Stock-Based Compensation - Summary of Activity in Corporation's Active Stock Plans (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Shares Available for Grant	1,157,413
Authorized, Shares Available for Grant	2,293,660
Granted, Shares Available for Grant	(10,500)
Stock options exercised, Shares Available for Grant	0
Stock awards vested, Shares Available for Grant	0
Forfeited, Shares Available for Grant	42,000
Cancelled/expired, Shares Available for Grant	0
Ending Balance, Shares Available for Grant	3,482,573
Beginning Balance, Director Deferred Stock Units Outstanding	27,724
Granted, Director Deferred Stock Units Outstanding	5,500
Stock options exercised, Director Deferred Stock Units Outstanding	0
Stock awards vested, Director Deferred Stock Units Outstanding	0
Forfeited, Director Deferred Stock Units Outstanding	0
Cancelled/expired, Director Deferred Stock Units Outstanding	0
Ending Balance, Director Deferred Stock Units Outstanding	33,224
Stock options exercised, Number of Shares	(1,249,874)	(197,961)
Non-Vested Stock Awards/Stock Units Outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares	188,560
Granted, Number of Shares	0
Stock options exercised, Number of Shares	0
Stock awards vested, Number of Shares	0
Forfeited, Number of Shares	0
Cancelled/expired, Number of Shares	0
Ending Balance, Number of Shares	188,560
Beginning Balance, Weighted-Average Grant-Date Fair Value	$ 51.67
Granted, Weighted-Average Grant-Date Fair Value	$ 0.00
Stock options exercised, Weighted-Average Grant-Date Fair Value	$ 0.00
Stock awards vested, Weighted-Average Grant-Date Fair Value	$ 0.00
Forfeited, Weighted-Average Grant-Date Fair Value	$ 0.00
Cancelled/expired, Weighted-Average Grant-Date Fair Value	$ 0.00
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 51.67
Stock Options Outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares	5,513,516
Granted, Number of Shares	5,000
Stock options exercised, Number of Shares	(1,249,874)
Stock awards vested, Number of Shares	0
Forfeited, Number of Shares	(42,000)
Cancelled/expired, Number of Shares	0
Ending Balance, Number of Shares	4,226,642
Beginning Balance, Weighted-Average Exercise Price	$ 51.94
Granted, Weighted-Average Exercise Price	$ 70.55
Stock options exercised, Weighted-Average Exercise Price	$ 52.03
Stock awards vested, Weighted-Average Exercise Price	$ 0.00
Forfeited, Weighted-Average Exercise Price	$ 51.42
Cancelled/expired, Weighted-Average Exercise Price	$ 0.00
Ending Balance, Weighted-Average Exercise Price	$ 51.94