Asset Disposals and Impairments - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Assets Held For Sale And Impairments [Line Items]
Sale value of aircraft	$ 4,200,000
Loss (gain) on disposal of assets	(242,000)	14,701,000	(1,315,000)	14,676,000
Carrying value of aircraft	822,742,000		822,742,000		785,472,000
Impairment loss		421,000	0	421,000
Light Aircraft [Member] | Air Medical [Member]
Assets Held For Sale And Impairments [Line Items]
Number of aircraft sold	2
Medium Aircraft [Member] | Air Medical [Member]
Assets Held For Sale And Impairments [Line Items]
Number of aircraft sold	1
Carrying value of aircraft		800,000		800,000
Current market value for aircraft		400,000		400,000
Impairment loss		400,000
Number Of Aircraft		2
Fixed Wing Aircraft [Member] | Oil And Gas [Member]
Assets Held For Sale And Impairments [Line Items]
Number of aircraft sold	1
Aircraft [Member] | Oil And Gas [Member]
Assets Held For Sale And Impairments [Line Items]
Sale value of aircraft		37,000,000
Loss (gain) on disposal of assets		16,400,000
Number of aircraft sold		2
Carrying value of aircraft		20,600,000		20,600,000
Loss on sale of assets		$ 1,700,000