Summary of Option Activity Outstanding (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Number of shares
Beginning balance	147,525
Forfeited or expired	42,425
Ending balance	105,100	147,525
Vested or expected to vest at end of period	105,100
Exercisable at end of period	105,100
Weighted average exercise price
Beginning Balance	$ 48
Forfeited or expired	$ 35.72
Ending Balance	$ 52.96	$ 48
Vested or expected to vest at end of period	$ 52.96
Exercisable at end of period	$ 52.96
Weighted average remaining contractual life (Years)
Weighted average remaining contractual life (Years)	3 years 8 months 12 days	3 years 6 months
Vested or expected to vest at end of period	3 years 8 months 12 days
Exercisable at end of period	3 years 8 months 12 days
Aggregate intrinsic value
Beginning Balance
Forfeited or expired
Ending Balance
Vested or expected to vest at end of period
Exercisable at end of period