Employee Stock Purchase Plan (Detail)	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
ESPP Shares Issued	2,977,712
Prior To Two Thousand Thirteen [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
ESPP Shares Issued	2,755,337
Price per ESPP Share Issued | $ / shares	$ 13.67
January 1 2014 To March 31 2014 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
ESPP Shares Issued	52,718
Price per ESPP Share Issued | $ / shares	$ 12.66
April 1 2014 To June 30 2014 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
ESPP Shares Issued	38,679
Price per ESPP Share Issued | $ / shares	$ 14.23
July 1 2014 To September 30 2014 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
ESPP Shares Issued	32,573
Price per ESPP Share Issued | $ / shares	$ 17.14
October 1 2014 To December 31 2014 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
ESPP Shares Issued	20,221
Price per ESPP Share Issued | $ / shares	$ 24.95
January 1 2015 To March 31 2015 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
ESPP Shares Issued	24,368
Price per ESPP Share Issued | $ / shares	$ 22.76
April 1 2015 To June 30 2015 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
ESPP Shares Issued	15,750
Price per ESPP Share Issued | $ / shares	$ 33.77
July 1 2015 To September 30 2015 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
ESPP Shares Issued	18,984
Price per ESPP Share Issued | $ / shares	$ 32.27
October 1 2015 To December 31 2015 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
ESPP Shares Issued	19,082
Price per ESPP Share Issued | $ / shares	$ 33.42