Revenue is primarily derived from services rendered to patients for inpatient psychiatric and substance abuse care, outpatient psychiatric care and residential treatment. The services provided by the Company have no fixed duration and can be terminated by the patient or the facility at any time, and therefore, each treatment is its own stand-alone contract.

As our performance obligations relate to contracts with a duration of one year or less, the Company elected the optional exemption in Accounting Standards Codification (“ASC”) ASC 606-10-50-14(a). Therefore, the Company is not required to disclose the transaction price for the remaining performance obligations at the end of the reporting period or when the Company expects to recognize the revenue. The Company has minimal unsatisfied performance obligations at the end of the reporting period as our patients typically are under no obligation to remain admitted in our facilities.

The Company disaggregates revenue from contracts with customers by service type and by payor within each of the Company’s segments.

The Company’s facilities in the United States (the “U.S. Facilities”) and services provided by the U.S. Facilities can generally be classified into the following categories: acute inpatient psychiatric facilities; specialty treatment facilities; residential treatment centers; and outpatient community-based facilities.

Acute inpatient psychiatric facilities. Acute inpatient psychiatric facilities provide a high level of care in order to stabilize patients that are either a threat to themselves or to others. The acute setting provides 24-hour observation, daily intervention and monitoring by psychiatrists.

Specialty treatment facilities. Specialty treatment facilities include residential recovery facilities, eating disorder facilities and comprehensive treatment centers. The Company provides a comprehensive continuum of care for adults with addictive disorders and co-occurring mental disorders. Inpatient, including detoxification and rehabilitation, partial hospitalization and outpatient treatment programs give patients access to the least restrictive level of care.

Residential treatment centers. Residential treatment centers treat patients with behavioral disorders in a non-hospital setting, including outdoor programs. The facilities balance therapy activities with social, academic and other activities.

Outpatient community-based facilities. Outpatient community-based programs are designed to provide therapeutic treatment to children and adolescents who have a clinically-defined emotional, psychiatric or chemical dependency disorder while enabling the youth to remain at home and within their community.

The table below presents total U.S. revenue attributed to each category (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Acute inpatient psychiatric facilities	$	229,128	$	203,535	$	445,725	$	399,426
Specialty treatment facilities		201,269		192,894		394,304		377,429
Residential treatment centers		74,084		74,133		147,308		145,690
Outpatient community-based facilities		5,332		10,908		10,436		21,330
Revenue	$	509,813	$	481,470	$	997,773	$	943,875

The Company receives payments from the following sources for services rendered in our U.S. Facilities: (i) state governments under their respective Medicaid and other programs; (ii) commercial insurers; (iii) the federal government under the Medicare program administered by the Centers for Medicare and Medicaid Services (“CMS”); and (iv) individual patients and clients.

The Company determines the transaction price based on established billing rates reduced by contractual adjustments provided to third-party payors, discounts provided to uninsured patients and implicit price concessions. Contractual adjustments and discounts are based on contractual agreements, discount policies and historical experience. Implicit price concessions are based on historical collection experience. Most of our U.S. Facilities have contracts containing variable consideration. However, it is unlikely a significant reversal of revenue will occur when the uncertainty is resolved, and therefore, the Company has included the variable consideration in the estimated transaction price. Subsequent changes resulting from a patient’s ability to pay are recorded as bad debt expense, which is included as a component of other operating expenses in the condensed consolidating statements of income. Bad debt expense for the three and six months ended June 30, 2019 and 2018 was not significant.

The following table presents revenue by payor type and as a percentage of revenue in our U.S. Facilities (in thousands):

	Three Months Ended June 30,										Six Months Ended June 30,
	2019					2018					2019					2018
	Amount		%			Amount		%			Amount		%			Amount		%
Commercial	$	146,917		28.8	%	$	147,279		30.6	%	$	286,344		28.7	%	$	284,898		30.2	%
Medicare		73,505		14.4	%		69,343		14.4	%		146,121		14.6	%		136,557		14.5	%
Medicaid		255,070		50.0	%		225,732		46.9	%		494,261		49.5	%		439,068		46.5	%
Self-Pay		29,624		5.8	%		33,379		6.9	%		61,356		6.2	%		70,286		7.4	%
Other		4,697		1.0	%		5,737		1.2	%		9,691		1.0	%		13,066		1.4	%
Revenue	$	509,813		100.0	%	$	481,470		100.0	%	$	997,773		100.0	%	$	943,875		100.0	%

The Company’s facilities located in the United Kingdom (the “U.K. Facilities”) and services provided by the U.K. Facilities can generally be classified into the following categories: healthcare facilities; education and children’s services; and adult care facilities.

Healthcare facilities. Healthcare facilities provide psychiatric treatment and nursing for sufferers of mental disorders, including for patients whose risk of harm to others and risk of escape from hospitals cannot be managed safely within other mental health settings. In order to manage the risks involved with treating patients, the facility is managed through the application of a range of security measures depending on the level of dependency and risk exhibited by the patient.

Education and children’s services. Education and children’s services provide specialist education for children and young people with special educational needs, including autism, Asperger’s Syndrome, social, emotional and mental health, and specific learning difficulties, such as dyslexia. The division also offers standalone children’s homes for children that require 52-week residential care to support complex and challenging behavior and fostering services.

Adult care facilities. Adult care focuses on care of individuals with a variety of learning difficulties, mental health illnesses and adult autism spectrum disorders. It also includes long-term, short-term and respite nursing care to high-dependency elderly individuals who are physically frail or suffering from dementia. Care is provided in a number of settings, including in residential care homes and through supported living.

The table below presents total U.K. revenue attributed to each category (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Healthcare facilities	$	155,553	$	158,894	$	307,261	$	313,509
Education and Children’s Services		46,142		48,065		92,264		96,150
Adult Care facilities		77,854		77,309		152,681		154,445
Revenue	$	279,549	$	284,268	$	552,206	$	564,104

On an annual basis, the Company receives payments from approximately 500 public funded sources in the U.K. (including the National Health Service (“NHS”), Clinical Commissioning Groups (“CCGs”) and local authorities in England, Scotland and Wales) and individual patients and clients. The Company determines the transaction price based on established billing rates by payor reduced by implicit price concessions. Implicit price concessions are insignificant in the U.K. Facilities.

The following table presents revenue by payor type and as a percentage of revenue in our U.K. Facilities (in thousands):

	Three Months Ended June 30,										Six Months Ended June 30,
	2019					2018					2019					2018
	Amount		%			Amount		%			Amount		%			Amount		%
U.K. public funded sources	$	252,332		90.3	%	$	256,881		90.4	%	$	497,745		90.1	%	$	510,175		90.4	%
Self-Pay		26,651		9.5	%		27,272		9.6	%		53,465		9.7	%		52,340		9.3	%
Other		566		0.2	%		115		0.0	%		996		0.2	%		1,589		0.3	%
Revenue	$	279,549		100.0	%	$	284,268		100.0	%	$	552,206		100.0	%	$	564,104		100.0	%

The Company’s contract liabilities primarily consist of unearned revenue in our U.K. Facilities due to the timing of payments received mainly in our education and children’s services and healthcare facilities. Contract liabilities are included in other accrued liabilities on the condensed consolidated balance sheets. A summary of the activity in unearned revenue in the U.K. Facilities is as follows (in thousands):