Net Income Available to Common Stockholders (Detail) - Anti-Dilutive Securities Not Included In Diluted Shares Outstanding Calculation In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Stock options outstanding [Member]
Weighted-average anti-dilutive securities	1,354	1,557	1,586	1,482
Restricted stock units outstanding [Member]
Weighted-average anti-dilutive securities	211	146	267	123
Shares of common stock subject to repurchase [Member]
Weighted-average anti-dilutive securities	31	809	45	1,146