Segment Reporting (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Revenues:
Rental	$ 132,338	$ 114,742
Sales	8,103	7,978
Other	213	807
Total revenues	140,654	123,527
Costs and expenses:
Rental, selling and general expenses	88,998	78,359
Cost of sales	5,391	5,112
Restructuring expenses	111	899	$ 2,886
Depreciation and amortization	16,823	15,264
Total costs and expenses	111,323	99,634
Income from operations	29,331	23,893
Interest expense, net of interest income	9,593	8,402
Income tax provision (benefit)	4,949	5,330
Capital expenditures for additions to rental fleet, excluding acquisitions	15,389	10,006
Storage Solutions
Revenues:
Rental	106,864	93,806
Sales	6,739	6,864
Other	169	673
Total revenues	113,772	101,343
Costs and expenses:
Rental, selling and general expenses	70,824	62,225
Cost of sales	4,569	4,601
Restructuring expenses	111	901
Depreciation and amortization	10,732	9,183
Total costs and expenses	86,236	76,910
Income from operations	27,536	24,433
Interest expense, net of interest income	6,892	5,694
Income tax provision (benefit)	5,415	6,345
Capital expenditures for additions to rental fleet, excluding acquisitions	11,853	8,294
Storage Solutions | North America
Revenues:
Rental	86,598	75,566
Sales	4,876	4,877
Other	129	564
Total revenues	91,603	81,007
Costs and expenses:
Rental, selling and general expenses	57,018	50,000
Cost of sales	3,024	3,008
Restructuring expenses	111	901
Depreciation and amortization	8,682	7,513
Total costs and expenses	68,835	61,422
Income from operations	22,768	19,585
Interest expense, net of interest income	6,686	5,568
Income tax provision (benefit)	4,597	5,608
Capital expenditures for additions to rental fleet, excluding acquisitions	8,279	4,865
Storage Solutions | United Kingdom
Revenues:
Rental	20,266	18,240
Sales	1,863	1,987
Other	40	109
Total revenues	22,169	20,336
Costs and expenses:
Rental, selling and general expenses	13,806	12,225
Cost of sales	1,545	1,593
Depreciation and amortization	2,050	1,670
Total costs and expenses	17,401	15,488
Income from operations	4,768	4,848
Interest expense, net of interest income	206	126
Income tax provision (benefit)	818	737
Capital expenditures for additions to rental fleet, excluding acquisitions	3,574	3,429
Tank & Pump Solutions Segment
Revenues:
Rental	25,474	20,936
Sales	1,364	1,114
Other	44	134
Total revenues	26,882	22,184
Costs and expenses:
Rental, selling and general expenses	18,174	16,134
Cost of sales	822	511
Restructuring expenses		(2)
Depreciation and amortization	6,091	6,081
Total costs and expenses	25,087	22,724
Income from operations	1,795	(540)
Interest expense, net of interest income	2,701	2,708
Income tax provision (benefit)	(466)	(1,015)
Capital expenditures for additions to rental fleet, excluding acquisitions	$ 3,536	$ 1,712