Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)		$ 466,201	$ 495,401	$ (47,156)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Provision for (recoveries of) loan losses		37,242	4,180	(15,004)
Depreciation and amortization		32,803	32,811	31,497
Amortization of discounts and premiums, net		(4,555)	(26,258)	(8,069)
Amortization of core deposit intangibles		208	2,391	5,344
Net gain on sales of securities		(29,924)	(3,347)	(4,054)
Gain on trading securities activity		(316)
Net gain on sales of loans		(87,301)	(57,398)	(65,649)
Stock-based compensation		36,029	32,661	30,205
Deferred tax expense (benefit)		21,444	44,746	(31,289)
Changes in operating assets and liabilities:
Decrease (increase) in other assets		451,873	326,790	(196,899)
Increase (decrease) in other liabilities		23,329	(4,336)	15,425
Purchases of securities held for trading		(202,450)
Proceeds from sales of securities held for trading		202,766
Origination of loans held for sale		(1,674,123)	(4,646,773)	(4,680,243)
Proceeds from sales of loans originated for sale		2,053,484	4,554,785	4,545,466
Net cash provided by (used in) operating activities		1,326,710	755,653	(420,426)
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from repayment of securities held to maturity		175,375	2,499,205	940,580
Proceeds from repayment of securities available for sale		387,772	50,192	9,889
Proceeds from sales of securities held to maturity		547,925	1,297	44,104
Proceeds from sales of securities available for sale		453,878	322,038	278,689
Purchases of securities held to maturity		(13,030)	(213,208)	(20,021)
Purchases of securities available for sale		(1,163,043)	(279,402)	(318,027)
Redemption of Federal Home Loan Bank stock		90,909	601,941	623,189
Purchases of Federal Home Loan Bank stock		(103,794)	(528,904)	(771,833)
Proceeds from sales of loans		2,289,377	1,675,550	1,923,208
Other changes in loans, net		(1,575,846)	(2,826,365)	(4,072,135)
Purchase of premises and equipment, net		(27,783)	(84,179)	(34,802)
Net cash provided by (used in) investing activities		1,061,740	1,218,165	(1,397,159)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase in deposits		214,260	461,145	98,024
Net (decrease) increase in short-term borrowed funds		(460,000)	(3,256,300)	768,100
Proceeds from long-term borrowed funds		3,000,000	1,181,000	11,243,500
Repayments of long-term borrowed funds		(3,300,000)		(10,489,682)
Tax effect of stock plans	[1]			2,486
Net proceeds from issuance of preferred stock		502,840
Proceeds received from follow-on common stock offering, net				629,682
Cash dividends paid on common stock		(332,147)	(330,810)	(453,981)
Cash dividends paid on preferred stock		(24,621)
Payments relating to treasury shares received for restricted stock award tax payments	[2]	(18,463)	(8,677)	(7,020)
Net cash (used in) provided by financing activities		(418,131)	(1,953,642)	1,791,109
Net increase (decrease) in cash and cash equivalents		1,970,319	20,176	(26,476)
Cash and cash equivalents at beginning of year		557,850	537,674	564,150
Cash and cash equivalents at end of year		2,528,169	557,850	537,674
Supplemental information:
Cash paid for interest		447,476	382,135	540,818
Cash paid for income taxes		217,682	180,238	187,608
Cash paid for prepayment penalties on borrowings				914,965
Non-cash investing and financing activities:
Transfers to other real estate owned from loans		9,973	20,099	47,096
Transfer of loans from held for investment to held for sale		1,910,121	1,659,743	1,897,075
Transfer of loans from held for sale to held for investment				153,578
Shares issued for restricted stock awards		11,028	$ 8,985	$ 7,708
Securities transferred from held to maturity to available for sale		$ 3,040,305

[1] See Note 2, "Summary of Significant Accounting Policies" for a discussion of the Company's adoption of Accounting Standards Update No. 2016-09. See accompanying notes to the consolidated financial statements.

[2] See Note 2, "Summary of Significant Accounting Policies" for a discussion of the Company's adoption of Accounting Standards Update No. 2016-09.