Stockholder's Equity - Shares of Common Stock Issued During 2014 Under Employee Stock Purchase Plan (Detail) (USD $)	3 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares available, Beginning balance			272,788
Shares issued during period (shares)	9,043	9,887	8,025
Shares available, Ending Balance	245,833
Shares issued during period (per share price)	$ 20.30	$ 20.96	$ 22.84