INVESTMENTS IN QUALIFIED AFFORDABLE HOUSING PARTNERSHIPS, TAX CREDIT AND OTHER INVESTMENTS, NET (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014		Jun. 30, 2015	Jun. 30, 2014		Dec. 31, 2014
Impact of new accounting guidance
Investments in qualified affordable housing partnerships, net	$ 176,566			$ 176,566			$ 178,962	[1]
Other assets - Deferred tax assets							389,601
Retained earnings	1,744,955			1,744,955			1,604,141	[1]
Noninterest expense - Amortization of tax credit and other investments	2,997	$ 5,490	[1]	9,296	$ 6,982	[1]
Income before income taxes	144,421	122,966	[1]	291,247	239,129	[1]
Income tax expense	45,673	38,661	[1]	92,472	80,653	[1]
Net income	$ 98,748	$ 84,305	[1]	$ 198,775	$ 158,476	[1]
EARNINGS PER SHARE
BASIC (in dollars per share)	$ 0.69	$ 0.59	[1]	$ 1.38	$ 1.11	[1]
DILUTED (in dollars per share)	$ 0.68	$ 0.59	[1]	$ 1.38	$ 1.11	[1]
Previously Reported
Impact of new accounting guidance
Investments in qualified affordable housing partnerships, net							178,652
Other assets - Deferred tax assets							384,367
Retained earnings							$ 1,598,598
Noninterest expense - Amortization of tax credit and other investments		$ 12,851			$ 18,815
Income before income taxes		115,606			227,296
Income tax expense		31,618			66,567
Net income		$ 83,988			$ 160,729
EARNINGS PER SHARE
BASIC (in dollars per share)		$ 0.59			$ 1.13
DILUTED (in dollars per share)		$ 0.58			$ 1.12

[1] Prior periods were restated to reflect the retrospective application of adopting the new accounting guidance related to the Company's investments in qualified affordable housing projects Accounting Standards Update ("ASU") 2014-01. See Note 10 of the Notes to Consolidated Financial Statements for additional information.