Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended								12 Months Ended
	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) Aircraft	Dec. 31, 2015 USD ($) Aircraft	Dec. 31, 2014 USD ($) Aircraft
Summary Of Significant Accounting Policies [Line Items]
Percentage of stock owned by CEO									70.90%
Maturities Period of liquid investments									Three months or less
Valuation reserves related to obsolescence and slow moving inventory	$ 17,300,000				$ 15,400,000				$ 17,300,000	$ 15,400,000
Gain or loss on sale of assets	(504,000)	$ (85,000)	$ 4,298,000	$ (359,000)	(577,000)	$ 165,000	$ 66,000	$ 7,000	3,350,000	(339,000)	$ (848,000)
Impairments of assets									407,000		10,508,000
Insurance retention per claim									250,000
Accrued liabilities related to health care claims	1,900,000				1,900,000				1,900,000	1,900,000
Amount deductible per incident									500,000
Accrued expense related to workers compensation claims	2,500,000				2,600,000				2,500,000	2,600,000
Amounts paid to offshore insurance captive									600,000	1,000,000
Allowance for contractual discounts against outstanding accounts receivable	111,900,000				103,600,000				111,900,000	103,600,000	96,600,000
Allowance for uncompensated care against outstanding accounts receivable	46,300,000				41,900,000				46,300,000	41,900,000	41,900,000
Value of uncompensated care services	8,800,000				9,300,000				8,800,000	9,300,000	9,100,000
Estimated cost of providing charity services	1,900,000				2,000,000				$ 1,900,000	2,000,000	$ 2,100,000
Percentage of reserved category of self pay									100.00%
Allowance for doubtful accounts	$ 6,000,000				$ 5,200,000				$ 6,000,000	$ 5,200,000
Percentage of consolidated operating revenues									24.00%	26.00%	30.00%
Percentage of trade receivables	16.00%				15.00%				16.00%	15.00%
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Unrealized losses recorded									$ 300,000
Light Aircraft [Member]
Summary Of Significant Accounting Policies [Line Items]
Impairments of assets									400,000	$ 0.0
Medium Aircraft [Member]
Summary Of Significant Accounting Policies [Line Items]
Impairments of assets											$ 10,500,000
Oil and Gas [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash proceeds									15,000,000	3,700,000
Gain on disposal of assets									$ 3,300,000
Carrying value of aircraft					$ 3,700,000					3,700,000
Gain or loss on sale of assets										$ 0
Oil and Gas [Member] | Light Aircraft [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of aircraft sold | Aircraft									12	8
Carrying value of aircraft	$ 1,800,000								$ 1,800,000
Number of Aircraft impaired | Aircraft									2
Oil and Gas [Member] | Light Aircraft [Member] | Fair Value, Inputs, Level 3 [Member]
Summary Of Significant Accounting Policies [Line Items]
Market value of aircraft	1,400,000								$ 1,400,000
Oil and Gas [Member] | Medium Aircraft [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of aircraft sold | Aircraft									11
Oil and Gas [Member] | Fixed Wing Aircraft [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of aircraft sold | Aircraft										6
Air Medical [Member]
Summary Of Significant Accounting Policies [Line Items]
Gain or loss on sale of assets										$ (300,000)
Allowance for contractual discounts against outstanding accounts receivable	111,900,000				103,600,000				$ 111,900,000	103,600,000	96,600,000
Allowance for uncompensated care against outstanding accounts receivable	$ 46,300,000				$ 41,900,000				$ 46,300,000	$ 41,900,000	41,900,000
Air Medical [Member] | Medium Aircraft [Member]
Summary Of Significant Accounting Policies [Line Items]
Carrying value of aircraft											$ 16,500,000
Number of Aircraft impaired | Aircraft											13
Market value of aircraft											$ 6,000,000
Air Medical and Technical Services [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of consolidated operating revenues									5.00%	9.00%
Percentage of trade receivables	13.00%				15.00%				13.00%	15.00%
Aircraft [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Salvage value of aircraft	54.00%								54.00%
Aircraft [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Salvage value of aircraft	25.00%								25.00%
Flight Equipment [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life									15 years
Flight Equipment [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life									5 years
Other Equipment [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life									10 years
Other Equipment [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life									3 years
Leasehold Improvements [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life									10 years
Leasehold Improvements [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life									6 years