Parent Company (Schedule of Condensed Financial Statements-Income Statement ) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Income before income tax expense	$ 326,503	$ 339,894	$ 263,191
Income tax expense	97,019	101,943	79,507
Net income	229,484	237,951	183,684
Parent
Condensed Financial Statements, Captions [Line Items]
Cash dividends from subsidiaries	103,500	82,642	81,715
Other income	480	437	483
Total Income	103,980	83,079	82,198
Interest and other expenses	27,096	30,613	29,684
Income before income tax expense	76,884	52,466	52,514
Income tax expense	(9,451)	(10,324)	(9,341)
Income before undistributed income of subsidiaries	86,335	62,790	61,855
Equity in undistributed income of subsidiaries	143,149	175,161	121,829
Net income	$ 229,484	$ 237,951	$ 183,684