Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total		Preferred Stock [Member]	Common stocks	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Noncontrolling Interest [Member]
Balance at beginning of period at Dec. 31, 2013	$ 1,044,791		$ 3,000	$ 135,065	$ 119,067	$ 787,609	$ 50
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	109,869					109,941	(72)
Other comprehensive income	139,343	[1]			139,343	0	0
Issuance of common stock under compensation plans	12,028			12,028
Purchase of common stock	(18,460)			(2,396)		(16,064)
Dividends on preferred stock	(150)					(150)
Dividends on common stock	(34,599)					(34,599)
Receipts related to noncontrolling interest	60						60
Balance at end of period at Dec. 31, 2014	1,252,882		3,000	144,697	258,410	846,737	38
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	113,473					113,527	(54)
Other comprehensive income	(143,878)	[1]			(143,878)	0	0
Issuance of common stock under compensation plans	5,022			5,022
Purchase of common stock	(3,742)			(399)		(3,343)
Dividends on preferred stock	(150)					(150)
Dividends on common stock	(89,197)					(89,197)
Receipts related to noncontrolling interest	64						64
Balance at end of period at Dec. 31, 2015	1,134,474		3,000	149,320	114,532	867,574	48
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	107,219					107,223	(4)
Other comprehensive income	35,023	[1]			35,023	0	0
Issuance of common stock under compensation plans	3,718			3,718
Purchase of common stock	(586)			(63)		(523)
Dividends on preferred stock	(150)					(150)
Dividends on common stock	(91,452)					(91,452)
Receipts related to noncontrolling interest	12						12
Balance at end of period at Dec. 31, 2016	$ 1,188,258		$ 3,000	$ 152,975	$ 149,555	$ 882,672	$ 56

[1] Other comprehensive income (loss) is recorded net of deferred income taxes and other adjustments for assumed changes in deferred acquisition costs, value of insurance in force acquired, unearned revenue reserve and policyholder liabilities.