Segment Disclosures - Schedule of Revenue from External Customers (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenue	$ 157,022	$ 180,269	$ 177,466	$ 204,726	$ 146,652	$ 165,145	$ 168,296	$ 197,078	$ 719,483	$ 677,171	$ 612,689
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenue									717,865	675,467	611,034
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenue									$ 1,618	$ 1,704	$ 1,655