaction
Components of short-term borrowings and other debt
Cash convertible note hedge transaction						20,500,000
Treasury Stock
Components of short-term borrowings and other debt
Cash convertible note hedge transaction						300,000
Letter of Credit, NY Office 1, Expires May 2017 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			$ 355,000		$ 355,000
Letter of Credit, NY Office 2, Expires July 2019 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			70,000		70,000
Letter of Credit, NY Office 3, Expires October 2016 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			695,000		695,000
Letter of Credit, NY Office 4, Expires October 2016 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			3,373,000		3,373,000
Letter of Credit, NY Office 5, Expires November 2016 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			1,600,000		1,600,000
Letter of Credit, San Francisco Office, Expires January 2017 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			710,000		710,000
Letter of Credit, NY Office, Expires January 2017 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			65,000		65,000
Letter of Credit, NY Office, Expires February 2017 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			1,000,000		1,000,000
Letter of Credit, Boston Office, Expires March 2017 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			382,000		382,000
Convertible Debt
Components of short-term borrowings and other debt
Debt Instrument, Face Amount										$ 149,500,000
Interest rate										3.00%
Principal amount of notes being converted										$ 1,000
Interest on Convertible Debt, Net of Tax			1,100,000	1,100,000	2,200,000	2,200,000
Debt Instrument, Convertible, Conversion Price | $ / shares										$ 5.33
Convertible debt, unamortized discount			21,400,000		21,400,000				$ 24,700,000	$ 35,700,000
Amortization of debt discount			1,700,000	1,600,000	3,400,000	3,100,000
Debt Instrument, Interest Rate, Effective Percentage										8.89%
Debt Issuance Cost					3,700,000
Repayments on long-term and short-term borrowings
2016			2,243,000		2,243,000
2017			4,485,000		4,485,000
2018			4,485,000		4,485,000
2019			151,743,000		151,743,000
2020			0		0
Thereafter			0		0
Subtotal			162,956,000		162,956,000
Less: Amount representing interest	[2]		(36,818,000)		(36,818,000)
Senior Notes
Components of short-term borrowings and other debt
Notes Payable			61,040,000		61,040,000
Debt Instrument, Face Amount		$ 63,300,000
Interest rate		8.25%
Interest on Convertible Debt, Net of Tax			1,300,000	$ 1,300,000	2,600,000	$ 2,600,000
Debt Issuance Cost		$ 2,900,000
Repayments on long-term and short-term borrowings
2016			2,609,000		2,609,000
2017			5,218,000		5,218,000
2018			5,218,000		5,218,000
2019			5,218,000		5,218,000
2020			5,218,000		5,218,000
Thereafter			68,468,000		68,468,000
Subtotal			91,949,000		91,949,000
Less: Amount representing interest	[2]		(30,909,000)		(30,909,000)
Insurance Note
Components of short-term borrowings and other debt
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year			2,720,000		2,720,000
Interest rate								1.38%
Debt Instrument, Periodic Payment, Principal					200,000
Short-term Debt, Maximum Amount Outstanding During Period					2,000,000
Other Notes Payable			1,100,000		1,100,000
Repayments on long-term and short-term borrowings
2017			4,238,000		4,238,000
2018			2,239,000		2,239,000
2019			3,716,000		3,716,000
2020			1,819,000		1,819,000
Thereafter			4,729,000		4,729,000
Subtotal			19,461,000		19,461,000
Less: Amount representing interest	[2]		(2,999,000)		(2,999,000)
3721 Aircraft [Member]
Components of short-term borrowings and other debt
Other Notes Payable			15,400,000		15,400,000
Interest Expense, Debt					300,000
3721 Aircraft [Member] | Minimum
Components of short-term borrowings and other debt
Interest rate								4.80%
3721 Aircraft [Member] | Maximum
Components of short-term borrowings and other debt
Interest rate								7.25%
Letter of Credit Reinsurance Agreement | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			$ 5,500,000		$ 5,500,000
Common Stock Class A
Components of short-term borrowings and other debt
Class of Warrant, Exercise Price of Warrants or Rights | $ / shares										$ 7.18

[1] The carrying amount of the convertible debt includes an unamortized discount of $21.4 million and $24.7 million as of June 30, 2016 and December 31, 2015.

[2] Amount necessary to reduce net minimum payments to present value calculated at the Company's implicit rate at inception. This amount also includes the unamortized discount on the convertible debt.