Commitments and Contingencies (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2014	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Loan commitments to extend credit	$ 3,812,544	$ 3,580,655
Standby letters of credit	217,610		$ 210,292
Commitments to purchase equipment being acquired for lease to others	0	$ 6,663
Total	$ 4,030,154		$ 3,797,610