Marketable Securities - Schedule of Amortized Cost and Estimated Fair Value of Debt Securities (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013
Available For Sale Securities Debt Maturities Fair Value [Abstract]
Due in one year or less, Amortized Cost	$ 91,669
Due after one year through three years, Amortized Cost	146,200
Due after three years through five years, Amortized Cost	58,173
Due after five years, Amortized Cost	41,572
Total amortized cost of debt securities	337,614
Due in one year or less, Estimated Fair Value	91,825
Due after one year through three years, Estimated Fair Value	146,284
Due after three years through five years, Estimated Fair Value	57,246
Due after five years, Estimated Fair Value	41,962
Total estimated fair value of debt securities	$ 337,317