Consolidated Statements of Changes in Shareholders' Equity (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Total shareholders' equity at beginning of period	$ 2,417,482	$ 2,283,537
Net income	55,188	61,033
Other comprehensive income (loss)	(23,678)	(3,338)
Stock option exercises (395,425 shares in 2013 and 108,800 shares in 2012)	20,446	5,542
Stock compensation expense recognized in earnings	2,342	2,555
Tax benefits (deficiencies) related to stock compensation	(209)	(377)
Issuance of preferred stock (6,000,000 shares in 2013)	144,539
Purchase of treasury stock (1,905,077 shares in 2013)	(115,200)
Accelerated share repurchase forward contract	(28,800)
Cash dividends declared on preferred stock
Cash dividends declared on common stock ($0.48 per share in 2013 and $0.46 per share in 2012)	(28,779)	(28,239)
Total shareholders' equity at end of period	$ 2,443,331	$ 2,320,713