Derivative Financial Instruments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Managing interest rate risk for senior notes and subordinated notes	To manage interest rate risk for our 6.05% Subordinated Notes, we entered into a fixed-for-floating interest rate swap agreement at the time of debt issuance based upon LIBOR with matched-terms.