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Accumulated Other Comprehensive Income (Loss) (Components of AOCI) (Details) - USD ($) $ in Thousands | 3 Months Ended |
--- | --- | ---
Mar. 31, 2018 | Mar. 31, 2017 | Dec. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Beginning balance |  | $ 3,841,951 | $ 3,427,741 |
Cumulative effect of change in accounting principle related to marketable equity securities | [1] |  |  | $ (160)
Net unrealized (losses) gains arising during the period |  | (10,513) | 6,062 |
Amounts reclassified from AOCI |  | (1,501) | (1,434) |
Other comprehensive (loss) income |  | (12,014) | 4,628 |
Ending balance |  | 3,978,755 | 3,565,954 |
Available- for-Sale Investment Securities |  |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Beginning balance |  | (30,898) | (28,772) |
Net unrealized (losses) gains arising during the period |  | (17,311) | 5,055 |
Amounts reclassified from AOCI |  | (1,501) | (1,434) |
Other comprehensive (loss) income |  | (18,812) | 3,621 |
Ending balance |  | (55,981) | (25,151) |
Available- for-Sale Investment Securities | ASU 2016-01 |  |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Cumulative effect of change in accounting principle related to marketable equity securities |  |  |  | 385
Available- for-Sale Investment Securities | ASU 2018-02 |  |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Reclassification of tax effects in AOCI resulting from the new federal corporate income tax rate |  | (6,656) |  |
Foreign Currency Translation Adjustments |  |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Beginning balance |  | (6,621) | (19,374) |
Net unrealized (losses) gains arising during the period |  | 6,798 | 1,007 |
Amounts reclassified from AOCI |  | 0 | 0 |
Other comprehensive (loss) income |  | 6,798 | 1,007 |
Ending balance |  | 177 | (18,367) |
AOCI, Net of Tax |  |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Beginning balance |  | (37,519) | (48,146) |
Cumulative effect of change in accounting principle related to marketable equity securities | [1] |  |  | 385
Reclassification of tax effects in AOCI resulting from the new federal corporate income tax rate | [2] | (6,656) |  |
Other comprehensive (loss) income |  | (12,014) | 4,628 |
Ending balance |  | (55,804) | $ (43,518) |
AOCI, Net of Tax | ASU 2016-01 |  |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Cumulative effect of change in accounting principle related to marketable equity securities |  |  |  | $ 385
AOCI, Net of Tax | ASU 2018-02 |  |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Reclassification of tax effects in AOCI resulting from the new federal corporate income tax rate |  | $ (6,656) |  |
[1] | Represents the impact of the adoption in the first quarter of 2018 of Accounting Standards Update (“ASU”) 2016-01, Financial Instruments — Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. Refer to Note 2 — Current Accounting Developments to the Consolidated Financial Statements for additional information.
[2] | Represents amounts reclassified from AOCI to retained earnings due to the early adoption of ASU 2018-02, Income Statement — Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income during the first quarter of 2018. Refer to Note 2 — Current Accounting Developments to the Consolidated Financial Statements for additional information.

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- Definition Amount of increase (decrease) in accumulated other comprehensive income (AOCI) for reclassification to retained earnings of tax effect from remeasurement of deferred tax pursuant to Tax Cuts and Jobs Act of 2017. + References No definition available. + Details
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
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