Amortized Cost and Fair Value of Marketable Securities Classified by Stated Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 112,458	$ 117,861
Fair Value	112,544	118,187
Due in 1 year or less [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	59,384	53,761
Fair Value	59,448	53,852
Due in 1 - 2 years [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	21,628	36,510
Fair Value	21,641	36,694
Due in 2 - 3 years [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,063	11,847
Fair Value	10,060	11,856
Due in 3 - 4 years [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		744
Fair Value		746
Due in 4 - 9 years [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,587	5,158
Fair Value	7,610	5,179
Due in 9 - 20 years [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,629	1,032
Fair Value	1,639	1,040
Due in 20 - 33 years [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,167	8,809
Fair Value	$ 12,146	$ 8,820