Long-Term Debt - Long-Term Debt (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Mar. 09, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Other long-term debt	$ 127,330		$ 126,760
Total long-term debt	507,341		374,371
Term Note Payable Maturing December 2015 [Member]
Debt Instrument [Line Items]
Term note payable	132,000		149,600
Subordinated Debt [Member] | Subordinated Notes Payable Maturing June 2045 [Member]
Debt Instrument [Line Items]
Subordinated notes payable	150,000	$ 150,000
Subordinated Debt [Member] | Subordinated Notes Payable Maturing April 2017 [Member]
Debt Instrument [Line Items]
Subordinated notes payable	$ 98,011		$ 98,011