Shareholders' Equity (Details) (USD $) In Thousands, except Share data	1 Months Ended		6 Months Ended
	Jun. 30, 2011	Apr. 30, 2011	Jun. 30, 2011		Jun. 30, 2010		Dec. 31, 2010
Components of accumulated other comprehensive income (loss)
Net unrealized gain on securities available-for-sale	$ 56,596		$ 56,596		$ 54,128		$ 36,386
Net unrealized gain on cash flow hedges	349		349		3,896		1,184
Pension liability adjustment	(652)		(652)		26		(717)
Total accumulated other comprehensive income	56,293		56,293		58,050		36,853
Components of total comprehensive income
Net income			88,230	[1]	58,086	[1]
Securities available for sale:
Net unrealized gain, net of taxes of $16,138 and $49,861 and reclassification of $1,099 and $1,193 included in net income			22,442		69,338
Net unrealized gain (loss) on securities available-for-sale, tax expense (benefit)			16,138		49,861
Net unrealized gain (loss) on securities available-for-sale, reclassification of net gain (loss) included in net income			1,099		1,193
Non-credit related impairment loss, net of taxes of ($1,605) and ($5,641)			(2,233)		(7,844)
Non-credit related impairment loss on investment securities, taxes			(1,605)		(5,641)
Net unrealized loss on cash flow hedges, net of taxes of $0 and $2,892 and reclassification of $485 and $3,249 included in net income			(834)		(475)
Net unrealized gain (loss) on cash flow hedges, tax expense (benefit)			0		2,892
Net unrealized gain (loss) on cash flow hedges, reclassification of net gain included in net income			485		3,249
Pension liability adjustment			65		80
Total other comprehensive income			19,440	[2]	61,099	[2]
Total comprehensive income			107,670		119,185
Net income attributable to redeemable noncontrolling interest			$ 1,120		$ 1,230
Common shares repurchased
Total number of Shares(or Units) Purchased (in shares)	554	4,000	4,554
Average Price Paid per Share (or Unit) (in dollars per share)	$ 52.80	$ 57.30	$ 56.75
Shares of common stock reserved for issuance (in shares)	1,400,000		1,400,000
Shares of unvested restricted stock (in shares)	900,000		900,000

[1] Net income excludes net income attributable to redeemable noncontrolling interest of $1,120 and $1,230 for the six-month periods ended June 30, 2011 and 2010, respectively. Redeemable noncontrolling interest is reflected in the mezzanine section of the consolidated balance sheets. See Note 17 of the Notes to the Unaudited Consolidated Financial Statements.

[2] See Note 9 for additional information on other comprehensive income.