Debt - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended
	Mar. 23, 2017	Mar. 31, 2017	Mar. 31, 2016	Mar. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Interest expense, including amortization of deferred issuance cost		$ 2,467	$ 2,215
7.875% Subordinated Notes due 2047
Debt Instrument [Line Items]
Debt instrument, face amount	$ 120,000	$ 130,000
Number of days granted to uderwriters option to purchase	30 days
Additional aggregate principal amount purchased pursuant to over-allotment option granted to the underwriters	$ 18,000
Subordinated Notes percentage		7.875%			7.875%
Debt instrument, interest rate terms		Payable quarterly in arrears on January 15, April 15, July 15, and October 15 of each year
Debt instrument, maturity date		Apr. 15, 2047
Debt instrument, redemption description		The Company has the right to redeem the 2047 Notes in $25 increments, in whole or in part, on and after April 15, 2022, or on any interest payment date thereafter, at a redemption price equal to 100% of the principal amount of the 2047 Notes being redeemed plus accrued and unpaid interest to, but not including, the date of redemption.
Debt instrument, redemption price, percentage of principal amount redeemed		100.00%
Deferred issuance costs		$ 4,200
Interest expense, including amortization of deferred issuance cost		200
7.875% Subordinated Notes due 2047 | Over-Allotment Option
Debt Instrument [Line Items]
Debt instrument, face amount				$ 10,000
7.75% Subordinated Notes due 2045
Debt Instrument [Line Items]
Debt instrument, face amount		$ 100,000
Subordinated Notes percentage		7.75%			7.75%