Summary of Significant Accounting Policies - Summary of Revenue by Type and by Applicable Accounting Standard (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Revenues	$ 345,974	$ 322,141	$ 310,364	$ 260,482	$ 294,666	$ 259,162	$ 249,363	$ 226,828	$ 1,238,961	$ 1,030,019	$ 978,137
Effect Before Topic 606 [Member]
Revenues:
Revenues										1,030,019	978,137
Topic 840 [Member]
Revenues:
Revenues									612,551	494,769	459,347
Topic 606 [Member]
Revenues:
Revenues									626,410	535,250	518,790
Topic 606 [Member] | Effect Before Topic 606 [Member]
Revenues:
Revenues										1,030,019	978,137
Equipment Rentals [Member]
Revenues:
Revenues									592,193	479,016	445,227
Equipment Rentals [Member] | Effect Before Topic 606 [Member]
Revenues:
Revenues										479,016	445,227
Equipment Rentals [Member] | Topic 840 [Member]
Revenues:
Revenues									590,858	476,978	443,148
Equipment Rentals [Member] | Topic 606 [Member]
Revenues:
Revenues									1,335	2,038	2,079
Equipment Rentals [Member] | Topic 606 [Member] | Effect Before Topic 606 [Member]
Revenues:
Revenues										479,016	445,227
New Equipment Sales [Member]
Revenues:
Revenues									262,948	203,301	196,688
New Equipment Sales [Member] | Effect Before Topic 606 [Member]
Revenues:
Revenues										203,301	196,688
New Equipment Sales [Member] | Topic 606 [Member]
Revenues:
Revenues									262,948	203,301	196,688
New Equipment Sales [Member] | Topic 606 [Member] | Effect Before Topic 606 [Member]
Revenues:
Revenues										203,301	196,688
Used Equipment Sales [Member]
Revenues:
Revenues									125,125	107,329	96,910
Used Equipment Sales [Member] | Effect Before Topic 606 [Member]
Revenues:
Revenues										107,329	96,910
Used Equipment Sales [Member] | Topic 606 [Member]
Revenues:
Revenues									125,125	107,329	96,910
Used Equipment Sales [Member] | Topic 606 [Member] | Effect Before Topic 606 [Member]
Revenues:
Revenues										107,329	96,910
Parts Sales [Member]
Revenues:
Revenues									120,454	114,253	115,989
Parts Sales [Member] | Effect Before Topic 606 [Member]
Revenues:
Revenues										114,253	115,989
Parts Sales [Member] | Topic 606 [Member]
Revenues:
Revenues									120,454	114,253	115,989
Parts Sales [Member] | Topic 606 [Member] | Effect Before Topic 606 [Member]
Revenues:
Revenues										107,384	109,147
Parts and Services [Member]
Revenues:
Revenues									63,488
Parts and Services [Member] | Effect Before Topic 606 [Member]
Revenues:
Revenues										62,873	64,673
Parts and Services [Member] | Topic 606 [Member]
Revenues:
Revenues									63,488	62,873	64,673
Other [Member]
Revenues:
Revenues									74,753	63,247	58,650
Other [Member] | Effect Before Topic 606 [Member]
Revenues:
Revenues										63,247	58,650
Other [Member] | Topic 840 [Member]
Revenues:
Revenues									21,693	17,791	16,199
Other [Member] | Topic 606 [Member]
Revenues:
Revenues									$ 53,060	45,456	42,451
Other [Member] | Topic 606 [Member] | Effect Before Topic 606 [Member]
Revenues:
Revenues										$ 70,116	$ 65,492