Schedule of Outstanding Debt (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Debt instruments maturity date	2016	2016
Industrial Development Debt Issues Payable Through 2022, 0.30%
Debt Instrument [Line Items]
Debt instruments maturity date	2022	2022
Senior Notes, interest rate	0.30%	0.30%
Senior Notes Payable Through 2021, 5.41%
Debt Instrument [Line Items]
Debt instruments maturity date	2021	2021
Senior Notes, interest rate	5.41%	5.41%
Senior Notes Payable Through 2021, 4.00%
Debt Instrument [Line Items]
Debt instruments maturity date	2021	2021
Senior Notes, interest rate	4.00%	4.00%