Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Increase in retained earnings	$ 7,505,706		$ 6,956,882
Increase (decrease) in accumulated other comprehensive income	$ (474,938)		$ 68,541
Accounting Standards Update 2014-09 | Difference Between Revenue Guidance In Effect Before And After Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Increase in retained earnings		$ 1,000
Retained earnings | Accounting Standards Update 2016-01
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect adjustment resulting from changes in accounting principles		291,000
Retained earnings | Accounting Standards Update 2018-02
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect adjustment resulting from changes in accounting principles		(76,000)
AOCI Including Portion Attributable to Noncontrolling Interest | Accounting Standards Update 2016-01
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Increase (decrease) in accumulated other comprehensive income		(291,000)
AOCI Including Portion Attributable to Noncontrolling Interest | Accounting Standards Update 2018-02
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Increase (decrease) in accumulated other comprehensive income		$ 76,000