ALLL Activity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for loan and lease losses
Balance at beginning of period				$ 130,351				$ 130,854	$ 130,351	$ 130,854	$ 137,516
Provision for loan losses	191	360	239	1,122	1,802	1,907	1,078	2,100	1,912	6,887	21,525
Charge-offs									(7,603)	(13,643)	(34,672)
Recoveries									5,093	6,253	6,485
Balance at end of period	129,753				130,351				129,753	130,351	130,854
Residential Real Estate
Allowance for loan and lease losses
Balance at beginning of period				14,067				15,482	14,067	15,482	17,227
Provision for loan losses									716	(921)	2,879
Charge-offs									(431)	(793)	(5,267)
Recoveries									328	299	643
Balance at end of period	14,680				14,067				14,680	14,067	15,482
Commercial Real Estate
Allowance for loan and lease losses
Balance at beginning of period				70,332				74,398	70,332	74,398	76,920
Provision for loan losses									(2,877)	(3,670)	11,012
Charge-offs									(1,802)	(3,736)	(16,339)
Recoveries									2,146	3,340	2,805
Balance at end of period	67,799				70,332				67,799	70,332	74,398
Other Commercial
Allowance for loan and lease losses
Balance at beginning of period				28,630				21,567	28,630	21,567	20,833
Provision for loan losses									3,708	10,271	4,690
Charge-offs									(3,058)	(4,671)	(5,239)
Recoveries									1,611	1,463	1,283
Balance at end of period	30,891				28,630				30,891	28,630	21,567
Home Equity
Allowance for loan and lease losses
Balance at beginning of period				9,299				10,659	9,299	10,659	13,616
Provision for loan losses									1,254	868	324
Charge-offs									(1,038)	(2,594)	(4,369)
Recoveries									448	366	1,088
Balance at end of period	9,963				9,299				9,963	9,299	10,659
Other Consumer
Allowance for loan and lease losses
Balance at beginning of period				8,023				8,748	8,023	8,748	8,920
Provision for loan losses									(889)	339	2,620
Charge-offs									(1,274)	(1,849)	(3,458)
Recoveries									560	785	666
Balance at end of period	$ 6,420				$ 8,023				$ 6,420	$ 8,023	$ 8,748