Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Consolidated Statements of Comprehensive Income
Net income (loss)	$ 1,553.7	$ 2,324.5	$ 1,361.8
Other comprehensive income (loss), net:
Net unrealized gains (losses) on available-for-sale securities	(1,529.6)	639.5	99.1
Noncredit component of impairment losses on fixed maturities, available-for-sale	26.4	31.2	(3.5)
Net unrealized gains (losses) on derivative instruments	16.0	(42.6)	15.5
Foreign currency translation adjustment	(287.6)	178.9	68.1
Net unrecognized postretirement benefit obligation	(60.9)	37.3	41.8
Other comprehensive income (loss)	(1,835.7)	844.3	221.0
Comprehensive income (loss)	(282.0)	3,168.8	1,582.8
Comprehensive income (loss) attributable to noncontrolling interest	2.7	17.7	49.7
Comprehensive income (loss) attributable to Principal Financial Group, Inc.	$ (284.7)	$ 3,151.1	$ 1,533.1