Customer Concentration (Total Revenues by Geographic Area) (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
Revenues From External Customers [Line Items]
United States									$ 133,824	$ 137,269	$ 130,070
Total revenues	86,046	85,231	125,904	77,344	72,808	83,770	122,127	83,336	374,525	362,041	344,975
Europe [Member]
Revenues From External Customers [Line Items]
Foreign revenues									240,626	224,472	213,677
Other Geographic Areas [Member]
Revenues From External Customers [Line Items]
Foreign revenues									$ 75	$ 300	$ 1,228