The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

Name:	us-gaap_AmortizationOfIntangibleAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Goodwill and Intangible Assets - Additional Information (Detail)	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2019 USD ($) store	Jun. 30, 2018 USD ($) store	Mar. 31, 2018 USD ($) store	Jun. 30, 2019 USD ($) store	Jun. 30, 2018 USD ($) store	Dec. 31, 2018 USD ($) store	May 30, 2019 store	Mar. 31, 2019 store	Dec. 31, 2017 store
Goodwill And Intangible Assets [Line Items]
Impairment charges				$ 0		$ 0
Number of owned and franchised locations \| store	1,859	1,608	1,565	1,859	1,608	1,742		1,806	1,518
Amortization of intangible assets	$ 4,019,000	$ 4,012,000		$ 8,025,000	$ 8,025,000
Favorable and Unfavorable Leases
Goodwill And Intangible Assets [Line Items]
Amortization of intangible assets			$ 92,000		$ 183,000
Maine Acquisition
Goodwill And Intangible Assets [Line Items]
Number of owned and franchised locations \| store							4