Loans and Allowance for Credit Losses - Schedule of Accretable Yield of Noncovered Purchased Credit Impaired Loans, or Income Expected to be Collected (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2016 USD ($)
Non Covered Purchased Credit Impaired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at January 1	$ 45,310
New loans purchased	3,217
Accretion of income	(12,990)
Reclassifications from (to) nonaccretable difference	5,619
Disposals/other adjustments	530
Balance at June 30	41,686
Acquisitions Prior to Two Thousand Fifteen [Member] | Non Covered Purchased Credit Impaired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at January 1	42,498
Accretion of income	(12,137)
Reclassifications from (to) nonaccretable difference	5,191
Disposals/other adjustments	487
Balance at June 30	36,039
Founders Financial Corporation [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at June 30	1,812
Founders Financial Corporation [Member] | Non Covered Purchased Credit Impaired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at January 1	2,812
Accretion of income	(505)
Reclassifications from (to) nonaccretable difference	428
Balance at June 30	2,735
Anchor BanCorp Wisconsin Inc [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at June 30	3,217
Anchor BanCorp Wisconsin Inc [Member] | Non Covered Purchased Credit Impaired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
New loans purchased	3,217
Accretion of income	(348)
Disposals/other adjustments	43
Balance at June 30	$ 2,912