Consolidated Statement of Changes in Shareholders' Equity (Unaudited) (USD $) In Thousands	Total	Common stock [Member]	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income	Treasury stock
Balance at Dec. 31, 2010	$ 3,296,432	$ 120,942	$ 954,332	$ 2,257,895	$ 97,186	$ (133,923)
Comprehensive income
Net earnings	176,905			176,905
Other comprehensive income
Change in net unrealized gain on investments, net of tax	104,776				104,776
Other, net of tax	56				56
Total other comprehensive income	104,832
Comprehensive income	281,737
Issuance of 1,458 shares for exercise of options, including tax effect	36,245	1,458	34,787
Purchase of 10,176 common shares	(307,840)					(307,840)
Stock-based compensation	9,727	261	9,466
Cash dividends declared, $0.445 per share	(49,162)			(49,162)
Balance at Sep. 30, 2011	$ 3,267,139	$ 122,661	$ 998,585	$ 2,385,638	$ 202,018	$ (441,763)