Convertible Debt and Notes Payable (Details)			12 Months Ended			40 Months Ended
		Dec. 05, 2016	Dec. 31, 2016 USD ($) letters_of_credit	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jan. 31, 2014 USD ($)	Sep. 29, 2016 USD ($)	Jan. 31, 2016	Oct. 10, 2014 USD ($)	Mar. 10, 2014 USD ($) $ / shares
Debt and Capital Lease Obligations [Line Items]
Stockholders' Equity Note, Stock Split, Conversion Ratio		0.25
Components of short-term borrowings and other debt
Convertible debt	[1]		$ 130,029,000	$ 122,401,000
Note payable			60,953,000	60,831,000
Other Notes Payable			14,237,000	0
Capital lease obligations			1,840,000	2,734,000
Debt, Long-term and Short-term, Combined Amount			207,059,000	190,966,000
Amortization of debt discount			6,885,000	6,302,000	$ 4,685,000
Cash convertible note hedge transaction			0	0	149,500,000
Capital Lease Obligations Incurred						$ 7,600,000
Capital Leases, Income Statement, Interest Expense			100,000	200,000	200,000
Future minimum lease payments for capital lease obligations
2017			938,000
2018			938,000
2019			78,000
2020			0
2021			0
Thereafter			0
Subtotal			1,954,000
Less: Amount representing interest	[2]		(114,000)
Capital lease obligations			$ 1,840,000	2,734,000
Number of Letters of Credit | letters_of_credit			9
Line of Credit Facility, Fair Value of Amount Outstanding			$ 0	5,000,000
Revolving Credit Facility
Components of short-term borrowings and other debt
Letter of credit, max borrowing capacity			$ 25,000,000				$ 25,000,000
Line of Credit Facility, Current Borrowing Capacity							$ 15,000,000
Line of Credit Facility, Commitment Fee Percentage			3.00%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage			0.38%
Interest Expense, Debt			$ 400,000	200,000
Minimum
Components of short-term borrowings and other debt
Capital Lease Obligation, Initial Term			48 months
Capital leases, interest rate			0.60%
Maximum
Components of short-term borrowings and other debt
Capital Lease Obligation, Initial Term			60 months
Capital leases, interest rate			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, San Francisco Office, Expires January 2017 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, max borrowing capacity			$ 710,000
Letter of Credit, Connecticut Office, Expires January 2017 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, max borrowing capacity			65,000
Letter of Credit, NY Office 6, Expires February 2017 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, max borrowing capacity			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, max borrowing capacity			382,000
Letter of Credit, NY Office 1, Expires May 2017 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, max borrowing capacity			355,000
Letter of Credit, NY Office 2, Expires May 2017 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, max borrowing capacity			70,000
Letter of Credit, NY Office 3, Expires October 2017 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, max borrowing capacity			695,000
Letter of Credit, NY Office 4, Expires October 2017 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, max borrowing capacity			2,811,000
Letter of Credit, NY Office 5, Expires November 2017 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, max borrowing capacity			1,600,000
Convertible Debt
Components of short-term borrowings and other debt
Note payable										$ 149,500,000
Interest rate										3.00%
Principal amount of notes being converted										$ 1,000
Interest on Convertible Debt, Net of Tax			4,500,000	4,500,000	3,600,000
Debt Instrument, Convertible, Conversion Price | $ / shares										$ 21.32
Convertible debt, unamortized discount			17,800,000	24,700,000						$ 35,700,000
Amortization of debt discount			6,900,000	6,300,000	$ 4,700,000
Debt Instrument, Interest Rate, Effective Percentage										8.89%
Debt Issuance Costs, Gross										$ 3,700,000
Repayments on long-term and short-term borrowings
2017			4,485,000
2018			4,485,000
2019			151,743,000
2020			0
2021			0
Thereafter			0
Subtotal			160,713,000
Less: Amount representing interest	[2]		(30,684,000)
Senior Notes
Components of short-term borrowings and other debt
Note payable			60,953,000						$ 63,300,000
Interest rate									8.25%
Interest on Convertible Debt, Net of Tax			5,200,000	$ 5,200,000
Debt Issuance Costs, Gross									$ 2,900,000
Repayments on long-term and short-term borrowings
2017			4,912,000
2018			5,218,000
2019			5,218,000
2020			5,218,000
2021			68,468,000
Thereafter			0
Subtotal			89,034,000
Less: Amount representing interest	[2]		(28,081,000)
Insurance Note
Components of short-term borrowings and other debt
Interest rate								1.38%
Debt Instrument, Periodic Payment, Principal			200,000
Short-term Debt, Maximum Amount Outstanding During Period			2,000,000
Repayments on long-term and short-term borrowings
2017			4,225,000
2018			2,225,000
2019			3,702,000
2020			1,805,000
2021			4,723,000
Thereafter			0
Subtotal			16,680,000
Less: Amount representing interest	[2]		(2,443,000)
Aircraft and related equipment
Components of short-term borrowings and other debt
Other Notes Payable			14,400,000
Interest Expense, Debt			800,000
Aircraft and related equipment | Minimum
Components of short-term borrowings and other debt
Interest rate								4.80%
Aircraft and related equipment | 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, max borrowing capacity			$ 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										$ 28.72

[1] The carrying amount of the convertible debt includes an unamortized discount of $17.8 million and $24.7 million as of December 31, 2016 and 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.