Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Person Location	Jun. 30, 2011
Summary Of Significant Accounting Policies [Line Items]
Number of states with service locations			48
Approximate percentage of revenue as reimbursement from government sources			61.00%	61.00%
Rentals as percentage of total revenues, approximate	53.20%	56.80%	53.60%	58.00%
Sale items as a percentage of total revenues, approximate	46.80%	43.20%	46.40%	42.00%
Cost of goods and services, depreciation	$ 30,400,000	$ 28,100,000	$ 59,500,000	$ 54,900,000
Allocation of customer service, distribution and administrative costs relating to the respiratory drug product line	14,200,000	13,600,000	28,100,000	27,500,000
Salary and related expenses for pharmacists and other service professionals	2,600,000	3,000,000	5,400,000	5,800,000
Number of operating centers			1,058
Operating center, number of customer service representatives			2
Operating center, number of center managers			1
Operating center, number of sales representatives			1
Salary and related expenses for Service Reps	28,900,000	28,300,000	57,800,000	55,900,000
Salary and related expenses included in selling, general, and administrative expenses	68,600,000	62,900,000	138,000,000	125,100,000
Salary and related expenses for respiratory therapists	$ 18,000,000	$ 17,900,000	$ 35,700,000	$ 34,500,000
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Operating center, approximate number of employees			7
Operating center, number of service representatives			2
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Operating center, approximate number of employees			8
Operating center, number of service representatives			3