Goodwill and other intangibles - Summary of Goodwill (Detail) - USD ($) $ in Thousands		12 Months Ended
Feb. 10, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Goodwill summary
Beginning balances		$ 217,722	$ 251,868
Re-allocation of goodwill			0
Acquisitions		300	7,220
Purchase adjustments			(5,268)
Impairment	$ (35,900)	0	(35,749)	$ 0
Disposals		(928)	(349)
Ending balances		217,094	217,722	251,868
Title
Goodwill summary
Beginning balances		211,255	202,002
Re-allocation of goodwill			3,951
Acquisitions		300	7,220
Purchase adjustments			0
Impairment		0	(1,569)	0
Disposals		(190)	(349)
Ending balances		211,365	211,255	202,002
Ancillary Services and Corporate
Goodwill summary
Beginning balances		6,467	49,866
Re-allocation of goodwill			(3,951)
Acquisitions		0	0
Purchase adjustments			(5,268)
Impairment		0	(34,180)	0
Disposals		(738)	0
Ending balances		$ 5,729	$ 6,467	$ 49,866

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of transfers into (out of) an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of divestiture of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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