Supplementary Balance Sheet Information - Contract Acquisition Costs, Net - Significant Components (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Identifiable intangible assets acquired
Contract acquisition costs, net of accumulated amortization	$ 151,758	$ 258,665
Contract cost assets
Identifiable intangible assets acquired
Accumulated amortization	179,600	176,400
Amortization expense	10,726	8,173
Contract acquisition costs, net of accumulated amortization	$ 151,758	139,249
Payments for processing rights
Identifiable intangible assets acquired
Amortization expense		5,219
Contract acquisition costs, net of accumulated amortization		119,416
Contract acquisition costs, accumulated amortization		$ 166,300