Investment Securities, All Classified as Available-for-Sale (Detail) - USD ($) $ in Thousands |
Sep. 30, 2016 |
Dec. 31, 2015 |
---|---|---|
Schedule of Available-for-sale Securities [Line Items] | ||
Amortized Cost | $ 434,658 | $ 112,996 |
Unrealized Gains | 562 | 12 |
Unrealized Losses | (40) | (14) |
Estimated Fair Value | 435,180 | 112,994 |
U.S. Treasury notes | ||
Schedule of Available-for-sale Securities [Line Items] | ||
Amortized Cost | 53,947 | 9,000 |
Unrealized Gains | 32 | |
Unrealized Losses | (1) | |
Estimated Fair Value | 53,979 | 8,999 |
Government sponsored enterprise securities | ||
Schedule of Available-for-sale Securities [Line Items] | ||
Amortized Cost | 128,245 | 103,996 |
Unrealized Gains | 37 | 12 |
Unrealized Losses | (13) | |
Estimated Fair Value | 128,282 | $ 103,995 |
Corporate debt securities | ||
Schedule of Available-for-sale Securities [Line Items] | ||
Amortized Cost | 68,664 | |
Unrealized Losses | (40) | |
Estimated Fair Value | 68,624 | |
Commercial paper | ||
Schedule of Available-for-sale Securities [Line Items] | ||
Amortized Cost | 183,802 | |
Unrealized Gains | 493 | |
Estimated Fair Value | $ 184,295 |