Earnings Per Common Share - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive options excluded from the computation of diluted earnings per share (in shares)	2,900,000.0	5,200,000.0	6,900,000.0
Minimum exercise price range	$ 70.96	$ 56.28	$ 45.75
Maximum exercise price range	$ 88.81	$ 88.81	$ 89.10
Warrant
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Warrants outstanding	6,400,000