Employee Stock Purchase Plan (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
ESPP Shares Issued	2,899,528
Prior To Two Thousand Twelve [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
ESPP Shares Issued	2,485,604
Price per ESPP Share Issued	13.95
January 1 2013 To March 31 2013 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
ESPP Shares Issued	90,799
Price per ESPP Share Issued	9.45
April 1 2013 To June 30 2013 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
ESPP Shares Issued	75,126
Price per ESPP Share Issued	9.86
July 1 2013 To September 30 2013 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
ESPP Shares Issued	50,982
Price per ESPP Share Issued	14.63
October 1 2013 To December 31 2013 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
ESPP Shares Issued	52,826
Price per ESPP Share Issued	12.44
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	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	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	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	24.95