Summary of Significant Accounting Policies - Cost and Carrying Value of Property Plant and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Cost	$ 56,516	$ 55,239
Accumulated Depreciation and Amortization	23,391	18,962
Carrying Value	33,125	36,277
Air Plane [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Cost	28,997	28,997
Accumulated Depreciation and Amortization	6,055	5,506
Carrying Value	22,942	23,491
Computer Software And Equipment [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Cost	17,905	17,470
Accumulated Depreciation and Amortization	9,513	6,339
Carrying Value	8,392	11,131
Leasehold Improvements [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Cost	7,623	6,881
Accumulated Depreciation and Amortization	6,066	5,471
Carrying Value	1,557	1,410
Other [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Cost	1,991	1,891
Accumulated Depreciation and Amortization	1,757	1,646
Carrying Value	$ 234	$ 245