Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Loan Losses:
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 110,162	$ 53,311	$ 49,804
Charged to Cost and Expenses	152,926	149,963	74,863
Charged to Other Accounts	17,199	7,270	7,129
Deductions— Write offs	(171,272)	(100,382)	(78,485)
Balance at End of Period	109,015	110,162	53,311
Deferred tax asset valuation allowance:
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	53,603	31,978	26,090
Charged to Cost and Expenses	(826)	(24,209)	(2,514)
Charged to Other Accounts	3,779	45,834	8,402
Deductions— Write offs	(18,805)	0	0
Balance at End of Period	$ 37,751	$ 53,603	$ 31,978