Schedule II - Condensed Financial Information of the Registrant (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Statements of Cash Flows
Net income	$ 11,652	$ 17,656	$ 18,059	$ 13,984	$ 9,571	$ 14,334	$ 16,956	$ 17,209	$ 61,351	$ 58,070	$ 13,702
Adjustments to reconcile net income to net cash provided by operating activities:
Earnings from consolidated subsidiaries									(148)
Other assets									3,084	(1,444)	2,151
Accounts payable and accrued liabilities									1,050	13,426	(2,135)
Net cash provided by operating activities									110,861	104,331	39,475
Proceeds from exercise of stock options									2,592	1,241	902
Dividends paid									(36,865)	(33,634)	(30,322)
Acquisition of treasury stock									(4,799)		(43)
Net cash used for financing activities									(39,072)	(32,393)	(29,463)
Net increase (decrease) in cash and cash equivalents									20,494	(2,507)	(2,401)
Cash and cash equivalents at beginning of year				35,383				37,890	35,383	37,890	40,291
Cash and cash equivalents at end of period	55,877				35,383				55,877	35,383	37,890
Registrant
Condensed Statements of Cash Flows
Net income									61,351	58,070	13,702
Adjustments to reconcile net income to net cash provided by operating activities:
Earnings from consolidated subsidiaries									(62,552)	(59,264)	(14,780)
Dividends received from consolidated subsidiaries									36,114	29,137	25,744
Amortization of restricted stock expense									4,153	4,430	4,747
Other assets									(61)	12	55
Accounts payable and accrued liabilities									67	8	(5)
Net cash provided by operating activities									39,072	32,393	29,463
Proceeds from exercise of stock options									2,592	1,241	902
Dividends paid									(36,865)	(33,634)	(30,322)
Acquisition of treasury stock									(4,799)		(43)
Net cash used for financing activities									$ (39,072)	$ (32,393)	$ (29,463)