Borrowings (Parenthetical) (Detail) (USD $)	3 Months Ended
	Mar. 31, 2012		Dec. 31, 2011
Debt Instrument [Line Items]
Amount outstanding	$ 240,293,000		$ 200,000,000
Revolver, available borrowing capacity	329,300,000
Notional fixed-for-floating interest rate swap contract	200,000,000
Debt, effective annual interest rate	3.43%
Term Loan
Debt Instrument [Line Items]
Amount outstanding	172,500,000		180,000,000
Eurodollar base rate	0.47%
Margin	1.50%
Revolver
Debt Instrument [Line Items]
Amount outstanding	67,793,000	[1],[2]	20,000,000	[1],[2]
Margin	1.50%
Minimum | Revolver
Debt Instrument [Line Items]
Eurodollar base rate	0.24%
Maximum | Revolver
Debt Instrument [Line Items]
Eurodollar base rate	0.47%
Credit Agreement 2010
Debt Instrument [Line Items]
Amount outstanding	67,500,000
Separate arrangement
Debt Instrument [Line Items]
Amount outstanding	$ 300,000

[1] The $67.8 million outstanding as of March 31, 2012 includes $67.5 million borrowed under the 2010 Credit Agreement and $0.3 million that was borrowed under a separate, short-term lending arrangement.

[2] The Company had $329.3 million of available borrowing capacity on the revolver (not including the expansion feature) as of March 31, 2012.