Investments in Term Deposits (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule of Investments [Line Items]
Cost	$ 340,349	$ 266,107	$ 190,771
Maturities of term deposits	288,719	194,873	159,566
Purchases of term deposits	$ 395,589	$ 277,116	$ 206,201