Stockholders' Equity - Additional Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Equity [Abstract]
Cash Dividend on Common Stock	$ 0.55	$ 0.55	$ 0.50	$ 1.10	$ 1.00
Aggregated Dividend Paid	$ 28.0	$ 27.9
Common stock Dividend Payable Date	Jul. 15, 2014	Apr. 14, 2014
Dividend payable date of record	Jun. 27, 2014	Mar. 28, 2014
Dividend payable date declared	May 06, 2014	Feb. 28, 2014
Company repurchased, shares					2.3
Repurchase agreement, Total cost					$ 100.0