Equity Compensation - Stock Options Granted, Forfeited, Exercised and Expired (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Shares, Outstanding at beginning of period	1,574,604
Number of Shares, Granted	0		156,500
Number of Shares, Forfeited	(2,667)
Number of Shares, Exercised	0		104,054
Number of Shares, Expired	(197,244)
Number of Shares, Outstanding at end of period	1,374,693
Number of Shares, Exercisable at end of period	1,225,187
Weighted Average Exercise Price, Outstanding at beginning of period	$ 84.90
Weighted Average Exercise Price, Granted	$ 0
Weighted Average Exercise Price, Forfeited	$ 74.99
Weighted Average Exercise Price, Exercised	$ 0
Weighted Average Exercise Price, Expired	$ 47.59
Weighted Average Exercise Price, Outstanding at end of period	$ 90.28
Weighted Average Exercise Price, Exercisable at end of period	$ 92.37
Aggregate Exercise Price
Aggregate Exercise Price, Outstanding at beginning of period	$ 133,691,000
Aggregate Exercise Price, Granted	0
Aggregate Exercise Price, Forfeited	(200,000)
Aggregate Exercise Price, Exercised	0
Aggregate Exercise Price, Expired	(9,387,000)
Aggregate Exercise Price, Outstanding at end of period	124,104,000
Aggregate Exercise Price, Exercisable at end of period	113,170,000
Weighted Average Remaining Contractual Term, Outstanding at end of period, years	3 years 1 month 6 days
Weighted Average Remaining Contractual Term, Exercisable at end of period, years	2 years 9 months 18 days
Aggregate Intrinsic Value, Outstanding at end of period	0	[1]
Aggregate Intrinsic Value, Exercisable at end of period	$ 0	[1]

[1] The aggregate intrinsic value of the stock options was calculated by identifying those stock options that had a lower exercise price than the closing market price of our common stock on March 28, 2013 and multiplying the difference between the closing market price of our common stock and the exercise price of each of those stock options by the number of shares subject to those stock options that were outstanding or exercisable, as applicable.