Shareholders' Equity - Schedule of AOCI (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at December 31, 2017	$ 2,755,422
Amounts reclassified from cumulative other comprehensive income to retained earnings	(78,715)
Current period other comprehensive loss	(93)
Balance at March 31, 2018	2,749,974
Unrealized Gain (Loss) on Investment Securities, net
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at December 31, 2017	78,715
Amounts reclassified from cumulative other comprehensive income to retained earnings	(78,715)
Current period other comprehensive loss	0
Balance at March 31, 2018	0
Equity in Unrealized Gain (Loss) of Investees
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at December 31, 2017	643
Amounts reclassified from cumulative other comprehensive income to retained earnings	0
Current period other comprehensive loss	(93)
Balance at March 31, 2018	550
Cumulative other comprehensive income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at December 31, 2017	79,358
Balance at March 31, 2018	$ 550