Quarterly report pursuant to Section 13 or 15(d)

OTHER COMPREHENSIVE INCOME OTHER COMPREHENSIVE INCOME - AOCI Roll Forward (Details)

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OTHER COMPREHENSIVE INCOME OTHER COMPREHENSIVE INCOME - AOCI Roll Forward (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2017
Sep. 30, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Balance, beginning of period   $ 10,308,146 $ 6,594,606
Other comprehensive income before reclassifications   16,293 53,275
Amounts reclassified from accumulated OCI to earnings   14,760 708
Period change     53,983
Balance, end of period $ 10,698,849 10,698,849 10,386,765
Unrealized gains and (losses) on debt securities | Debt Securities      
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Balance, beginning of period   (192,764) 8,361
Other comprehensive income before reclassifications   15,465 47,934
Amounts reclassified from accumulated OCI to earnings   12,007 (1,314)
Period change 27,472   46,620
Balance, end of period (165,292) (165,292) 54,981
Unrealized gains and (losses) on debt securities | Marketable equity securities      
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Balance, beginning of period   287 176
Other comprehensive income before reclassifications   0 110
Amounts reclassified from accumulated OCI to earnings   0 0
Period change 0   110
Balance, end of period 287 287 286
Unrealized gains and (losses) on cash flow hedging derivatives      
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Balance, beginning of period   (2,634) (3,948)
Other comprehensive income before reclassifications   828 5,231
Amounts reclassified from accumulated OCI to earnings   735 (500)
Period change 1,563   4,731
Balance, end of period (1,071) (1,071) 783
Unrealized gains (losses) for pension and other post- retirement obligations      
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Balance, beginning of period   (205,905) (230,747)
Other comprehensive income before reclassifications   0 0
Amounts reclassified from accumulated OCI to earnings   2,018 2,522
Period change 2,018   2,522
Balance, end of period (203,887) (203,887) (228,225)
Accumulated Other Comprehensive Loss      
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Balance, beginning of period   (401,016) (226,158)
Period change 31,053    
Balance, end of period $ (369,963) (369,963) (172,175)
Reclassification out of Accumulated Other Comprehensive Income      
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Net unrealized loss on securities transfer   $ (97,000) $ (82,000)