Organization and Basis of Presentation - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended	1 Months Ended
	May 31, 2014	Mar. 31, 2015 Director	Feb. 28, 2014
Basis Of Presentation And Significant Accounting Policies [Line Items]
Dividend declared	$ 0.02
Contran
Basis Of Presentation And Significant Accounting Policies [Line Items]
Parent company ownership interest		93.00%
Common stock, voting rights		The voting agreement expires in February 2017 (unless Ms. Lisa Simmons, Ms. Connelly and Ms. Annette Simmons otherwise mutually agree), and the ability of Ms. Lisa Simmons, Ms. Connelly, and Ms. Annette Simmons to each designate one member of the Contran board is dependent upon each of their continued beneficial ownership of at least 5% of the combined voting stock of Contran.
Voting agreement expiration date		2017-02
Size of board of directors		5
Contran | Minimum
Basis Of Presentation And Significant Accounting Policies [Line Items]
Minimum percentage of voting stock ownership required to designate a board member			5.00%