Borrowings (Convertible Senior Notes Due 2013) (Detail) (USD $)	1 Months Ended	12 Months Ended
	Mar. 07, 2008	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Debt Instrument [Line Items]
Difference between proceeds from issuance of debt and fair value of liability, deferred taxes		$ 6,900,000
Debt Instrument, Equity Components [Member]
Debt Instrument [Line Items]
Difference between proceeds from issuance of debt and fair value of liability, net of deferred taxes		12,800,000
Convertible Senior Notes Due 2013 [Member]
Debt Instrument [Line Items]
Debt instrument issuance amount	310,000,000
Interest rate percentage on issued debt	3.00%
Year of maturity of debt	2013
Converted share	14.7113
Principal amount of initial conversion rate	1,000
Accrued interest		2,700,000
Convertible senior notes discount rate		4.50%
Expected life for accretion of discount rate, start date		2008-03-07
Expected life for accretion of discount rate, end date		2013-03-15
Pre tax non-cash interest expense recognized in consolidated statement of operations		4,300,000	4,100,000	3,900,000
Accumulated amortization related to debt discount		15,400,000	11,100,000
Annual pre-tax increase in non-cash interest expense		4,300,000
Convertible Senior Notes Due 2013 [Member] | Debt Instrument, Liability Components [Member]
Debt Instrument [Line Items]
Debt instrument issuance amount		290,300,000
Convertible Senior Notes Due 2013 [Member] | Debt Instrument, Equity Components [Member]
Debt Instrument [Line Items]
Debt instrument issuance amount		$ 19,700,000