Subsequent Events - Additional Data (Detail) (Subsequent Event, USD $)	1 Months Ended
	Jun. 27, 2012 Dividend Declared	Jul. 03, 2012 Issuance of Debt Senior Unsecured Notes	Jul. 03, 2012 Issuance of Debt Senior Unsecured Notes Maximum
Subsequent Event [Line Items]
Principal amount			$ 150,000,000
Notes maturity period		12 years
Debt, interest rate		4.60%
Dividend declared, per share	$ 0.13
Increase from previous dividend declarations, amount per share	$ 0.01
Dividend payable, date declared	Jun. 27, 2012
Dividends payable, date to be paid	Sep. 28, 2012
Dividend payable, record date	Sep. 14, 2012