Revenues by Geographic Area (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
Schedule Of Revenues From External Customers [Line Items]
Total revenue	$ 340,903	$ 345,389	$ 351,296	$ 340,285	$ 350,977	$ 330,191	$ 344,827	$ 347,066	$ 1,377,873	$ 1,373,061	$ 1,446,325
United States [Member]
Schedule Of Revenues From External Customers [Line Items]
Total revenue									1,327,840	1,321,779	1,387,304
Canada [Member]
Schedule Of Revenues From External Customers [Line Items]
Total revenue									20,727	24,999	23,909
Other International [Member]
Schedule Of Revenues From External Customers [Line Items]
Total revenue									$ 29,306	$ 26,283	$ 35,112