Earnings Per Share - Additional Information (Detail) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 03, 2014 tranche	Apr. 30, 2014	May 01, 2014	May 10, 2013	Nov. 17, 2014	Dec. 19, 2013	Feb. 12, 2013	Oct. 13, 2011
Earnings Per Share Disclosure [Line Items]
Common stock equivalents not included in computation of diluted earnings per share (in dollars per shares)	662,259
Preferred stock, shares authorized (in shares)	15,000,000
Payment for repurchase of common stock	$ 150,000,000	$ 582,298,000	$ 63,575,000
Shares available for repurchase	3,749,340
Common Stock
Earnings Per Share Disclosure [Line Items]
Shares repurchased (in shares)	2,190,254	9,198,056	1,092,767
Maximum
Earnings Per Share Disclosure [Line Items]
Stock repurchase program, number of shares authorized to be repurchased (in shares)										15,000,000	5,000,000
Restricted Stock
Earnings Per Share Disclosure [Line Items]
Number of shares containing nonforfeitable rights to dividends	5,600
Merrill Lynch | Accelerated Share Repurchase Agreement
Earnings Per Share Disclosure [Line Items]
Forward purchase contract adjustment to fair value (in dollars per share)	$ 0.77
Stock repurchase program, authorized amount				50,000,000
Number of tranches				2
Authorized amount per tranche purchased				25,000,000
Merrill Lynch | Initial Delivery | Accelerated Share Repurchase Agreement
Earnings Per Share Disclosure [Line Items]
Payment for repurchase of common stock				50,000,000
Repurchase of common stock shares (in shares)				623,248
Stock repurchased during period, value				40,000,000
Merrill Lynch | Final Settlement | Accelerated Share Repurchase Agreement
Earnings Per Share Disclosure [Line Items]
Repurchase of common stock shares (in shares)					150,504
Merrill Lynch | Total | Accelerated Share Repurchase Agreement
Earnings Per Share Disclosure [Line Items]
Repurchase of common stock shares (in shares)	773,752
JP Morgan | Accelerated Share Repurchase Agreement
Earnings Per Share Disclosure [Line Items]
Forward purchase contract adjustment to fair value (in dollars per share)		$ 1.01
Stock repurchase program, authorized amount					100,000,000
Number of tranches					2
Authorized amount per tranche purchased					50,000,000
JP Morgan | Initial Delivery | Accelerated Share Repurchase Agreement
Earnings Per Share Disclosure [Line Items]
Payment for repurchase of common stock						100,000,000	450,000,000
Repurchase of common stock shares (in shares)						1,193,317	5,680,921
Stock repurchased during period, value						$ 80,000,000	$ 360,000,000
JP Morgan | Final Settlement | Accelerated Share Repurchase Agreement
Earnings Per Share Disclosure [Line Items]
Repurchase of common stock shares (in shares)								223,185	1,384,011
JP Morgan | Total | Accelerated Share Repurchase Agreement
Earnings Per Share Disclosure [Line Items]
Repurchase of common stock shares (in shares)	1,416,502	7,064,932