Marketable securities - Additional Information (Detail) (TIMET Common Stock [Member], USD $) In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
TIMET Common Stock [Member]
Equity [Line Items]
Common stock outstanding, shares	6.5	6.5
TIMET's common stock	$ 12.83	$ 14.98

Balance held at close of period in number of shares.

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