Consolidated Statements of Changes in Shareholders' Equity (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Statement of Stockholders' Equity [Abstract]
Total shareholders’ equity at beginning of period	$ 2,417,482	$ 2,283,537
Net income	175,295	177,764
Other comprehensive income (loss)	(92,321)	26,989
Stock option exercises (1,249,874 shares in 2013 and 197,961 shares in 2012)	65,026	10,092
Stock compensation expense recognized in earnings	7,310	7,942
Tax benefits (deficiencies) related to stock compensation	1,854	(425)
Issuance of preferred stock (6,000,000 shares in 2013)	144,486	0
Purchase of treasury stock (2,236,748 shares in 2013)	(144,000)	0
Cash dividends – preferred stock (approximately $0.78 per share in 2013)	(4,703)	0
Cash dividends – common stock ($1.48 per share in 2013 and $1.42 per share in 2012)	(89,261)	(87,282)
Total shareholders’ equity at end of period	$ 2,481,168	$ 2,418,617