LONG TERM DEBT - Additional Information (Detail)						9 Months Ended
	Apr. 15, 2016 USD ($)	Apr. 06, 2015 USD ($)	May 21, 2014 USD ($) $ / shares shares	Dec. 07, 2012 USD ($)	Apr. 23, 2012 USD ($) $ / note	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Dec. 06, 2012 USD ($) $ / note
Debt Instrument [Line Items]
Net proceeds from issuance of long term debt						$ 0	$ 172,304,000
Debt extinguishment cost	$ 2,700,000
Senior Notes
Debt Instrument [Line Items]
Redemption price, percentage						100.00%
Redemption period						90 days
Minimum redemption period notice required						30 days
Maximum redemption period notice required						60 days
Senior Notes | 7.50% Senior Notes Due April 15, 2020
Debt Instrument [Line Items]
Aggregate principal amount issued					$ 33,000,000			$ 45,000,000
Stated interest rate					7.50%
Sale price of notes to public | $ / note					25.00			25.00
Net proceeds from issuance of long term debt				$ 50,100,000	$ 31,700,000
Exercise of underwriters' overallotment option				$ 6,800,000
Redemption price, percentage	100.00%
Senior Notes | 5.25% Senior Notes Due April 15, 2025
Debt Instrument [Line Items]
Aggregate principal amount issued		$ 175,000,000
Stated interest rate		5.25%
Net proceeds from issuance of long term debt		$ 172,800,000
Junior Subordinated Debt | 7.50% Amortizing Note Due May 15, 2017
Debt Instrument [Line Items]
Stated interest rate			7.50%
Gross proceeds from issuance of tangible equity units			$ 69,000,000
Tangible equity units dividend rate			8.00%
Tangible equity units issued during period, shares | shares			1,380,000
Tangible equity units issued to underwriter during period, shares | shares			180,000
Tangible equity units, price per share (in dollars per share) | $ / shares			$ 50.00
Tangible equity units, convertible, conversion ratio			10.604556
Fair value of debt instrument			$ 14,600,000
Adjustments to additional paid in capital, issuance of tangible equity units			54,400,000
Tangible equity units issued, issuance costs			4,000,000
Tangible equity units issued, issuance costs, underwriter discount			3,300,000
Debt instrument, deferred finance cost			857,000
Adjustments to additional paid in capital, tangible equity units issued, issuance costs			$ 3,200,000