Schedule II - Condensed Financial Information of Registrant (Notes To Condensed Financial Statements) (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Dividends from subsidiaries	$ 466,000	$ 479,000	$ 488,376
Stock-based compensation not involving cash	28,664	32,203	25,642
Interest paid	74,792	77,066	81,322
Income taxes received	$ 110,650	$ 100,922	128,771
Preferred stock, shares outstanding	0	0
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Dividends from subsidiaries	$ 466,416	$ 478,840	488,376
Stock-based compensation not involving cash	28,664	32,203	25,642
Dividend of subsidiary to Parent	0	0	1,246,557
Dividend of subsidiary applied to loan balance	0	0	72,000
Borrowed money from affiliate	56,503	0	0
Investment in subsidiaries	39,206	0	0
Interest paid	77,920	77,663	85,443
Purchase of agent debit balances	17,297	0	0
Income taxes received	$ (22,009)	$ (25,581)	$ (27,820)
Preferred stock, liquidation distribution available to stockholders, per share in thousands	$ 1,000
Preferred stock, liquidating distribution legally available, aggregate value	$ 351,000
Cumulative Series A Preferred Stock [Member] | Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Preferred stock, shares issued	351,000
Preferred stock, shares outstanding	351,000
6.50% Cumulative Preferred Stock, Series A [Member] | Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Preferred stock, shares issued	280,000
Preferred stock, shares outstanding	280,000
Preferred stock, dividend rate, percentage	6.50%
7.15% Cumulative Preferred Stock, Series A [Member] | Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Preferred stock, shares issued	71,000
Preferred stock, shares outstanding	71,000
Preferred stock, dividend rate, percentage	7.15%