Geographic Information for Long-Lived Assets and Revenues in United States and other Countries (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Long-lived assets:
Long-lived assets	$ 440,069				$ 418,502				$ 440,069	$ 418,502	$ 340,759
Revenues:
Revenues	153,622	151,134	177,614	163,166	158,123	167,083	149,669	150,830	645,536	625,705	473,082
UNITED STATES
Long-lived assets:
Long-lived assets	403,534				377,667				403,534	377,667	294,368
Revenues:
Revenues									500,106	495,777	365,346
CANADA
Revenues:
Revenues									30,929	34,001	28,926
Other International
Revenues:
Revenues									114,501	95,927	78,810
International, Primarily China and Russia
Long-lived assets:
Long-lived assets	$ 36,535				$ 40,835				$ 36,535	$ 40,835	$ 46,391