Borrowings - Additional Information (Detail) (USD $) In Billions, unless otherwise specified	1 Months Ended
	Jun. 30, 2012
Bank Facility
Debt Instrument [Line Items]
Line of credit facility maximum borrowing capacity	$ 2.25
Line of credit facility, maturity period	5 years
Bank Facility | Minimum
Debt Instrument [Line Items]
Line of credit facility, spread above LIBOR rate	0.26%
Bank Facility | Maximum
Debt Instrument [Line Items]
Line of credit facility, spread above LIBOR rate	1.93%
Existing Line Of Credit
Debt Instrument [Line Items]
Line of credit facility maximum borrowing capacity	2.25
Line of credit facility, maturity year	2015
Replaced three-year facility
Debt Instrument [Line Items]
Line of credit facility maximum borrowing capacity	$ 2.25
Line of credit facility, maturity year	2013
Line of credit facility, maturity period	3 years