Stockholders' Equity - Additional Information (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Class B Common Stock [Member]
Class of Stock [Line Items]
Certain Class B stockholders converted into Class A	818,910	289,480	1,074,432	299,776
Class A Common Stock [Member]
Class of Stock [Line Items]
Shares issued as a part of conversion	818,910	289,480	1,074,432	299,776