XML 77 R54.htm IDEA: XBRL DOCUMENT v3.7.0.1
Benefit Plans (Narrative) (Details)
$ / shares in Units, $ in Millions
3 Months Ended
Mar. 31, 2017
USD ($)
$ / shares
shares
Defined Benefit Plan Disclosure [Line Items]  
Unrecognized compensation cost | $ $ 14.0
Minimum [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Unrecognized compensation cost recognized over a weighted average period 1 year
Maximum [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Unrecognized compensation cost recognized over a weighted average period 2 years
IPL [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Unrecognized compensation cost | $ $ 7.6
WPL [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Unrecognized compensation cost | $ $ 5.9
Performance Contingent Restricted Stock [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Nonvested, March 31 (in shares/awards) | shares 90,806
Nonvested, March 31, weighted average grant date fair value (in dollars per share) | $ / shares $ 32.55
Performance Contingent Cash Awards [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Nonvested, March 31 (in shares/awards) | shares 79,616
2014 Grant [Member] | Performance Contingent Restricted Stock [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Vested (in shares/awards) | shares (99,438)
2014 Grant [Member] | Performance Contingent Cash Awards [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Vested (in shares/awards) | shares (79,719)
Cash payout value | $ $ 3.1