Components Of Equity - Additional Information (Detail) (USD $)	3 Months Ended	0 Months Ended
	Mar. 31, 2015	May 06, 2015
Non-Discretionary Plan
Class of Stock [Line Items]
Shares repurchased	458,991
Average price per share	$ 47.84
Discretionary Plan
Class of Stock [Line Items]
Shares repurchased	1,157,523
Average price per share	$ 47.87
Expected common stock shares issued and outstanding	188,000,000
Subsequent Event
Class of Stock [Line Items]
Date of declaration of dividends		May 06, 2015
Dividend declared per share		$ 0.36
Date of dividend payment		Jun. 15, 2015
Dividends payable to shareholders date of record		Jun. 01, 2015