Investment in Affiliates, Net (Details) $ in Thousands, NZD in Millions	3 Months Ended										12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Sep. 30, 2013 USD ($)	Sep. 30, 2013 NZD	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2015 NZD	Sep. 01, 2013
Schedule of Investments [Line Items]
Income tax expense on earnings of investments in affiliates											$ 9,100	$ 8,900	$ 16,500
Dividends received from investments in affiliates											30,084	38,655	36,680
Operating revenue	$ 390,886	$ 386,439	$ 386,013	$ 364,772	$ 345,512	$ 367,454	$ 365,970	$ 326,104			1,528,110	1,405,040	1,404,401
Operating expenses											1,325,186	1,235,282	1,262,259
Gain on investments and other, net											31,592	3,882	12,032
Investment in affiliates, net	69,205				103,598						69,205	103,598
Goodwill	1,881,547				1,780,758						1,881,547	1,780,758	$ 1,390,674
Other intangible assets, net	352,148				278,270						352,148	278,270
Mandatorily redeemable noncontrolling interests	$ 18,981				$ 0						$ 18,981	$ 0
PIQ Acquisition [Member]
Schedule of Investments [Line Items]
Noncontrolling interest, ownership percentage by parent									60.00%	60.00%
Additional percentage of ownership acquired	40.00%										40.00%			40.00%	10.00%
Amount paid to acquire business									$ 2,600	NZD 3.3
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain									$ 6,600
Mandatorily redeemable noncontrolling interests	$ 19,000										$ 19,000			NZD 27.8
RELS LLC [Member]
Schedule of Investments [Line Items]
Ownership percentage in equity method investment	49.90%										49.90%			49.90%
Gain on investments and other, net	$ 34,300
Noncontrolling interest, ownership percentage by parent	100.00%										100.00%			100.00%
Joint Venture Loan Originations Products and Services [Member]
Schedule of Investments [Line Items]
Ownership percentage in equity method investment	50.10%										50.10%			50.10%
Percentage of income in equity earnings of affiliates, net of tax											84.90%	80.00%	70.70%
Joint Venture Loan Originations Products and Services [Member]
Schedule of Investments [Line Items]
Operating revenue											$ 18,200	$ 19,000	$ 15,400
Operating expenses											$ 13,000	$ 12,900	$ 13,500
Symbility [Member]
Schedule of Investments [Line Items]
Ownership percentage in equity method investment								29.40%
Investment in affiliates, net								$ 18,300
Difference between the purchase price and interest in the net assets								11,300
Goodwill								2,000
Other intangible assets, net								$ 9,400
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life								15 years