Segment Disclosures - Schedule of Revenue from External Customers (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 195,142	$ 207,723	$ 211,016	$ 241,459	$ 178,785	$ 199,794	$ 197,015	$ 224,238	$ 855,340	$ 799,832	$ 750,422
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									853,802	798,420	748,971
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									$ 1,538	$ 1,412	$ 1,451